ANX6930

     The ANX6930 is a highly compact white LED driver especially optimized for thin-film transistor (TFT) liquid crystal displays (LCDs) backlight. The chip can drive up to six strings of LEDs and up to 10 LEDs in series per string.

    The device offers a built-in high efficiency current mode boost converter. The six integrated current sink regulators provide high precision current regulation and matching for LED currents up to 60mA. The feedback loop senses LED current sink voltages and compensates for the non-uniformity of the LED forward voltage accumulated on the LED strings. To minimize the power loss, the output voltage of the boost converter is automatically adjusted by monitoring the highest forward voltage of the LED strings. An unused LED channel can be disabled by connecting the channel to ground.

     The ANX6930 controls LED dimming from PWM interface and supports direct dimming mode, mixed dimming mode, and programmable output frequency dimming mode. In direct PWM mode, the LED current is turned on and off in response to the duty cycle and frequency applied at the PWM pin. In mixed dimming mode, the input PWM duty cycle information is translated to analog signal to control the LED current linearly over 25% to 100% input PWM duty. In programmable output frequency dimming mode, the LED current of each channel is turned on and off based on the duty controllered by the input PWM signal, but the frquency is determined by the resistor on RFPWM pin. Auto phase shift dimming is applied in this mode, each channel is shifted accordingly.

     The ANX6930 features overcurrent protection (OCP), overtemperature protection (OTP), overvoltage protection (OVP), and LED string open and short detection. Once the device is turned on, the soft-start function raises the output voltage gradually to avoid voltage overshoot and inrush current.