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ADS8664: RST pin , easy to be disturbed

Yue TANG
Expert 8485 points
Part Number: ADS8664
Other Parts Discussed in Thread: ADS8864,

Hi experts,

My customer was evaluating ADS8664 and found ADS8864 is easy to reset 。 could you please check their design and help to comment how to improve this ?

thanks.

  • 0
    TI__Mastermind 35550 points

    Hello Yue Tang,

    Is the pin2 (/RST/PD) only connected to GND_AD via R263 and C285? was there any interference signal observed on this pin 2?

    Thanks&regards

    Dale

  • 0 in reply to Dale Li
    TI__Expert 8485 points

    Dale,

    They also use a MCU Io to control the RST of ADS8664. but they don't think it was caused by MCU. This happened in their end customer and  the input range changed. for example, they set to +-10V at the beginning , but after running for a period of time， it changed back to default 0-5V. If MCU reset, it should set the ADC parameters back. 

    They think  the RST timing of  ADS8664 is too short according to the datasheet, only 400ns,  and they also tried to increase the RC value, but can't be completely avoided. 

    They wonder if there is a SW approach to increase the RST timing or mechanism to avoid this happen[MCU not reset, but ADC doest]

  • 0 in reply to Yue TANG
    TI__Mastermind 35550 points

    Hello Yue Tang,

    Since a logic low state on the /RST/PD pin is required to implement a reset, so this pin should be connected to logic high (DVDD), a good example is shown on the EVM board. Hence, R263 is suggested to connect to DVDD instead of GND_AD. Also, extend the low pulse time longer than 400ns for expected reset if it is possible to change.

    Best regards,

    Dale