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CAT3661 led driver circuit

This Led driver circuit is designed using the CAT3661 high efficiency low power LED driver, that can be used for low power LCD display backlight, or low power hand-held device backlight. CAT2261 circuit use a charge pump that drives one LED with up to 5 mA of current.
The quad-mode charge pump supports a wide range of input voltages from 2.0 V to 5.5 V.
The CAT3661 circuit has a built in circuitry to provide feedback to a microcontroller of Open/Short LED and Low battery events. Also it has an soft-start current limiting and shortcircuit protection functions optimized for use with coin cell batteries.
As you can see in the circuit diagram , this led driver circuit require few external components and is very easy to design .

The low battery indicator trip point can be calculated by the following formula: VLB =VADJxGADJ where , VLB = Low Battery Voltage Trip Point , VADJ = Low Battery Comparator Trip point (0.6 V) and GADJ = Resistor Divider Gain (4 internally) .

If you want to modify the resistor divider gain , you can apply the following formula :
GADJM =(RADJ+RH)/[(RADJ/GADJ)+RL] where , GADJM = Modified resistor divider gain , RADJ = Total resistance of divider (800 kohms typ.) , RH = High external resistor (ADJH to VIN) , RL = Low external resistor (ADHL to GND) .
The current in the LED channel can be calculate by the following equation :
ILED =(0.6/RSET)300
cat3661 led driver circuit diagram

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