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ADS8675: shortest setup time

Renan Santos Adriano
Genius 16530 points
Part Number: ADS8675

Hello Team,

My Customer intends to use the ADS8675 to measure 210 different analog channels through a multiplexer. The input range would need are +-10.24V, +-5.12V, +-2.56V. The channel measuring sequence requires measurement randomly change in-between the above 3 ranges for each MUX setting. It is a bit unclear how fast the PGA gain setting can be changed to a new setting with the build in 15 KHz antialiasing filter.

What are the shortest setup time in-between each measurement for the PGA setup and the assonated ADC conversion needed in order to achieve:
14bit precision?
13bit precision?
12bit precision?

Regards,

Renan

  • 0
    TI__Mastermind 35550 points

    Hi Renan,

    We do not have a settling time data for PGA on this ADC, however the key impact to the sampling rate is dominated by the internal 15kHz LPF when more signals are switched on external multiplexers. this is equivalent to a time constant of T=10.6us. For 14-bit settling -> 9.7T, so 103us is required for signals to settle. I would say a conversion time of 110 us per channel can be achieved, this is equivalent to around 9ksps conversion rate per channel of ADC. If you are using a 8-ch multiplexer, that will be ~1ksps per actual signal channel. Note that a delay on the multiplexer and any other components including amplifiers should be considered and you have to check their specifications.

    Best regards,

    Dale