JAJSKX2A August 2019 – May 2021 TPS53676
PRODUCTION DATA
TPS53676 achieves fast load transient performance using the inherently variable switching frequency characteristics of DCAP+ control. #T5605938-12 illustrates the load insertion behavior, in which PWM pulses are generated with faster frequency than the steady-state frequency, to provide more energy to the output voltage, improving undershoot performance. #T5605938-13 illustrates the load release behavior, in which PWM pulses can be delayed to avoid charging extra energy to the load until the output voltage reaches the peak overshoot.
When there is a sudden load increase, the output voltage immediately drops. The controller device reacts to this drop by lowering the voltage on internal VCOMP signal. This forces PWM pulses to fire more frequently, which causes the inductor current to rapidly increase. As the converter output current reaches the new load current, the device reaches a steady-state operating condition and the PWM switching resumes the steady-state frequency.When there is a sudden load release, the output voltage immediately overshoots. The control loop reacts to this rise by increasing the voltage of the internal VCOMP signal. This rise forces the PWM pulses to be delayed until the converter output current reaches the new load current. At that point, the switching resumes and steady-state switching continues. In #T5605938-12 and #T5605938-13, the ripples on VOUT , and VCOMP voltages are not shown for simplicity.