Considering AD7606B but need more PGA ranges (down to +-20mV)

Hi Steve,

Is you input range fixed at +/-20mV, or should it cover from a variety of input ranges, including +/-20mV?

For the AD7606B, I do not have a recommended (tested) front-end amplifier as of today, but we can help review your signal chain design. For the AD7771, it has gains up to 8, that would allow you to get closer to the +/-Vref input range. However, note they are at different level of performance (16b SAR vs 24b SD), not sure what the requirements are.

Regards,

Lluis.

Hi Steve,

Is you input range fixed at +/-20mV, or should it cover from a variety of input ranges, including +/-20mV?

For the AD7606B, I do not have a recommended (tested) front-end amplifier as of today, but we can help review your signal chain design. For the AD7771, it has gains up to 8, that would allow you to get closer to the +/-Vref input range. However, note they are at different level of performance (16b SAR vs 24b SD), not sure what the requirements are.

Regards,

Lluis.

Hi Lluis, thank you for your reply.

Our current system uses multiple SD ADS1672 ADCs with our own AFE. We only use the top 16 bits and only sample at 40ksps (!).

I am looking to save cost by moving to a multi-channel ADC with simplified AFE. I want to make incremental improvements in sampling rates and resolution - where practicable (i.e. nice to haves). I do like the oversampling capability of the AD7606B and can push the anti-alias filter from 20kHz to 160kHz or so and I'll sample at 640kHz.

I am investigating the use of PGA280 as an AFE - does Analog have an equivalent that could help me build a 10V to 10mV system?

Steve 

Hi Steve,

How about  ADA4254? Although I haven´t looked your signal chain to know if that would match with AD7606B inputs. I´d suggest looking at the model we have on AD7606B´s product page. You can learn its frequency response, configure front end RC filter, and learn how it works in general: oversampling performance, interface, calibration, CRC, etc.

https://www.analog.com/media/en/engineering-tools/design-tools/AD7606X-Software-Model-2-0-1.zip

Regards,

Lluis.

Thanks Lluis - I downloaded and ran the AD7606B software model the other week - it really helps with understanding and comparing functionality. Great tool!

I have ordered the AD7606B Eval Board so will see how it looks. 

I'll take a look at the AD4254 too.

Thanks,

Steve

Hi Lluis - I like the performance of the AD4254 so I've ordered that eval kit too.

I already have an AD7768 eval and an AD9542 eval so I should have enough to hook the whole lot up.

Steve

Hello Liuis,

I'm getting to know the ADA4254 - this is a nice device that solves a lot of problems for me. I had it hooked up to the AD7768 eval today and got some very good results.

However, my challenge will be synchronising the AD7768 to sample at multiples of 40kHz.

I know I can clock the AD7606B at 640kHz and oversample as required down to 40ksps.

However, I do need to level-shift and amplify the differential output of the ADA4254 to a single-ended signal to suit the AD7606B, along with some simple anti-aliasing.

What Op Amp would you recommend to drive the AD7606B? I have +-15V available.

Thanks, Steve

One more question, if I'm clocking the AD7606B at 640kHz, what frequency should I clock the ADS4254 at?

Steve 

Hi Steve, for the ADA4254 questions, would you mind posting the question on Instrumentation amplifier community as there you may reach better point of info. Sorry about that.

For the AD7606B question, there is no recommended amplifier now, would you rather it supported differential ranges, like the AD7609 (older generation)?

Regards,

Lluis.

Hi Lluis - something like an AD7609B that I can clock at 640kHz, oversample to yield 40ksps or 80ksps and has a fast serial interface would be perfect. 

Steve