The built-in Power Save Mode of the TPS6215xA-Q1 is entered seamlessly, if the load current decreases. This secures a high efficiency in light load operation. The device remains in Power Save Mode as long as the inductor current is discontinuous.
In Power Save Mode, the switching frequency decreases linearly with the load current maintaining high efficiency. The transition into and out of Power Save Mode happens within the entire regulation scheme and is seamless in both directions.
TPS6215xA-Q1 includes a fixed on-time circuitry. This on-time, in steady-state operation with FSW=Low, can be estimated as:
For very small output voltages, an absolute minimum on-time of about 80ns is kept to limit switching losses. The operating frequency is thereby reduced from its nominal value, which keeps efficiency high. Also the off-time can reach its minimum value at high duty cycles. The output voltage remains regulated in such case. Using tON, the typical peak inductor current in Power Save Mode can be approximated by:
When VIN decreases to typically 15% above VOUT, the TPS6215xA-Q1 won't enter Power Save Mode, regardless of the load current. The device maintains output regulation in PWM mode.