WEBENCH® Tools/TPS54340: PCB based on the following schematic doesn't work

All the converts have no output?

For the TPS54340, you can use the WEBENCH to design the circuit and get the reference value of the BOM

All the converter schematics above have been designed using WebBench. I am testing the PCB now and am not seeing the desired behavior. Hence, would like a TI engineer to validate these designs.

The TPS5430 design looks ok. The TPS54340 has input of 12V and output of 12V. It is not a normal operation of a buck converter, the output should always be lower than the input voltage. What is the input voltage you put in for that Webench design?

Note that PCB layout is also an importance part of a power converter design, not just the schematic and component selections.

-Yang

Thank you for the response YangZhang . The input on TPS54340 is 12.8V for a 12V output. These were the values I input in webench. Can you please let me know if TPS54340 and TPS62177 schematic looks good?

You are using three separate regulator part numbers. You will probably need to make separate posts about the TPS5430 and TPS62177 issues as each part will likely be supported by a different team. In this thread you can post your overall general questions. I do not personally support any of these devices, but I know TPS54340 and TPS54340 quite well. Can you tell me what voltages you are seeing at each output? These are switching regulators. Can you post the waveform of each switching node (U7-8, U8-9, U10-8)? I can tell you directly, that you cannot get 12 V output from 12 V input for U2. There has to be some headroom voltage between Vin and Vout.

What is the load current you need from the output of the TPS54340? The 12.8V to 12V design is really a boundary operation condition for this part. With your design, the peak to peak current ripple is only a little above 100mA. This part is peak current mode controlled, certain amount of current ripple is needed for control loop's signal to noise ratio. For that concern, I recommend slower down the switching frequency and/or reduce the inductance to make the ripple larger. I'd say at least 300mA of ripple. Ripple can be estimated by (Vout/L)*(1-D)/fs, where D=Vout/Vin.

Note that there will always be a voltage drop from input voltage to output voltage in buck converters. More drop with higher load current, due to the losses and convertion limitations of the circuit. When you have lower Vin and/or higher load current, you may not have 12V output at the output.

I am not familiar with tps62177 myself.

-Yang

JohnTucker I appreciate the response. First, I am taking a Vin of 12.8V-24V for these regulators.
I am actually not seeing any output from the regulators. I suspect the chip has fried. Because the continuity test is positive for Ground and pins 6,7,8 on the TPS5430. Pin 6 is ground, 7 in Vin, 8 in PH.
Can you tell me under what circumstances should I expect see such a result? I believe this is not a PCB problem since the other piece does not show a short on those pins.
The second piece of PCB has never been connected to a power supply- and doesn't show a short. The PCB which was connected to 24VDC is the one showing a short.

Hope you can provide some insights

I am on business travel right now. I can possibly look t it later today.

YangZhang I tried with an input of 24V.
But I think the IC has been fried. I do not see any voltage output- and I see the following behavior:
Continuity test is positive for Ground and pins 6,7,8 on the TPS5430. Pin 6 is ground, 7 in Vin, 8 in PH.
Can you tell me under what circumstances should I expect see such a result? I believe this is not a PCB problem since the other piece does not show a short on those pins.
The second piece of PCB has never been connected to a power supply- and doesn't show a short.

The part could be damaged at power on if the layout of the PCB generates too much noise. Or if there's long connection cable to the supply, since there's only ceramic capacitors at the input side, with long cable, the parasitic inductance with oscillate with the ceramic caps. I haven't seen your layout and test setup, there could be various possibilities to damage the IC.

If you are designing for 12.8V to 24V input voltage to 12V output voltage with TPS54340, it is different than only design for 12.8V input. Please design for the most likely voltage of the input, and check the operation range at the min and max of the input voltage.