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Thursday, March 25, 2010

Li-Ion Driver for 6 White LEDs with External PWM Dimming

The TPS61160/1 is a boost converter that drives up to 10 LEDs in series with a 40-V rated integrated switch FET. To reduce output ripple, improve convertion efficiency, and allows for the use of small external component, the boost converter is very usefull. The default white LED current is set with the external sensor resistor Rset, and the feedback voltage is regulated to 200mV. We can controll LED current during the operation using 1-wire digital interface through the CTRL pin or with pulse width modulation (PWM) signal that applied to the CTRL pin through the duty cycle determines the feedback reference voltage. To prevent the output from exceeding the absolute maximum ratings during open LED condition, the device has a feature of integrated open LED protection that disable the TPS1160/1. This is the figure of the circuit.


This device has a lot of features such as has input range between 2.7V to 18V. TPS61160 is used for 26V Open LED Protection for 6 LEDs and TPS61161 is used for 38V Open LED Protection for 10 LEDs. Voltage reference is 200mV with 2% accuracy. It has flexible digital and PWM brightness control. This device built-in soft start and has efficiency up to 90% and the last is 2mmx2mmx0.8mm 6-pin QFN Packacge with Thermal Pad. Cellular Phones, Portable Media Players, Ultra Mobile Devices, GPS Receivers, White LED Backlighting for Media Form Factor Display are kinds of application where this device can be applied.

[Circuit schematic source: Texas Instruments Application Note]

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