The TPS65261 can enter high efficiency pulse skipping mode (PSM) operation at light load current.

When a controller is enabled for PSM operation, the peak inductor current is sensed and compared with 230mA current typically. Because the integrated current comparator catches the peak inductor current only, the average load current entering PSM varies with applications and external output filters. In PSM, the sensed peak inductor current is clamped at 230mA.

When a controller operates in PSM, the inductor current is not allowed to reverse. The reverse current comparator turns off the low-side MOSFET when the inductor current reaches zero, preventing it from reversing and going negative.

Due to the delay in the circuit and current comparator tdly (typical 50ns at V_IN = 12V), the real peak inductor current threshold to turn off high-side power MOSFET, can shift higher depending on inductor inductance and input/output voltages. The threshold of peak inductor current to turn off high-side power MOSFET can be calculated by Equation 11.

Equation 11.

After the charge accumulated on the Vout capacitor is more than loading need, COMP pin voltage drops to low voltage driven by the error amplifier. There is an internal comparator at the COMP pin. If COMP voltage is lower than 0.35V, the power stage stops switching to save power.

Figure 7-13 PSM Current Comparator