07-19-2018 06:29 AM
I have two issues:
1. We have used commercial grade part -4C in design, then on the temperature we are not seeing issue with the design.
However, when we have used -5C/4I part in the design and when we provides heat to the FPGA part then module is not working correctly.
We require -4I part in our design, however if this FPGA provides -5 part performance, logic written inside FGPA will not work correctly.
On the temperature, FPGA speed performance is not as per -4 part. In datasheet of Spartan 3A, Xilinx FPGA can provide guaranteed speed grade and temperature range performance if device is single marked.
We need 4ns performance on industrial grade to match our existing logic. We cant modify our working logic. Please suggest us solution.
We have selected part number XC3S400A-4FG400I or XC3S400A-4FGG400I in our design.
2. We have used CPLD XC95288XL-10TQG144I in our design from last 2-3 months. Earlier device was XC95288XL-10TQG144C commercial grade one. However, we are facing issues with both the devices which are manufactured after 2013. Before 2013 devices batch works well on same board. If we test 2013 onward CPLD devices same board starts malfunctioning. Board is failing when heat is applied on CPLD area.
Please suggest us solution.
07-19-2018 06:51 AM
In both cases, what is your slack? What is the actual junction temperature (as measured using the internal temperature sense diode)?
Likely either your designs either have zero slack (where jitter will cause data errors); or most likely, the junction temperature is beyond what is specified.
Last to check: are power supply voltages in specification (table 2, data sheet)?
07-19-2018 06:58 AM
If we use commercial grade CPLD component board passes all the test. IF we use industrial grade CPLD component then only we are seeing issue. Power supply voltage is as per specified limit. Ambient temperature is maximum 75 deg C for test.
07-19-2018 07:15 AM
Junction temperature is the required specification,
Ambient will affect junction, but is unspecified.
Any particular lot may be faster than specified (process variability) so it is likely some parts will work beyond their specified junction temperature. Only performance below max junction is guaranteed.
Very likely you are well beyond the junction max temp. You probably need fans and heatsinks.
07-19-2018 07:24 AM
How commercial grade is passing the test and not industrial grade one?
Ideally limit of junction temperature of commercial grade part is lower compare to industrial grade one.
07-19-2018 08:40 AM
In any lot of devices on a wafer, some may be faster, some slower. Fewer will be very fast, and a few very slow. The tester grades to speed needed to meet orders, speed grade as marked meets the grade, the device is likely faster, but never slower. So, an extremely fast part may be marked as slowest speed grade to meet the order for shipment.
"Fast enough" to meet the grade as marked. Thus, your 'slower' as marked devices are possibly the fastest possible silicon, and not slow at all.
So, the fact some parts work tells you nothing useful. Your junction temperature is out of specification. There is no guarantee a device will work. That some do, is due to luck, not design, not your skill.
07-20-2018 04:55 AM
We would like to know if there is any process variation happened by Xilinx.
If it is happened, whats the solution for us?
07-20-2018 06:58 AM
I do not understand your question.
Use the device within specifications, and operation is guaranteed. Start by staying within the junction temperature for the speed grade for your device.
Hopefully someone else provides you a helpful answer, I have done the best I can to explain what Xilinx guarantees, how they test and grade devices, and the natural cause of variation (it is intrinsic to any CMOS process from all foundries).
07-23-2018 12:47 AM
1. In the spartan 3A datasheet its written that Xilinx FPGA can provide guaranteed speed grade and temperature range performance if single marking is written on the device. On our device 5C/4I both marking has been mentioned and this is the case for FPGA. Please confirm how can we get guaranteed -4 performance of speed grade with this part. We need -4 part as per our design.
2. We have used CPLD of -10 speed grade with industrial grade part. However, if we use part manufactured after 2013 on the board then our boards are failing. If we use CPLD parts manufactured in 2012 or before then same boards are passing. We need to know whats the difference between these two parts. How can we resolve this issue?
08-15-2018 04:15 AM