SLVSCG7A July 2014 – September 2021 TPS55340-EP
PRODUCTION DATA
The TPS55340-EP has a built-in soft-start circuit which significantly reduces the start-up current spike and output voltage overshoot. When the IC is enabled, an internal bias current source (6 µA typical) charges a capacitor (CSS) on the SS pin. The voltage at the capacitor clamps the output of the internal error amplifier that determines the peak current and duty cycle of PWM controller. Limiting the peak switch current during start-up with a slow ramp on the SS pin reduces in-rush current and output voltage overshoot. After the capacitor reaches 1.8 V, the soft-start cycle is completed and the soft-start voltage no longer clamps the error amplifier output. When the EN is pulled low for at least 1 ms, the IC enters the shutdown mode and the SS capacitor is discharged through a 5-kΩ resistor to prepare for the next soft-start sequence.