MP8715 – 4A, 21V, 500kHz, STEP DOWN CONVERTER WITH 100% DUTY CYCLE OPERATION

MP8715 Rev. 1.01

www.MonolithicPower.com

5

6/13/2013

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PIN FUNCTIONS

SOIC8E

Pin#

3x4 QFN14

Pin #

Name

Description

1

1

VIN

Supply Voltage. The MP8715 operates from a +4.5V to +21V input rail.

C1 is required to decouple the input rail. Use wide PCB traces and

multiple vias to make the connection.

2

2,3,4,5

SW

Switch Output. It is the source of high-side power device.

3

6

BST

Bootstrap. This capacitor is needed to drive the power switch’s gate

above the supply voltage. It is connected between SW and BST pins to

form a floating supply across the power switch driver. An on-chip regulator

and charge pump are both used to charge up the external boot-strap

capacitor.

4

7

EN/SYNC

EN=1 to enable the MP8715. External clock can be applied to EN pin for

changing switching frequency. For automatic start-up, connect EN pin to

VIN with 100KΩ resistor.

5

8

FB

Feedback. An external resistor divider from the output to GND, tapped to

the FB pin, sets the output voltage. To prevent current limit run away

during a short circuit fault condition the frequency fold-back comparator

lowers the oscillator frequency when the FB voltage is below 400mV.

6

9

POK

Power good signal. When FB is less than 90% of 0.8V, POK is low. It is

an open-drain output. Use a high value pull-up resistor externally to pull it

up to system power supply.

7

10

VCC

Bias Supply. It’s the internal regulator output. Decouple with 0.1µF

capacitor.

8

14

SS

Connect to an external capacitor used for Soft-Start.

9

11,12,13,

Exposed

Pad

GND

Ground (Exposed Pad, also serves as thermal pad)