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ADS5296A: VCM drive

Zeev Gerber
Intellectual 500 points
Part Number: ADS5296A
Other Parts Discussed in Thread: THS4541,

Hi,

I have design with ADS5296A drive by 8 units of THS4541.

The feedback resistor of the THS4541 is 402 ohm per DS recommendation. (around 2.5 ma per amplifier for VCM drive)

The VCM drive of the ADC is 5 ma which couldn't drive 8 unit of the amplifier.

Pls. recommend who to drive the VCM.

Do I need to use precision op-amp with high drive of more then 20 ma?

Regardes

zeev gerber

  • 0
    TI__Expert 6790 points

    Hi Zeev,

    Yes you are right, the VCM pin can source a maximum of 5 mA current at 0.95V to generate the common mode for the driver amplifiers and it would not be able to drive 8 THS4541 devices. 

    You would require a buffer after the VCM pin to support the drivers.

    Please allow me some time to check internally about the specifications for the buffer driver. I will get back to you with part recommendation on it in 2-3 days. You can also reach out to our amplifier team for a product recommendation.

    Thanks & regards,

    Abhishek

  • 0 in reply to Abhishek Vishwa1
    TI__Expert 6790 points

    Hi Zeev,

    The VCM output of the device is basically a dc with range 0.95 +/- 0.05V hence any opamp such as OPA201 or similar shall work in this application. 

    You will have to use an opamp to drive THS4541 cm pin.

    Thanks & regards,
    Abhishek