3

Date: 09/27/05

SP6655 High Efficiency 400mA Synchronous Buck Regulator

© Copyright 2004 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

BLON

Open drain battery low output. (V

node to ground. (V

4D1

Digital mode control input. See table I for definition.

5D0

Digital mode control input. See table I for definition.

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

D1

D0

00

Shutdown. All internal circuitry is disabled and the power switches are opened.

01

Device enabled, falling UVLO threshold =2.70V

10

Device enabled, falling UVLO threshold =2.85V

11

Device enabled, falling UVLO threshold =3.00V

Table 1. Operating Mode Definition

V

IN

Zero_X

DRVON

Q

R

Q

S

Min Ton

BLON

D0

P

VIN

OVR_I

MIN Ton

OVR_I

K

V

IN

LX

T

UVLO

BLANK = T

V

OUT

ILIM/M

REF

1

VOLOW

_

FB

+-

V

RAMP

RST

P

GND

TSD

BLANK

+

-

300mV

+

-

C

UVLO

Internal Supply

REF'

OVR_I

V

OUT

+

-

C

DRVON

BLANK

ILIM/M

D1

VOLOW

+

-

C

T

ONOVER

Min T

Ref

One-Shot

DRVON

+

-

C

Block

FB'

GND

REF

M

+-

Vos

DRIVER

DRVON

=100ns

T

ONOVER