I have produced a design for a converter from 12-14 V to 12 V (3 A) using the TPS55288 buck-boost converter.

Unfortunately, it is not producing the desired output.

I have laid it out as presented in the datasheet, and used same parts as suggested or same alternatives.

The output produces a 0.9 V. It seems as if it is charging a capacitance when I supply the input power.

The enable pin voltage is over the UVLO threshold. All values are according to the webench tool (https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=5B8D198B88C0AEB0).

12-24 to 12v3A schematic
12v converter layout

Pin 10 was routed after the production process.

What is missing?

Do I need to add anything?

  • \$\begingroup\$ Please show oscillograms and what you measure on which pin of the IC. \$\endgroup\$
    – winny
    Oct 11 at 14:20
  • 1
    \$\begingroup\$ Why do you have SW1 & SW2 connected together to the 'output' side of the inductor? The typical application circuits in the datasheet show SW1 connected to the 'input' side. \$\endgroup\$
    – brhans
    Oct 11 at 14:21
  • \$\begingroup\$ They aren't connected. SW2 has two pins, labelled SW2_1 and SW2_2. These are connected together while SW1 is separate. \$\endgroup\$
    – Codo
    Oct 11 at 19:20
  • \$\begingroup\$ It seems that the power ground (pins 11 and 26) are only connected through vias, probably going to a ground plane on the bottom side. The output capacitors are connected to a ground fill on the top side. It creates a long and problematic return path for the high current. It would probably be better to stick to the proposed PCB, which otherwise seem to be mostly the case. \$\endgroup\$
    – Codo
    Oct 11 at 19:32

The circuit works.

The problem was that it wasn't configured correctly via the I2C interface.

Other considerations wich would improve performance is designing the GND laypout better, and use 6 layers for better ground and signal routing to the surrounding systems.


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