• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 47 subscribers
  • Views 1319 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS8688 - the method of data output(using Manual Channel n Select) and reset command

Hirotaka Matsumoto
Guru 27525 points
Other Parts Discussed in Thread: ADS8688, SN74CB3T1G125

HI all,

Would you mind if we ask ADS8688?

<Question1>
Please refer to attachment file.
0525.20141112_ADS8688_data output.pdf

<Question2>
About reset command(Reset program registers(8500h)),
is there the prohabition command of reset command(8500h)?
If the corruption of serial data(SDI) occurs, we guess that it is possible to protect  mis - operating reset. 

Could you let know us above?

Kind regards,

Hirotaka Matsumoto

  • 0
    Guru 27525 points

    Hi team,

    We guess that your days are so busy, but could you let know us?

    We need your help.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Intellectual 1130 points

    Hi Hirotaka-san

    We apologize for the delay in response to this query.

    I would like to take this discussion in details with you outside the forum. Can you please provide me an email ID where I can contact you with regards to all your querries?

    Thanks

    Vinay 

  • 0 in reply to Vinay Agarwal
    Prodigy 20 points
    Hi Vinay,

    I am also facing same problem. ADS8688 internal program registers get reset to default values after few minutes.

    at power up ADC settings are initialized for input range 0 to 1.25xVref (0- 1.25x2.5) . this is the only program register is modified from default value.In Manual channel selection mode it works fine for few minutes after that it sets to default range (± 2.5x2.5(Vref)).
    SPI clk = 16 MHz.

    received sample are verified with applied voltages at analog channel. when it remains in set input range.

    please let us know your comments.

    Thanks
    Malik
  • 0 in reply to Malik
    TI__Mastermind 35570 points

    Hi Malik,

    ADS8688 doesn't have a command to disable the software reset command(8500h). There are two solutions which could be used:

    1.  Make your circuit and system robust by improving pcb layout or other ways on system level, No interference signal coupled into SDI.

    2.  Suggest to use Auto sequencing mode to select the channels you expect, after configuring ADC,  the SDI signal can be switched out and disabled, for example, SN74CB3T1G125 which is a Single Channel Low-Voltage Bus Switch with disable function can be used to achieve this function shown in the blockdiagram as below.

    When want to change ADC's configuration, the SDI can be enabled again by enabling SN74CB3T1G125. The pull-down resistor on SDI can make sure the command data is 0x0 gotten by ADC (Continue operation in previous mode) after disable SDI.

    By the way, ADS8688's reference voltage is 4.096V, not 2.5V. Thanks.

    Thanks.

    Regards

    Dale

  • 0 in reply to Dale Li
    Prodigy 20 points
    Thanks Dale,

    Auto sequence mode may not serve our purpose. we need to select channel in sequence like
    ch0-->ch1-->ch0-->ch2--> ch0-->ch3-->ch0-->ch3--> ch0-->ch4-->ch0-->ch5--> ch0-->ch6-->ch0-->ch7--> ch0-> ......
    I will try first option .

    I am using external Vref (2.5 V) .

    Thanks and regards
    Malik.
  • 0 in reply to Malik
    TI__Mastermind 35570 points

    Hi Malik,

    You can't use 2.5V extternal reference, the voltage reference can be accepted by ADS8688 is 4.096V (4.046~4.146V range) shown in No. 10 page of datasheet.

    Regards

    Dale