ADS1258 driving PGA281

Norman Pellet

Other Parts Discussed in Thread: PGA281, ADS1258, THS4521, TLV1704

Hello,

I'd like to use the ADS1258 and place a PGA281 between the MUX and the converter inputs. This way I can have the (great!) autoscan feature with a common gain for all channels (which I'm ok with).

So I have two questions:

Do I need to add a low-pass filter after the PGA and use THS4521 to buffer the signal just before the A/D ? Or a low-pass filter directly fed into the A/D is ok ?

Also, I'd like to use the PGA GPIO to drive the PGA gain. Problem is, on the ADS, the DGND is at 0V, DVDD is 3.3V and on the PGA, VSON is at -2.5V and DVDD is at 2.5V. So I need to make some kind of level shifting. Is there any easy way to do this ?

Thanks in advance !

Norman

over 9 years ago

0 Christopher Hall over 9 years ago

TI__Mastermind 44760 points

Hi Norman,

The PGA281 ought to be able to drive the ADC inputs without needing to use an additional THS4521 buffer. You should be okay just using the PGA281 and low-pass filter, so long as the R and C values are small (I would recommend R < 25 Ohms and C < 500 pF).

For the level-shifter, you could use a quad-comparator (such as the TLV1704), like so:

Best Regards,
Chris

0 Norman Pellet over 9 years ago in reply to Christopher Hall

Prodigy 110 points

Hey Chris,

Sorry for the delay. The answer is perfect, thanks ! That's what I'm doing now.

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ADS1258 driving PGA281