DP83848K: DP83848K

gorden tsai

Prodigy 210 points

Part Number: DP83848K

HI Sir:

As below schematic ,If Transformer center tap let it NC ,What will affect the function?

Thanks

Gorden

over 6 years ago

0 Rob Rodrigues over 6 years ago

TI__Mastermind 19780 points

Hi Gorden,

The center taps need to be pulled up or unknown affects will be found.

The EMI/EMC emissions could be very high. Immunity could be very low by not keeping the centertap at a known potential.

There may also be issues of voltage drop for the magnetics that could affect the receiver of the device.

Best Regards,

0 gorden tsai over 6 years ago in reply to Rob Rodrigues

Prodigy 210 points

HI Rob:

Thanks Quick Reply.

The other question as below:

1.As below Block diagram Fig1 ,The DP83848 +3.3V with transformer center taps +3.3V_IO was come from different power source .

Power sequence is +3.3V_IO ahead +3.3V 24.2ms (Fig 2),My question : Does it possible damage PHY ,If Yes Why ?

Thanks

Gorden

Fig1:

Fig 2:

0 Rob Rodrigues over 6 years ago in reply to gorden tsai

TI__Mastermind 19780 points

Hi Gordon,

It will possibly damage the PHY because you are applying a high voltage to the TD/RD pins when AVDD = 0V.

The abs max of the DP83848 device is VCC + 0.5V. In this case VCC = 0, and 3.3V is applied to TD/RD.

The ESD diodes protecting TD/RD will be biased and turned on. They will degrade over time. The DP83848 will also be backpowered during this event.

Best Regards,