4.5-V to 20-V, 20-A, synchronous buck controller with power good and synchronization

The TPS40195 is a flexible synchronous buck controller that operates from a nominal 4.5-V to 20-V supply. This controller implements voltage mode control with the switching frequency adjustable from 100 kHz to 600 kHz. Flexible features found on this device include selectable soft-start time, programmable short-circuit limit, programmable undervoltage lockout (UVLO) and synchronization capability. An adaptive anti-cross conduction scheme is used to prevent shoot through current in the power FETs. Overcurrent detection is done by sensing the voltage drop across the low-side MOSFET when it is on, and comparing it with a user-programmable threshold.

The threshold is set with a single external resistor connected from ILIM to GND. Pulse-by-pulse limiting (to prevent current runaway) is provided by sensing the voltage across the high-side MOSFET when it is on and terminating the cycle when the voltage drop rises above a fixed threshold of 550 mV. When the controller senses an output short circuit, both MOSFETs are turned off and a timeout period is observed before attempting to restart. This provides limited power dissipation in the event of a sustained fault. Synchronization on this device is bi-directional. Devices can be synchronized 180° out of phase to a chosen master TPS40195 running at a fixed 250 kHz or 500 kHz, or can be synchronized to an outside clock source anywhere in the 100 kHz to 600 kHz range.