a709wft-40 ADD Microtech Inc., a709wft-40 Datasheet - Page 5

• Manufacturer Part Number: a709wft-40
• Description: Advanced Current Regulator
• Manufacturer: ADD Microtech Inc.

Efficiency
the efficiency compared to Inductive Boost type or Capacitor Charge Pump type LED driver. The system efficiency,
defined as the ratio between the LEDs power and the input supplied power, is:
Li-ion Battery Voltage Supply
than 3V while the white/blue LED forward voltage (V
voltage range and LED forward voltage can be set to fully utilize Li-ion battery energy. For example, if the forward
voltage of white LED is 3.2V at 20mA, the Li-ion battery can discharge until output voltage reaches 3.275V (normally
around 1% ~ 3% power left in the battery). When Li-ion battery voltage is lower than the 3.275V, the LED current
(brightness) will start to decrease.
Copyright © 2008 ADDtek Corp.
The ACR (Advanced Current Regulator) architecture offers ultra low output dropout that significantly improves
The A709 can work with Li-ion battery. The supply voltage of Li-ion battery ranges from 4.5V down to lower
Where, V
Efficiency
F
is the forward voltage of LED.
=
V
DD
×
V
F
(
I
×
DD
I
OUT
+
Battery
Li-ion
I
OUT
APPLICATION INFORMATION
)
≅
V
V
C
DD
F
BP
×
×
F
) is in the range of 2.9V to 3.5V at 20~40mA current. The supply
I
I
V
OUT
OUT
DD
5
=
V
V
V
DD
DD
F
A709
LED
GND
DD090_A -- SEPTEMBER 2008
A709