ZHCSFQ9B November 2016 – June 2018 TPS54200 , TPS54201
PRODUCTION DATA.
The device uses a fixed-frequency and peak-current-mode control. The LED current is sensed by a resistor in series with the LED string. The sensed voltage is fed to the FB pin through an RC filter, and then compared to an internal voltage reference by an error amplifier. An internal oscillator initiates the turnon of the high-side power switch. The error amplifier output is compared to the current of the high-side power switch. When the power-switch current reaches the error-amplifier output-voltage level, the high-side power switch is turned off and the low-side power switch is turned on. Thus, the error amplifier output voltage regulates inductor peak current, and in turn the LED current, to a target value. The device implements a current limit by clamping the error amplifier voltage to a maximum level and also implements a minimum clamp for improved transient-response performance.