3

Date: 3/6/06

SP6656, 400mA Synchronous Buck Regulator with Dynamically Adjustable Voltage Output

© Copyright 2006 Sipex Corporation

PIN DESCRIPTION

PIN NUMBER

PIN NAME

DESCRIPTION

Input voltage power pin. Inductor charging current passes through this pin.

Internal supply voltage. Control circuitry powered from this pin.

3

OVSO

Output Voltage Selection Output. OVSI = 1 pulls this node to

GND, OVSI = 0, this node is open.

4

OVSI

Output Voltage Select Input. See table 1 for definition.

5EN

EN = 1, device is enabled. EN = 0, All internal circuitry is disabled and

power switches are opened.

6FB

External feedback network input connection. Connect a resistor from

FB to ground and FB to V

regulates to the internal bandgap reference voltage of 0.8V.

Output voltage sense pin. Used by the timing circuit to set minimum on

and off times.

8

GND

Internal ground pin. Control circuitry returns current to this pin.

Power ground pin. Synchronous rectifier current returns through this pin.

10

LX

Inductor switching node. Inductor tied between this pin and the output

capacitor to create regulated output voltage.

FUNCTIONAL DIAGRAM

Table 1. Output Voltage Selection

VO

FB

OVSO

CF

22pF

Zero_X

DRVON

Q

R

Q

S

Min Ton

P

VIN

OVR_I

MIN Ton

OVR_I

K

V

IN

LX

T

UVLO

BLANK = T

ILIM/M

REF

1

VOLOW

_

FB

+-

V

RAMP

RST

P

GND

TSD

BLANK

+

-

C

Internal Supply

REF'

OVR_I

V

OUT

+

-

C

DRVON

BLANK

ILIM/M

VOLOW

+

-

C

T

ONOVER

Min T

Ref

One-Shot

DRVON

Block

FB'

GND

REF

M

+-

Vos

DRIVER

DRVON

=100ns

T

ONOVER

OVSI

EN

OVSO

OVSI

OVSO

Output Voltage

0

Open

V

OUT_LOW

I

1Short to GND

A