ACE517

WLED Linear Driver for Li-lon Battery Application

VER 1.2

4

Typical Application Circuit

Li-Ion Battery

VCC

GND

LED 1

LED 2

LED 3

EN

On/Off Control

LED 4

Only Available in ACE517

Detailed Description

ACE517 works with a wide range of supply voltage, from 2.7V to 6V. The forward voltage of commercial

white/blue LED is in the range of 2.9V to 3.5V at a current level of 20mA. Proper selection of the LED to

match the supply voltage can fully utilize the Li-ion battery. For example, there is 1% ~ 3% power left in

the Li-ion battery when its voltage reaches 3.275V. So a LED with a forward voltage value of 3.2V can use

up to 99% of the battery power under normal working condition. When the voltage of the battery drops

below 3.2V, the current through the LED (hence the brightness) starts to decrease.

Due to its uniquely designed current regulator, ACE517 offer low output dropout and provide superior

efficiency performance over standard inductive boost type and capacitive charge pump type LED driver.

The EN pin controls the on/off state of the device. A high level state turns on the device and a low level

turns off the device, results in the low off state current. This pin needs to be terminated since a floating

level of the EN pin will cause the instability of the device.

The sink current has a constant value of 20mA. The brightness of the LED can be adjusted by controlling

the duty cycle of the ACE517 LEDn pin. Hence, in order to normally modulate the output of LEDn in every

cycle, the width of dimming signal applied CE pin have to be no less than 6us. For example, when a

dimming signal of 20KHz is applied, the minimum range of dimming is about 12%, that is , the average

output current on each channel is 2.4mA.