TPS629210-Q1: XTPS629210QDRLRQ1 3.3V Flucuations

colin WIERKS

Part Number: TPS629210-Q1
Other Parts Discussed in Thread: TPS629210EVM

Tool/software:

I am looking for some help with some power supply fluctuations I am having with a XTPS629210QDRLRQ1. I have designed the board with the 2.2uH inductor and 22uF capacitor as close as possible to the IC with the same schematic as the TPS629210EVM evaluation board.

The load is 12mA, 35mA or spikes at 250mA. There seems to be a power fluctuation at 35mA constant draw at a 1.5uS frequency where it drops down to 1.8V and recovers back to 3.3V and if the load is reduced to 12mA it seems to fluctuate with similar magnitudes every 30uS. I have notice the series resistance of the inductor I am using is 10x higher roughly than the evaluation board but i am not sure if this is the root cause. Can someone give me some help as to what is going on?

8 months ago

0 Colin Chen 8 months ago

TI__Mastermind 21161 points

Hi Colin,

Could you show us the waveforms of SW, Vout and I-load you mentioned. It can better help me to dubug.

Thanks,

Colin

0 colin WIERKS 8 months ago in reply to Colin Chen

Prodigy 10 points

The magnitude of the oscillation seems to be roughly independent of load but the frequency when it happens increases as the load increases. Ch1 Yellow is Vout, Ch 2 Aqua is just after a 10Ω burden resistor to measure 3.3V load, Purple is the voltage across the 10Ω resistor and Ch4 Blue is the SW output.

2.5ma 3.3V draw, this oscillation happens every 120uS

Here
The efficiency of the IC seems to fairly far off the datasheet too, something like 70% at higher load and 50% on the lower end. I imagine this the a good indication of what is going on causing that.
If you need anything else let me know.

0 colin WIERKS 8 months ago in reply to Colin Chen

Prodigy 10 points

Hi Colin, can you help further?

0 Colin Chen 7 months ago in reply to colin WIERKS

TI__Mastermind 21161 points

Hi Colin,

Sorry, i cannot download your files in above link.

Could you send it by email？

colin-chen@ti.com

Thanks

0 colin WIERKS 7 months ago in reply to Colin Chen

Prodigy 10 points

Hi Colin, I have sent an email on January 20th have received no response.

0 Colin Chen 7 months ago in reply to colin WIERKS

TI__Mastermind 21161 points

Hi Colin,

Sorry for late response due to CNY holiday.

I saw the email you sent. It is normal switching behavior of PFM mode at light load.

There is nothing need to concern,

Thanks,

Colin

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TPS629210-Q1: XTPS629210QDRLRQ1 3.3V Flucuations