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ADS8686S: Over range settings

ttd
Mastermind 8600 points
Part Number: ADS8686S

Dear Technical Support Team,

I'd like to use analog input with ±12V.

Q1) 

Both 0x08H and 0x0AH should be set same value for AIN_xA. Also both 0x09H and 0x0Bh should be set same value for AIN_xB.

Is it correct? 

I confirmed the ±12V input operation with these settings, however register map on datasheet doesn't describe the details of  "0x08H and 0x09H". 

If you have any information, could you share it?

 

Q2)

GUI shows 0x08H and 0x09H are reserve and read only. Is it correct?

When checking "Over Range", then "Both 0x08H and 0x0AH" and  "Both 0x09H and 0x0Bh" are changed automatically.

■Datasheet

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In software mode, an individual analog input range can be configured per channel. The device also supports a 20% overrange feature on all input channels in software mode. Program the D[7:0] bits from the 0x08H and 0x0AH registers to individually enable the overrange feature for channels AIN_xA. Program the same value in both registers. Program the D[7:0] bits from the 0x09H and 0x0Bh registers to individually enable the overrange feature for channels AIN_xB. Program the same value in both registers. See the 0x0AH and 0x0BH register details for the programmed register values. The programmed range of the selected channel is increased by 20%. For example, if channel AIN_0A is programmed for a ±10-V range with the overrange feature, the resultant input range is ±12 V.

-----------

Best Regards,

ttd

  • 0
    TI__Mastermind 45805 points

    Hi ttd,

    1. 0x08H and 0x09H should be removed from the description. 20% over range for AIN_xA channels are determined and enabled by 0x0A register and 0x04/0x05 registers. Also, 20% over range for AIN_xB channels are determined and enabled by 0x0B register and 0x06/0x07 registers.

    2. It's correct, 0x08/09 address are reserved.

    Regards,

    Dale

  • 0 in reply to Dale Li
    Mastermind 8600 points

    Hi Dale,

    In my board, just setting to 0x0A, 0x04 / 0x05 and 0x0B, 0x06 / 0x07 does not work ± 12V, but works ± 10V.
    When additional write the same value as 0x0A and 0x0B to 0x08H and 0x09H, it operate  ± 12V. I have confirmed that 0x04 and 0x05 are set correctly when writing and reading.
    Should the register be set like this? It seems the following datasheet description.

    I'm curious that the datasheet says to access registers that there is no information(reserved) on the register map.

    I would appreciate your cooperation in further investigation.

    -----

    Program the D[7:0] bits from the 0x08H and 0x0AH registers to individually enable the overrange feature for channels AIN_xA. Program the same value in both registers. Program the D[7:0] bits from the 0x09H and 0x0Bh registers to individually enable the overrange feature for channels AIN_xB. Program the same value in both registers. See the 0x0AH and 0x0BH register details for the programmed register values. 

    ----

    Best Regards,

    ttd

  • 0 in reply to ttd
    TI__Mastermind 45805 points

    Hi ttd,

    Thank you for your additional information. Let me check and I will get it back to you early next week.

    Best regards,

    Dale

  • 0 in reply to Dale Li
    TI__Mastermind 45805 points

    Hi ttd,

    I have confirmed that you have to write the content in 0x0AH and 0x0BH and also have to write the same information into register 0x08H and 0x09H to change the gain settings when you want to program Over-range (even if they are shown as read only in the GUI). I apologized for the confusion to you.

    Best regards,

    Dale

  • 0 in reply to Dale Li
    Mastermind 8600 points

    Hi Dale,

    Your answer says that the description in the datasheet is correct and matches my actual operation.
    It is very helpful to get the correct information promptly.

    I have only one request.
    These aren't  hidden registers, but an officially supported feature, so I'd like to add  0x08H and 0x09H (R / W) to the register map (7.6 Register Maps) to enable 20% overrange on the datasheet.
    Since the GUI is also reserved(R only).

    it is easier for user to understand if you modify them.

    Best Regards,

    ttd

  • +1 in reply to ttd
    TI__Mastermind 45805 points

    Hi ttd,

    Thanks for your feedback, we will see how we can make it clear when have a chance to update the datasheet in the future.

    Regards,

    Dale