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Dangerous Prototypes

Dangerous Prototypes => Bus Pirate Development => Topic started by: jdesbonnet on December 12, 2011, 07:32:42 pm

Title: 400mV p-p ripple (6.667kHz) on my BusPirate v3b 3.3V line
Post by: jdesbonnet on December 12, 2011, 07:32:42 pm
I notice that the 3.3V line of my BusPirate (v3b from purchased from SeeedStudio) is rather noisy with a 400mV peak-to-peak ripple with frequency 6.6667kHz (150µs period). 5V line is clean. Is that normal? It seems a bit excessive.
Title: Re: 400mV p-p ripple (6.667kHz) on my BusPirate v3b 3.3V lin
Post by: sqkybeaver on December 12, 2011, 08:16:20 pm
that is definitely excessive, look for missing/burnt caps.
Title: Re: 400mV p-p ripple (6.667kHz) on my BusPirate v3b 3.3V lin
Post by: jlvern on November 18, 2012, 02:04:52 am
I have the same problem (400mV p-p, 10kHz, v3.6 purchased from SeeedStudio). I think that the regulator is not really very stable :-(
Title: Re: 400mV p-p ripple (6.667kHz) on my BusPirate v3b 3.3V lin
Post by: tayken on November 18, 2012, 09:05:16 am
[quote author="jlvern"]I have the same problem (400mV p-p, 10kHz, v3.6 purchased from SeeedStudio). I think that the regulator is not really very stable :-([/quote]
Just for the heck of it, can you check out the soldering of the caps near the resistor? There may be a problem with one of the joints.
Title: Re: 400mV p-p ripple (6.667kHz) on my BusPirate v3b 3.3V lin
Post by: jlvern on November 18, 2012, 01:13:45 pm
Thanks... No... The problem is not the joints.
I try with another output capacitor (X7R 10uF), and now the oscillation is 3.4kHz. I try to put an input capacitor (10uF X7R) directly on the regulators pins : no effect...

Well, no problem, I remove the  Grrr/!§% Torex regulator and I put a good TPS79933 TI regulator (same pinout)
and now, all is OK with this good (fast and low noise) regulator !
Title: Re: 400mV p-p ripple (6.667kHz) on my BusPirate v3b 3.3V lin
Post by: ian on December 05, 2012, 08:30:15 am
Thanks for the update and investigation, I added this to the tracker and will source a different part or change caps on the next batch.
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