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ADS5263 External VCM

NAOKI AOYAMA
Guru 11215 points
Other Parts Discussed in Thread: ADS5263

Hello,

My customer uses the ADS5263 with external reference mode.

He try to input zero V to VCM, but it is remain 0.3V-0.4V at analog input pin of ADS5263.

What is the cause of this effect?

Is it an output characteristics of internal REF Amp?

He wants to zero V output at analog input pin when an OpAmp the front of ADS5263 is shutdown.

Regards,

Naoki Aoyama

  • 0
    TI__Mastermind 49176 points

    Hello Naoki,

    Can you check with the customer if the register bits shown in Table 8 of the ADS5263 datasheet is set to enable the external reference mode?

    As per the datasheet the voltage applied on VCM must be 1.5V +/- 50mV. If this spec is violated, proper operation of the device cannot be guaranteed.

    Can you find out if internal clamp mode (Reg 0x09 <EN_CLAMP> bit) is enabled? With internal clamp mode, the voltages on INP and INM pins are VCM + 0.3V and VCM - 0.3V respectively. With no input signal applied and VCM = 0V, I am suspecting if the ctm is noticing the 0.3V clamp voltage on the input pins.

      

    Regards

    Praveen.

  • 0 in reply to Praveen Aroul
    Guru 11215 points

    Hi Praveen,

    Thank you for your very fast reply.

    My customer's configuration is external reference mode correctly, apply VCM 1.5V at normal

    operation.

    But I forget check internal clamp mode.

    I will confirm customer's configuration.

    Thanks.

    Naoki Aoyama

  • 0 in reply to Praveen Aroul
    Guru 11215 points

    Hi Praveen,

    I have checked customer's configuration about clamp mode register.

    He uses the ADS5263 with 16bit mode. The clamp works only for the 14bit mode.

    So there is no problem.

    Regards,

    Naoki Aoyama