The LP8550 is a white-LED driver with integrated boost converter. It has six adjustable
current sinks which can be controlled by PWM input or with
I2C-compatible serial interface. The boost
converter has adaptive output voltage control based on the LED driver voltages. This feature
minimizes the power consumption by adjusting the voltage to lowest sufficient level in all
LED outputs have 8-bit current resolution and up to 13-bit PWM resolution with additional
1- to 3-bit dithering to achieve smooth and precise brightness control. Proprietary Phase Shift PWM
control is used for LED outputs to reduce peak current from the boost converter, thus making the
boost capacitors smaller. The Phase Shifting scheme also eliminates audible noise.
Automatic PWM dimming at lower brightness values and current dimming at higher brightness
values can be used to improve the optical efficiency. Internal EEPROM is used for storing the
configuration data. This makes it possible to have minimum external component count and make the
solution very small.
The LP8550 has safety features which make it possible to detect LED outputs with open or
short fault — low input voltage and boost overcurrent conditions are monitored, and chip is turned
off in case of these events. Thermal de-rating function prevents overheating of the device by
reducing backlight brightness when set temperature has been reached.
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