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AFE4403 in Common Anode Configuration has Huge Leakage Current

Ming Liao
Intellectual 450 points
Other Parts Discussed in Thread: AFE4403

Hello Praveen,

 

Here is the connection for AFE4403 as Figure 52 and 53 of the spec:

  1. 3 LEDs are in common anode configuration.

  2. The 3 LEDs’ anodes connect to 5.0V.

  3. Both LED_DRV_SUP and TX_CTRL_SUP connect to 3.0V

 

However, there is an huge leakage current of more than 15mA from TXP/TXN to LED_DRV_SUP/TX_CTRL_SUP (3.0V) and force the 3.0V to be higher. After cutting off the PCB traces of TXP/TXN, the leakage is gone. The date code of the AFE4403 is 48AXZDI.

 

In this formal project, we have met this leakage issue, but in our evaluation board, the connection (except LED_DRV_SUP and TX_CTRL_SUP to 3.3V) is no problem. Please comment.

 

Thanks.

Ming

  • 0
    TI__Mastermind 49956 points

    Hello Ming,

    In the common anode configuration, LED_DRV_SUP supply can be the same supply that the anodes of the LEDs are tied to. In case there is some reason to tie the LEDs to a different supply, then care should be taken to ensure that the
    LED external supply is within 0.3V of the LED_DRV_SUP. This is to prevent the ESD diodes inside the AFE from turning on
    during the OFF state of the LEDs. The reason for the huge leakage current could be the ESD diodes turning on.

  • 0 in reply to Praveen Aroul
    Intellectual 450 points
    Hi Praveen,
    In the common anode configuration, can the anodes of TXP and TXN (the 2 diodes forward voltage: 2.0V), LED_DRV_SUP and TX_CTRL_SUP connect to 3.0V, and the anode of TX3 to 5.0V (the forward voltage: 4.0V)? Or do all anodes, LED_DRV_SUP and TX_CTRL_SUP have to connect to 5.0V due to the higher forwrd voltage of TX3 diode?

    Thanks.
    Ming
  • 0 in reply to Ming Liao
    TI__Mastermind 49956 points
    Ming,

    Connect all LED anodes, LED_DRV_SUP and TX_CTRL_SUP to 5V.