ZHCSHA3D NOVEMBER 2009 – March 2018 TPS40303 , TPS40304 , TPS40305
PRODUCTION DATA.
The TPS4030x contains a circuit to prevent current from being pulled from the output during start-up in the condition the output is prebiased. There are no PWM pulses until the internal soft-start voltage rises above the error amplifier input (FB pin), if the output is prebiased. Once the soft-start voltage exceeds the error amplifier input, the controller slowly initiates synchronous rectification by starting the synchronous rectifier with a narrow on time. The controller then increments that on time on a cycle-by-cycle basis until it coincides with the time dictated by (1-D), where D is the duty cycle of the converter. This approach prevents the sinking of current from a prebiased output, and ensures the output voltage start-up and ramp to regulation is smooth and controlled.