MP2161
2A, 6V, 1.5MHz, 17μA IQ, COT
Synchronous Step Down Switcher
In 8-pin TSOT23
MP2161 Rev. 1.03 www.MonolihicPower.com 1
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The Future of Analog IC Technology
DESCRIPTION
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 with
excellent load and line regulation. The output
voltage can be regulated as low as 0.6V.
The Constant-On-Time control scheme
provides 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 of
readily available standard external components.
The MP2161 is ideal for a wide range of
applications including High Performance DSPs,
FPGAs, PDAs, and portable instruments.
FEATURES
• Very Low IQ: 17A
• 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
• 100m and 60m 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 Power
All 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 of
Monolithic Power Systems, Inc.
TYPICAL APPLICATION
MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER
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ORDERING INFORMATION
Part Number* Package Top Marking
MP2161GJ TSOT23-8 AEB
* For Tape & Reel, add suffix –Z (e.g. MP2161GJ–Z);
PACKAGE REFERENCE
PG
VIN
SW
PGND
EN
FB
AGND
OUT
1
2
3
4
8
7
6
5
TOP VIEW
TSOT23-8
ABSOLUTE MAXIMUM RATINGS (1)
Supply Voltage VIN ...................................... 6.5V
VSW ......................................................................
-0.3V (-1.5V for <10ns) to 6.5V (7V for <10ns)
All Other Pins................................-0.3V to 6.5 V
Junction Temperature...............................150°C
Lead Temperature ....................................260°C
Continuous Power Dissipation (TA = +25°C) (2)
……….….. ............................................... 1.25W
Storage Temperature............... -65°C to +150°C
Recommended Operating Conditions (3)
Supply Voltage VIN .............................2.5V to 6V
Operating Junction Temp. (TJ). -40°C to +125°C
Thermal Resistance (4) θJA θJC
TSOT23-8.............................. 100 ..... 55... °C/W
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-to-
ambient thermal resistance JA, and the ambient temperature
TA. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by PD (MAX) = (TJ
(MAX)-TA)/JA. Exceeding the maximum allowable powe
r
dissipation will cause excessive die temperature, and the
regulator 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.
MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER
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ELECTRICAL CHARACTERISTICS (5)
VIN = 5V, TA = +25°C, unless otherwise noted.
Parameter Symbol Condition Min Typ Max Units
2.5V VIN 6V -3% 0.600 +3%
Feedback Voltage VFB TA=-40oC to +85oC (6) -3.5% +3.5% V/%
Feedback Current IFB V
FB = 0.6V 10 50 nA
PFET Switch On Resistance RDSON_P 100 m
NFET Switch On Resistance RDSON_N 60 m
Switch Leakage VEN = 0V, VIN = 6V
VSW = 0V and 6V 0 1 A
PFET Current Limit 2.7 3.2 4.0 A
VIN=5V, VOUT=1.2V 185
ON Time TON VIN=3.6V, VOUT=1.2V 245
ns
VOUT=1.2V -20% 1500 +20% kHz/%
Switching frequency Fs TA=-40oC to +85oC(6) -25% 1500 +25% kHz/%
Minimum Off Time TMIN-OFF 60 ns
Soft-Start Time TSS-ON 1.5 ms
Power Good Upper Trip Threshold PGH FB voltage respect to the
regulation +10 %
Power Good Lower Trip Threshold PGL -10 %
Power Good Delay PGD 50 s
Power Good Sink Current
Capability VPG-L Sink 1mA 0.4 V
Power Good Logic High Voltage VPG-H V
IN=5V, VFB=0.6V 4.9 V
Power Good Internal Pull Up
Resistor RPG 550 k
Under Voltage Lockout Threshold
Rising 2.15 2.3 2.45 V
Under Voltage Lockout Threshold
Hysteresis 260 mV
EN Input Logic Low Voltage 0.4 V
EN Input Logic High Voltage 1.2 V
VEN=2V 1.5 A
EN Input Current VEN=0V 0 A
Supply Current (Shutdown) VEN=0V, VIN=3V 20 100 nA
Supply Current (Quiescent) VEN=2V, VFB=0.63V, VIN=5V 17 20 A
Thermal Shutdown(5) 150
°C
Thermal Hysteresis(5) 30
°C
Notes:
5) Guaranteed by design.
6) Guaranteed by characterization test.
MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER
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TYPICAL 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
Load Regulation
Line Regulation Case Temp Rise
V
IN
=3V, V
OUT
=1.2V
Case Temp Rise
V
IN
=5V, V
OUT
=3.3V
Efficiency
0
10
20
30
40
2 2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)
0
0.0005
0.001
0.0015
0.002
0.0025
0.003
2 2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)
-2.00
-1.50
-1.00
-0.50
0.00
0.50
1.00
1.50
2.00
0 0.5 1 1.5 2 2.5
LOAD CURRENT (A)
V
IN
=5V
V
IN
=6V
-1.00
-0.80
-0.60
-0.40
-0.20
0.00
0.20
0.40
0.60
0.80
1.00
23456
INPUT VOLTAGE (V)
Load=1A Load=2A
Load=0A
0
5
10
15
20
25
30
35
40
45
50
0 0.5 1 1.5 2 2.5
OUTPUT CURRENT (A)
0
5
10
15
20
25
30
35
40
45
50
0 0.5 1 1.5 2 2.5
OUTPUT CURRENT (A)
50
55
60
65
70
75
80
85
90
95
100
1 10 100 1000 10000
LOAD CURRENT(mA)
V
IN
=3.3V
V
IN
=5V V
IN
=6V
I
OUT
(A)
Efficiency
5/3.3V
IN
to 1.8V
OUT
Efficiency
5V
IN
to 3.3V
OUT
I
OUT
(A)
50
60
70
80
90
100
0 0.5 1 1.5 2 2.5
V
IN
=5V V
IN
=3.3V
50
60
70
80
90
100
0 0.5 1 1.5 2 2.5
MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 5V, VOUT = 1.2V, L = 1.0µH, TA = +25ºC, unless otherwise noted.
MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER
MP2161 Rev. 1.03 www.MonolihicPower.com 6
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 5V, VOUT = 1.2V, L = 1.0µH, TA = +25ºC, unless otherwise noted
MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER
MP2161 Rev. 1.03 www.MonolihicPower.com 7
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PIN FUNCTIONS
Pin # Name Description
1 PG
Power Good Indicator. The output of this pin is an open drain with internal pull up resistor
to IN. PGOOD is pulled up to IN when the FB voltage is within 10% of the regulation
level, if FB voltage is out of that regulation range, it is LOW.
2 VIN
Supply Voltage. The MP2161 operates from a +2.5V to +6V unregulated input. C1 is
needed to prevent large voltage spikes from appearing at the input.
3 SW Switch Output
4 PGND Power ground
5 OUT Input sense pin for output voltage
6 AGND Analogy ground for internal control circuit
7 FB
Feedback pin. An external resistor divider from the output to GND, tapped to the FB pin,
sets the output voltage.
8 EN On/Off Control
MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER
MP2161 Rev. 1.03 www.MonolihicPower.com 8
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BLOCK DIAGRAM
Main
Switch
(PCH)
Synchronous
Rectifier
(NCH)
Constant
On- Time
Pulse
PWM
Bias
&
Voltage
Reference
0.6 V
EN
FB
SW
COMP
+
-
VIN
+
+
-
FBCOMP EN
Driver
PDRV
NDRV
Soft star t
GND
OUT
PW M
COMP
+
-
COMP
+
-
0. 66 V
0. 54 V PG
Hi-Z
FB for
fixed output
IN
E.A.
+
-
+
Ramp
generator
COMP
+
-
VOUT
RST
SW
Lo - Iq
Lo-Iq
Lo-Iq
Lo-Iq
Lo-Iq
VTH
Figure 1: MP2161 Block Diagram
MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER
MP2161 Rev. 1.03 www.MonolihicPower.com 9
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OPERATION
MP2161 uses constant on-time control with
input voltage feed forward to stabilize the
switching frequency over full input range. At
light load, MP2161 employs a proprietary
control of low side switch and inductor current
to eliminate ringing on switching node and
improve efficiency.
Constant On-time Control
Compare to fixed frequency PWM control,
constant on-time control offers the advantage of
simpler 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 on-
time of the switching pulse can be estimated as:
OUT
ON
IN
V
T0.667s
V
=⋅μ
To prevent inductor current run away during load
transient, MP2161 fixes the minimum off time to
be 60ns. However, this minimum off time limit will
not affect operation of MP2161 in steady state in
any way.
Light Load Operation
In light load condition, MP2161 uses a
proprietary control scheme to save power and
improve efficiency. The MP2161 will turn off the
low side switch when inductor current starts to
reverse. Then MP2161 works in discontinuous
conduction mode (DCM) operation.
Enable
When input voltage is greater than the under-
voltage lockout threshold (UVLO), typically 2.3V,
MP2161 can be enabled by pulling EN pin to
higher than 1.2V. Leaving EN pin float or pull
down to ground will disable MP2161. There is
an internal 1Meg Ohm resistor from EN pin to
ground.
Soft Start
MP2161 has built-in soft start that ramps up the
output 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 550k 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 IN
by the internal resistor. If FB pin voltage is out
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 the
high side switch. When the high side switch hits
current 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 the
components.
Short Circuit and Recovery
MP2161 enters short circuit protection mode
also when the current limit is hit, and tries to
recover 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 soft-
start ends, MP2161 repeats this operation cycle
till short circuit disappears and output rises
back to regulation level.
MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER
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APPLICATION INFORMATION
COMPONENT SELECTION
Setting the Output Voltage
The external resistor divider is used to set the
output voltage (see Typical Application on page
1). The feedback resistor R1 can not be too
large neither too small considering the trade-off
for stability and dynamic. Choose R1 to be
around 120k to 200k. R2 is then given by:
out
R1
R2 V1
0.6
=
−
The feedback circuit is shown as Figure 2.
R1
R2
Vout
FB
MP2161
Figure 2: Feedback Network
Table 1 lists the recommended resistors value
for common output voltages.
Table 1—Resistor Selection for Common
Output Voltages
VOUT (V) R1 (kΩ) R2 (kΩ)
1.0 200(1%) 300(1%)
1.2 200(1%) 200(1%)
1.8 200(1%) 100(1%)
2.5 200(1%) 63.2(1%)
3.3 200(1%) 44.2(1%)
Selecting the Inductor
A 0.68µH to 2.2µH inductor is recommended for
most applications. For highest efficiency, the
inductor DC resistance should be less than
15m. For most designs, the inductance value
can be derived from the following equation.
OUT IN OUT
1
IN L OSC
V(VV)
LVIf
×−
=×Δ ×
Where IL is the inductor ripple current.
Choose inductor current to be approximately
30% of the maximum load current. The
maximum inductor peak current is:
2
I
II L
LOAD)MAX(L
Δ
+=
Selecting the Input Capacitor
The input current to the step-down converter is
discontinuous, therefore a capacitor is required to
supply 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 are
highly recommended because of their low ESR
and small temperature coefficients. For most
applications, a 10µF capacitor is sufficient. For
higher output voltage, 47uF may be needed for
more 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:
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
×−×=
IN
OUT
IN
OUT
LOAD1C V
V
1
V
V
II
The worse case condition occurs at VIN = 2VOUT,
where:
2
I
ILOAD
1C =
For simplification, choose the input capacitor
whose RMS current rating greater than half of
the 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. 0.1F, should be placed as close
to the IC as possible. When using ceramic
capacitors, make sure that they have enough
capacitance to provide sufficient charge to
prevent excessive voltage ripple at input. The
input voltage ripple caused by capacitance can
be estimated by:
LOAD OUT OUT
IN IN
SIN
IV V
V1
fC1V V
⎛⎞
Δ= × ×−
⎜⎟
×⎝⎠
MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER
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Selecting the Output Capacitor
The output capacitor (C2) is required to
maintain the DC output voltage. Ceramic
capacitors are recommended. Low ESR
capacitors are preferred to keep the output
voltage ripple low. The output voltage ripple can
be estimated by:
OUT OUT
OUT ESR
S1 IN S
VV 1
V1R
fL V 8fC2
⎛⎞
⎛⎞
Δ= ×− × +
⎜⎟
⎜⎟
×××
⎝⎠
⎝⎠
Where L1 is the inductor value and RESR is the
equivalent series resistance (ESR) value of the
output capacitor.
Using ceramic capacitors, the impedance at the
switching frequency is dominated by the
capacitance. The output voltage ripple is mainly
caused by the capacitance. For simplification,
the output voltage ripple can be estimated by:
OUT OUT
OUT 2
IN
S1
VV
V1
V
8f L C2
⎛⎞
=×−
⎜⎟
××× ⎝⎠
In the case of tantalum or electrolytic capacitors,
the ESR dominates the impedance at the
switching frequency. For simplification, the
output ripple can be approximated to:
OUT OUT
OUT ESR
IN
S1
VV
V1R
fL V
⎛⎞
=×−×
⎜⎟
×⎝⎠
The characteristics of the output capacitor also
affect the stability of the regulation system.
PCB Layout
Proper layout of the switching power supplies is
very 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 with
short, direct and wide traces. The input
capacitor needs to be as close as possible to
the IN and GND pins. The external feedback
resistors should be placed next to the FB pin.
Keep the switching node SW short and away
from the feedback network.
EN
AGND
OUT
GND
VIN
PG
R1
C2
R2
C1
8
7
6
5
1
2
3
4
SW
Figure 3: PCB Layout Recommendation
Design Example
Below is a design example following the
application guidelines for the specifications:
Table 2: Design Example
VIN 5V
VOUT 1.2V
fSW 1500kHz
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 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER
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TYPICAL APPLICATION CIRCUITS
Figure 4: Typical Application Circuit
MP2161 – 2A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER
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. 1.03 www.MonolithicPower.com 13
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PACKAGE INFORMATION
TSOT23-8
FRONT VI EW
NOTE:
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 AFTER
FORMING) 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 MARK
FROM LEFT TO RIGHT, (SEE EXAMPLE TOP MARK)
TO P VI EW RECOMMENDED LAND PATTERN
SEATING PLANE
SIDE VIEW
DE T AIL ' 'A' '
SEE DETAIL ''A''
IAAAA
PIN 1 ID
See note 7
EXAMPLE
TOP M AR K
Mouser Electronics
Authorized Distributor
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