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Power Supplies 101 Slide 24

The unique control architecture from Semtech shown here is referred to as “Adaptive ON-Time” control. This control does not use an error amp and hence provides extremely fast loop and transient response. It uses ripple voltage to trigger the on-time of the controller. The adaptive on-time is determined by an internal one-shot timer as shown. When the one-shot timer has been triggered by the output ripple, the device sends a single on-time pulse to the high-side MOSFET. This pulse period is determined by VOUT and VIN. The period is proportional to the output voltage and inversely proportional to input voltage. This arrangement automatically anticipates the on-time required to regulate VOUT for the present VIN and at the selected switching frequency.

PTM Published on: 2011-09-27