MP8642 — DUAL 3A, 23V, 600kHz STEP-DOWN CONVERTER

MP8642 Rev. 1.0

www.MonolithicPower.com

4

9/13/2012

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© 2012 MPS. All Rights Reserved.

PIN FUNCTIONS

Pin #

Name

Description

1, 2, 3, 4

SW1

Switch Output Channel 1

5

BST1

Bootstrap Channel 1. This capacitor is needed to drive the power switch’s gate above the

supply voltage. It is connected between SW1 and BST1pins to form a floating supply

across the power switch driver.

6

VCC1

BG Driver Bias Supply Channel 1. Decouple with a 1µF ceramic capacitor.

7

BG1

Gate Driver Output Channel 1. Connect this pin to the synchronous MOSFET Gate

8

GND1

Ground Channel 1.

9

EN/SYNC1 On/Off Control and External Frequency Synchronization Input Channel 1.

10

PG1

Power Good Indicator Channel 1. Connect this pin to VCC or VOUT by a 100kΩ pull-up

resistor. The output of this pin is low if the output voltage is 10% less than the nominal

voltage, otherwise it is an open drain.

11

FB1

Feedback Channel 1. An external resistor divider from the output1 to GND1, tapped to the

FB1 pin sets the output voltage. To prevent current limit run away during a short circuit

fault condition the frequency foldback comparator lowers the oscillator frequency when

the FB voltage is below 250mV.

12, 13

GND2

Ground Channel 2.

14

BG2

Gate Driver Output Channel 2. Connect this pin to the synchronous MOSFET Gate

15

VCC2

G Driver Bias Supply Channel 2. Decouple with a 1µF ceramic capacitor.

16

BST2

Bootstrap channel 2. This capacitor is needed to drive the power switch’s gate above the

supply voltage. It is connected between SW2 and BST2 pins to form a floating supply

across the power switch driver.

17

FB2

Feedback Channel 2. An external resistor divider from the output2 to GND2, tapped to the

FB2 pin sets the output voltage. To prevent current limit run away during a short circuit

fault condition the frequency foldback comparator lowers the oscillator frequency when

the FB voltage is below 250mV.

18

PG2

resistor. The output of this pin is low if the output voltage is 10% less than the nominal

voltage, otherwise it is an open drain.

19

EN/SYNC2 On/Off Control and External Frequency Synchronization Input Channel 2.

20, 28,

32

N/C

No Connect

21, 22,

23, 24

IN2

Supply Voltage Channel 2. The MP8642 operates from a +4.5V to +23V unregulated

input.

25, 26,

27

SW2

Switch Output Channel 2

29, 30,

31

IN1

Supply Voltage Channel 1. The MP8642 operates from a +4.5V to +23V unregulated

input.