switched off. The voltage applied at the EN pin of the TPSM8281x is compared to a fixed threshold of 1.1V for a

rising voltage.

The enable input threshold for a falling edge is typically 100mV lower than the rising edge threshold. The Precise

Enable input provides a user-programmable undervoltage lockout by adding a resistor divider to the input of the

EN pin. The Precise Enable input also allows you to drive the pin by a slowly changing voltage and enables

the use of an external RC network to achieve a precise power-up delay. See the Achieving a Clean Start-up by

Using a DC/DC Converter with a Precise Enable-pin Threshold analog design journal for more details.

8.3.2 Output Discharge

The purpose of the discharge function is to make sure of a defined down-ramp of the output voltage when the

device is disabled and keep the output voltage close to 0V when the device is off. The output discharge feature

is only active after the TPSM8281x has been enabled at least once since the supply voltage was applied. The

discharge function is enabled as soon as the device is disabled, in thermal shutdown, or in undervoltage lockout.

The minimum supply voltage required for the discharge function to remain active is typically 1V.

8.3.3 COMP/FSET

This pin sets two different parameters independently:

• Internal compensation settings for the control loop (three settings available)

• The switching frequency in PWM mode from 1.8MHz to 4MHz

A resistor from COMP/FSET to GND changes the compensation as well as the switching frequency. The change

in compensation adapts the device to different values of output capacitance. The resistor must be placed close

to the pin to keep the parasitic capacitance on the pin to a minimum. The compensation setting is set after

enabling the converter, so a change in the resistor during operation only has an effect on the switching frequency

but not on the compensation.

To save external components, the pin can also be directly tied to VIN or GND to set a pre-defined switching

frequency and compensation. Do not leave the pin floating.

The switching frequency must be selected based on the maximum input voltage and the output voltage to meet

the specifications for the minimum on-time.

Example: VIN = 5.5V, VOUT = 1V

fSw,max= VOUT

VIN × tON,min=  1 V

5.5 V × 75 ns =2.42 MHz

(1)

The compensation range has to be chosen based on the minimum effective capacitance used. The capacitance

can be increased from the minimum value as given in Table 8-1 up to the maximum of 470µF in all of the

three compensation ranges. The higher compensation settings give better load transient response, when larger

output capacitances are used. If the capacitance of an output changes during operation, for example, when load

switches are used to connect or disconnect parts of the circuitry, the compensation has to be chosen for the

minimum capacitance on the output. Compensating for large output capacitance but placing less capacitance on

the output can lead to instability.

The value of RCF for the intended switching frequency and compensation setting is determined by the equations

in the following table.

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TPSM82810, TPSM82813

SLUSDN6D – SEPTEMBER 2019 – REVISED JUNE 2026

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