AMC7110/1/3/4
APPLICATION INFORMATION
Enable
The EN pin enables and disables the device. Pulling the EN pin high will enable the device beginning sink
current on LED pins. Pulling the EN pin to ground will shutdown the device reducing the IDD current to typical 0.1uA.
This pin should not be left floating and need to be terminated.
LED Brightness Control
The LED sink current was fixed at 20mA or 15mA. Apply PWM signal to EN pin and control the duty that could
control the LED brightness from 0% to maximum.
EN
PWM Signal
VDD
Li-Ion
Battery
CBP
LED1
LED2
LED4
GND
Supply Voltage and Li-ion battery low warning
AMC711X works with supply voltage range from 2.7V to 6V. The white/blue LED forward voltage is in the range
of 2.9V to 3.5V at 20mA current. The supply voltage range and LED forward voltage (Vf) should be set to fully ultilize
Li-ion battery energy. For example, the maximum white LED forward voltage limit at 3.2V (@ 20mA) when Li-ion
battery discharg reaches 3.275V( normally around 1% ~ 3% power left in the battery). When Li-ion battery voltage is
lower than the presetted low level, the LED current(brightness) will start to decrease.
Efficiency
The ACR (Advanced Current Regulator) architecture offers ultra low output dropout that significantly improves
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:
Efficiency = (Vf1 x ILED1 + Vf2 x ILED2 + Vf3 x ILED3 + Vf4 x ILED4) / (VDD x IDD
Where, Vf is the forward voltage of LED.
)
Copyright © 2007 ADDtek Corp.
4
DD028_F -- JUNE 2007
ADDTEK [ ADDTEK CORP ]
