9.2.2.2 Programming the Output Voltage

The output voltage of the TPSM8281x is adjustable. Choose resistors R1 and R2 to set the output voltage within

a range of 0.6V to 5.5V according to Equation 10. To keep the feedback (FB) net robust from noise, set R2

equal to or lower than 100kΩ to have at least 6µA of current in the voltage divider. Lower values of FB resistors

achieve better noise immunity, and lower light load efficiency, as explained in the Design Considerations for a

Resistive Feedback Divider in a DC/DC Converter analog design journal.

OUT

OUT

FB

V

V

R1

R2

1

R2

1

V

0.6V

§

·

§

·

u

u

¨

¸

¨

¸

©

¹

©

¹

(10)

9.2.2.3 Feedforward capacitor

A feedforward capacitor (CFF) is recommended in parallel with R1 in order to improve the transient response.

Regardless of the FB resistor values, the CFF value must always be 10pF.

9.2.2.4 Input Capacitor

For most applications, a 22µF nominal ceramic capacitor is recommended. The input capacitor buffers the input

voltage for transient events and also decouples the converter from the supply. A X7R or X7T multilayer ceramic

capacitor (MLCC) is recommended for best filtering and must be placed between VIN and GND as close as

possible to those pins. For applications with ambient temperatures below 85°C, a capacitor with X5R dielectric

can be used. Ceramic capacitors have a DC-Bias effect, which has a strong influence on the final effective

capacitance. Choose the right capacitor carefully in combination with considering the package size and voltage

rating. The minimum required input capacitance is 5µF.

9.2.2.5 Output Capacitor

The architecture of the TPSM8281x allows the use of ceramic output capacitors which have low equivalent

series resistance (ESR). These capacitors provide low output voltage ripple and are recommended. To keep

the low resistance up to high frequencies and to get a narrow capacitance variation with temperature, it is

recommended to use an X7R or X7T dielectric. At temperatures below 85°C, an X5R dielectric can be used.

Using a higher capacitance value has advantages like smaller voltage ripple and a tighter DC output accuracy in

power save mode. By changing the device compensation with a resistor from COMP/FSET to GND, the device

can be compensated in three steps based on the minimum capacitance used on the output. The maximum

capacitance is 470µF in any of the compensation settings. The minimum capacitance required on the output

depends on the compensation setting and output voltage as shown in Table 8-1. For output voltages below 1V,

the minimum required capacitance increases linearly from 32µF at 1V to 53µF at 0.6V with the compensation

setting for smallest output capacitance. Other compensation settings scale the same. Ceramic capacitors have

a DC-Bias effect, which has a strong influence on the final effective capacitance. Choose the right capacitor

carefully in combination with considering the package size and voltage rating.

TPSM82810, TPSM82813

SLUSDN6B – SEPTEMBER 2019 – REVISED JULY 2024

www.ti.com

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