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An Issue about Selecting one of ADS131xxx ADC family

Memet Dolatshahi
Prodigy 115 points
Other Parts Discussed in Thread: ADS131A02

hi

I'm already using Analog Devices AD7606 and AD7770 ADCs for smart grid IEDs application.

I looked to the TI cross references and found that the ADS131xxx family is proper substitution for Analog Devices ADCs. but I have some questions about ADS131 specifications!!!

I want to connect sensors directly to ADC input and I need High Impedance input in ADC, the ADS131e0x series have Input Impedance in range of Megaohm but ADS131a0x series have Input Impedance in Range of 100k to 200kohm based on Sampling Frequency! so If I want to choose for example ADS131a02, I have to use an amplifier for driving ADC inputs for connecting CT or PT or Shunt or Resistor Divider for measuring phase Current and Voltage application or not?

Also these ADCs have Simultaneously sampling feature so Do I need an extra clock for sample and Hold or when give an external conversion start clock the ADC do it by self?

  • 0
    TI__Mastermind 38745 points
    Hello Memet,

    Great questions!

    The ADS131A0x inputs are connected directly to the sample and hold circuitry so the inputs will not be high impedance. If you require true high impedance, you will need a buffer in the front end.

    The ADS131A0xs will simultaneously sample with the clock that is provided. Each channel on an ADS131A0x will always sample simultaneously automatically. If multiple are daisy-chained, there just need to be a few simple hardware connections for all the devices to sample at the same time. More details about daisy-chaining can be found in the datasheet.

    Regards,
    Brian Pisani