7.3.16 Overvoltage Transient Protection (OVTP)

The TPS57140-EP incorporates an OVTP circuit to minimize voltage overshoot when recovering from output fault conditions or strong unload transients on power-supply designs with low-value output capacitance. For example, with the power-supply output overloaded, the error amplifier compares the actual output voltage to the internal reference voltage. If the VSENSE pin voltage is lower than the internal reference voltage for a considerable time, the output of the error amplifier responds by clamping the error-amplifier output to a high voltage, thus requesting the maximum output current. On removal of the condition, the regulator output rises and the error-amplifier output transitions to the steady-state duty cycle. In some applications, the power-supply output voltage can respond faster than the error-amplifier output can respond; this actuality leads to the possibility of an output overshoot. The OVTP feature minimizes the output overshoot when using a low-value output capacitor by implementing a circuit to compare the VSENSE pin voltage to OVTP threshold, which is 109% of the internal voltage reference. A VSENSE pin voltage greater than the OVTP threshold disables the high-side MOSFET, preventing current from flowing to the output and minimizing output overshoot. The VSENSE voltage dropping lower than the OVTP threshold allows the high-side MOSFET to turn on at the next clock cycle.