ON Semiconductor
Is Now

To learn more about onsemi™, please visit our website atwww.onsemi.com

onsemi andand other names, marks, and brands are registered and/or common law trademarks of Semiconductor Components Industries, LLC dba “onsemi” or its affiliates and/or
subsidiaries in the United States and/or other countries. onsemi owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of onsemi
product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent-Marking.pdf. onsemi reserves the right to make changes at any time to any products or information herein, without
notice. The information herein is provided “as-is” and onsemi makes no warranty, representation or guarantee regarding the accuracy of the information, product features, availability, functionality,or suitability of its products for any particular purpose, nor does onsemi assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all
liability, including without limitation special, consequential or incidental damages. Buyer is responsible for its products and applications using onsemi products, including compliance with all laws,
regulations and safety requirements or standards, regardless of any support or applications information provided by onsemi. “Typical” parameters which may be provided in onsemi data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application
by customer’s technical experts. onsemi does not convey any license under any of its intellectual property rights nor the rights of others. onsemi products are not designed, intended, or authorized
for use as a critical component in life support systems or any FDA Class 3 medical devices or medical devices with a same or similar classification in a foreign jurisdiction or any devices intended for
implantation in the human body. Should Buyer purchase or use onsemi products for any such unintended or unauthorized application, Buyer shall indemnify and hold onsemi and its officers, employees,
subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or deathassociated with such unintended or unauthorized use, even if such claim alleges that onsemi was negligent regarding the design or manufacture of the part. onsemi is an Equal Opportunity/Affirmative
Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner. Other names and brands may be claimed as the property of others.

TND6093/D
Low VCE(sat) BJT's
in Automotive Applications
Introduction

Low VCE(sat) Bipolar Transistors (BJTs) are an attractive
alternative to planar MOSFETs for power switching in
automotive management circuits. They are proving to be
more ESD robust, consume less power than comparative
size planar MOSFETs and often lower cost resulting ina lower system cost. This application note will address theuse of Low VCE(sat) BJTs in automotive power management
circuits.
ON Semiconductor’s family of low VCE(sat) Bipolar
Junction Transistors (BJT) are surface mount devices
featuring ultra low saturation voltage VCE(sat) and highcurrent gain capability in thermally efficient packages. In
the automotive industry they are used as a load switch in air
bag deployment, pre-drivers for high current Trench
MOSFETs in fuel pumps, over voltage protection, low dropout regulation, LED backlight switching, Royer converter
for LCD backlights in instrument cluster. The Linear Gain
(Beta) of Low VCE(sat) BJT makes them ideal components
in analog amplifiers and for driving directly from logic
circuits.

www.onsemi.com

TECHNICAL NOTETechnology

The Low VCE(sat) BJT devices use a technology that was
first developed over 30 years ago and was primarily used toachieve similar performance in a smaller die (die shrink).
This technology is called a “Perforated Emitter” and today
is being focused towards reducing the forward saturation
voltage to achieve very low forward resistance.
The perforated emitter is a method of extending the baseelectrical layer across the complete die to contact multiple
perforations through the emitter. Each of these perforations
creates miniature transistors within the device and thus
allows the current to be distributed evenly and with greater
efficiency.
Collector is
Substrate

Base Electrical
Layer Fingers
and Perforations

Base Contact

Emitter Contact

Figure 1. Photograph 1

per die area. The Low VCE(sat) BJT’s block voltage in two
directions, as specified by their V(BR)EBO or V(BR)ECO
characteristic, which can eliminate the need for a series
diode. The Low VCE(sat) BJT’s are extremely rugged to ESD
damage, and they have no difficulty passing Human Body
Model discharge tests. Compared to MOSFETs where ESD
damage always remains a risk, often resulting are ruptured
or damaged gates.

Some of the new Low VCE(sat) BJT’s are now available
with a saturation voltage at 1 A of well under 50 mV. Thisequates to a forward resistance of under 50 mW, and proves
very competitive against a higher cost MOSFET.
The Low VCE(sat) BJT’s exhibit a temperature coefficientof resistance of approximately half that of MOSFETs, which
can lead to higher efficiency at operating temperature,cooler running at high current densities and higher current© Semiconductor Components Industries, LLC, 2016

December, 2016 − Rev. 1

1

Publication Order Number:
TND6093/D

TND6093/D
BOARD DESIGN
Package Thermal Design Considerations

ESD tolerance is becoming more critical as the proximityof ESD charges close to or on connectors is becoming more
prominent. Due to the structure of a BJT (HB > 8000 V), it
is dramatically more ESD tolerant than a MOSFET(HB > 300 V) and the need for external ESD protection isoften eliminated, reducing component count.
Switching efficiency is important for circuits in which thelosses caused by the switching time of the pass element
would adversely affect the circuit operation. The High Pulse
current capability makes them ideal for driving High PowerMOSFETs. Low VCE(sat) BJT’s are also suited forautomotive applications where EMI and Harmonic Noisemaybe a problem because there switching speed can beeasily slowed through the use of a small capacitor, reducing
the switching signature.
The Low turn on voltage is an attractive feature of the Low
VCE(sat) BJT (0.7 V typical) compared to a MOSFET(typically 4.0–10.0 V). This makes them very attractive forlow voltage circuits in situations where a controlled power
down is required as the battery voltage drops and in the new“Stop Start” modes where the battery voltage drop for justa short period. The low turn on voltage would also eliminate
the need for an oscillator and charge pump, normally needed
for a MOSFET.
The Temperature Coefficient of the Low VCE(sat)) BJT is
typically better compared to a MOSFET. The variation from
Cold to Hot is significantly less, resulting in a moreconsistent design compared to a design using a MOSFET.
The Low VCE(sat) BJT coefficient is a little positive,
resulting in the circuit becoming more efficient as it warms
up. The MOSFET circuit becoming less efficient as the
RDS-ON often doubles at high temperature.
The High Gain of the Low VCE(sat) BJT makes them idealfor driving directly from low voltage logic circuit. By
connecting a Low VCE(sat) BJT to a logic gate the circuit
becomes a Power Logic circuit.
The Low Cost of the Low VCE(sat) BJT will reduce thetotal system cost. Comparing the listed price to a similar
MOSFET results in a $0.24 savings.
NTF2955T1G 60 V 2.6 A SOT−223 Web price $0.42
NSS60600MZ4T1G 60 V 6.0 A SOT−223 Web Price $0.18

The Low VCE(sat) BJT is a current driven device,compared to the MOSFET which is a voltage driven device.
For this reason the designer needs to understand thelimitations of the power control circuits being used, todetermine the specific circuit requirements when designingwith a Low VCE(sat) BJT. For example, if the Low VCE(sat)
BJT is to control a current of 1 Amp and it has a worst casegain (hFE) of 100 then the base current will need to bea minimum of 10 mA (IB) to ensure the Low VCE(sat) BJT
goes into saturation. The output of the power control circuit
must be able to supply the 10 mA for the Low VCE(sat) BJT
to be driven directly; otherwise an additional drive stage
would be required.
The power rating of the package for the Low VCE(sat) BJT
has to be consider. For Example; the ON Semiconductor
Low VCE(sat) BJT NSS40200LT1G in a SOT−23 package ismounted on a FR4 printed circuit board 500 mm2 1 ozcopper pad. The maximum power rating (PD) with thespecified pad is 540 mW.
The input voltage to be switched is < 40 V. The ambient
temperature is 25°C. The typical VCE(sat) for the
NSS40200LT1G at 1.0 A is 80 mV. This equates to a power
dissipation of 80 mW. The Minimum Gain (hFE) at 1.0 A is180. Thus the drive current (IB) would need to be a little over6.0 mA. The maximum limit on VCE(sat) at 1.0 A is 170 mV(from Data Sheet with beta 100), this equating to 170 mW,
well below the 540 mW rating for the package at 25°C.
Derating the Device for Temperature

The Thermal Resistance de-rating with 500 mm2 1 ozcopper is 4.3 mW/°C (From Data Sheet). The formula for
de-rating the maximum power for the package is:
P D @ 25 oC * ((Board Temp * 25 oC)

De−rate)(eq. 1)

For an application with a maximum temperature of 85°C, themaximum allowable power dissipation for the package
would become:P D + 540 * ((85 * 25)4.3) + 282 mW(eq. 2)The maximum calculated power of 170 mW still falls below
the adjusted power when the device is de-rated for a higher
temperature of 85°C.
PCB footprint, package height and drive circuit
configuration play a major role as the designer tries toaccommodate the ever increasing challenge to fit more intoless space. The fewer devices to be placed on the PCB andthe smaller the components are, the smaller the final
product. SOT−723 feature a very thin profile 0.55 m & small
footprint (1.2 × 1.2 mm), representing the best solution fortoday’s infotainment requirements. If package height andfootprint are not critical, then the designer has a wide
selection of device packages to choose from.

www.onsemi.com
2

TND6093/D
APPLICATIONSASIC with an External Pass Transistor

using MOSFETs. Low VCE(sat) BJTs perform the samefunction as a MOSFET at a lower cost, and as an added
bonus, in many cases provide for improved power
consumption.

The need for smaller size and more intelligence in thecontrol circuit is causing a migration to dedicated ASICs foreach functional area in the vehicle. The circuits, for thecontrol of currents under 500 mA, are typically all imbedded
within the ASIC, including the final pass transistor.
However, for the control of currents from 500 mA to 5 A an
external pass transistor (MOSFET) is the typical design ofchoice. An alternative to the MOSFET is to use a lower cost
Low VCE(sat) BJT. The new family of Low VCE(sat) BJTs
offer potential savings of 5 to 20 cents compared to designs

Load Switch – Back Light Control in Automotive
Dashboards

Dashboards often use multiple arrays of LEDs forillumination of the different functions. Figure 2 is an
illustration using a Low VCE(sat) BJT to control the LED
backlights.

Boost
Circuit

NSI45025JZT1GNSS60201LT1G

QA

Host
Controller

QB

QC

QD

QE

QF

QG

QH

74HC595

Figure 2. Large LED Array using a Logic Gate to Control the Low VCE(sat) BJT Switch
Load Switch – Seat Warmer

is good example, Figure 3 is an illustration of the use ofa Low VCE(sat) BJTs, being controlled with a Digital
Transistor, to turn the seat warmer on and off.

A Low VCE(sat) BJTs is an ideal switch for controlling
functions within a vehicle that are on or off. The seat warmer
VBAT

Seat Heater

NSS404000CF8T1G

Seat Heater ON

Figure 3. Load Switch − Seat Warmer

www.onsemi.com
3

TND6093/D
MOSFET Gate Driving

One of the most popular and cost-effective drive circuits
is a bipolar, non-inverting totem-pole driver. As power
dissipation is low, this can use a co-packaged
complementary pairs in small outline surface mountpackages (NSS40302PDR2G).

High Power low RDS(on) MOSFETs need to be switchedat high frequencies to satisfy the power conversion
reqirements of high efficiency. To achieve this the gate
driver circuit has to deliver instantaneous currents of several
amps. Low VCE(sat) BJTs are very suitable as they feature
superior switching in linear mode, high pulse-current
capability through high current density.

VCC
VDRIVERLAOD

NSS40302PDR2G

RGATE

RBIAS

Figure 4. MOSFET Gate Driving
H-Bridge Drive for Window Motors

Turning on Q1 and Q4 the motor turns forward. Turning
on Q2 and Q3 the motor reverses.
VCC

Q1

Q2

Motor
Q3

Q4

Figure 5. H-Bridge Drive for Window Motors

www.onsemi.com
4

TND6093/D
Over Voltage Protection

The Low VCE(sat) BJTs are ideal for a simple over voltage
protection circuit. Zener D1 is selected for the trip voltage,
Zener D2 is selected to ensure higher peaks that may get past

the BJT are still clamped from reaching the load. Diode D3
acts as a Bakers Clamp improving the switching time of Q1
to under 100 ns.
Q1
NSS40200LT1G

13.5 VR1
2.7 kW
D3
BAT54XV2T1G

R2
6.8 kWD1
MMSZ18T1G

Q2
MMBT2907LT1G

D2
MMSZ20T1G

Load

R3
680 W

Figure 6. Over Voltage Protection
Conclusion

Low VCE(sat) Bipolar Transistors (BJTs) are an attractive
alternative to planar MOSFETs for power switching in
automotive management circuits. They are proving to be

more ESD robust, consume less power and often resulting
in a small Bill Of Material (BOM) and thus lower system
cost.

Table 1.
Application

FeatureBenefit

Load Switch• Low VCE(sat)• hFE > 200• Low RCE/mm2• Small Size − 5.4 mm2• Low Profile – 1.0 mm• PNP Transistor• High Efficiency• High Gain
• Low Cost vs. MOSFET• Less Board Space• More Compact Design• High Side Control

MosFET Gate Drive• High Pulse Current• High Frequency• hFE > 200• Low RCE/mm2• Small Size − 5.4 mm2• Low Profile – 1.0 mm• PNP/NPN Transistor• Fast Switching Time• Fast Switching Time
• High Current gain
• Low Cost vs. MOSFET• Less Board Space• More Compact Design• High/Low Switch

Low Drop Out (LDO) Regulator• Low VCE(sat)• High Power Dissipation/mm2• hFE > 200• Low RCE/mm2• Small Size − 5.4 mm2• Low Profile – 1.0 mm• PNP/NPN Transistor• High Efficiency• High Current Control• High Gain
• Low Cost vs. MOSFET• Less Board Space• More Compact Design• High or Low Side Control

Servo Motor Drive• PNP/NPN Transistor• Low VCE(sat)• High Frequency• hFE > 200• Low RCE/mm2• Small Size − 5.4 mm2• Low Profile – 1.0 mm• High/Low Bridge• High Efficiency• Low Switching Losses• High Current Gain – Lower Control Current• Low Cost vs. MOSFET• Less Board Space• Design Flexibility

Over Voltage Protection• PNP/NPN Transistor• Low VCE(sat)• High Power Dissipation/mm2• High Frequency• hFE > 200• Low RCE/mm2• Small Size − 5.4 mm2• Low Profile – 1.0 mm• High/Low Bridge• High Efficiency• High Current Control• Low Switching Losses• High Current Gain – Lower Control Current• Low Cost vs. MOSFET• Less Board Space• Design Flexibility

www.onsemi.com
5

TND6093/D
Table 2. PNP PORTFOLIO OF LOW VCE(sat) BJT

Package

TypicalVCE(sat) 1 A
Beta 10

TypicalhFE @ 5 V,
100 mA

Status

WDFN3

400 mV300

Released2

SOT−723280 mV

250

Released1

2

SOT−563

280 mV

250

Released

2

3

SC−88

150 mV

250

Released122

4

SOT−2365 mV

250

Released

12

5

7

WDFN3

55 mV

250

Released

NSS20200L

20

2

4

SOT−2365 mV

250

Released

NSS20300MR6

20

3

5

TSOP−680 mV

250

Released

NSS20500UW3

20

5

7

WDFN3

60 mV

250

Released

NSS30070MR6

30

0.7

2

SC−74

205 mV

310

Released

NSS30100L

30

1

2

SOT−23200 mV98

Released

NSS35200MR6

35

2

5

TSOP−678 mV

234

Released

NSS35200CF8

35

2

7

ChipFET

79 mV

253

Released

NSS40200L

40

2

4

SOT−2380 mV

300

Released

NSS40200UW6

40

2

4

WDFN6

100 mV

250

Released

NSS40300MZ4

40

3

5

SOT−223

50 mV

250

Released

NSS40500UW3

40

5

6

WDFN3

65 mV

250

Released

NSS40600CF8

40

6

8

ChipFET

50 mV

250

Released

NSS60200L

60

2

4

SOT−2380 mV

250

Released

NSS60600MZ4

60

6

12

SOT−223

80 mV

250

Released

NSS1C200L

100

2

4

SOT−23

100 mV300

Released

NSS1C200MZ4

100

2

3

SOT−223125 mV

250

Released

NSS1C300E

100

3

6

DPAK

150 mV180

Released

TypicalhFE @ 5 V,
100 mA

StatusPart Number

VCE
(V)

IC DC
(A)

IC Peak(A)

NSS12100UW3

12

1

2

NSS12100M312

1

NSS12100XV6

12

NSS12200W

12

NSS12200L
NSS12500UW3

Table 3. NPN PORTFOLIO OF LOW VCE(sat) BJT
VCE
(V)

IC DC
(A)

IC Peak(A)

Package

TypicalVCE(sat) 1 A
Beta 10

NSS12201L

12

2

4

SOT−2335 mV

300

Released

NSS12501UW3

12

5

7

WDFN3

31 mV

300

Released

NSS12601CF8

12

6

8

ChipFET

30 mV

300

Released

NSS20101J

20

1

2

SC−89

220 mV

500

Released

NSS20201L

20

2

4

SOT−2337 mV

300

Released

NSS20201MR6

20

2

3

TSOP−6103 mV

200

Released

NSS20501UW3

20

5

7

WDFN3

31 mV

300

Released

NSS20601CF8

20

6

8

ChipFET

31 mV

300

Released

NSS30071MR6

30

0.7

2

SC−74

205 mV

317

Released

NSS30101L

30

1

2

SOT−23103 mV

200

Released

NSS30201MR6

30

2

3

TSOP−6103 mV

200

Released

NSS40201L

40

2

4

SOT−2344 mV

300

Released

NSS40301MZ4

40

3

5

SOT−223

50 mV

250

Released

NSS40501UW3

40

5

7

WDFN3

38 mV

300

Released

NSS40601CF8

40

6

8

ChipFET

31 mV

300

Released

NSS60201L

60

2

4

SOT−2380 mV

250

ReleasedPart Number

www.onsemi.com
6

TND6093/D
Table 3. NPN PORTFOLIO OF LOW VCE(sat) BJT (continued)

Package

TypicalVCE(sat) 1 A
Beta 10

TypicalhFE @ 5 V,
100 mA

Status

SOT−223

80 mV

250

Released4

SOT−23

100 mV

250

Released3

SOT−223

100 mV

250

Released

6

DPAK

45 mV

200

ReleasedPart Number

VCE
(V)

IC DC
(A)

IC Peak(A)

NSS60601MZ4

60

6

12

NSS1C201L

100

2

NSS1C201MZ4100

2

NSS1C301E

100

2

Table 4. DUAL PNP/NPN/COMPLEMENTARY PORTFOLIO OF LOW VCE(sat) BJT
IC DC
(A)

IC Peak(A)

Package

TypicalVCE(sat) 1 A
Beta 10

TypicalhFE @ 2 V, 1 A

StatusPart Number

Polarity

VCE(V)

NSS40301MD

NPN

40

3

6

SOIC−844 mV

340

Released

NSS40300MD

PNP

40

3

6

SOIC−875 mV

300

Released

NSS40300DD

PNP

40

3

6

SOIC−875 mV

300

Released

NSS40302PD

NPN/PNP40

3

6SOIC−844/75 mV

340/300

Released

ON Semiconductor andare trademarks of Semiconductor Components Industries, LLC dba ON Semiconductor or its subsidiaries in the United States and/or other countries.
ON Semiconductor owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of ON Semiconductor’s product/patent coverage
may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. ON Semiconductor reserves the right to make changes without further notice to any products herein.
ON Semiconductor makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does ON Semiconductor assume any liability
arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. Buyer
is responsible for its products and applications using ON Semiconductor products, including compliance with all laws, regulations and safety requirements or standards, regardless ofany support or applications information provided by ON Semiconductor. “Typical” parameters which may be provided in ON Semiconductor data sheets and/or specifications can anddo vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s
technical experts. ON Semiconductor does not convey any license under its patent rights nor the rights of others. ON Semiconductor products are not designed, intended, or authorized
for use as a critical component in life support systems or any FDA Class 3 medical devices or medical devices with a same or similar classification in a foreign jurisdiction or any devices
intended for implantation in the human body. Should Buyer purchase or use ON Semiconductor products for any such unintended or unauthorized application, Buyer shall indemnify andhold ON Semiconductor and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees
arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that ON Semiconductor was
negligent regarding the design or manufacture of the part. ON Semiconductor is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyrightlaws and is not for resale in any manner.

PUBLICATION ORDERING INFORMATION
LITERATURE FULFILLMENT:
Literature Distribution Center for ON Semiconductor
19521 E. 32nd Pkwy, Aurora, Colorado 80011 USA
Phone: 303−675−2175 or 800−344−3860 Toll Free USA/Canada
Fax: 303−675−2176 or 800−344−3867 Toll Free USA/Canada
Email: orderlit@onsemi.com◊

N. American Technical Support: 800−282−9855 Toll Free
USA/Canada
Europe, Middle East and Africa Technical Support:
Phone: 421 33 790 2910
Japan Customer Focus Center
Phone: 81−3−5817−1050

www.onsemi.com
7

ON Semiconductor Website: www.onsemi.com
Order Literature: http://www.onsemi.com/orderlit
For additional information, please contact your local
Sales Representative

TND6093/D