ACE77LE9

High Efficiency Low Noise PFM Step-Up DC/DC Converter

VER 1.1

1

Description

The ACE77LE9 PFM step-up DC/DC Converter drives white LEDs with a constant current to provide

backlight in cell phones, PDAs, and other hand-held devices. It features allowing series connection of the

white LEDs so that the LED currents are identical for uniform brightness. An enable input can be pulsed

repeatedly to adjust LEDs brightness. The fast 500kHz to 2MHz operation frequency allows for smaller

capacitor and inductor. Fault condition protection uses cycle-by-cycle current limiting to sense maximum

inductor current and over-voltage protection. The 0.2V low reference voltage minimizes the power loss

across the current sense resistor.

The converter can operate from 2V to 6V, and capable of delivering maximum 200mA output current at

4-LEDs application with 3V input voltage. Quiescent current drawn from power source is as low as 120uA.

All of these features make ACE77LE9 be suitable for the portable devices, which are supplied by a single

battery.

Features



Up to 24V Output Voltage



Wide Operation Range: 2V to 6V



Maximum 2MHz Operating Frequency



PWM Dimming Control



Shutdown Current <1μA



Current Limit Cycle-by-Cycle



Low Current Sense Threshold: 200mV



24V Over Output Voltage Protection



Compact SOT23-6 Package

Application



Compact Back Light Module



Power Source for LED



Constant Current Source

Absolute Maximum Ratings

Symbol

Parameter

Value

Unit

V

IN

Supply Voltage on VIN

-0.3 to 8.0

V

V

CE

Voltages on Pin CE

-0.3 to VIN+0.3

V

I

LX

LX Pin Output Current

1.6

A

V

LX

LX Pin Voltage

24

V

P

D

Continuous Power Dissipation

250

mW

T

A

Operating Ambient Temperature

-40 to 85

°C

T

J

Operating Junction Temperature

125

°C

T

STG

Storage Temperature Range

-40 to 150

°C

T

L

Maximum Lead Temperature for

Soldering 10 Seconds

260

°C