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MP1657
16V, 2A, 800kHz, High-Efficiency,
Synchronous, Step-Down Converter
In a SOT563 Package

DESCRIPTION FEATURES
The MP1657 is a fully integrated, high-  Wide 4.5V to 16V Operating Input Range
frequency, synchronous, rectified, step-down,  130mΩ/75mΩ Low RDS(ON) Internal Power
switch-mode converter with internal power MOSFETs
MOSFETs. The MP1657 offers a very compact  190μA Low IQ
solution that achieves 2A of continuous output  High-Efficiency Synchronous Mode
current with excellent load and line regulation Operation
over a wide input range. The MP1657 uses  Power-Save Mode (PSM) at Light Load
synchronous-mode operation for higher  Fast Load Transient Response
efficiency over the output current-load range.  800kHz Switching Frequency
Constant-on-time (COT) control operation  Internal Soft Start (SS)
provides very fast transient response, easy loop  Over-Current Protection (OCP) and Hiccup
design, and very tight output regulation.  Thermal Shutdown
Full protection features include short-circuit  Output Adjustable from 0.8V
protection (SCP), over-current protection (OCP),  Available in a SOT563 Package
under-voltage protection (UVP), and thermal
APPLICATIONS
shutdown.
 Security Cameras
The MP1657 requires a minimal number of  Digital Set-Top Boxes
readily available, standard, external  Flat-Panel Television and Monitors
components and is available in a space-saving
 General Purposes
SOT563 package.
All MPS parts are lead-free, halogen-free, and adhere to the RoHS directive. For
MPS green status, please visit the MPS website under Quality Assurance. “MPS”
and “The Future of Analog IC Technology” are registered trademarks of
Monolithic Power Systems, Inc.

TYPICAL APPLICATION

R4
10Ω
C3
1μF
12V L1 3.3V/2A
VIN BST
4.7μH
VOUT
VIN SW
C1 R1
22μF R3 40.2kΩ C2
47kΩ 22μF
MP1657 FB
R2
13kΩ
EN
EN GND

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MP1657 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

ORDERING INFORMATION
Part Number* Package Top Marking
MP1657GTF SOT563 See Below
* For Tape & Reel, add suffix –Z (e.g. MP1657GTF–Z)

TOP MARKING

AWH: Product code of MP1657GTF

Y: Year code
LLL: Lot number

PACKAGE REFERENCE
TOP VIEW

VIN 1 6 FB

SW 2 MP1657 5 EN

GND 3 4 BST

SOT563

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MP1657 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance θJA θJC

VIN ................................................ -0.3V to 20V SOT563
VSW ............................ -0.6V (-6.5V for <10ns) to EV1657-TF-00A (5) ................ 55 ....... 21 ... °C/W
VIN + 0.3V (21V for <10ns) JESD51-7 (6) ........................ 130 ...... 60 ... °C/W
VBST .....................................................VSW + 5V
NOTES:
VEN .............................................. -0.3V to 5V (2) 1) Exceeding these ratings may damage the device.
All other pins .................................... -0.3V to 5V 2) For details on ENs ABS max rating, please refer to the
Enable Control section on page 11.
Continuous power dissipation (TA = +25°C) (3)(5) 3) The maximum allowable power dissipation is a function of the
..................................................................2.2W maximum junction temperature TJ (MAX), the junction-to-
ambient thermal resistance θJA, and the ambient temperature
Junction temperature ............................... 150°C TA. The maximum allowable continuous power dissipation at
Lead temperature .................................... 260°C any ambient temperature is calculated by PD (MAX) = (TJ
Storage temperature .................. -65°C to 150°C (MAX)-TA)/θJA. Exceeding the maximum allowable power
dissipation produces an excessive die temperature, causing
the regulator to go into thermal shutdown. Internal thermal
Recommended Operating Conditions (4) shutdown circuitry protects the device from permanent
Supply voltage (VIN) ....................... 4.5V to 16V damage.
4) The device is not guaranteed to function outside of its
Output Voltage (VOUT) ...... 0.8V to VIN x Dmax or operating conditions.
10V max 5) Measured on EV1657-TF-00A, 2-layer PCB.
Operating junction temp. (TJ) ... -40°C to +125°C 6) Measured on JESD51-7, 4-layer PCB.

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MP1657 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

ELECTRICAL CHARACTERISTICS
VIN = 12V, TJ = -40°C to +125°C (7), typical value is tested at TJ = +25°C, unless otherwise noted.
Parameter Symbol Condition Min Typ Max Units
Supply current (shutdown) IIN VEN = 0V 10 μA
TJ = -40°C to +125°C, VEN = 2V,
0.15 0.19 0.3 mA
VFB = 0.85V
Supply current (quiescent) IQ
TJ = +25°C, VEN = 2V,
0.16 0.19 0.23 mA
VFB = 0.85V
HS switch on resistance HSRDS(ON) VBST-SW = 3.3V 130 mΩ
LS switch on resistance LSRDS(ON) 75 mΩ
Switch leakage SW LKG VEN = 0V, VSW = 12V 10 μA
Valley current limit ILIMIT VOUT = 0A 1.8 2.4 3.8 A
VOUT = 3.3V, Lo = 4.7μH,
ZCD IZCD -150 -20 150 mA
IOUT = 0A
Oscillator frequency fSW VFB = 0.75V 600 800 1000 kHz
Minimum on time (8) τON_MIN 45 ns
Minimum off time (8) τOFF_MIN 180 ns
TJ = +25°C 795 807 819
Feedback voltage VREF mV
TJ = -40°C to 125°C 791 807 823
Feedback current IFB 10 100 nA
FB UV threshold (H to L) VUV_th Hiccup entry 75% VREF
Hiccup duty cycle (8) DHiccup 25 %
EN rising threshold VEN_RISING 1.14 1.2 1.26 V
EN hysteresis VEN_HYS 100 mV
EN input current IEN VEN = 2V 2 µA
VIN under-voltage lockout
INUVVth 3.7 4.1 4.18 V
threshold rising
VIN under-voltage lockout
INUVHYS 330 mV
threshold hysteresis
Soft-start period τSS 1 1.4 2 ms
Thermal shutdown (8) TSD 150 °C
Thermal hysteresis (8) TSDHYS 20 °C
TJ = +25°C 795 807 819
Feedback voltage VREF mV
TJ = -40°C to 85°C 791 807 823
NOTES:
7) Not tested in production. Guaranteed by over-temperature correlation.
8) Guaranteed by design and engineering sample characterization.

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MP1657 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

TYPICAL PERFORMANCE CHARACTERISTICS

VIN = 12V, VOUT = 3.3V, L = 4.7µH, TA = +25°C, unless otherwise noted.

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MP1657 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

TYPICAL PERFORMANCE CHARACTERISTICS (continued)

VIN = 12V, VOUT = 3.3V, L = 4.7µH, TA = +25°C, unless otherwise noted.

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MP1657 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

TYPICAL PERFORMANCE CHARACTERISTICS (continued)

VIN = 12V, VOUT = 3.3V, L = 4.7µH, TA = +25°C, unless otherwise noted.

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MP1657 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

TYPICAL PERFORMANCE CHARACTERISTICS (continued)

VIN = 12V, VOUT = 3.3V, L = 4.7µH, TA = +25°C, unless otherwise noted.

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MP1657 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

PIN FUNCTIONS
Package
Name Description
Pin #
Supply voltage. The MP1657 operates from a 4.5V to 16V input rail. A capacitor (C1) is
1 VIN
required to decouple the input rail. Connect VIN using a wide PCB trace.
2 SW Switch output. Connect SW using a wide PCB trace.
System ground. GND is the reference ground of the regulated output voltage. GND
3 GND
requires extra care during the PCB layout. Connect GND with copper traces and vias.
Bootstrap. Connect a 1µF BST capacitor and a resistor between SW and BST to form a
4 BST
floating supply across the high-side switch driver.
Enable. Drive EN high to enable the MP1657. For automatic start-up, connect EN to VIN
5 EN
through a 100kΩ pull-up resistor.
Feedback. Connect FB to the tap of an external resistor divider from the output to GND to
set the output voltage. The frequency foldback comparator lowers the oscillator frequency
6 FB
when the FB voltage drops below 600mV to prevent current-limit runaway during a short-
circuit fault.

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MP1657 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

BLOCK DIAGRAM

VIN

Bias & Bootstrap

EN BST
Voltage Regulator
1MΩ reference

VCC
Regulator

Main
On HS Switch(NCH)
Timer Driver
Iss
SW
Logic
Control
PWM VCC

FB LS
Driver

Current Synchronous
Modulator Switch (NCH)
Current Sense
Amplifier

GND

Figure 1: Functional Block Diagram

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MP1657 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

OPERATION shorter, the HS-FET turns on more frequently,

and the switching frequency increases in turn.
The MP1657 is a fully integrated, synchronous,
The output current reaches the critical level
rectified, step-down, switch-mode converter.
when the current modulator time is zero and
Constant-on-time (COT) control is employed to
can be determined with Equation (1):
provide fast transient response and ease loop
stabilization. At the beginning of each cycle, the (VIN  VOUT )  VOUT
IOUT  (1)
high-side MOSFET (HS-FET) is turned on when 2  L  FSW  VIN
the FB voltage (VFB) drops below the reference
voltage (VREF). The HS-FET is turned on for a The device reverts to pulse-width modulation
fixed interval determined by the one-shot on- (PWM) mode once the output current exceeds
timer. The on-timer is determined by both the the critical level. Afterward, the switching
output voltage and input voltage to make the frequency remains fairly constant over the
switching frequency fairly constant over the output current range.
input voltage range. Enable (EN) Control
After the on period elapses, the HS-FET is EN is a digital control pin that turns the
turned off until the next period. By repeating regulator on and off. Drive EN high to turn on
operation this way, the converter regulates the the regulator. Drive EN low to turn off the
output voltage. regulator. An internal 1MΩ resistor from EN to
GND allows EN to float to shut down the IC.
Continuous conduction mode (CCM) is when
the output current is high and the inductor EN is clamped internally using a 2.8V series
current is always above zero amps. The low- Zener diode (see Figure 2). Connecting the EN
side MOSFET (LS-FET) is turned on when the input through a pull-up resistor to VIN limits the
HS-FET is in its off state to minimize conduction EN input current to less than 100μA to prevent
loss. There is a dead short between the input damaging the Zener diode. For example, when
and GND if both the HS-FET and LS-FET are connecting a 100kΩ pull-up resistor to 12V VIN,
turned on at the same time. This is called a IZener = (12V - 2.8V) / (100kΩ + 35kΩ) = 68µA.
shoot-through. To avoid shoot-through, a dead- EN
time is generated internally between the HS- 1MΩ 35kΩ
EN
FET off and LS-FET on period or LS-FET off Logic
2.8V
and HS-FET on period. GND

When the MP1657 works in pulse-frequency Figure 2: Zener Diode between EN and GND
modulation (PFM) mode during light-load
operation, the MP1657 reduces the switching Under-Voltage Lockout (UVLO)
frequency automatically to maintain high Under-voltage lockout (UVLO) protects the chip
efficiency, and the inductor current drops from operating at an insufficient supply voltage.
almost to zero. When the inductor current The MP1657 UVLO comparator monitors the
reaches zero, the low-side driver goes into tri- output voltage of the internal regulator (VCC).
state (Hi-Z). The output capacitors discharge The UVLO rising threshold is about 4.1V, while
slowly to GND through R1 and R2. When VFB its falling threshold is consistently 3.77V.
drops below VREF, the HS-FET is turned on.
Internal Soft Start (SS)
This operation improves device efficiency
greatly when the output current is low. Soft start prevents the converter output voltage
from overshooting during start-up. When the
Light-load operation is also called skip mode chip starts up, the internal circuitry generates a
because the HS-FET does not turn on as soft-start voltage (SS) that ramps up from 0V to
frequently as it does during heavy-load 1.2V. When SS is lower than REF, SS
conditions. The frequency at which the HS-FET overrides REF so the error amplifier uses SS as
turns on is a function of the output current. As the reference. When SS exceeds REF, the
the output current increases, the current error amplifier uses REF as the reference. The
modulator regulation time period becomes SS time is set to 1.4ms internally.

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Over-Current Protection (OCP) and Short- Floating Driver and Bootstrap Charging
Circuit Protection (SCP) An external bootstrap capacitor powers the
The MP1657 has a valley current-limit control. floating power MOSFET driver. This floating
During the LS-FET on state, the inductor driver has its own UVLO protection with a rising
current is monitored. When the sensed inductor threshold of 2.2V and a hysteresis of 150mV.
current reaches the valley current limit, the low- VIN regulates the bootstrap capacitor voltage
side limit comparator turns over. The device internally through D1, M1, C3, L1, and C2 (see
enters over-current protection (OCP) mode, and Figure 3). If VIN - VSW exceeds 3.3V, U2
the HS-FET waits until the valley current limit regulates M1 to maintain a 3.3V BST voltage
disappears before turning on again. Meanwhile, across C3.
the output voltage drops until VFB is below the
under-voltage (UV) threshold (typically 75%
below the reference). Once UV is triggered, the
MP1657 enters hiccup mode to restart the part
periodically.
During OCP, the device attempts to recover
from over-current fault with hiccup mode. The
chip disables the output power stage,
discharges the soft start, and attempts to soft
start again automatically. If the over-current
condition still remains after the soft start ends,
the device repeats this operation cycle until Figure 3: Internal Bootstrap Charger
over-current condition is removed, and the Start-Up and Shutdown Circuit
output rises back to regulation level. OCP is a If both VIN and EN exceed their respective
non-latch protection. thresholds, the chip starts up. The reference
Pre-Bias Start-Up block starts first, generating a stable reference
The MP1657 is designed for monotonic start-up voltage and currents, and then the internal
into pre-biased loads. If the output is pre-biased regulator is enabled. The regulator provides a
to a certain voltage during start-up, the BST stable supply for the remaining circuits.
voltage is refreshed and charged, and the Three events can shut down the chip: EN low,
voltage on the soft start is charged as well. If VIN low, and thermal shutdown. The shutdown
the BST voltage exceeds its rising threshold procedure starts by blocking the signaling path
voltage and the soft-start voltage exceeds the initially to avoid any fault triggering. The internal
sensed output voltage at FB, the MP1657 starts supply rail is then pulled down.
working normally.
Thermal Shutdown
Thermal shutdown prevents the chip from
operating at exceedingly high temperatures.
When the silicon die temperature exceeds
150°C, the entire chip shuts down. When the
temperature falls below its lower threshold
(typically 130°C), the chip is enabled again.

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MP1657 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

APPLICATION INFORMATION Selecting the Inductor

Setting the Output Voltage An inductor is necessary for supplying constant
current to the output load while being driven by
An external resistor divider is used to set the
the switched input voltage. A larger-value
output voltage. First, choose a value for R2. R2
inductor results in less ripple current and a
should be chosen reasonably, since a small R2
lower output ripple voltage, but also has a
leads to considerable quiescent current loss,
larger physical footprint, higher series
while a large R2 makes FB noise-sensitive. R2
resistance, and lower saturation current. A good
should be within 5 - 100kΩ. Typically, set the
rule for determining the inductance value is to
current through R2 to be between 5 - 30µA for a
design the peak-to-peak ripple current in the
good balance between system stability and no-
inductor to be in the range of 30 - 40% of the
load loss. Then determine R1 with Equation (2):
maximum output current, and that the peak
VOUT  VREF inductor current is below the maximum switch
R1   R2 (2)
current limit. The inductance value can be
VREF
calculated with Equation (3):
The feedback circuit is shown in Figure 4.
VOUT V
VOUT L  (1  OUT ) (3)
FSW  IL VIN
MP1657
R1
RT Where ∆IL is the peak-to-peak inductor ripple
FB current.
R2
The inductor should not saturate under the
maximum inductor peak current. The peak
inductor current can be calculated with
Figure 4: Feedback Network
Equation (4):
Table 1 and Table 2 list the recommended
VOUT V
parameters for common output voltages. ILP  IOUT   (1  OUT ) (4)
2FSW  L VIN
Table 1: Parameters Selection for Common
Output Voltages, COUT = 22µF (9) Selecting the Input Capacitor
VOUT (V) R1 (kΩ) R2 (kΩ) RT (kΩ) L (μH) The input current to the step-down converter is
5 40.2 7.68 47 4.7 discontinuous and therefore requires a
3.3 40.2 13 47 4.7 capacitor to supply AC current to the step-down
2.5 40.2 19.1 62 3.3 converter while maintaining the DC input
1.8 40.2 32.4 75 2.2 voltage. Ceramic capacitors are recommended
1.5 40.2 45.3 86.6 2.2 for the best performance and should be placed
1.2 40.2 82 105 1.5 as close to VIN as possible. Capacitors with
1 20.5 84.5 160 1.5 X5R and X7R ceramic dielectrics are
NOTE: recommended because they are fairly stable
9) For a detailed design circuit, please refer to the Typical with temperature fluctuations.
Application Circuits on page 16 to page 18.

Table 2: Parameters Selection for Common The capacitors must also have a ripple current
Output Voltages, COUT = 22µF*2 rating greater than the maximum input ripple
current of the converter. The input ripple current
VOUT (V) R1 (kΩ) R2 (kΩ) RT (kΩ) L (μH)
can be estimated with Equation (5):
5 40.2 7.68 0 4.7
3.3 40.2 13 0 4.7 VOUT V
2.5 40.2 19.1 10 3.3 ICIN  IOUT   (1  OUT ) (5)
VIN VIN
1.8 40.2 32.4 10 2.2
1.5 40.2 45.3 20 2.2
1.2 40.2 82 25 1.5
1 20.5 84.5 51 1.5

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The worst-case condition occurs at VIN = 2VOUT, For simplification, the output ripple can be
shown in Equation (6): approximated with Equation (11):
IOUT VOUT V
ICIN  (6) VOUT   (1  OUT )  RESR (11)
2 FSW  L VIN
For simplification, choose an input capacitor A larger output capacitor also can achieve a
with an RMS current rating greater than half of better load transient response, but be sure to
the maximum load current. consider the maximum output capacitor
The input capacitance value determines the limitation in the design application. If the output
input voltage ripple of the converter. If there is capacitor value is too high, the output voltage
an input voltage ripple requirement in the cannot reach the design value during the soft-
system, choose the input capacitor that meets start time and fails to regulate. The maximum
the specification. output capacitor value (Co_max) can be limited
approximately with Equation (12):
The input voltage ripple can be estimated with
Equation (7): CO _ MAX  (ILIM _ AVG  IOUT )  Tss / VOUT (12)
IOUT V V Where ILIM_AVG is the average start-up current
VIN   OUT  (1  OUT ) (7)
FSW  CIN VIN VIN during the soft-start period, and Tss is the soft-
start time.
The worst-case condition occurs at VIN = 2VOUT,
PCB Layout Guidelines
shown in Equation (8):
Efficient PCB layout of the switching power
1 I supplies is critical for stable operation. A poor
VIN   OUT (8)
4 FSW  CIN layout design can result in poor line or load
regulation and stability issues. For best results,
Selecting the Output Capacitor refer to Figure 5 and follow the guidelines below.
An output capacitor is required to maintain the 1) Place the high-current paths (GND, VIN,
DC output voltage. Ceramic or POSCAP and SW) very close to the device with short,
capacitors are recommended. The output direct, and wide traces.
voltage ripple can be estimated with Equation
(9): 2) Place the input capacitor as close to VIN
and GND as possible (within 1mm).
VOUT V 1
VOUT   (1  OUT )  (RESR  ) (9) 3) Place the external feedback resistors next
FSW  L VIN 8  FSW  COUT
to FB.
In the case of ceramic capacitors, the 4) Keep the switching node (SW) short and
impedance at the switching frequency is away from the feedback network.
dominated by the capacitance. The output
voltage ripple is caused mainly by the
capacitance. For simplification, the output
voltage ripple can be estimated with Equation
(10):
VOUT V (10)
VOUT   (1  OUT )
8  FSW 2  L  COUT VIN

In the case of POSCAP capacitors, the ESR

dominates the impedance at the switching
frequency.

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MP1657 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

Design Example
GND Table 3 shows a design example when ceramic
capacitors are applied.
Table 3: Design Example
VIN 12V
VOUT 3.3V
IOUT 2A
VIN OUT The detailed application schematics are shown
GND in Figure 6 through Figure 12. The typical
performance and waveforms are shown in the
Typical Performance Characteristics section.
Top Layer
For more devices applications, please refer to
the related evaluation board datasheet.
VIN

VOUT

GND

Bottom Layer
Figure 5: Recommended Layout

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TYPICAL APPLICATION CIRCUITS

10Ω

22µF 0.1µF

1µF
MP1657 4.7µH
5V/2A

22µF
100kΩ 10pF

47kΩ 40.2kΩ

7.68kΩ

Figure 6: 12VIN, 5V/2A Output

10Ω

22µF 0.1µF

1µF
MP1657 4.7µH

22µF
100kΩ 10pF

47kΩ 40.2kΩ

13kΩ

Figure 7: 12VIN, 3.3V/2A Output

10Ω

22µF 0.1µF

1µF
MP1657 3.3µH 2.5V/2A

22µF
100kΩ 10pF

62kΩ 40.2kΩ

19.1kΩ

Figure 8: 12VIN, 2.5V/2A Output

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TYPICAL APPLICATION CIRCUITS (continued)

10Ω

22µF 0.1µF

1µF
MP1657 2.2µH 1.8V/2A

22µF
100kΩ 10pF

75kΩ 40.2kΩ

32.4kΩ

Figure 9: 12VIN, 1.8V/2A Output

10

MP1657 2.2µH 1.5V/2A

100K 10pF

86.6K

45.3K

Figure 10: 12VIN, 1.5V/2A Output

10Ω

22µF 0.1µF

1µF
MP1657 1.5µH 1.2V/2A

22µF
100kΩ 10pF

105kΩ 40.2kΩ

82kΩ

Figure 11: 12VIN, 1.2V/2A Output

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MP1657 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

TYPICAL APPLICATION CIRCUITS (continued)

10Ω

22µF 0.1µF

1µF
MP1657 1.5µH 1V/2A

22µF
100kΩ 10pF

160kΩ 20.5kΩ

84.5kΩ

Figure 12: 12VIN, 1V/2A Output

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 MPS Confidential - For A-UNIT Use Only
MP1657 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

PACKAGE INFORMATION
SOT563

NOTICE: The information in this document is subject to change without notice. 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.

MP1657 Rev. 1.0 www.MonolithicPower.com 19

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© 2017 MPS. All Rights Reserved.