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ADS124S08: I made the board as designed, but it is not work.

Hidetoshi Takagi
Prodigy 20 points
Part Number: ADS124S08

I use ADS124S now.
I check various things
With the IC mounted.
Is the resistance value between DVDD-GND and IO VDD-GND low?
Some have a few hundred Ω.

  • 0
    TI__Guru** 113765 points

    Hello Hidetoshi,

    The off state of the device pins are not measured for a specific Ohmic value in device validation, so I can't tell you what to expect.  It appears as though you are attempting to troubleshoot your board.  Can you send me your schematic and gerber files for your board?

    Sometimes there can be solder shorts around various pins.  This is especially true if the QFN package version of the ADS124S08 is being used. 

    Can you tell me what specifically you see is not working?  One method of checking the device internal startup and operation is to hold the START pin high and monitor the DRDY pin with an oscilloscope.  You should see a pulse on this pin approximately every 50ms.  If you see this pulse, then verify that all your communication to the ADS124S08 meets the SPI timing diagram as shown in the datasheet.  CS must be held low throughout the entire communication transaction and must not toggle between bytes.  Also, SCLK must dwell low and data should change on the rising edge of SCLK and hold steady on the falling edge.

    If you do not see the DRDY toggling, then make sure that RESET is pulled high (not floating), the CLK pin is tied low, and that all supplies (IOVDD, DVDD, and AVDD/AVSS) are operating at nominal voltages.  If any supply is missing the ADS124S08 is held in a reset condition.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 20 points

    Hello Bob
    Thank you for your advice.

    I check the board pattern many times to make sure there are no shorts.
    In addition,
    although I made some of sheets, there are some that work and some that do not work,
    and those that do not work have low resistance values.
    By lowering the resistance value here
    It is known that the overall circuit voltage will drop.

    There are two types of conditions, good and bad.
    I'm wondering
    There are more bad things.

  • 0 in reply to Hidetoshi Takagi
    TI__Guru** 113765 points

    Hello Hidetoshi,

    At this point there is not much more information I can give you.  This would appear to be a board issue when installing the devices.

    • Which package are you using?
    • Are you hand soldering the devices or using a reflow oven?

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 20 points

    Hello Bob,

    ・I used to TQFP-32 package.
    ・After mounting by hand, soldering is done by reflow.

    Best regards
    Hidetoshi

  • 0 in reply to Hidetoshi Takagi
    TI__Guru** 113765 points

    Hello Hidetoshi,

    At this point it is difficult to say what may have happened.  It would be helpful to see a schematic.  One possible issue is connecting/disconnecting a power source to the ADS124S08 with the source turned on.  Another possible issue is having the ADS124S08 unpowered while connected to a powered microcontroller.  Verify that you are not destroying devices by accidently exceeding any of the Absolute Maximum Ratings as specified in the ADS124S08 datasheet.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 20 points

    Hello Bob

    There is a situation that the resistance value drops when the power is not turned on after mounting.
    Will heat or static electricity cause such a condition?

    Best regards,
    Hidetoshi

  • 0 in reply to Hidetoshi Takagi
    TI__Guru** 113765 points

    Hello Hidetoshi,

    As I said in my original post, measuring the pin to pin resistance is not a good method of determining if the part has been damaged.  In fact, it is possible, depending on the Ohmmeter you are using, that the meter itself can damage the device by over driving the pins beyond the absolute maximum ratings.  Also, you will see different results based on the placement and direction of the leads.

    Ways that the device can be damaged include ESD by improper handling of the device (see section 7.2 of the datasheet).  Also, if the heat applied to the device is outside of the reflow profile.  Additional information can be found here.

    Best regards,

    Bob B