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Request ADC(32CH x 1EA or 16ch X 2EA or 8ch X 4EA)

Inho Jeon
Expert 1452 points
Other Parts Discussed in Thread: ADS7953, ADS112U04, ADS122U04, ADS7961

I am looking for a multi-channel analog to digital converter (ADC).
Approximate specifications are as follows.

- 32 analog inputs per set: 32ch X 1EA or 16ch x 2EA or 8Ch X 4EA to be configured (need to check which configuration is better for MC)
- Analog input range up to 5V or 3.3V
- Digital output is I/O level 3.3V, I/F is UART or I2C method.
- Purpose: Expansion purpose due to insufficient number of ADC input channels of MCU.

Please recommend an ADC that satisfies the above specifications.

  • 0
    TI__Guru**** 177081 points

    Hi Inho,

    If you can manage with an SPI interface, I would recommend that you take a look at the ADS7953 family of devices.  There are 16, 12, 8 and 4 channel options that are all pin compatible.  This would allow you to expand your channel count without the need to change your hardware.  If UART or I2C are the only options you have for communication with the ADC, the ADS112U04 and ADS122U04 both have a UART interface with 4 input channels.  We have 4 and 8 channel I2C options as well in SAR and Delta-Sigma architectures - you can find a list of products here:

    https://www.ti.com/data-converters/adc-circuit/products.html#p1028=4;32&p1918=I2C;UART&sort=p1918;desc

  • 0 in reply to Tom Hendrick
    Expert 1452 points

    Dear Tom,

    Thank you for reply.

    I have questions about ADS7961.

    Below this block diagram, looks like ADC Inputs mixed.  Are ADC inputs working independent? (Because I'd like to work in the ADC inputs simultaneously.)

    And, Is it need to 'high impedance PGA' and 'REF5025' for working ADS7961?

    I'd like to apply 5Volt range input ADC level.

    But on below this electrical characteristics marked red square, that is range about 3Volt. 

    I confused about this range of ADC level for ADS7961.

    How can I do for use 5V input ADC level for ADS7961.    

  • 0 in reply to Inho Jeon
    TI__Guru**** 177081 points

    Hi Inho,

    The ADS7961 has a 16-CH multiplexor, it does not simultaneously sample the inputs.  The need for a buffer (assuming the signals at the 16 input channels are similar) between MUXO and AINP is going to depend pretty much on the nature of the signal chain ahead of the ADC as well as the speed at which you plan to run the device.  Section 9.1.1 in the datasheet gives a good description of the sampling behavior and sections 9.2.1 and 9.2.2 go into detail on how and when the signal should be buffered.  Those sections also describe the '2xVREF' operating mode which allows you to use a 5V power supply and achieve a 0-5V input range on this family of ADC's.

  • 0 in reply to Tom Hendrick
    Expert 1452 points

    Dear Tom 

    You mean ADS7961 does not simultaneously sample the inputs, is that right?

    Please recommand  part ADC inputs working independent.

  • 0 in reply to Inho Jeon
    TI__Guru**** 177081 points

    That is correct Inho, there is only one sample/hold circuit in the ADS7961.  It cannot simultaneously sample the inputs.