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Contributor
Contributor
1,241 Views
Registered: ‎03-16-2012

Ultrascale+ MPSOC PS GTR during power down

Hello

 

According to the Ultrascale+ MPSOC datasheet (DS925):

 

Table 56. PS-GTR Transceiver DC Specifications

 

VIN Single-ended input voltage. Voltage measured at the pin referenced to GND.

Min. 75mV

Max. VPS_MGTRAVCC

 

I want to have an Ethernet PHY connected to one of the PS GTR transceivers via SGMII. The SGMII will be AC coupled. I will be supporting Wake-On-Lan with this Ethernet PHY so there will be a scenario where the Ethernet PHY will be powered up but the Ultrascale+ MPSOC will be powered down (the Ethernet PHY supports detection of the WOL Magic Packet).

 

My question is as follows:

Does the Max specification above relate to DC coupled signals or AC coupled signals? In other words, if the SGMII interface is AC coupled, will it be OK that the Ethernet PHY is transmitting to the MPSOC PS GTR but VPS_MGTRAVCC will be 0V?

 

If not OK, then I have found high speed serial switch devices which can be used to isolate the MPSOC PS GTR from the Ethernet PHY while it is powered down. This will add cost and consume space so I thought I would just check whether AC coupling will provide sufficient isolation?

 

Thank you

 

 

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Scholar austin
Scholar
1,210 Views
Registered: ‎02-27-2008

Re: Ultrascale+ MPSOC PS GTR during power down

DC, or AC:

 

Generally a bad idea to drive any signals, AC coupled or not, into a device that is powered down.

 

Seems to me, it is not allowed by the specification.  VPS_MGTRAVCC = 0 when powered down, so 75 mV is the limit.

Austin Lesea
Principal Engineer
Xilinx San Jose
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