POWER MANAGEMENT

1

SC631

Fixed 4.4V Output

Charge Pump Regulator

© 2008 Semtech Corporation

Features

Input voltage range — 2.9V to 5.5V

V

OUT

tolerance — 4.4V ±3%

Continuous output current — 250mA

Peak output current — 500mA

Three charge pump modes: 1x, 1.5x and 2x

Output ripple ≤ 30mV

PP

for I

OUT

≤ 400mA

Short circuit, over-voltage, and over-temperature

protection

Soft-start functionality

Shutdown current — 0.1μA, typical

Ultra thin package — 2 x 2 x 0.6 (mm)

Fully WEEE and RoHS compliant

Applications

Mobile phones

Multi-LED backlit LCDs

PMPs

Digital video cameras

Digital still cameras

PDAs

LED camera flash

Audio amplifier power

Description

The SC631 is a high-current voltage regulator using

Semtech’s proprietary low-noise charge pump technol-

ogy. Performance is optimized for use in single Li-Ion

battery cell applications. The regulator provides the per-

formance of a linear, low drop-out (LDO) voltage regulator

when the input is greater than 4.4V. Unlike an LDO, drop-

out is avoided when the input is less than 4.4V. Instead, a

charge pump is activated to provide voltage boost and

the head-room needed for voltage regulation.

the full output current. The charge pump provides a low

EMI solution compared to inductive boost regulators.

The SC631’s charge pump has three modes of operation:

2x, 1.5x, and 1x modes. The 2x and 1.5x modes deliver

current to the load in each of two phases. The 1x mode

turns off the charge pump, delivering current through an

LDO. When active, the charge pump provides low-ripple

operation at 200kHz, which is typically less than 30mVpp

at the output. The SC631 is capable of delivering 250mA

output capacitor is used for decoupling the load and for

smoothing mode transitions. Hysteresis is provided to

prevent chatter between charge pump modes.

The micro lead-frame package is both small and thermally

efficient, measuring 2 x 2 x 0.6 (mm).

SC631

OUT

C1+

IN

GND

EN

C1-

C2+

C2-

22μF

22μF

2.2μF

2.2μF

Chip

enable

Typical Application Circuit

July 24, 2008

Patents Pending