MP8736– HIGHEFFICIENCY,FAST TRANSIENT,6A, 19V SYNCHRONOUSBUCKCONVERTERIN ATINY3X4mmPACKAGE

MP8736 Rev. 1.34

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4

4/18/2012

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PIN FUNCTIONS

Pin #

Name

Description

1

AGND

Analog Ground.

2

FREQ

Frequency Set during CCM operation. The ON period is determined by the input

voltage and the frequency-set resistor connected to FREQ pin. Connect a resistor

to IN for line feed forward. Decouple with a 1nF capacitor.

3

FB

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

pin, sets the output voltage.

4

SS

Soft Start. Connect an external SS capacitor to program the soft start time for the

switch mode regulator. When the EN pin becomes high, an internal current source

(8.5uA) charges up the SS capacitor and the SS voltage slowly ramps up from 0 to

discharges the SS capacitor and the SS voltage slowly ramps down.

5

EN

EN=1 to enable the MP8736. For automatic start-up, connect EN pin to IN with a

100kΩ resistor. Includes an internal 1MΩ pull-down.

6

PGOOD

Power Good Output. The output of this pin is an open drain and is high if the

output voltage is higher than 90% of the nominal voltage. There is delay from FB ≥

90% to PGOOD high, which is 50% of SS time plus 0.5ms.

7

BST

Bootstrap. A 0.1μF to 1μF capacitor connected between SW and BST pins is

required to form a floating supply across the high-side switch driver.

8, 19

IN

Supply Voltage. The MP8736 operates from a +4.5V to +19V input rail. CIN is

needed to decouple the input rail. Use wide PCB traces and multiple vias to make

the connection.

9, 10, 17, 18

SW

Switch Output. Use wide PCB traces and multiple vias to make the connection.

11-16

PGND

System Ground. This pin is the reference ground of the regulated output voltage.

For this reason care must be taken in PCB layout.

20

VCC

Internal Bias Supply. Decouple with a 1µF capacitor as close to the pin as

possible.