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AFE4490: Abnormal TX_REF value

Shivani T
Prodigy 10 points
Part Number: AFE4490


Hello.

According to the datasheet, TX_REF value should be obtained as 0.75V, but the value obtained is 0V. The designed schematic is similar to the one provided in the development guide. The crystal oscillator output is obtained as 4MHz, VCM is obtained as 0.9V. Faint LED light glows but no reading is obtained.

Thank you.

  • 0
    TI__Intellectual 2030 points

    Hello Shivani,

    How are you measuring TX_REF? And are you providing a reset to the AFE4490 before measuring TX_REF?

    For troubleshooting, I would recommend:

    1) Ensure all of your AFE power supplies (RX_ANA_SUP, RX_DIG_SUP, TX_CTRL_SUP, LED_DRV_SUP) are providing the expected voltages as recommended by Section 10: Power-Supply Recommendations.

    2) Set RESETZ and AFE_PDNZ to a logic high, then measure the following:

    • TX_REF (pin #9, expecting 0.75V)
    • BG (pin #7, expecting 1V)
    • VCM (pin #4, expecting 0.9V)

    Let me know the results of this test.

    Regards,

    Payton

  • 0 in reply to Payton Schubel
    Prodigy 10 points

    Hello,

    Through an Oscilloscope with a voltage probe. Yes I provided a reset to the AFE before measuring TX_REF

    1) Yes, I verified all the AFE power supplies and they are providing expected voltages (5V and 3V)

    2) RESETZ and AFE_PDNZ are connected to MCU. When measured I am getting: 

    • TX_REF 0V
    • BG 0V
    • VCM 0.9V
  • 0 in reply to Shivani T
    TI__Intellectual 2030 points

    Hello Shivani,

    • Just to double check, have you verified all power supplies at the AFE pins themselves (or as close to the pins as possible)?
    • Is this behavior observed on all of your devices, or just a single device?
    • Can you measure the current draw on each power line to the AFE4490? If you have a functioning device, can you compare the current draws of this device to the functioning device?

    Regards,

    Payton