ZHCSQD3A october 2022 – march 2023 TPS62992-Q1
PRODUCTION DATA
When the MODE/S-CONF pin is configured for power save mode (auto PFM and PWM). The device operates in PWM mode as long the output current is higher than half of the ripple current of the inductor, and seamlessly transitions to PSM operation as the load decreases. In power save mode, the device operates in PFM mode by reducing the switching frequency linearly with the load current to maintain high efficiency under light load operation. The device remains in power save mode as long as the inductor current remains discontinuous, and the transition out of PSM also occurs seamlessly when the load current increases above the DCM boundary.
In addition to operating in PFM under light load, when the 2.5 MHz FSW option is selected, the TPS62992-Q1 further adjusts the on time (TON), depending on the input voltage and the output voltage to maintain highest efficiency using the AEE function as described in Section 8.4.3 .
In power save mode, the TON time can be estimated using Equation 4 for 1 MHz and Equation 8 for 2.5 MHz.
For higher input voltages and small output voltages, an absolute minimum on time of approximately 30 ns is kept to limit switching losses. The operating frequency is thereby reduced from its nominal value, which keeps efficiency high. Using TON, the typical peak inductor current in power save mode is approximated by Equation 5:
The output voltage ripple in power save mode is given by Equation 6:
where