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AD74412R 在CURRENT INPUT EXTERNALLY POWERED模式下adc值异常

ad74412r的其他模式下,工作正常,adc值读取符合预期。

但是在CURRENT INPUT EXTERNALLY POWERED模式下adc值异常,当外接电源输出1-4ma时(即ad74412r输入电流为1-4ma时),读取的adc值的范围0x300至0xcb00。

当然后增大电流时,adc又从0x1000上升到0xcb00范围。

输入电流:2ma adc code:0x3a92
输入电流:3ma adc code:0x72c0
输入电流:4ma adc code:0xa8ba
输入电流:4ma adc code:0xa955
输入电流:5ma adc code:0xcf2b
输入电流:5ma adc code:0xcf2b
输入电流:6ma adc code:0xf546
输入电流:7ma adc code:0x6557
输入电流:8ma adc code:0x33c5
输入电流:9ma adc code:0x30ad
输入电流:10ma adc code:0x2cec
输入电流:11ma adc code:0x1e21

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  • Hi,

    would it be possible to know more about your setup? 

    What is exactly is connected as current input at this channel? What is the value of the ADC_CONFIGx register for the channel you are using in this setup?  

    Regards,

    Arnost


  •                                                                             I/OP_x and I/ON_x voltage     Rsense voltage
    input current 1ma, adc code:6753 (decimalism)            0.9v                                  0.1v
    input current 2ma, adc code:20161
    input current 3ma, adc code:44071
    input current 4ma, adc code:54154
    input current 4.5ma, adc code:59038
    input current 5ma, adc code:60497                               1.44v                              0.5v
    input current 6ma, adc code:12454
    input current 7ma, adc code:9995
    input current 8ma, adc code:5737
    input current 9ma, adc code:126
    input current 10ma, adc code:0                                        2.3v                              1v
    input current 11ma, adc code:0                                         2.47                            1.1v
    input current 12ma, adc code:1251
    input current 13ma, adc code:34076
    input current 14ma, adc code:36696
    input current 15ma, adc code:39315
    input current 16ma, adc code:41937
    input current 17ma, adc code:44568
    input current 18ma, adc code:47189
    input current 19ma, adc code:49812
    input current 20ma, adc code:52434                            4v                                       2v

    The voltages of terminals I/OP_x and I/ON_x increase monotonically.
    The voltage across the sampling resistor also increases monotonically.
    The voltage of the sampling resistor is as expected

  • Hi,

    thank you for the clarification concerning the setup.

    Can you please confirm, that the data indicated above are read directly from the ADC_RESULTx register (Address: 0x26 to 0x29 - depending on the used channel). 

    Regards,

    Arnost

  • I'm sure I'm reading the value of the corresponding channel at register addresses 0x26 to 0x29.

  • Hi,

    are you using your own board or EVAL-AD74412R board? 

    # Would it be possible to check the following board voltages: AVDD, AVSS, REFIN, REFOUT, ALDO1V8, ALDO5V, DVCC, IOVDD.

    Please provide measured voltages. 

    # Could you please provide data from the following procedure:

    1. Reset the part

    2. Clear Alert Status register (Address: 0x2E, Reset: 0x8000, Name: ALERT_STATUS)

    3. Configure part as needed (CH_FUNC_SETUPx, ADC_CONFIGx)

    4. Read ADC measurements 

    5. Read alert status again  (Address: 0x2E, Reset: 0x8000, Name: ALERT_STATUS)

    And provide ADC measurements, including the value of the ALERT_STATUS register. 

    Regards,

    Arnost

  • thank you very much!

    Haven't dealt with this for a long time.

    According to your hint, I got the CHARGE_PUMP_ERR error. Then check the schematic and find that AVSS is directly grounded. Now that the AVSS is cut off from the ground, the situation has improved.

    now  0x2E,ALERT_STATUS is 0.

    The measured value is now linear in this mode, but the calculated value is much smaller according to the formula 2500*adc/(65535*100).

    input:4ma    get:2.4ma

    input:8ma    get:5ma

    input:12ma    get:6ma

    input:16ma    get:10ma

    input:20ma    get:12ma

    DVSS=5.13V

    AVSS=-4.39V,In the chip manual AVSS = NEGATIVE DVCC.

    Excuse me, is this caused by the AVSS not being connected to the capacitor?

     

Reply
  • thank you very much!

    Haven't dealt with this for a long time.

    According to your hint, I got the CHARGE_PUMP_ERR error. Then check the schematic and find that AVSS is directly grounded. Now that the AVSS is cut off from the ground, the situation has improved.

    now  0x2E,ALERT_STATUS is 0.

    The measured value is now linear in this mode, but the calculated value is much smaller according to the formula 2500*adc/(65535*100).

    input:4ma    get:2.4ma

    input:8ma    get:5ma

    input:12ma    get:6ma

    input:16ma    get:10ma

    input:20ma    get:12ma

    DVSS=5.13V

    AVSS=-4.39V,In the chip manual AVSS = NEGATIVE DVCC.

    Excuse me, is this caused by the AVSS not being connected to the capacitor?

     

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