TPSM82821 datasheet(12/54 Pages) TI

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9.2.1.1 Design Requirements

The design guidelines provide a component selection to operate the device within the recommended operating

conditions.

Table 9-1 lists the components used for Figure 9-1. Table 9-2 lists the components used for Figure 9-2.

Table 9-1. List of Components

REFERENCE

DESCRIPTION

MANUFACTURER

Ceramic capacitor, 4.7 µF, 6.3 V, X7R, size (0603), JMK107BB7475MA

Taiyo Yuden

Ceramic capacitor, 2 × 10 µF, 10 V, X7R, size (0603), GRM188Z71A106MA73D

muRata

Ceramic capacitor, 1 × 22 µF, 6.3 V, X6S, size (0603), JMK107BC6226MA-T

Taiyo Yuden

Ceramic capacitor, 120 pF, 50 V, size (0603), 06035A121JAT2A

AVX

Resistor, 200 kΩ, 1% accuracy

std

Resistor, 100 kΩ, 1% accuracy

std

Resistor, 100 kΩ, 1% accuracy

std

Table 9-2. List of Components

REFERENCE

DESCRIPTION

MANUFACTURER

Ceramic capacitor, 4.7 µF, 6.3 V, X7R, size (0603), JMK107BB7475MA

Taiyo Yuden

Ceramic capacitor, 22 µF, 4 V, X5R, size (0402), AMK105EBJ226MV-F

Taiyo Yuden

Resistor, 100 kΩ, 1% accuracy

std

9.2.1.2 Detailed Design Procedure

9.2.1.2.1 Setting the Output Voltage

Choose resistors R1 and R2 to set the output voltage within a range of 0.6 V to 4 V according to Equation 5.

To keep the feedback (FB) net robust from noise, set R2 equal to or lower than 100 kΩ to have at least 6 µA 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

Technical Brief.

OUT

0.6V

(5)

For devices with a fixed output voltage, the FB pin must be connected to VOUT. R1, R2 and C3 are not needed.

The fixed output voltage devices have an internal feed forward capacitor.

9.2.1.2.2 Feedforward capacitor

A feedforward capacitor (C3) is required in parallel with R1. Equation 6 calculates the C3 value. For the

recommended 100-kΩ value for R2, a 120-pF feedforward capacitor is used.

12 s

(6)

9.2.1.2.3 Input and Output Capacitor Selection

For the best output and input voltage filtering, ceramic capacitors are required. The input capacitor minimizes

input voltage ripple, suppresses input voltage spikes, and provides a stable system rail for the device. A 4.7-µF

or larger input capacitor is required. The output capacitor value can range from 10 µF up to 47 µF. The

recommended typical output capacitor value is 2 × 10-µF or 1 × 22-µF with an X5R or X7R dielectric. Values

over 47 µF can degrade the loop stability of the converter. A feedforward capacitor is required for best transient

performance.

TPSM82823, TPSM82822, TPSM82821, TPSM82823A, TPSM82822A, TPSM82821A

SLVSEP0F – AUGUST 2019 – REVISED NOVEMBER 2021

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