© 2010 Semtech Corporation

POWER MANAGEMENT

1

SC122

Low Voltage Synchronous

Boost Converter

Features

Input voltage — 0.7V to 1.6V

Minimum start-up voltage — 0.85V

Output voltage fixed at 3.3V

Peak input current limit — 350mA typically

Output current 95mA at V

IN

= 1.6V, 50mA at V

IN

= 0.9V

Efficiency up to 80%

Internal synchronous rectifier

Switching frequency — 1.2MHz

Power save (voltage hysteretic) control

Anti-ringing circuit

Operating supply current (measured at OUT) — 40μA

No forward conduction path during shutdown

MLPD-UT-6 1.5 × 2.0 × 0.6 (mm) package

Lead-free and halogen-free

WEEE and RoHS compliant

Applications

Electric toothbrushes

Personal medical products

Single-cell alkaline, NiCd, or NiMH applications

Description

The SC122 is a high efficiency, low noise, synchronous

step-up DC-DC converter. It produces a fixed 3.3V output

from a single cell alkaline or NiMH battery. It features an

internal 1.2A switch and synchronous rectifier to achieve

high efficiency and to eliminate the need for an external

Schottky diode.

The SC122 operates exclusively in voltage-hysteretic

power save mode (PSAVE) for high efficiency under light

load conditions. It features anti-ringing circuitry for

reduced EMI in noise sensitive applications. While dis-

abled, the output remains in a high impedance state to

preserve the charge on the output capacitor. This permits

ultra-low idle quiescent currents in applications in which

the SC122 can be periodically enabled by an external con-

troller to recharge the output capacitor.

Low quiescent current is obtained despite a high 1.2MHz

operating frequency. Small external components and the

space saving MLPD-UT-6, 1.5×2.0×0.6 (mm) package,

make this device an excellent choice for small handheld

applications that require the longest possible battery life.

L1

3.3V

Single

Cell

(1.2V)

IN

OUT

LX

EN

GND

SC122

GND

Typical Application Circuit

February 1, 2010