because the output voltage is higher than the input voltage. When the inductor current hits the valley current

threshold determined by the output of the error amplifier, the next switching cycle starts again.

The TPSM81033 has a built-in compensation circuit that can accommodate a wide range of input voltage, output

voltage, inductor value, and output capacitor value for stable operation.

6.4.2 Power-Save Mode

The TPSM81033 integrates a power-save mode with PFM to improve efficiency at light load. When the load

current decreases, the inductor valley current set by the output of the error amplifier no longer regulates the

output voltage. When the inductor valley current hits the low limit, the output voltage exceeds the setting voltage

as the load current decreases further. When the FB voltage hits the PFM reference voltage, the TPSM81033

goes into the power-save mode. In the power-save mode, when the FB voltage rises and hits the PFM reference

voltage, the device continues switching for several cycles because of the delay time of the internal comparator

— then it stops switching. The load is supplied by the output capacitor, and the output voltage declines. When

the FB voltage falls below the PFM reference voltage, after the delay time of the comparator, the device starts

switching again to ramp up the output voltage.

Output

Voltage

VOUT_NOM

1.01 x VOUT_NOM

PFM mode at light load

PWM mode at heavy load

Figure 6-2. Output Voltage in PWM Mode and PFM Mode

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TPSM81033

SLVSHL0B – JUNE 2024 – REVISED JULY 2024

Copyright © 2024 Texas Instruments Incorporated

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