MP2161

2A, 6V, 1.5MHz, 17μA IQ, COT
Synchronous Step Down Switcher
In 8-pin TSOT23

The Future of Analog IC Technology

DESCRIPTIONFEATURES

The MP2161 is a monolithic step-down switch
mode converter with built-in internal power
MOSFETs. It achieves 2A continuous output
current from a 2.5V to 6V input voltage withexcellent load and line regulation. The output
voltage can be regulated as low as 0.6V.






The
Constant-On-Time
controlschemeprovides fast transient response and eases loop
stabilization. Fault condition protection includes
cycle-by-cycle current limiting and thermal
shutdown.
The MP2161 is available in the small TSOT23-8
package and requires a minimum number ofreadily available standard external components.
The MP2161 is ideal for a wide range ofapplications including High Performance DSPs,
FPGAs, PDAs, and portable instruments.









Very Low IQ: 17μA
Default 1.5MHz Switching Frequency
EN and Power Good for Power Sequencing
Wide 2.5V to 6V Operating Input Range
Output Adjustable from 0.6V
Up to 2A Output Current
100% Duty Cycle in Dropout
100mΩ and 60mΩ Internal Power MOSFET
Switches
Cycle-by-Cycle Over Current Protection
Short Circuit Protect with Hiccup Mode
Stable with Low ESR Output Ceramic
Capacitors
Available in a TSOT23-8 Package

APPLICATIONS

Wireless/Networking Cards
Portable Instruments
Battery Powered Devices
Low Voltage I/O System PowerAll MPS parts are lead-free and adhere to the RoHS directive. For MPS green
status, please visit MPS website under Products, Quality Assurance page.
“MPS” and “The Future of Analog IC Technology” are registered trademarks ofMonolithic Power Systems, Inc.

TYPICAL APPLICATION

MP2161 Rev. 1.1
1/18/2017

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER

ORDERING INFORMATIONPart Number*
MP2161GJ

Package
TSOT23-8

Top Marking
See Below* For Tape & Reel, add suffix –Z (e.g. MP2161GJ–Z);

TOP MARKINGAEB: product code of MP2161GJ;
Y: year code;

PACKAGE REFERENCETOP VIEW
PG

1

8

EN

VIN

2

7

FB

SW

3

6

AGND

PGND

4

5

OUT

TSOT23-8

ABSOLUTE MAXIMUM RATINGS (1)Thermal Resistance

Supply Voltage VIN ...................................... 6.5V
VSW .....................................................................
-0.3V (-1.5V for <20ns&-4V for <8ns) to 6.5V
(10V for <10ns)
All Other Pins ................................ -0.3V to 6.5 V
Junction Temperature ...............................150C
Lead Temperature ....................................260C(2)
Continuous Power Dissipation (TA = +25°C)……….….. ............................................... 1.25W
Storage Temperature ............... -65C to +150C

TSOT23-8 .............................. 100 ..... 55... C/W

Recommended Operating Conditions(3)

Supply Voltage VIN ............................. 2.5V to 6V
Operating Junction Temp. (TJ). -40°C to +125°C

MP2161 Rev. 1.1
1/18/2017

(4)

θJA

θJC

Notes:
1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature TJ (MAX), the junction-toambient thermal resistance θJA, and the ambient temperature
TA. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by PD (MAX) = (TJ(MAX)-TA)/θJA. Exceeding the maximum allowable power
dissipation will cause excessive die temperature, and theregulator will go into thermal shutdown. Internal thermal
shutdown circuitry protects the device from permanent
damage.
3) The device is not guaranteed to function outside of its
operating conditions.
4) Measured on JESD51-7, 4-layer PCB.

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHERELECTRICAL CHARACTERISTICS (5)VIN = 5V, TA = +25C, unless otherwise noted.
Parameter

SymbolFeedback Voltage

VFB

Feedback Current
PFET Switch On Resistance
NFET Switch On Resistance

IFB

Condition
2.5V ≤ VIN ≤ 6Voo

TA=-40 C to +85 C

(6)

Min

Typ

Max

-3%

0.600

+3%

-3.5%

VFB = 0.6V

RDSON PRDSON N
VEN = 0V, VIN = 6V
VSW = 0V and 6V

Switch Leakage
PFET Current Limit

2.7

ON TimeTON

Switching frequency

Fs

Minimum Off Time
Soft-Start Time

TMIN-OFFTSS-ONPower Good Upper Trip Threshold

PGH

Power Good Lower Trip Threshold
Power Good Delay
Power Good Sink Current
Capability
Power Good Logic High Voltage
Power Good Internal Pull Up
Resistor
Under Voltage Lockout Threshold
RisingUnder Voltage Lockout Threshold
Hysteresis
EN Input Logic Low Voltage
EN Input Logic High Voltage

PGL
PGD

EN Input Current
Supply Current (Shutdown)
Supply Current (Quiescent)

VIN=5V, VOUT=1.2V
VIN=3.6V, VOUT=1.2V
VOUT=1.2V
TA=-40oC to +85oC(6)

-20%
-25%

FB voltage respect to theregulation

VPG-L

Sink 1mA

VPG-H

VIN=5V, VFB=0.6V

+3.5%
50

nA
mΩ
mΩ

0

1

μA

3.2
185
245
1500
1500
60
1.5

4.0

A
ns

+20%
+25%

%

-10
50

%
μs
V
V

550
2.3

kΩ
2.45

260
1.2
1.5
0
20
17

V
mV

0.4
VEN=2V
VEN=0V
VEN=0V, VIN=3V
VEN=2V, VFB=0.63V, VIN=5V

kHz/%
kHz/%
ns
ms

+10

4.9

2.15

V/%

10
100
60

0.4

RPG

Units

100
20

V
V
μA
μA
nA
μA

Thermal Shutdown(5)

150

C

(5)

30

C

Thermal Hysteresis

Notes:
5) Guaranteed by design.
6) Guaranteed by characterization test.

MP2161 Rev. 1.1
1/18/2017

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHERTYPICAL PERFORMANCE CHARACTERISTICS
VIN = 5V, VOUT = 1.2V, L = 1.0µH, TA = +25ºC, unless otherwise noted.
Quiescent Current vs.
Input Voltage

Shutdown Current vs.
Input Voltage

40

Load Regulation
2.00

0.003

1.50

0.0025

VIN=5V

1.00

30

20

0.002

0.50

0.0015

0.00
-0.50

0.001

VIN=6V-1.00

100.0005

-1.50

0

0
2

2.5

3

3.5

4

4.5 5

-2.00
2

5.5 6

2.5 3

3.5

4 4.5

5 5.5

6

0

INPUT VOLTAGE (V)INPUT VOLTAGE (V)Line Regulation

50
45

40

40

35

35

0.20

30

30

0.00

25

25

-0.20

20

20

15

15

-0.60

10

10

-0.80

5
0

5
0

0.40

Load=1A

-0.40

-1.00

Load=2A

Load=0A

2

3

4

5

0

6

1

1.5

2

0

2.5

100

2.5

0.5

1

1.5

2

2.5

OUTPUT CURRENT (A)Efficiency

Efficiency
100
95
90

0.5

OUTPUT CURRENT (A)INPUT VOLTAGE (V)2

VIN=5V, VOUT=3.3V

50
45

0.60

1.5

Case Temp Rise

Case Temp Rise

0.80

1

LOAD CURRENT (A)VIN=3V, VOUT=1.2V
1.00

0.5

Efficiency

5/3.3VIN to 1.8VOUT

5VIN to 3.3VOUT100

VIN=3.3V
90

90

85
80

80
75

VIN=6V

VIN=5V70

VIN=5V80

VIN=3.3V

70

70

60

60

65
60
55
50

1

10

100

1000 10000

LOAD CURRENT(mA)

MP2161 Rev. 1.1
1/18/2017

50
0

0.5

1
1.5
IOUT (A)

2

2.5

50

0

0.5

1
1.5
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2.5

4

MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHERTYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 5V, VOUT = 1.2V, L = 1.0µH, TA = +25ºC, unless otherwise noted.

MP2161 Rev. 1.1
1/18/2017

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHERTYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 5V, VOUT = 1.2V, L = 1.0µH, TA = +25ºC, unless otherwise noted

MP2161 Rev. 1.1
1/18/2017

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHERPIN FUNCTIONS
Pin #
1
2
3
4
5
6
7
8

MP2161 Rev. 1.1
1/18/2017

Name

Description
Power Good Indicator. The output of this pin is an open drain with internal pull up resistor
PG
to VIN. PGOOD is pulled up to VIN when the FB voltage is within 10% of the regulationlevel, if FB voltage is out of that regulation range, it is LOW.
Supply Voltage. The MP2161 operates from a +2.5V to +6V unregulated input. C1 is
VIN
needed to prevent large voltage spikes from appearing at the input.
SW
Switch Output
PGND Power ground
OUT Input sense pin for output voltage
AGND Analogy ground for internal control circuit
Feedback pin. An external resistor divider from the output to GND, tapped to the FB pin,
FB
sets the output voltage.
EN
On/Off Control

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHERBLOCK DIAGRAM
VIN
Bias
&
Voltage
Reference

EN

Soft start

+

COMP

VTH

Lo-Iq

0.6V
RST

+
+ E.A.
-

Constant
On -Time
Pulse

PDRV
PWM

Main
Switch
(PCH)

PWM

+

Lo-Iq

FB

SW

EN

+ FBCOMPDriver

VOUT
Lo-Iq
Ramp
Generator

Synchronous
Rectifier( NCH)

SW
Lo-Iq

Hi-Z

NDRV

OUT
GND

VIN
FB forFixed Output

0.66V

+

+

COMP

COMP

-

Lo-Iq

+
COMP
0.54V

PG

-

Figure 1: MP2161 Block Diagram

MP2161 Rev. 1.1
1/18/2017

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHEROPERATION
MP2161 uses constant on-time control with
input voltage feed forward to stabilize theswitching frequency over full input range. At
light load, MP2161 employs a proprietarycontrol of low side switch and inductor current
to eliminate ringing on switching node andimprove efficiency.
Constant On-time Control
Compare to fixed frequency PWM control,
constant on-time control offers the advantage ofsimpler control loop and faster transient response.
By using input voltage feed forward, MP2161
maintains a nearly constant switching frequency
across input and output voltage range. The ontime of the switching pulse can be estimated as:
TON 

VOUT
 0.667s
VIN

To prevent inductor current run away during loadtransient, MP2161 fixes the minimum off time to
be 60ns. However, this minimum off time limit will
not affect operation of MP2161 in steady state inany way.
Light Load Operation
In light load condition, MP2161 uses a
proprietary control scheme to save power andimprove efficiency. The MP2161 will turn off the
low side switch when inductor current starts toreverse. Then MP2161 works in discontinuous
conduction mode (DCM) operation.
The DCM mode happens only after low sideswitch turned off by ZCD circuit. Considering
the ZCD circuit propagation time, the typicaldelay is 30ns. It means the inductor current still
fall after the ZCD is trigger during this delay. If
the inductor current falling slew rate is fast (Vovoltage is high or close to Vin), the low side
MOSFET is turned off at the moment inductor
current may be negative. This phenomena willcause MP2161 can not enter DCM operation. If
the DCM mode is required, the off time of low
side MOSFET in CCM should be longer than
60ns. It means the maximum duty is 90% toguarantee DCM mode at light load.
For example, VIN is 3.4V and VOUT is 3.3V, theoff time in CCM is 20ns. It is difficult to enter
MP2161 Rev. 1.1
1/18/2017

DCM at light load. And using smaller inductor
can improve it and make it enter DCM easily.
EnableWhen input voltage is greater than the undervoltage lockout threshold (UVLO), typically 2.3V,
MP2161 can be enabled by pulling EN pin tohigher than 1.2V. Leaving EN pin float or pull
down to ground will disable MP2161. There isan internal 1Meg Ohm resistor from EN pin toground.
Soft Start
MP2161 has built-in soft start that ramps up theoutput voltage in a controlled slew rate,
avoiding overshoot at startup. The soft start
time is about 1.5ms typical.
Power GOOD Indictor
MP2161 has an open drain with 550kΩ pull-up
resistor pin for power good indicator PGOOD.
When FB pin is within +/-10% of regulation
voltage, i.e. 0.6V, PGOOD pin is pulled up to
VIN by the internal resistor. If FB pin voltage isout of the +/-10% window, PGOOD pin is pulled
down to ground by an internal MOS FET. The
MOS FET has a maximum Rdson of less than
100 Ohm.
Current limit
MP2161 has a typical 3.2A current limit for thehigh side switch. When the high side switch hitscurrent limit, MP2161 will touch the hiccup
threshold until the current lower down. This will
prevent inductor current from continuing to build
up which will result in damage of thecomponents.
Short Circuit and Recovery
MP2161 enters short circuit protection mode
also when the current limit is hit, and tries torecover from short circuit with hiccup mode. In
short circuit protection, MP2161 will disable
output power stage, discharge soft-start cap
and then automatically try to soft-start again. If
the short circuit condition still holds after softstart ends, MP2161 repeats this operation cycle
till short circuit disappears and output rises
back to regulation level.

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHERAPPLICATION INFORMATIONCOMPONENT SELECTION
Setting the Output Voltage
The external resistor divider is used to set theoutput voltage (see Typical Application on page1). The feedback resistor R1 can not be toolarge neither too small considering the trade-off
for stability and dynamic. Choose R1 to bearound 120kΩ to 200kΩ. R2 is then given by:
R2 

R1
Vout
1
0.6

The feedback circuit is shown as Figure 2.
Vout

MP2161R1FB

Figure 2: Feedback Network
Table 1 lists the recommended resistors value
for common output voltages.
Table 1—Resistor Selection for Common
Output Voltages
R1 (kΩ)
200(1%)
200(1%)
200(1%)
200(1%)
200(1%)R2 (kΩ)
300(1%)
200(1%)
100(1%)
63.2(1%)44.2(1%)

Selecting the Inductor
A 0.68µH to 2.2µH inductor is recommended formost applications. For highest efficiency, theinductor DC resistance should be less than
15mΩ. For most designs, the inductance value
can be derived from the following equation.

L1 

VOUT  (VIN  VOUT )VIN  IL  fOSC

Where ∆IL is the inductor ripple current.

MP2161 Rev. 1.1
1/18/2017

IL(MAX)  ILOAD I L
2Selecting the Input Capacitor
The input current to the step-down converter isdiscontinuous, therefore a capacitor is required tosupply the AC current to the step-down converter
while maintaining the DC input voltage. Use low
ESR capacitors for the best performance. Ceramic
capacitors with X5R or X7R dielectrics arehighly recommended because of their low ESR
and small temperature coefficients. For mostapplications, a 10µF capacitor is sufficient. For
higher output voltage, 47uF may be needed formore stable system.
Since the input capacitor absorbs the input
switching current it requires an adequate ripple
current rating. The RMS current in the input
capacitor can be estimated by:

R2

VOUT (V)
1.0
1.2
1.8
2.5
3.3

Choose inductor current to be approximately
30% of the maximum load current. The
maximum inductor peak current is:

I C1  ILOAD 

VOUT  VOUT 
 1
VIN 
VIN 

The worse case condition occurs at VIN = 2VOUT,
where:I
IC1  LOAD
2

For simplification, choose the input capacitor
whose RMS current rating greater than half ofthe maximum load current.
The input capacitor can be electrolytic, tantalum
or ceramic. When using electrolytic or tantalum
capacitors, a small and high quality ceramic
capacitor, i.e. 0.1μF, should be placed as close
to the IC as possible. When using ceramic
capacitors, make sure that they have enoughcapacitance to provide sufficient charge toprevent excessive voltage ripple at input. The
input voltage ripple caused by capacitance canbe estimated by:
VIN 



ILOAD
V
V
 OUT   1  OUT 
fS  C1 VIN 
VIN 

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER
Selecting the Output Capacitor
The output capacitor (C2) is required tomaintain the DC output voltage. Ceramic
capacitors are recommended. Low ESR
capacitors are preferred to keep the output
voltage ripple low. The output voltage ripple canbe estimated by:
VOUT 
VOUT  VOUT  1
 1    RESR 
fS  L1 
VIN  8  fS  C2 

Where L1 is the inductor value and RESR is theequivalent series resistance (ESR) value of theoutput capacitor.
Using ceramic capacitors, the impedance at theswitching frequency is dominated by thecapacitance. The output voltage ripple is mainly
caused by the capacitance. For simplification,
the output voltage ripple can be estimated by:

Proper layout of the switching power supplies isvery important, and sometimes critical for
proper function. For the high-frequency
switching converter, poor layout design can
result in poor line or load regulation and stability
issues.
The high current paths (GND, IN and SW)
should be placed very close to the device withshort, direct and wide traces. The input
capacitor needs to be as close as possible tothe IN and GND pins. The external feedback
resistors should be placed next to the FB pin.
Keep the switching node SW short and awayfrom the feedback network.
PG

AGND

 V 
VOUT
  1  OUT 2
VIN 
8  fS  L1  C2 

C1In the case of tantalum or electrolytic capacitors,
the ESR dominates the impedance at theswitching frequency. For simplification, theoutput ripple can be approximated to:∆VOUT VOUT 
V  1  OUT   RESR
fS  L1 
VIN 

The characteristics of the output capacitor also
affect the stability of the regulation system.

EN

1
2
3
4

8
7
6
5

R2
R1

∆VOUT PCB Layout

C2

SW

VIN

GND

OUT

Figure 3: PCB Layout Recommendation
Design Example
Below is a design example following theapplication guidelines for the specifications:
Table 2: Design Example
5V
VIN
1.2V
VOUT
1500kHzfSW
The detailed application schematic is shown in
Figure 4. The typical performance and circuit
waveforms have been shown in the Typical
Performance Characteristics section. For more
device applications, please refer to the related
Evaluation Board Datasheets.

MP2161 Rev. 1.1
1/18/2017

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHERTYPICAL APPLICATION CIRCUITS

Figure 4: Typical Application Circuit

MP2161 Rev. 1.1
1/18/2017

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MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER

PACKAGE INFORMATIONTSOT23-8

See note 7
EXAMPLETOP MARKPIN 1 IDIAAAA

RECOMMENDED LAND PATTERNTOP VIEWSEATING PLANESEE DETAIL''A''

FRONT VIEW

SIDE VIEWNOTE:

DETAIL ''A''

1) ALL DIMENSIONS ARE IN MILLIMETERS.
2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH,PROTRUSION OR GATE BURR.
3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD
FLASH OR PROTRUSION.
4) LEAD COPLANARITY(BOTTOM OF LEADS AFTERFORMING) SHALL BE 0.10 MILLIMETERS MAX.
5) JEDEC REFERENCE IS MO-193, VARIATION BA.
6) DRAWING IS NOT TO SCALE.
7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARKFROM LEFT TO RIGHT, (SEE EXAMPLE TOP MARK)NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications.
Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS
products into any application. MPS will not assume any legal responsibility for any said applications.
MP2161 Rev. 1.1
1/18/2017

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