The TPS61177 IC provides a highly integrated WLED driver solution for notebook
LCD backlight. This device has a built-in high efficiency boost regulator with integrated 1.8A /40V
power MOSFET. The six current sink regulators provide high precision current regulation and
matching. In total, the device can support up to 72 WLEDs. In addition, the boost output
automatically adjusts its voltage to the WLED forward voltage to optimize efficiency.
The TPS61177 supports the analog dimming, analog/PWM dimming and direct PWM
dimming method. During analog dimming mode, each CS current linearly varies depending on the duty
cycle information on the PWMB pins. During analog and PWM mixed dimming mode, the input PWM duty
cycle information is translated to analog signal to control the WLED current linearly over 25% to
100% brightness area. And the device also allows adding PWM dimming when the analog current down to
25%. Below 25%, the analog signal will translate to PWM duty cycle information to control the
on/off of WLED current and average the WLED current down to 1%. The frequency of adding PWM dimming
is same to input PWM frequency on the PWMB pin. While the TPS61177 also supports direct PWM dimming method, in direct PWM dimming mode
the WLED current is turned on/off synchronized with the input PWM signal.
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