DP83849C: DP83849C transformer TCT RCT pin

Frank Lee96

Part Number: DP83849C

Hi TI,

I'm using DP83849C,the circuit on the datasheet,the TCT and RCT pins are pulled up to 3.3V,BUT in some other network transformer circuit,the TCT and RCT pins are pulled down to ground by capacitor.

I want to know the real reason or theory basis why some chose to pull down when some chose to pull up?

Best regard,

Frank

over 5 years ago

0 Rob Rodrigues over 5 years ago

TI__Mastermind 19780 points

Hi Frank,

The difference is the architecture of the line driver. If the CT's are pulled to ground, and there are no termination resistors, then it is likely a voltage mode line driver.

The DP83848 has a current mode line driver, and as such, needs external resistors and pull-ups.

Compare the CML and VML sections of this app note: www.ti.com/.../slla120.pdf

Best Regards,

Interface

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DP83849C: DP83849C transformer TCT RCT pin