TLK10232: RX differential Vp-p is over SPEC

Hi Yaser

You miss understanding customer's question.

The SFP+ module output spec is only 850mV maximum but they saw 1200~1500mV on TLK10232 input of their PCB as below block diagram.

customer want to know why? does TLK10232 has register for internal termination impedance setting?

Hi Yaser

1. Remove TLK10232 to measure HSRX Diff PAD of TLK10232 ,the Vpp is 1.5V

2. Remove TLK10232 and mount a 100ohm resistor between HSRX Diff PAD , the Vpp is 800mV

Have anything I need to do ?

Hi Malik

Trace impedance : Differential 100ohm

Trace length Diff+: 1179.26 mil

Trace length Diff- : 1179.25 mil

Maybe need your fully support to check this issue 

Hi Malik,

Sorry for late reply for the last 3 days are the public holidays in Taiwan.

The attachment is the related part of the schematic.

Please check it.

Regards,

Roger C.

ATEN Inc.

TLK10232_ckt_for_TI.pdf

Hi Malik,

Any idea?

Regards,

Roger C.

ATEN Inc.

Hi Malik,

Could you let us know your detail method and steps to measure the termination in your lab?

We will try to duplicate it in our lib.

Right now, we are trying to use the network analyzer to measure the trace impedance between SFP+ and TLK10232 (D1_XFI_RXIN_P / D1_XFI_RXIN_N)

to verify it with the impedance setting of our PCB layout rule.

Following is the related schematic and PCB layout rule, FYI.

Kai,

The test was very simple. I measured the DC resistance as seen across the RX diff pair using a multi-meter.

• Power up TLK10232EVM.
• Ensure receiver termination is enabled through HS_ENRX bit field. 
• Measure the RX termination with multi-meter via the on board SMA connectors. 

The method you are using right now is good to verify the trace impedance but be sure to try an measure the DC resistance at the RX diff pairs of TLK10232 when it is powered on and the HS_ENRX bit is high.

Hi Malik

Please kindly help to check my question ,May I know your idea?

1. Yes!! We follow your test step ,we can measure the 100ohm on HSRX pin ,but in this moment we use differential probe to measure the HSRX pin's waveform

the eye amplitude is 1300mVpp and over SFP+ spec (SPEC is 300~800mVpp) 

2. When we remove TLK10232 IC on our board and add a 100ohm on HSRX pin ,the amplitude is 796mVpp (meet SPF+ SPEC) ,

Kai,

Are you using a high impedance probe?  What are the termination settings on the scope that you are using? The first image seems to be affected by the loading caused by the probes and potential improper termination on the scope. What model of scope is being used in this test?