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Visitor zhangxixi
Visitor
701 Views
Registered: ‎07-23-2018

ZCU102 SFP+ connector power measurement

Is there any method that I can evaluate the power consumption of the SFP+ connector?

 

Thanks,

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8 Replies
Xilinx Employee
Xilinx Employee
683 Views
Registered: ‎08-25-2010

回复: ZCU102 SFP+ connector power measurement

Hi @zhangxixi,

 

You can monitor/estimate the current of 0X1A by the Maxim PowerTool when one or two of SFP+ is enable/disable using RT_TX_DISABLE.

 

 

Thanks
Simon
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Visitor zhangxixi
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Registered: ‎07-23-2018

回复: ZCU102 SFP+ connector power measurement

Hi @simon,

 

Thank you for your info.

You mean enable RT_TX and then disable it, to get the current difference, right?

Voltage is a constant, then I can get the power of it.

 

For the tool "Maximum Power Tool", is XPE the correct one?

 

Thank you. 

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676 Views
Registered: ‎01-08-2012

Re: ZCU102 SFP+ connector power measurement

There are multiple methods.

 

Referring to UG1182, we see (in figure 3-26) that the SFP socket is powered from the UTIL_3V3 supply rail.  That rail comes from a Maxim DC/DC controller that supports PMBus commands that (I believe) include the ability to read back output current.  However, (see figure 3-44) the UTIL_3V3 rail supplies more than just the SFP socket, meaning you would need to somehow measure the current with the SFP unplugged, measure the current with the SFP plugged in, then subtract.

 

Referring to UG1182, we see (in figure 3-26) that the SFP socket is powered from the UTIL_3V3 supply rail via some inductors.  You could use a multimeter to measure the DC resistance of those inductors (with the power off), then measure the voltage drop (with the power on) across the inductors and calculate the current (and hence the power) from that.

 

The SFP socket has an I2C interface to allow software to interrogate registers inside the SFP module.  These registers are defined in SFF-8472.  SFP modules don't actually measure their supply current or power consumption, but they do advertise a "power class" which describes the maximum power they will (supposedly) draw in the steady state.  From SFF-8431, these are:

Power Level I modules -  Up to 1.0W

Power Level II modules -  Up to 1.5W

Power Level III modules -  Up to 2.0W

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Xilinx Employee
Xilinx Employee
673 Views
Registered: ‎08-25-2010

回复: ZCU102 SFP+ connector power measurement

Hi @zhangxixi,

 

Yes, correct.

Thanks
Simon
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Visitor zhangxixi
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Registered: ‎07-23-2018

回复: ZCU102 SFP+ connector power measurement

@simon

 

Thank you!

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Visitor zhangxixi
Visitor
660 Views
Registered: ‎07-23-2018

Re: ZCU102 SFP+ connector power measurement

@allanherriman

 

Thank you very much!

It looks like SFP+ has an upper bound of power consumption. It is good for me.

I will definitely try the first two methods.

 

Thanks,

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649 Views
Registered: ‎01-08-2012

Re: ZCU102 SFP+ connector power measurement

If you try the "voltage drop across the inductor" method, the accuracy will be limited by the resistance measurement.  As the resistance will be quite low (I guess at about 10mohm, which is less than the resistance of multimeter leads), try to use a four-terminal resistance measurement which will be available on a desktop (rather than a handheld) multimeter.

 

Also, the inductor will use wire made of copper, which has a poor temperature coefficient of resistance.  I suggest measuring the resistance both before and after measuring the voltage drop to avoid errors due to temperature changes.

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Xilinx Employee
Xilinx Employee
648 Views
Registered: ‎08-25-2010

回复: ZCU102 SFP+ connector power measurement

Hi @zhangxixi,

 

Maxim power tool is not XPE, which is used to monitor current by PMBUS:

https://www.maximintegrated.com/en.html

Thanks
Simon
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