cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 
frbeck
Visitor
Visitor
521 Views
Registered: ‎12-08-2020

Temperature sensing diode pin location

Hi

Can you tell me where the temperature sensing diode pins (DXP_0 and DXN_0) are located on Xylinx ZYNC chip ( XC7020) on the CLG400 package?

Is the temperature measured at the pins (where the chip connects to the board) or at the junction inside the chip? I know the relative location is in the center, but I want to know where it is measured locally.

 

Thanks!

 

 

 

 

 

 
 

 

0 Kudos
5 Replies
drjohnsmith
Teacher
Teacher
507 Views
Registered: ‎07-09-2009

As I understand it , the diode is just formed as part of the silicon

   its not a separate item

  silicon I understand is a good conductor of heat , and high power chips tend to have a heat spreader which further equaliseds the heat 

      so the diode is a measure of the silicon temperature,

 

 

<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>
derekm_
Voyager
Voyager
487 Views
Registered: ‎01-16-2019

Like @drjohnsmith said, the temperature sensing element is almost certainly part of the silicon, usually just a substrate PNP transistor in CMOS technology. It's unlikely to be a diode (i.e. PN junction), as, contrary to common belief, diodes aren't a great temperature sensor (too many inaccuracies).  Instead it's usually a diode-connected PNP or NPN transistor, which eliminates a lot of the inaccuracies of a simple PN junction.

So unless someone from Xilinx tells you differently, assume that it's part of the silicon, and not related in any way to the pins. I believe the pins are just there so you can use a more accurate external temperature sensor IC if you want. Xilinx specs for the internal XADC temperature sensor are +/- 6 degrees over -55 to +125, which isn't great. You might get better than +/- 1 degree with an external IC.

frbeck
Visitor
Visitor
382 Views
Registered: ‎12-08-2020

Thanks! 

Do you know if there is anyway to measure the junction temperature of the ZYNC?

 

0 Kudos
derekm_
Voyager
Voyager
377 Views
Registered: ‎01-16-2019

Yes, you can just use the XADC which is part of all Zynq devices. One of the fixed ADC inputs is the temperature sensing element. You can either develop a software application using the xadcps_vX_X drivers without implementing any logic on the FPGA (although the PL section must be powered up, as far as I know), or you can implement the LogicCORE AXI XADC IP block and use the sysmon_vX_X drivers in your software app (my favourite method). You can even view the temperature in the hardware manager in Vivado.

0 Kudos
drjohnsmith
Teacher
Teacher
362 Views
Registered: ‎07-09-2009

As above,

i do not think the Zynq ha sits own diode, 

The zynq is just part of the silicon I think

    so the diode you menton is the sensor to use,

 

 I also think, though some one more knowledgeable on details will be able to say

    but the external diode and the internal diode used to measure temperature are either co located or are even the same ,

 

<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>
0 Kudos