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Please help me with simultaneous sampling on AD7616, AD7367,AD7864-1

Question asked by Mihai on Feb 14, 2018
Latest reply on Feb 20, 2018 by Mihai

Hello Analog Devices Gurus,

 

I have an old control design consisting of three AD7864-1 and one microcontroller on parallel bus.

The AD7864-1 are sharing the same conversion start pin and they are triggered in the same time.

The old board is produced at around 2000 pices per year. Input signals frequency is 50 Hz range +/-10V.

I need to come up with new design and I want to select another ADC chip. Potentially selected candidates AD7367 or AD7616

 

The critical thing is the requirement that groups of three phase signals should be sampled at the same time with no phase error between them. The conversion time and data read time from all the mentioned ADC chips is acceptable in my application.

 

And here are my questions.

According to AD7864-1 datasheet on CNVST (conversion start transition) all the 4 analog inputs are sampled at the same time and after that the internal multiplexer switches and the ADC converts one by one the 4-channel sequence.  This means that all the channels are sampled in the same time, converted at different moments.

Is this correct?

 

Something similar I’ve found in the datasheet of AD7367 (it has 4channels and 2 ADC multiplexed) and SPI interface.

In theory if I have three AD7367 chips sharing one CNVST signal all 12 channels could be sampled in the same time?

 

I would like to use the AD7616 because it has 16 channels and I will need only one chip.

The only thing it has only two ADC and can simultaneously sample only 2 channels? But here according to the datasheet and the application note AN-1409 the use of bust mode combined with sequencer can achieve pseudosimultaneous sampling with marginal phase error between the channels. For this I need to configure the sequencer to go up from channel 0 to 7 and then down to 0 and it will need 15 samples. The busy signal will stay longer active comparing to the above cases but I can tolerate the extra time.

Then the phase error calculated in the AN-1409 will be achieved.

 Is this correct?

 

And the final question.

Can you tell me how long is the product life cycle of those ADC chips?

AD 7616 is recommended for new designs

AD7864-1 and AD7367 are in production (until when ?)

Thank you in advance and sorry for the long poetry  

 

Kind Regards,

 

Mihai.

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