APPLICATION NOTE
www.onsemi.com

Introduction to onsemi High Current Dual Half
Bridge Modules for Automotive Mild Hybrid
Applications
AND90235/D
Series of Modules Available

onsemi has introduced a series of isolated 80 V MOSFET
modules in a variety of packages that are suitable for 48 V
battery−driven mild hybrid electric vehicles (MHEV) andlow voltage traction systems. The series offers options forthe insulating ceramic DBC substrate to provide standard
and premium thermal performance, various RDS(on) ratings
to match the end user’s current requirements, and a varietyof pin−out options to enable different system designs. The
entire series of modules is qualified to AQG324
Recommended
Practice,
manufactured
with
AEC−Q101−qualified components. This series of modules
further augments onsemi’s line of high performance, highreliability transfer−molded modules for automotive
applications.
Figure 1. Package Varieties: Standard, Pressfit,
and Side PCB−Mount Pins

Available Part Numbers and Brief Description

All modules are configured as dual half bridges, a.k.a.
2−phase modules, which are easily connected externally toform a single half bridge suitable for twice the phase current,
according to the schematic of Figure 2. Therefore,
according to the end user’s requirements, three modules may
be configured to drive a 3−phase motor or 6−phase motor.
The series consists of the following part numbers:
 NXV08H250DT1 – Al2O3 substrate with maximum
0.762 mW RDS(ON) at 25C with Standard Pins
 NXV08H250DPT2 – Al2O3 substrate with maximum
0.710 mW RDS(ON) at 25C with Pressfit Pins
 NXV08H300DT1 – Al2O3 substrate with maximum
0.580 mW RDS(ON) at 25C with Standard Pins
 NXV08H350XT1 – HAlN substrate with maximum
0.762 mW RDS(ON) at 25C with Standard Pins
 NXV08H400XT1 – HAlN substrate with maximum
0.580 mW RDS(ON) at 25C with Standard Pins
 NXV08H400XT2 – HAlN substrate with maximum
0.580 mW RDS(ON) at 25C with Side PCB−Mount Pins

 Semiconductor Components Industries, LLC, 2023

June, 2023 − Rev. 0

Figure 2. Module Schematic

1

Publication Order Number:AND90235/D

AND90235/D
INTRODUCTION
The NXV08HxxxyTz series1 of automotive power
modules (APM) has been designed specifically for highcurrent, high power density designs of 48 V mild hybrid
electric vehicle and low voltage traction applications. Belt
starter generator systems (in which the electric machine ismounted on the vehicle’s front end accessory drive belt) andintegrated starter generator systems (in which the electricmachine is integrated into the gearbox) are equallywell−served by this series of modules. Three modules may
be configured to drive 3−phase or 6−phase motors as
illustrated in Figure 3.

B+ #1

B+ #2

B+ #1

B+ #2

PH1

PH1

PH2

PH2

B+ #1

Further technical details for each module are provided in
the module data sheets available at www.onsemi.com.
APPLICATION ANALYSIS FOR USE OF APM17
MODULES
Automotive engineers involved in the design ofelectrified powertrains, including MHEV and light vehicle
electric propulsion systems, recognize that there are many
trade−offs to be performed and many competing
requirements to be met to achieve a high performance, lowcost, highly reliable electric drive system. Here we areassuming a 48 V power net is provided, which may beeffectively inverted with 80 V rated MOSFETs. This
assumption implies proper management of the charging anddischarging of the battery to maintain the dc input voltage
within the constraints of vehicle manufacturer standards,
e.g., ISO21780 [1], keeping low total power loop
inductance, and properly monitoring the bus voltage.
Starter/generator applications typically result in several
operating modes that have different current requirements.
These include continuous and peak power, engine cranking,hill hold, and active short circuit. End users specify theengine cranking torque required to start the engine and an
active short circuit mode to protect the inverter and maintaincontrol of the dc link voltage in the event of a fault. Theremay be other operating points that are not included here.

B+ #2

PH1
PH2
3−PHASE
MOTOR

GND

B+ #1

GND

GND
MODULE 1

B+ #2

MODULE 2

B+ #1

B+ #2

PH1

PH1

PH2

PH2

GND

B+ #1

B+ #2

PH1
PH2
6−PHASE
MOTOR

GND

GND
MODULE 1

MODULE 3

MODULE 2

Continuous and Peak Power

MODULE 3

Continuous power requirements range from 5 kW to
15 kW for these systems, with transient peak power
conditions as high as 25 kW. With the nominal range of DC
voltages for unlimited operation of the motor drive from36 V to 52 V [1], for the mentioned power levels we can saythat maximum continuous phase currents will fall in therange shown in Table 1.

Figure 3. 3− and 6−phase Motor Drive Arrangements

The transfer molded body with integrated, electricallyisolated DBC ceramic substrate provides robust reliability
and high thermal performance, suitable for bolted or
clamped assembly to a heatsink. Power leads are suitable forwelding to the assembly’s bus bar structure for low
inductance connection to the dc link input filter. Signal leads
are available in solderable and pressfit configurations.
These modules are rated for ambient temperature range−40C to 125C, and the maximum junction temperature is
175C. High voltage isolation is tested to 3 kVac for
1 second. Each module is fitted with a temperature−sensing
NTC with 25C value of 10 kW, and dual RC snubbers (1 W,
15 nF) closely coupled to the MOSFET half bridges forgood switching noise suppression.
To enable a variety of motor drives to use the best−suitedmodule, onsemi has designed this range of modules withvarious thermal impedances and MOSFET on−resistancevalues. With die size variations and substrate material
selections, we have provided modules with maximum 25C
RDS(ON) values between 0.58 and 0.762 mW andjunction−to−case thermal resistance values between 0.19
and 0.54C/W. Later in the application note we will
demonstrate potential system level performance achievablewith these modules.

Table 1. Phase Current Required for Range of PowerEngine Cranking

Engine cranking refers to the operation of starting the
combustion engine. Since the engine is not yet rotating,motor RPM will start at zero (stall), and increase in responseto the starting torque until it reaches a speed sufficient for the
combustion engine to run. Depending on the gear ratio
between BSG/ISG machine and the combustion engine,
motor RPM will reach perhaps as high as 3000 rpm at the endof the cranking operation. Typically, the current amplitude
will be about the same as peak power level for ~300 msec

1 “xxx” refers to approximate current rating, “y” refers to the DBC

substrate (D = Al2O3, X = HALN), and “z” refers to the pin
configuration.

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2

AND90235/D
fault conditions. Suppressing the back−EMF at high motor
speeds is particularly important to avoid an over−voltage
condition on the inverter components that would otherwise
destroy them. Welchko, et al [2], provides details of thisoperation from the point of view of motor design for interior
permanent magnet synchronous machines, but the end user
will have to determine the detailed conditions appropriate
for their specific motor design and operating conditions. For
the purposes of our examples, we will refer to Figure 6,
which is taken from [2], and assume a steady state ASC
current of 150% of the rated phase current given in Table 1,with a transient peak of 200% of rated, lasting 10 msec.

and then reduced to near continuous power levels foranother 500 msec to 2 sec. An example of an engine cranking
current profile is given in Figure 4.

Figure 4. Example Starting Current Profile
Hill Hold

Hill hold refers to the situation where the BSG/ISG is used
to mimic the conventional vehicle behavior when stopped
on an incline, where the engine’s idling speed and torqueoperate through the torque converter to produce enoughtorque to hold the vehicle still on the incline, without the useof the friction brakes.
Figure 6. Steady State 3−Phase ASC Current(from [2])COOLING SYSTEM AND THERMAL RESPONSE
Depending on the application, the higher power systems
will likely be liquid cooled, and we may expect nominal
coolant temperatures to be in the range of 65C to 105C.
End users will approach the heat sinking of the modules
in a way consistent with their system design concept.
A common approach is to employ an aluminum casting withflat surface for module mounting with the reverse side
containing pin−fins submerged into the coolant fluid flow,e.g., as shown in Figure 7.
Figure 5. Example Hill Hold Current PWM Pattern

Under these conditions, for a three phase BSG/ISG motor,
stall current is required for the duration of the event, and the
duty cycle of the PWM will have a particular pattern slightly
above 50% duty. The worst−case condition will occur when
the rotor is at an angular position such that one phase is at thepeak of the sinewave current and the other two phases are at−1/2 peak. This can be represented simply as shown in
Figure 5, where we assume Phase A is at peak current.

Figure 7. Example Heatsink and Busbar Assembly

Of key importance in assessing the module performancein the application is to obtain the transient thermal response
from the module MOSFET junction−to−coolant to ensurethat the MOSFETs remain below the data sheet value forTJ(MAX) = 175C. End user designs will vary depending on

Active Short Circuit

Active short circuit (ASC) refers to the intentional
shorting together of the motor terminals via the inverter
switches (either all upper switches or all lower switches) to
suppress the back−EMF of the motor under some detected

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AND90235/D
numerous factors such as thickness of the aluminum,
specific aluminum alloy, pin−fin shape and density, coolant
channel shape, coolant flow rate, coolant chemistry, thermalinterface material used to mount the module, mountingpressure or screw torque, etc. Each end user will optimize
their own system to achieve their design goals. For purposesof analysis in this application note, we will consider a typicaldesign.
onsemi has used CFD analysis and testing to determine
the junction−to−case transient thermal impedance for each
module, and publishes the maximum value, Rthjc, in thedata sheets. Table 2 summarizes this value for each partnumber. The transient thermal impedance, Zthjc, isconveniently represented by a Cauer or Foster thermal RC
network which is easily used in circuit simulation or
dynamic analysis to assess the junction temperature. An
example Zthjc curve is given in Figure 8, while Table 3
provides the Cauer network RC values to represent each
module part number thermal response.

As an example, we examine the transient thermal responseof the NXV08H400XT1 module. From CFD software andconfirmed by testing, we obtained the Zthjc curve shown in
Figure 8. From this time response curve, a Cauer RC
network can be found to represent the physical behavior of
the module. We select the Cauer network so that it can be“cascaded” with the end user’s network representing theirheatsink design.

Table 2. DATA SHEET VALUES FOR MAX Rthjc PER
SINGLE FETPart Number

Max

Units

NXV08H250DT1

0.54

C/W

NXV08H250DPT2

0.53

C/W

NXV08H300DT1

0.49

C/W

NXV08H350XT1

0.21

C/W

NXV08H400XT1

0.19

C/W

NXV08H400XT2

0.19

C/W

Figure 8. Zthjc Reference Curve, NXV08H400XT1/XT2The values for the thermal−equivalent RC Cauer network
to represent the six modules are given in Table 3. For
completeness and reference, Table 4 provides the Foster
network RC values.
For interested readers there is a thorough reference
application note AND90096/D [3] available atwww.onsemi.com on the proper techniques for using
onsemi electrothermal MOSFET simulation models(so−called 5−pin or 6−pin models) in concert with external
system−level thermal networks as, for example, for a liquid
cooled heatsink.

Table 3. MODULE Zthjc(t) CAUER RC NETWORK VALUESNXV08H250DT1

NXV08H250DPT2

NXV08H300DT1

NXV08H350XT1

NXV08H400XT1/XT2

R, W

C, F

R, W

C, F

R, W

C, F

R, W

C, F

R, W

C, F

1

2.114E−02

3.520E−04

2.075E−02

3.586E−04

6.098E−03

1.190E−03

8.221E−03

9.094E−03

7.439E−03

1.000E−03

2

1.121E−01

6.250E−04

1.101E−01

6.369E−04

3.041E−02

2.261E−03

4.361E−02

1.607E−03

3.946E−02

1.800E−0332.446E−01

8.363E−03

2.401E−01

8.521E−03

7.733E−02

4.884E−02

9.513E−02

2.150E−02

8.607E−02

2.380E−02

41.572E−01

1.607E−01

1.542E−01

1.637E−01

3.635E−01

6.507E−02

6.113E−02

4.132E−01

5.530E−02

4.567E−01

54.770E−03

3.355E+01

4.683E−03

3.417E+01

9.488E−03

2.254E+01

1.855E−03

8.625E+01

1.679E−03

9.532E+01

6

1.419E−04

8.298E+02

1.392E−04

8.463E+02

3.178E−3

4.624E+01

5.500E−05

2.141E+03

4.990E−05

2.363E+03

Node

Table 4. MODULE Zthjc(t) FOSTER RC NETWORK VALUESNXV08H250DT1

NXV08H250DPT2

NXV08H300DT1

NXV08H350XT1

NXV08H400XT1/XT2

Node

R, W

C, F

R, W

C, F

R, W

C, F

R, W

C, F

R, W

C, F

1

8.008E−03

5.795E−04

7.860E−03

5.905E−04

2.428E−03

1.910E−03

3.114E−03

1.490E−03

2.818E−03

1.647E−0329.987E−02

1.002E−03

9.802E−02

1.021E−03

2.976E−02

3.369E−03

3.884E−02

2.576E−03

3.514E−02

2.848E−0332.388E−01

9.043E−03

2.344E−01

9.214E−03

2.304E−02

9.333E−02

9.288E−02

2.325E−02

8.403E−02

2.570E−0241.861E−01

1.435E−01

1.826E−01

1.462E−01

4.156E−01

1.065E−01

7.236E−02

3.690E−01

6.547E−02

4.078E−01

56.360E−03

2.760E+01

6.242E−03

2.812E+01

1.577E−02

2.166E+01

2.473E−03

7.096E+01

2.238E−03

7.843E+0168.526E−04

1.567E+02

8.369E−04

1.291E+02

3.442E−03

2.691E+01

3.316E−04

3.259E+02

3.000E−04

3.602E+−2

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4

AND90235/D
ASSESSING MODULE PERFORMANCE UNDERAPPLICATION CONDITIONSAssessing the performance of these modules in a motor
drive or other application may be done in various ways. Here
we describe a bottom−up simulation effort that makes use of
onsemi physical and scalable models [4] available atwww.onsemi.com for pSpice [5], SIMetrix [6], and LTSpice[7] (and other simulators upon request). These are highly
accurate dynamic models that may be employed to evaluate
the product prior to the availability of any hardware.
By “bottom−up” we mean that the reader may use circuit
simulation or data sheet information to create a suitable
module model and exercise that model with usage profiles
in a manner to obtain insights into how well the module willmeet their requirements. In this section we describe in detailthis process.

the user’s bus bar and filtering design. For the purposes of
discussion here, the bus bar and 48 V power distribution ismodeled as shown in Figure 10. A suitable value for Cbulk
is 3 mF to 5 mF, and for LS a good layout will yield strayinductance on the order of 5 nH.
B1+{Ls} IC=0

IB+1

Rs1
25u

L600
B2+

IB+2
L26

L27

500n IC=0211p

LinkCap_VDC

+

R28

R30

550u

10m

Cbulk
{Cb} IC={VDC}

{VDC}
V4

Module_VDC

Module Basic Electrical and Thermal Performance

GND

To evaluate the electrical performance of the module,
a circuit simulator like SIMetrix [6] can be used. onsemi
uses ANSYS Q3D [8] to determine a parasitic model of the
package, which is verified by test. Figure 9 showsa simplified version of the module model for the
NXV08H400XT1 as an example.

{Ls}

Ignd

L25

25u
R29

Figure 10. 48 V Battery and Bus Bar Simulation
Model

By way of example, the gate drive circuit model shown in
Figure 11 can be used. The reader can use this circuit toinitiate a simulation, modifying it to represent their design
as it evolves, in order to meet their own performance targets.
10

Q6
TIP31

R22
Vcc1

R31
3

{VCC}

R33

V1

3

0

4.7

R43

R42

Q1Gate

51

4.7

R24

R36

Q2Gate

Q99
TIP32
R38
10k

Q2SS
Q1SS

10

Q7
TIP31

R39
Vcc

R40

{VCC}

3

R23
3

V3

0

4.7

R34

R35

Q3Gate

51

4.7

R32

R37

Q4Gate

Q8
TIP32
R41

Figure 9. Simplified NXV08H400XT1 Package Modelin SIMetrix

10k
Q4SS
Q3SS

Figure 11. Representative Gate Drive Circuitry

Such a model provides a means to evaluate conduction
and switching losses and obtain information about drain andgate waveforms. To use this model correctly, a bare diemodel of the 80 V MOSFETs must be obtained fromonsemi. External to the schematic shown in Figure 9 theuser must add a gate drive circuit and power supply for 48 V,
with parasitic stray inductance as appropriate to represent

Such a set of schematics can be used to produce a varietyof results, including classic two−pulse switching waveforms
that are useful for extracting switching energy curves, or forevaluating the variation of RDS(on) as a function of TJ. This
information could then be used in a system simulation as

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5AND90235/D
might be implemented in Matlab [9] or a spreadsheet, forexample.
With the simulation process described above, a user candevelop the necessary information needed to performsystem level simulations of a motor drive to determine
which module best meets their requirements. onsemi has
carried out both simulation and tests to acquire comparable
data for use in an Excel−based system analysis tool. The
parameters needed for this system analysis include RDS(on)as a function of junction temperature, total switching energy
for the desired gate drive, dc link voltage, and parasitic
impedance conditions, and the thermal impedance function
from junction to desired reference temperature (case, heatsink, or coolant).
For the purposes of this application note, we havecollected data for junction−coolant thermal impedance foran assembly similar to that shown in Figure 7. Salientfeatures of the example heat sink assembly are: 3 mm thickaluminum plate with a thermal interface material applied
30 mm thick with thermal conductivity of 2.1 W/(m−K).
With these assumptions, the steady state values of thermal
resistance from junction to coolant are shown in Table 5.
An example of the transient thermal impedance curve for
the NXV08H400XT1 mounted on the described heat sink isshown in Figure 12. Similar data has been collected for all
the model part numbers and the thermal equivalent Cauerand Foster network values are given in Tables 6 and 7.

Figure 12. Transient Thermal Impedance
Junction−Coolant for NXV08H400XT1/XT2 Module

Table 5. THERMAL RESISTANCE, JUNCTION TO
COOLANTPart Number

Max

Units

NXV08H250DPT2/DT1

0.969

C/W

NXV08H300DT1

0.860

C/W

NXV08H350XT1

0.755

C/W

NXV08H400XT1/XT2

0.656

C/W

Table 6. MODULE Zthj−coolant(t) CAUER RC NETWORK VALUESNXV08H250DT1/DPT2

NXV08H300DT1

NXV08H350XT1

NXV08H400XT1/XT2

Node

R, W

C, F

R, W

C, F

R, W

C, F

R, W

C, F

1

6.720E−03

1.086E−03

5.321E−03

1.372E−03

7.141E−03

1.019E−03

6.205E−03

1.173E−03

2

3.513E−02

2.014E−03

2.763E−02

2.585E−03

3.606E−02

1.924E−03

3.134E−02

2.214E−0331.140E−01

2.785E−02

9.660E−02

3.416E−02

9.162E−02

3.508E−02

7.959E−02

4.038E−02

45.663E−01

5.175E−02

4.924E−01

5.774E−02

4.502E−01

6.635E−02

3.912E−01

7.637E−0252.414E−01

2.443E+00

2.326E−01

2.497E+00

1.663E−01

3.510E+00

1.445E−01

4.040E+00

6

5.312E−03

2.346E+02

5.425E−03

2.352E+02

3.594E−03

3.608E+02

3.129E−03

4.148E+02

Table 7. MODULE Zthj−coolant(t) FOSTER RC NETWORK VALUESNXV08H250DT1/DPT2
Node

R, W

C, F

1

2.633E−0323.176E−0234.527E−02

456

NXV08H300DT1

NXV08H350XT1

NXV08H400XT1/XT2

R, W

C, F

R, W

C, F

R, W

C, F

1.758E−03

2.111E−03

2.205E−03

2.831E−03

1.640E−03

2.460E−03

1.887E−03

3.152E−03

2.478E−02

4.036E−03

3.473E−02

2.913E−03

2.987E−02

3.352E−03

4.754E−02

3.522E−02

6.119E−02

3.764E−02

5.735E−02

3.270E−02

6.601E−02

5.982E−01

7.776E−02

5.162E−01

9.065E−02

4.790E−01

9.773E−02

4.162E−01

1.125E−01

2.702E−01

2.217E+00

2.616E−01

2.266E+00

1.882E−01

3.144E+00

1.635E−01

3.619E+00

2.090E−02

6.087E+01

2.008E−02

6.485E+01

1.292E−02

1.022E+02

1.123E−02

1.177E+02

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6

AND90235/D
Switching energy can be determined from 2−pulse testingor simulation. With the simulation circuits shown in Figures
9–11, we have been able to match switching energy
measurements made in our applications laboratory for the
NXV08H400XT1 and have extended those results to the fullline of modules based on simulation (see Tables 9 & 10).
For example, a range of gate resistance values and dc link
voltages have been tested and the collected waveforms havebeen used to validate the simulation circuit. In Figures 13
and 14, simulation results for the turn−off and turn−on
events are shown for NXV08H400XT1, for Rg external
values of 5, 15, and 30 Ohms. This demonstrates the impact
on turn−on and turn−off losses as well as the transient
overshoot voltage on the drain due to stray inductancecoupling with the resulting di/dt of the drain current.

conduction and switching losses and resulting dietemperatures for operating conditions of interest. As
mentioned above, an Excel−based system analysis tool isused to determine these quantities. An example ofcontinuous power operation is given for the following
conditions: Rg(on) = Rg(off) = 15 W
 Switching Frequency fsw = 16 kHz
 Fundamental Frequency f1 = 200 Hz Lockout Time = 500 ns
 Vdc = 48 V
 Iphase = 650 Arms
 Tcoolant = 65C

Figure 15. System Simulation Loss Component
Inputs – NXV08H400XT1(a) Waveforms

Figure 16 shows the output of the analysis – dietemperature and losses. The analysis is run for ~3.5 secondsof simulated time to obtain to steady state temperatures. The
time necessary to achieve steady state can be observed fromthe thermal impedance curve in Figure 12.
Figure 16 shows the full progression of the MOSFET
junction temperature, which reaches approximately 95C,
and also a zoomed in view of the temperature ripple that
occurs at the fundamental frequency of 200 Hz.

(b) Turn−off Energy

Figure 13. Simulated Turn−Off Switching Waveforms
and Energy for Range of Rg(off, ext), 250 A per Die(a) Waveforms(b) Turn−on Energy

Figure 14. Simulated Turn−On Switching Waveforms
and Energy for Range of Rg(on, ext), 250A per Die

By exercising the SIMetrix (or Spice) simulations, theuser can develop enough loss information to accurately
perform system simulations of any given operating point of
the BSG/ISG system. The module losses are accurately
captured by temperature−dependent values of RDS(on) andoperating condition−depended switching energy. Examplesof this information are given in Figure 15, again for
NXV08H400XT1. Coupled with the thermal impedance
characteristic, this information is sufficient to compute

Figure 16. System Simulation Output Variables –NXV08H400XT1

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7AND90235/D
The breakdown in losses is shown for the low side
MOSFET, between conduction, switching, body diode, andtotal. As is known, the body diode only conducts during theso−called dead−time or lockout time between the high andlow side FET conduction periods, thus contributing
a relatively modest amount of loss to the total.
Table 8 shows a summary of the peak and average
conditions experienced during this continuous power
operation.
Table 8. SUMMARY STATISTICS FROM SYSTEMANALYSIS

Figure 18. Total Time Engine Cranking Results

In Figure 18, we see the full profile of high side MOSFET
loss, and then a “zoomed in” view of the low side MOSFET
loss near the end of the starting profile.
In Figure 19 we examine the initial startup transient where
the motor starts from zero speed and ramps to the startingrpm in response to the motor torque. One can see the
500 Arms current developing from 0 Hz to near 200 Hz at
0.1 seconds. Due to the low initial frequency, larger
temperature pulses are observed.

Similarly, this analysis approach can be used to examine
other operating modes of the BSG/ISG, such as hill hold orengine cranking. For example, Figure 4 above introduceda sample engine cranking RMS current profile, andFigure 17 provides a detailed time−based equivalent of thisphase current (first 0.5 seconds only).

Figure 17. Example Engine Cranking Current Profile

For this condition, we assume that the initial junction
temperature is elevated to 110C. Other conditions
described for the continuous power operation above still
apply. One can observe in Figure 18 the phase current
starting from stall and accelerating to the starting speed of
200 Hz. An initial burst of 500 Arms for 300 msec followed
by 340 Arms for an additional 2 seconds is given.
From the analysis output shown in Figures 18 and 19, we
can see the development of losses and junction temperaturein response to the engine cranking current profile.

Figure 19. Initial 100 ms of Engine Cranking Results

The above two examples of system analysis are provided
for continuous operation and for the engine cranking
operation of the NXV08H400XT1 module as a means ofillustrating the strong performance of the new onsemi highcurrent dual half bridge modules. With basic performance
information relating to conduction losses, switching losses,

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and thermal impedance the system analyst can quickly
evaluate the suitability of the modules for their application.
Thermal impedance characteristics are given for all
modules in Tables 3 and 4 (junction−to−case) and Tables 6
and 7 (example junction−to−coolant) as Foster and Cauer
RC networks. The normalized RDS(on) and total switchingloss curves shown in Figure 15 for the NXV08H400XT1
can be generated from polynomial expressions for each of
the six modules discussed in this application note.
To model RDS(on) as a function of temperature, the user
can employ the information in Table 9 below in conjunction
with the following equations:
2

R DS(on)(normalized) + a @ T J ) b @ T J ) c(eq. 1)

R DS(on)(T J) + R DS(on)(25C) @ R DS(on)(normalized)(eq. 2)

Table 10. TOTAL SWITCHING ENERGY (PER DIE)
MODELING INFORMATION FOR MODULES
Part
Number
NXV08H…

Table 9. RDS(ON) (PER DIE) MODELING INFORMATIONFOR MODULESRDS(on) (25C), mW
Typ

Max

a

b

c

250DT1

0.549

0.762

3.1705e−6

1.70e−30.887

250DPT2

0.56

0.71

3.1705e−6

1.70e−30.887

300DT10.46

0.58

6.0667e−64.1057e−3

0.891

350XT1

0.549

0.762

3.1705e−6

1.70e−3

0.887

400XT10.46

0.58

6.0667e−64.1057e−3

0.891

400XT20.46

0.58

6.0667e−64.1057e−3

0.891

Rg(on/off) = 30/15 W

k

n

k

n

x

250DT1
250DPT2
350XT14.26e−6

1.258

9.95e−6

1.175

1.185

300DT1
400XT1
400XT23.00e−6

1.296

7.22e−6

1.208

1.798

GATE DRIVER RECOMMENDATIONS
onsemi provides solutions for 48 V BSG/ISG
applications beyond the boundary of the power modules
described in this application note, as can be seen from our
website www.onsemi.com, and the 48 V system block
diagram shown in Figure 20. Of particular interest for thisapplication note are the gate drivers that are available fromonsemi.
Two series of gate driver IC’s available from onsemi are
particularly useful for driving the NVX08H−series of power
modules: the FAD3151/3171 [10] and NCV5707B [11].
These drivers provide high current and voltage capability
suitable to drive the large die MOSFETs in the modules, anddesaturation detection and soft turn off features to handle
overcurrent or short circuit current conditions.
If the user’s system is required to protect against shortcircuit conditions, it is necessary to manage well thedetection and soft turn off operation in order to achievea fault−tolerant design.

Note that the data in Table 9 is for each die in the module.
The data sheet lists different values for Q1 and Q2 (high sidedie) versus Q3 and Q3 (low side die). As indicated in the data
sheets, this is due to the kelvin sense points used to measure
RDS(on) at final test. From the perspective of determining dietemperature and losses, the lower value of these (the low sidedie) is more appropriate to use because it is a closer
representation of the actual die on−resistance.

Part
Number
NXV08H…

Rg(on/off) = 15/15 W

In a similar manner, the switching losses for each model
can be simply characterized by a power law representing the
curve as shown previously in Figure 15. The equation below
relates drain current and DC voltage to the total switchinglosses, for a range of DC voltage from ~36 V to ~56 V. Vref
for all cases is 48 V. The values for k, n, and x for the onsemi
modules are given in Table 10.
E SWǒI D, V DCǓ + k @ I D @
n

ǒ Ǔ
V DC
V ref

x

Figure 20. 48 V BSG/ISG Application Block Diagram(eq. 3)www.onsemi.com
9AND90235/D
FAD3151/3171

As shown in application schematic in Figure 21, the desat
diode D1, resistor R1, blanking capacitor CBL, andP−channel JFET P1 are the minimum external components
required to operate the desaturation protection scheme. The
driver needs an external pull−down transistor P1 todischarge IDESAT and CBL as soon as the driver output turns
off.
Otherwise, the blanking capacitor will continue to charge
up and eventually trigger desat. The presence of a normallyon P1 also enhances noise immunity of the desat blanking
capacitor against false triggering during the turn−on event ofcomplementary power switch. The external desat
components can be modified to adjust the blanking time andthe desat detection threshold for a given application.
If the power switch is turned off rapidly during a heavy
load condition, the high currents may generate a voltage
overshoot across the power switch that could potentiallydamage it. In order to protect the devices, the driver has a soft
shutdown feature, which activates upon desat detection. The
output is then driven low through a large turn−off resistance(RSOFT) which provides a significantly higher resistancepath for the gate capacitance to discharge than during theregular turn−off process. As a result, the possibility of an
abrupt overvoltage spike on the power switches is reduced.
When the voltage at the desaturation pin exceeds thedefined desat threshold, following protection sequence isperformed:
 The gate driver initiates a soft shutdown. The driver will
provide a high resistance path through an internal resistor
for gate capacitance to discharge slowly as shown in
Figure 22.
 The fall rate of HO is determined by the time constant of
the RC discharge path. The driver also triggers an internalfault and pulls down the fault pin for the period equivalent
to Fault Locking duration (typ. 550 ms).

The FAD3151 and FAD3171 are single channel floating
automotive gate drivers suitable for driving high−speed
power MOSFETs up to 110 V. Designed in a SOI
technology, the drivers are ideal for applications that requirenoise immunity against severe negative transients andground offset up to −80 V. They operate as a pair of ICs as
shown in the application schematic in Figure 21.
The FAD3151/3171 drivers have an integrated
desaturation detection to protect the power switches during
short circuit and over current conditions. The drivers are also
equipped with a soft shutdown feature, which initiates a soft
shutdown of driver outputs upon desat detection, thus
preventing possible overvoltage across power MOSFETs
during a heavy−load condition.
The FAD3151/3171 drivers are equipped withbidirectional fault reporting pin that can generate a fault
output during desat and under−voltage lockout (UVLO)
condition. The bidirectional nature of the fault−reporting pin
allows the driver to respond to external fault commands,
thereby facilitating fault communication across the system.
In addition, the FAD3171 has an integrated charge pump to
support 100% duty cycle operation of high side MOSFETs.
The gate driver has a desaturation detection circuit thatmonitors the drain to source voltage VDS of the power
MOSFET through the desaturation detection pin. This
circuit consists of: An internal current source that provides a continuous
current toward the power stage to monitor the VDS
voltage. The desat current source (IDESAT) is supplied
from the VB pin and is continuously active as soon as the
VDD is higher than the UVLOVDD+, independent of thestatus of the input logic.
 An internal comparator that compares the voltage at thedesat pin (VDESAT) with the defined desat threshold(VDESAT,TH) of 3 V (typ). When VDESAT exceeds
VDESAT,TH, the comparator simultaneously turns off theoutput ‘slowly’ and triggers a fault condition by pulling
down the fault pin internally.

Figure 22. FAD3151/3171 Desaturation Detection andSoft Shutdown

Additional details regarding the operation of the
FAD3151/3171 are given in [10]. Here we simply highlight

Figure 21. Application Diagram for FAD3151/3171
Driver IC

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10AND90235/D
Therefore, the comparison is delayed by a configurable time
period (so−called blanking time) to prevent false triggeringof the DESAT protection before the MOSFET drain−source
voltage falls below the saturation level. Blanking time is set
by the value of the capacitor CBLANK.
The exact principle of operation of DESAT protection is
described with reference to Figure 23. At the turned−off
output state of the driver, the DESAT pin is shorted to ground
via the discharging transistor (QDIS). Therefore, theinverting input holds the comparator output at low level.

the necessary desat detection and soft turn−off capability ofthis IC to enable short circuit protection in the
NXV08H−series of modules.
NCV5707B

The automotive qualified NCV5707B is an 8−pin SOIC
part in a series of high current, high performance standalone
drivers for high power applications that include the
BSG/ISG modules. The devices offer a cost−effective
solution by eliminating the need for an external output
buffer. Protection features include accurate Undervoltage
Lockout (UVLO), desaturation protection (DESAT) andactive open drain FAULT output.
The drivers also feature an accurate 5.0 V output. The
drivers are designed to accommodate a wide voltage rangeof bias supplies. The NCV5707B accommodates bipolar
voltages.
A companion part (NCV5707A) also includes Active
Miller Clamp and separate high and low (VOH and VOL)
driver outputs for system design convenience (NCx5707C).
To emphasize the desat detection and soft turn−offfeatures of the IC which are necessary to protect against
short circuit conditions in the NXV08H−series of modules,
the following information about the NCV5707B is provided
from [11].
The desaturation detection feature monitors VDS in theturned−on state. When the MOSFET is fully turned on, it
operates in the RDS(on) region. VDS is usually low because
it is RDS(on) * ID, and RDS(on) for these parts is below 1 mW,
well below 3 V in the NXV08H−series modules. It could
indicate an overcurrent or similar stress event on the
MOSFET if the drain−source voltage rises above thesaturation voltage, after the MOSFET is fully turned on.
Therefore, the DESAT protection circuit compares thedrain−source voltage with a voltage level VDESAT−THR tocheck if the MOSFET is experiencing extreme levels of ID.
It will activate FLT output and shut down driver output (thusturn off the MOSFET), if the drain−source voltage rises
above the VDESAT−THR. This protection works on every turnon phase of the MOSFET switching period.
To prevent the voltage overshoot damage caused byturning off the MOSFET, the NCV5707B driver is equippedwith a “Soft Turn Off” (STO) function. This function is
activated when the DESAT protection is activated andreduces the turn off voltage overshoot by adding a large
internal turn off resistance in series with the externalRg(off).
At the beginning of MOSFET turn−on, the drain−source
voltage is much higher than the voltage which is present
after the MOSFET is fully turned on. It may take ~1 ms
between the start of the MOSFET turn−on and the moment
when the drain−source voltage falls to the fully on level.

Figure 23. NCV5707B Desaturation Protection
Schematic

At the turned−on output state of the driver, the current
IDESAT−CHG from current source starts to flow to theblanking capacitor CBLANK, connected to DESAT pin.
An appropriate value of this capacitor has to be selected
to ensure that the DESAT pin voltage does not rise above thethreshold level VDESAT−THR before the MOSFET fully
turns on.
The blanking time is given by following expression.
According to this expression, a 47 pF CBLANK will providea blanking time of 47 pF * 6.5 V/0.25 mA = 1.22 ms.
t BLANK + C BLANK @V DESAT*THRI DESAT*CHG(eq. 4)After the MOSFET is fully turned−on, the IDESAT−CHG
flows through the DESAT pin to the series resistor RS−DESAT
and through the high voltage diode and then through thedrain and source. Care must be taken to select the resistor
RS−DESAT value so that the sum of the saturation voltage,
drop on the HV diode and drop on the RS−DESAT caused bycurrent IDESAT−CHG flowing from DESAT source current issmaller than the DESAT threshold voltage. Following
expression can be used for the DESAT threshold voltage:
V DESAT*THR u R S*DESAT @ I DESAT*CHG ) V F*HVdiode ) V DS

where VDS is the drain−source voltage under high− or
short−circuit current levels.

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Figure 25. General Assembly Methods

For high power modules, the power terminals can beconnected directly to the busbar through a welding process,such as resistive welding, according to the customer’s
preferred technique. It is preferred to connect the power
terminals directly to the bus bar to avoid bringing
excessively high current onto a PCB, since this would
require special PCB construction and materials to handle thecurrent efficiently.

Figure 24. NCV5707B Desaturation Protection
Schematic

Package Surface Specification

It is important that the high voltage diode is rated at 80 V
for the NXV08H−series modules, with a safety margin if
desired by the end user. The typical waveforms for the
MOSFET overcurrent condition are outlined in Figure 24.

The measurement area for the warpage of the package
surface is specified by the package center and the four
outside corners, as shown in Figure 26. Warpage for themodules is as specified in Table 11. When assembled withrecommended screws and torque, the surface will be
flattened and the thermal compound between module andheatsink will spread out and fill the microscopic air gaps
between the two contact partners, finally ensuring fullthermal contact. Warpage is guaranteed to be concave up(so−called “smile shape”) such that the screw torque will
flatten the module onto the heatsink surface.

MECHANICAL MOUNTING CONSIDERATIONS
The dual half−bridge APM module is a compact
semiconductor
power
modulewithlowpower−consumption and high reliability. Target
applications are inverter motor drives for 48 V MHEVs. To
achieve the high performance and long life needed for thisdemanding application, proper mounting with good thermal
performance and low mechanical stress is needed. In thissection, we provide mounting guidance for this series ofmodules.
Figure 25 shows the two general methods of assembly fortypical transfer molded power modules. Assembly iscommonly done using method 1 or method 2 based on thecustomer’s preference. This application note is intended toprovide recommendations for proper handling, assembly of
the package and potential rework in conjunction withindustry standards. We also outline appropriate thermalinterface material (TIM) application and heat sink mounting
as well as soldering procedures to ensure a reliable printed
circuit board (PCB) connection. Recommendations in thisnote are based on simulation and experimental results fromlaboratory and field tests.

Figure 26. Determination of Package Warpage

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Module mounting to the heat sink first, then soldering to
the board and/or welding power terminals.
When the module is mounted onto the heat sink before
PCB mounting, a process flow as illustrated in Figure 28 isrecommended. First, apply TIM on the surface of themodule or heat sink and place the module on the heat sink(a). Tighten the screws down to heat sink (b). Then themodule with the heat sink is placed onto the PCB (c). Finally,
the solder joint between signal pins and PCB is formed(wave soldering process or manual soldering)
Manual soldering, wave soldering, and selective
soldering are possible techniques to assemble the module
onto the PCB. For the power terminals, a laser or resistive
welding process can be used to connect the power terminals
directly to the bus bar. With manual soldering, both bottomside and top side soldering is available. Wave solderingsystems consist typically of solder fluxing, preheating zone,
solder wave and the cooling zone. As the board enters theconveyorized process, solder flux is sprayed or foamed onto
the modules.
Then it moves to the preheating zone, normally done byconvection, where the flux is activated. The assembly thenmoves to wave soldering. The assembly is then slowly
cooled down.

Table 11. SPECIFICATION OF THE APM PACKAGEWARPAGE
Module

Min

Typ

Max

NXV08H250DT1
NXV08H250DPT2
NXV08H300DT1
NXV08H350XT1
NXV08H400XT1
NXV08H400XT2+35 mm+55 mm+150 mmHeat Sink Surface Specification

The thermal performance of a module is influenced by thequality of the surface contact to the heat sink. To maximize
the heat transfer it is required to maintain a high quality heatsink surface, that is, surface flatness and roughness must be
properly specified and controlled when manufacturing theheat sink. To obtain best performance, the specifications
given in Table 12 and Figure 27 should be followed in theheatsink design and manufacture. Additionally, the desiredheat flow from heat sink to ambient for the customer’s
application conditions must be achieved. The surface of theheat sink must be clean and free of particles during assembly.
Table 12. HEAT SINK SURFACE REQUIREMENTS
Flatness of Heat Sink

−50 ~ 100 (mm)Geometrical Surface Roughness (Rz)

10 (mm) to
DIN EN ISO 4287(a) Apply thermal interface materialon the module or heat sink surface
and place module onto the heatsink.

(b) Tighten the APM to the heat sinkusing M3 screw and washer(c) Place the PCB then solder the signal leads to the PCB

Figure 27. Determination of Package Warpage

Figure 28. Process Flow of Soldering APM Package(When Heat Sink Mounting First)

Assembly Sequences

The assembly process can be done in two ways: either
mounting the module onto the heat sink first and thenproceeding to soldering the signal pins; or soldering themodule on the PCB first followed by mounting on the heatsink.

Soldering to the PCB, then mounting to the heat sinkIf the module is assembled with the PCB first and heat sink
mounting is conducted second, the process flow describedin Figure 29 is recommended. First, the module is place on

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the PCB (a). Then, soldering signal leads to the PCB is done(b). After PCB assembly is complete, thermal interface
material is applied on the surface of the module or heat sink(c). The module/PCB assembly is then placed onto the heatsink and fixed to the heat sink via screws (d).

(a) Place the module on the PCB (withairgap between PCB and module)(b) Solder the signal leads to the PCB(c) Apply thermal interface material(d) Place the APM module onto theheat sink and fasten the screws

Figure 29. Process Flow of Soldering APM Package(When PCB Mounting First)

System considerations (Optional per designs)
After the module is assembled to the PCB and the heatsink as described above, the overall structural integrity
needs to be considered in terms of mechanical stress to anyof the system components. In case the PCB is large andheavy with other components assembled to it, there is somerisk the PCB can bend, creating mechanical stress to themodule and the PCB. In addition, when multiple modules
are applied to the same PCB, height tolerances between
modules can result in mechanical stresses to the board andmodules. Figure 30 illustrates one method to prevent PCB
bending and stress by using spacers between the PCB andheat sink. Various types of spacers could be added on theheat sink, to prevent any possible movement of the PCB.

Figure 31. Examples of the Spacer Type

Figure 31 shows examples of possible spacer types.
Option 1 shows individual spacers between the heat sink and
PCB concentric with the PCB mounting screws. Option 2
illustrates a heatsink with integrated standoffs to provide thespacing. Option 3 shows a separate spacer situated between
the module and the PCB.
Thermal Interface Materials (TIM) for Electronics
Cooling

Since the contact surfaces are not perfectly flat, multiple
air gaps can form between two solid contact surfaces. Air isa poor heat conductor preventing the heat transfer andlimiting the effective contact area. Thermal Interface
Materials (TIM) need to be applied between the heat sinkand the module surface to fill any air gaps and to achieve a
low thermal resistance. The following are generalconsiderations when choosing the material for theapplication. Besides its thermal conductivity, handling andrework performance may be important factors while
selecting the proper TIM.

 High thermal conductivity
 Ease of distribution (spreading) with low contact pressure
 Minimal thickness (electrical isolation not needed) Degradation of characteristics over time Environmental impact
 Ease in handling during application or removal

Figure 30. Robust Assembly Method of APM
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Figure 33 shows and example of thermal paste application
process using a manual screen print.

Although thermal interface materials with improved
performance are available nowadays, the most commonlyused in the industry is still thermal grease.
Users should make sure that the TIM is applied withdesired thickness and spread evenly across the interface,based on the TIM datasheet and desired thermal resistance.
The viscosity of the TIM will impact the thickness of the
TIM after mounting the module. Only a small amount ofcompound is required to fill the gap between the contacting
surfaces. One of the recommended interface materials is
Electrolube HTCP (Heat Transfer Compound Plus)
thermal grease [12]. HTCP is a non−curing, non−silicone
heat transfer paste suitable for the application wheresilicones are prohibited, thus avoiding issues with silicone
and low molecular weight siloxane migration. It is RoHS−2
compliant.
As an alternative, high thermal conductivity graphite
sheets provide improved reliability, high thermal
performance, and lower overall costs due to a simplified
assembly process. However, the thermal resistance depends
on the thickness of the graphite sheet. Hence, the thickness
and thermal conductivity should be carefully reviewed
before the selection. It is recommended to contact your local
onsemi representative for more information.
Manual TIM Application
Thermal grease can be applied to the heat sink or themodule back surface using a rubber roller or spatula, by
screen printing or auto dispenser. A rubber roller, as shownin Figure 32, is an easy and fast method for applying thermal
grease. Since the thermal grease has the lowest thermal
conductivity in the thermal path, a layer as thin as possible
is necessary to keep the overall thermal resistance low.
Recommended thickness of printing layer is uniform
dispense of a minimum 150 mm. The thermal grease
thickness can be checked using thickness gauges, such as
wet film combs or wet film wheels. Since manual control ofprinting pressure and speed can be learned by experience,
training is needed to achieve a technique for good quality
printing in the application.
TIM Application by Manual Screen PrinterStencil/screen printing can be utilized for the applicationof thermal paste. It allows a fast, clean and easy handling of
spreadable TIMs. They can be applied to the substrate area,leaving out other parts of the module package using
specifically designed stencils. An optimization of the screenmask pattern and thickness is required to achieve a goodquality of the print and finally and optimum contact.

Figure 32. Example of Thermal Grease Application
Using a Rubber Roller

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Figure 34. Dimension of Screw Clamping Zone (mm)Table 13. SCREW AND WASHER INFORMATION
Parameter

Description

Mounting Screw

Metric M3 Screw

Spring Washer

D (Norminal) = ø5.5 (mm), t = 1.2

Plain Washer

D (Norminal) = ø7.0 (mm), t = 0.5 (mm)Recommended thread engagement for screws with property
class 4.8 to 6.8 for different materials

In case of the usage of special screw without the washer,such as using TAP TITE screw without washer, the diameterof the screw head is important. If the screw mount torque isover 0.8 N.m, it is recommended to use the screw witha minimum 6.2 mm diameter screw head.
Figure 33. Example (APM19 Package) of Thermal
Paste Application Using a Manual Screen Print

Table 14. MOUNTING TORQUE SPECIFICATION
FOR (M3)

Fully automated screen printing is recommended in mass
production. It yields a high quality printing layer with highaccuracy and repeatability.

Parameter
Pre−TorqueConsiderations on Screw Tightening

Final TorqueAPM packages should be secured on the heat sink via two
M3 screws. The location of the screw holes is illustrated in
Figure 34. Table 13 shows the screw specification and
Table 14 is showing the recommended torque ranges for the
APM19 and APM21 package. Contact pressure andmounting torque may affect the thermal performance. The
thermal resistance specified can be achieved with theminimum specified torque in the Table 14. Electricscrewdrivers can tighten the screws with the specified
torque. Figure 35 shows SEMS (pre−assembled washers
and screw) which is a recommended screw type.

Unit

Min.

Max.

[N∙m]

0.2

0.4

[kgf∙cm]

2.0

4.1

[N∙m]

0.6

1.4

[kgf∙cm]

6.1

14.3

Generally, pre−torque is 20−30% of the final torqueFigure 35. SEMS (Pre−assembled Washers andScrew, Spring Washer j 5.5 and Plain Washer j 7.0

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Thermal Performance under Various Mounting TorqueSince the module surface and heat sink are not perfectly
flat, contact pressure and mounting torque can affect thermal
performance. According to the results shown in Figure 36(typical for APM packages), thermal resistance values(Rthjc) achieve stable values at torque levels ranging
between 5~7 (kgf−cm) with APM packages with M3 screws.

Rthjc (Trend), C/W

Pre−Torque: Step 1  Step 2

Mounting Torque [kgVf−cm]

Figure 36. Rthjc under Various Mounting
Screw Tightening Method

Final Torque: Step 3  Step 4

Screw tightening can be done in various ways. Figure 37
describes one recommended method for fastening themodule to the heat sink. Fasten two screws with final torquesimultaneously to prevent tilting or rising of top side ofmodule during fastening.

Figure 38. Illustration of Screw Clampingwith Heat Sink
Notes on Assembly: Avoid applying over torque when mounting screws.

Excessive fastening force may cause damage to thesemiconductor devices, the package or its isolation, as
well as damage to the screws or heat−sink.
 Uneven mounting can cause the ceramic substrate to bedamaged. A smooth surface free of burrs and protrusions
or indentations is required. No foreign materials except
thermal interface materials are allowed between surfaceof the module and the heat sink.
 The mounting area should be treated as a functional layer.
Do not touch the mounting area of the heat sink and thesubstrate of the module.

Figure 37. Illustration of Screw Clampingwith Heat Sink

Potential Failure Modes

Alternatively, Figure 38 shows another recommended
method to tighten the screws. Fasten the first screw withpre−torque to prevent one side tilting or rising of the module(Step 1). Then insert the second screw to the other side withsame pre−torque (Step 2). The pre−screwing torque is set to20−30 % of final torque rating. After that, apply full final
torque to the first screw (Step 3). Finally, apply full torqueto the second screw for proper mounting to the heat sink
(Step 4). An insufficient tightening torque may cause anincreased thermal resistance or loosening of the screws
during operation.

The following are possible root causes of mounting
failures which should be avoided during the mounting
process. Table 15 lists representative examples of mounting
failure mode.
 Excessive torque is applied without pre−torque Misalignment of screw during tightening with heat sink
 Mechanical stress by mounting height tolerances when
multiple module mounted on the same PCB
 Inappropriate type of screws are used

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REFERENCE DESIGN HARDWARE AND TESTRESULTSA 25 kW BSG/ISG reference design was created for the
purposes of testing the NXV08H−series of power modules.
This design included a liquid−cooled heat sink, dc bus
capacitor bank, dc and ac bus bar, and gate drive PCB withexternal interfaces to a separate controller. A photo is shownin Figure 39, along with a CAD representation of theassembly without the PCB.
A general requirements specification for this reference
design was provided to the design team as shown below:
 3−Phase Automotive Liquid Cooled Power Inverter Stage Input Voltage Rating (Nominal): 48 V
 Input Voltage Range: 36 V  VDC  52 V
 Continuous Current Rating: IPHASE  400 Arms
 Peak Current Rating (30s): IPHASE  700 Arms
 Isolated Input Control and Fault Feedback Signals
 Active Over−Temp and Over−Current Protection with
Auto−Shutdown Two Isolated Phase Current Feedback Sensors
 Coolant Temperature: 70C−85C

Table 15. EXAMPLES OF MOUNTING FAILURE
MODES

EMC broken due toexcessive torque

EMC crack due tonon−flat heatsink

Cracked ceramic substrate

Broken fasteners

Clip Mounting

As an alternative method, “Clip mounting” can be used tofasten the module to the heat sink. In such a case, the screw
mount holes can be used for locating pins, while two side
contact points provide vertical pressure to the module.
For this method, detailed mechanical design of clip andpressure force is required. It is recommended to contact yourlocal onsemi representative for more information to validate
the system design using clip mounting methodology. Thereis no general guidance for clip, so the customer’s design
must be validated case by case for the specific clip design.
The NXV08H−series of APM modules incorporates an
exposed copper exterior surface of the ceramic substrate tofacilitate improved heat spreading and heat transfer. The
surface of the copper layer may oxidize during
manufacturing, storage, and transportation. This is not aconcern for the performance of the module, and further
details may be obtained in [13].

Inverter Construction

The inverter assembly is constructed in a stacked format,
as shown in Figure 39, employing three of the
NXV08H400XT1 modules. At the top of the stack, the PCB
contains the logic and interface circuitry as well as the phasecurrent sensors. Below the PCB are the power modules,
shown with small bus sections that route the phaseconnections between the modules and the phase output
connectors. The inverter 3−phase output connectors arelocated on top of three threaded posts. These posts passthrough the current sensors. Next, are the main bus bar
assembly which connects the input terminals, the bus
capacitors and the module DC connections. Finally, the heatsink cools the power modules and the capacitor bank andprovides a mounting surface for all the pieces. The internal
housing of the heatsink is formed with a pin−fin structure to
more effectively remove the module heat while maintaining
a low pressure drop. It is constructed as a two−pieceassembly, with the bottom cover connecting to the top
section with threaded fasteners and an o−ring for sealing.
Output Section

The output section of the inverter consists of threehalf−bridge NXV08H400XT1 power modules, shown in
Figure 40. As we know, the module embodies two
independent half−bridge sections, having common power

Figure 39. Photo of 25 kW BSG/ISG

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AND90235/D
connections. It can be used either as two half−bridges or,when connected in parallel, as a single half−bridge. In thisapplication the two half−bridges are connected in parallel
and the module is operated in a single half−bridge
configuration. The three modules are connected to
a common 48 V power bus, with each of the modules’ ac
outputs being connected to one of the three output phaseconnections.

The FAN7191 is capable of sourcing and sinking
4.5 amps. It has an under−voltage lockout, matched dual
channel propagation delay and can tolerate up to a −9.8 V ofnegative level shift. The HO and LO pins are connected tothe module gates through 10 W resistors, with each channel
driving the gates of the two paralleled MOSFETs. Even
though the internal devices are connected in parallel, they
still have separate gate connections. An example circuit
diagram of the FAN7191 is shown in Figure 41.
Bench Test Results

The inverter assembly was tested on the bench setup
shown in Figure 42, under the following conditions: Passive RL load with L~46 mH, R~1 mW per phase 50/50 water/glycol coolant at ~4 LPM flow rate
 48 V < VDC < 54 V Fundamental frequency 50 to 200 Hz Sine−triangle PWM switching at 10 kHz
 Dead−time (lockout) ~ 1.4 ms
 Control by LabView via CompactRIO [16]The system was tested with phase current up to 700 ARMS.
Under these conditions, the losses for the inverter stage (DCinput power to ac output power) ranged up to 2.6 kW. The
loss curves are shown in Figures 43 and 44 for coolant
temperatures of 25C and 65C. The passive RL loadpresents a very low power factor (~2%) which is not realistic
for a motor drive but which nonetheless provides theopportunity to determine the losses as a function of motor
phase current. The MOSFET inverter losses have minimal
sensitivity to power factor or modulation index, unlike and
IGBT/diode based inverter.

Figure 40. Stack Assembly Inverter and Module
Gate Driver Circuitry

Since this inverter was designed for use with an external
system controller, cross−conduction protection is provided
on−board. The FAN73832 [14] half−bridge gate driver wasused to provide the dead−time function, which may be
adjusted from 400 ns to 1.6 ms. The FAN73832 operates
with a single input and single output disable pin, permitting
both PWM and ENABLE control signals. In this application
it acts only as a logic support device. The output of the
FAN73832 is connected directly to a cascaded gate drive IC,
the FAN7191 [15], which is responsible for providing thedrive current necessary to drive the module MOSFETs’gates.

Figure 42. Photo of Test Bench Setup
Figure 41. FAN7191 Application Circuit

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AND90235/D(a) 575 A

Figure 43. Inverter Loss, 255C coolant, 48 VDC,
10 kHz Switching Frequency(b) 880 A

Figure 44. Inverter Loss, 655C coolant, 54 VDC,
10 kHz Switching Frequency

Switching waveforms for the inverter operating at peakcurrents of approximately 575 A, 880 A, and 990 A are
shown in Figure 45. Channel 1 is VGS of Q1, Channel 2 is
VGS of Q4, Channel 3 is VDS of Q1, and Channel 4 is
IPHASE.

(c) 990 A

Figure 45. Switching Waveforms

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AND90235/D
REFERENCES[1] “Road vehicles – Supply voltage of 48 V – Electricalrequirements and tests,” ISO21780.
[2] Brian A. Welchko, et al, “IPM Synchronous Machine
Drive Response to Symmetrical and Asymmetrical
Short Circuit Faults,” IEEE Transactions on Energy
Conversion, Vol. 18, No. 2, June 2003, pp. 291−298.
[3] AND90096/D, “Usage of SIMetrix to Study
MOSFETs Thermal Behaviors on Heatsink,” March,
2021.
[4] AND9783/D, “How to Use Physical and Scalable
Models with SIMetrix, OrCAD and LTSpice,”
August 2018.
[5] “OrCAD PSpice Designer,” OrCAD Cadence PCB
Solutions website,
https://www.orcad.com/products/orcad−pspice−desig
ner/overview[6] “SIMetrix,” SIMetrix Technologies website,
https://www.simetrix.co.uk/products/simetrix.html[7] “LTspice,” Analog Devices website,
https://www.analog.com/en/design−center/design−tools−and−calculators/ltspice−simulator.html[8] ANSYS Q3D Extractor, Multiphysics Parasitic
Extraction & Analysis,
www.ansys.com/products/electronics/ansys−dq3d−extractor.
[9] MathWorks MATLAB,
www.mathworks.com/products/matlab.html[10] onsemi Data Sheet FAD3151/3171, “110 V 2.5 A
Single Channel Floating Gate Drivers with
Desaturation Protection and Charge Pump”,
www.onsemi.com/download/data−sheet/pdf/fad3152
mxa−d.pdf[11] onsemi Data Sheet NVV5707B, “High Current
IGBT/MOSFET Gate Drivers,”
www.onsemi.com/download/data−sheet/pdf/ncv5707−d.pdf[12] “HTCP Heat Transfer Compound Plus Technical
Bulletin,” Electrolube, www.electrolube.com,
11 January 2022.
[13] AN−9090 “Impact of DBC Oxidation on (A)SPM
Module Performance,” onsemi, Sept. 2019.
[14] onsemi Data Sheet FAN73832, “Half−Bridge Gate
Drive IC,”
www.onsemi.com/download/data−sheet/pdf/fan7383
2−d.pdf[15] onsemi Data Sheet FAN7191, “Automotive Grade
Driver IC, High and Low Side 600V, 4.5A,”
www.onsemi.com/download/data−sheet/pdf/fan7191−f085−d.pdf[16] ni.com, CompactRIO Controller,
www.ni.com/en−us/shop/hardware/products/compact
rio−controller.html

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