DP83822I: Absolute MAX current on MDC input pin / Any issue on MDC pin with external pull-up?

Hi Hattori,

We do not recommend adding any kind of pull-up to the MDC line, only MDIO needs a 2.2 kOhm pull-up. 

Regards,

Alvaro

Hi, Alvaro-san,

Could you please let us know whether my understanding is correct under the MDC pin's behavior?   Please advise us.

According to power-up behavior, MDC pin is pull-down during RESET.  After RESET is de-asserted, MDC pin moves No pull-down pin (Removing pull-down function).

Thanks and best regards,
M.HATTORI.

Hi Hattori,

MDC is an input pin to the PHY, where the clock is provided by the MAC. You are correct that when the PHY is in reset, MDC is a pull down.

Could you help me understand your concern?

Regards,

Alvaro

Hi,

Processor requires External Pull-up.  So before processor starts clock output, MDC line remains 1.56V.    I understand this is not good situation for DP83822.  But do you think any issues are occurred?   Please let us know your comments again.

Thanks and best regards,
M.HATTORI.

Hi Hattori,

So the processor requires a Pull up, but once the clock starts producing the MDC it should be okay for the PHY. Have you been able to read/write to the PHY? If you're able to read/write registers then all is well.

Regards,

Alvaro