MP4470/4470A–HIGH-EFFICIENCY, FAST-TRANSIENT, SYNCHRONOUS, STEP-DOWN CONVERTER

MP4470/4470A Rev. 1.1

www.MonolithicPower.com

7

8/26/2013

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PIN FUNCTIONS

Pin #

Name

Description

1

AGND

Analog Ground.

2

FREQ

Frequency Set (for CCM). The input voltage and the frequency-set resistor

connected to GND determine the ON period. Decouple with a 1nF capacitor.

3

FB

Feedback. The tap of external resistor divider from the output to GND sets the

output voltage.

4

SS

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

switch-mode regulator. When the EN pin goes HIGH, an internal current source

(8.5µA) charges up the capacitor and the SS voltage slowly and smoothly ramps

discharges the capacitor and the SS voltage slowly ramps down.

5

EN

Enable. EN=1 to enable the MP4470/4470A. For automatic start-up, connect EN

pin to IN with a 100kΩ resistor. It includes an internal 1MΩ pull-down resistor.

6

PGOOD

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

output voltage exceeds 90% of the nominal voltage. There is delay of ~700µs from

FB ≥ 90% to PGOOD HIGH.

7

BST

Bootstrap. Requires a 0.1µF-to-1µF capacitor connected between SW and BS pins

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

8, 19,

Exposed pads

21, 22, 23

IN

Supply Voltage. The MP4470/4470A operates from a 4.5V-to-36V input rail.

multiple vias.

9, 10, 17, 18,

Exposed pads

24, 25

SW

Switch Output. Connect using wide PCB traces and multiple vias.

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.