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Parallel sampling adc

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Mosaic

Well-Known Member
Hi all:
I have an app which requires monitoring of about 4 adc channels simultaneously is there an i2c device that can talk to a PIC that does this that anyone can recommend?

thx
 
How simultaneously, how fast and how many bits?

Depending on the answer, you could use 4 (external) sample and hold circuits and the pics ADC channels.

Edit, remember, even a slow pic can sample in 50uS.

Mike.
 
That's interesting Pommie.
I like that idea..
I have about 250uS to get the 4 bytes.
What do u suggest for the sample and hold? Would a schottky driving a cap (.1uf) from an opamp be ok? If I place a 1k ohm series resistor between the PIC pin and the cap I can cycle the pin as a digital low after the adc sample to ensure the next capture reflects the true OPA drive less the diode drop? I can have 4 OPA with 4 S&H then.

Hmm, hoping to run from a 3.6V cell...now I need to find low voltage, low current OPA....any suggestions on that front? SOIC preferably.
 
I would suggest something like a 4066 or 4016 driving smaller capacitors. The internal caps in a pic are around 10pF and therefore don't need a big cap to charge them. The size of the caps depend on how fast your signals are changing. I wouldn't use the pic to discharge them and would simply allow the analogue switches to charge/discharge as needed. Most of the newer pics will sample in 20uS and so you can have 100uS of on time for the sample and hold and still have plenty of time.

Mike.
 
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