12 V to 3.3 V

2.2 MHz

After 2nd L-C

300 mA to 3 A to 300 mA

Figure 8-14. Load Transient

8.3 Power Supply Recommendations

The power supply to the TPSM8291x must have a current rating according to the supply voltage, output voltage,

and output current of the TPSM8291x.

8.4 Layout

8.4.1 Layout Guidelines

A proper layout is critical for the operation of any switched mode power supply, especially at high switching

frequencies. Therefore, the PCB layout of the TPSM8291x demands careful attention to ensure best

performance. A poor layout can lead to issues like bad line and load regulation, instability, increased EMI

radiation, and noise sensitivity. Refer to the Five Steps to a Great PCB Layout for a Step-Down Converter

technical brief for a detailed discussion of general best practices. Specific recommendations for the device are

listed below.

• The TPSM8291x has an integrated input capacitor. However, placement of the input capacitors must be

placed as close as possible to the VIN and PGND pins of the device. Route the input capacitors directly to

the VIN and PGND pins avoiding vias.

• Place the output capacitor ground close to the PGND pin and route it directly avoiding vias.

• Sensitive traces, such as the connections to the NR/SS and FB pins must be connected with short traces and

be routed away from any noise source.

• Connect the PSNS pin directly to the system GND plane with a via.

• The SW pin must not be connected and must be left floating. If the pin is soldered to PCB copper, the pour

needs to be as small as possible with no inner layer connections. The pin is provided for probing the internal

SW only, and not to be connected to any external component, as shown on the EVM.

• Place the second L-C filter, Lf and Cf, near the load to reduce any radiated coupling around the second L-C

filter

• Place the FB resistors, R1 and R2, close to the FB pin and route the VOUT connection from R1 to the load as

a remote sense trace. If a second L-C filter is used, this connection must be made after Lf.

• The recommended layout is implemented on the EVM and shown in the EVM user's guide.

www.ti.com

TPSM82913

SLVSGJ4A – OCTOBER 2022 – REVISED DECEMBER 2022

Copyright © 2022 Texas Instruments Incorporated

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Product Folder Links: TPSM82913