MPM3686 – 18V 20A STEP-DOWN POWER MODULE

MPM3686 Rev. 1.02

www.MonolithicPower.com

7

10/13/2016

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PIN FUNCTIONS

Pin #

Name

Description

1, 2, 55, 58,

60

AGND

Analog/Signal Ground. It needs to be connected to GND on PCB layout.

3

>DC_trim

Output Voltage DC Trimming. Connect this pin to pin DC_trim> first, and then to the

output voltage sense point through a resistor. The resistor value can be chosen

based on equation 1.

4,6,23, 32,

44, 49

N/C

Not connected. Keep these pins floating.

5

AC_trim

Output Voltage AC Trimming. Connect these pins to the output through a capacitor.

The capacitor value can be chosen based on equation 2.

7- 22, 61, 62

SW

Switch Output. Keep them floating.

24-31, 63

VOUT

Module voltage output node.

33- 43, 64

GND

System Power Ground. Reference ground of the regulated output voltage. PCB

layout requires extra care. Connect using wide PCB traces.

45-48, 65

VIN

Supply Voltage. Supply power to the internal MOSFET and regulator. The MPM3686

operates from a +2.5V to +18V input rail with 5V external bias and from a +4.5V to

+18V input rail with internal bias. It requires input decoupling capacitors. Connect

using wide PCB traces and multiple vias.

50

>FREQ

Frequency Set In. An internal 430K frequency set resistor is used if connecting this

pin to Pin FREQ<. Keep this pin floating if values other than 300K are needed.

51

EN

Enable. Digital input that turns the regulator on or off. Drive EN high to turn on the

regulator, drive it low to turn it off. Connect EN to IN through a pull-up resistor or a

resistive voltage divider for automatic startup. Do not float this pin.

52

FREQ>

Frequency Set Out. An internal 430K frequency set resistor is used if connecting this

pin to Pin FREQ>. If values other than 430K are needed, connect the resistor

between this pin and pin VIN.

53

DC_trim>

Output Voltage DC Trimming. Connect this pin to pin >DC_trim first, and then to the

output voltage sense point through a resistor. The resistor value can be chosen

based on equation 1.

54

SS

Soft Start. Floating this pin has the default 3ms SS time. The SS time can be

extended by connecting an external capacitor between SS and AGND pins.

56

PG

Power Good. The output is an open drain signal. Require a pull-up resistor to a DC

voltage to indicate high if the output voltage exceeds 91% of the nominal voltage.

There is a 2.5ms delay from FB ≥ 91% to PG goes high.

57

VCC

Internal 4.8V LDO Output. Power the driver and control circuits. Keep this pin floating.

Applying a 5V external bias can disable the internal LDO to boost the efficiency.

59

BST

Bootstrap. Keep this pin floating.