ZHCSHF4J May 2004 – January 2018 TPS51116
PRODUCTION DATA.
TPS51116 includes an adaptive on-time control scheme and does not have a dedicated oscillator on board. However, the device runs with fixed 400-kHz pseudo-constant frequency by feed-forwarding the input and output voltage into the on-time one-shot timer. The on-time is controlled inverse proportional to the input voltage and proportional to the output voltage so that the duty ratio is kept as VOUT/VIN technically with the same cycle time. Although the TPS51116 does not have a pin connected to VIN, the input voltage is monitored at LL pin during the ON state. This helps pin count reduction to make the part compact without sacrificing its performance. In order to secure minimum ON-time during startup, feed-forward from the output voltage is enabled after the output becomes 750 mV or larger.