TPS5430: Ringing on the PH pin

TIMM Srl

Part Number: TPS5430

Hello,

we are using two TPS5430 running from the same voltage source (12V), they are set to output 5V. We are experiencing lots of ringing on the PH pin waveforms which is making the regulators inusable (i.e. it's not switching at 500khz).

Here's the schematic:

C16 and C19 are GRM31CR6YA106KA12L (CAP CER 10UF 35V X5R 1206)

C17 and C20 are TCJD227M010R0040 (Tant poly 220 µF, 10 V, ± 20%, D, 0.04 ohm)

L1 and L2 are SRU1063-220Y (22µH 3A 60 mOhm max)

Here's the PCB layout, red is the TOP copper, due to a production error there's no BOTTOM copper (e.g. GND)

This layout shows, as I said before, lots of ringing on the PH pin thus making the regulators unusable.

As we are making a second revision of the board, here's the updated layout, TOP and BOTTOM:

Does this new design look reasonably good to you? What may be the case for ringing on the PH pin in the old layout?

Thanks

over 6 years ago

0 Frank De Stasi over 6 years ago

TI__Guru 63405 points

I would try to get the ground of the input capacitor and the diode ground next to each other.
Also, a small 100nF or so, input bypass cap can sometimes be helpful. This should be close to the
Vin and GND of the device.
It looks like your bottom ground plane is broken with small traces running through it; I would try to avoid this type of thing.