MP8756 – 26V, 6A, SYNCHRONOUS, STEP-DOWN CONVERTER

MP8756 Rev. 1.1

www.MonolithicPower.com

10

4/13/2017

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PIN FUNCTIONS

PIN #

Name

Description

1

VIN

Supply voltage. VIN supplies power for the internal MOSFET and regulator. The MP8756

operates from a 4.5V to 26V input rail. Decouple the input rail with an input capacitor. Use

wide PCB traces and multiple vias to make the connection. Apply at least two layers for

this input trace.

2

PGND

Power ground. Connect using wide PCB traces and multiple vias large enough to handle

the load current.

3

PG

Power good output. The output of PG is an open-drain signal. PG is high if the output

voltage is higher than 95% or lower than 105% of the nominal voltage.

4

NC

Do not connect. NC must be left floating.

5

VOUT

VOUT is used to sense the output voltage of the buck regulator. Connect VOUT to

the output capacitor of the regulator directly. Keep the VOUT sensing trace far away from

the SW node. Vias should also be avoided on the VOUT sensing trace. A trace larger

than 25mil is required.

6

MODE

USM, PFM, PWM selection. Pull MODE higher than 2.6V to operate the MP8756 in

forced PWM mode. Float MODE to operate the MP8756 in PFM mode with ultrasonic

mode (USM) at light load. Connect MODE to ground to operate the MP8756 in PFM mode

without USM.

7

SW

Switch output. Connect SW to the inductor and bootstrap capacitor. SW is driven up to

VIN by the high-side switch during the PWM duty cycle on-time. The inductor current

drives SW negative during the off time. The on resistance of the low-side switch and the

internal diode fixes the negative voltage. Use wide and short PCB traces to make the

connection. Keep the SW pattern area minimized.

8

BST

Bootstrap. A capacitor connected between SW and BST is required to form a floating

supply across the high-side switch driver.

9

VCC

Internal VCC LDO output. The driver and control circuits are powered by VCC. Decouple

with a minimum 1µF ceramic capacitor placed as close to VCC as possible. X7R or X5R

grade dielectric ceramic capacitors are recommended for their stable temperature

characteristics.

10

AGND

Signal logic ground. AGND is the Kelvin connection to PGND.

11

FB

Feedback. FB sets the output voltage when connected to the tap of an external resistor

divider connected between output and GND.

12

EN

Enable. EN is a digital input that turns the regulator on or off. When the power supply of

the control circuit is ready, drive EN high to turn on the regulator. Drive EN low to turn off

the regulator.