Topic: VADJ mismatch between FMC126(2.5V required) and VC707(output 1.8V)  (Read 7994 times)

peiyk June 27, 2014, 12:28 AM

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Dear,
[size=0pt]On the developement board VC707, XC7VX485T-2FFG1761 has no 2.5V HR I/O or 3.3V HR I/O, instead, it has only 1.8V HR I/Os.[/size]
[size=0pt]VADJ and the level of VCCO is 1.8V at the most on board VC707, which can cause a problem when FMC126 mounting on the FMC1 interface of board VC707. [/size]
[size=0pt]There is only one bank of XC7VX485T-2FFG1761 powered by FMC1_VIO_B_M2C, which is strangely supplied by FMC126.[/size]
[size=0pt] In theory, FMC1_VIO_B_M2C should be 1.8V, but unfortunately, it is only 1.67V, which can not reach the minimum requirement of 1.71V.[/size]
[size=0pt]Maybe the input(VADJ from VC707) to the LDO  in FMC126 is just 1.8V [/size] [/size][size=0pt], so the output cannot be up to 1.8V. And in ML605, the VADJ is 2.5V, the [/size][/size]FMC_VIO_B_M2C is 1.8V and everything is OK.
[/size][size=0pt] As a result, FMC126 can not transmit data to XC7VX485T-2FFG1761, and we can not get A/D data using chipscope. [/size]
In a word, FMC126 requires that the VADJ form VC707 is 2.5V, but VC707 just outputs 1.8V.[/font]
[size=0pt]Why does this happen? Please do me a favor and give me a solution.[/size]

arnaudNL June 27, 2014, 06:44 AM (#1)

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Dear Sir,


You need a new FMC126 to be used on VC707. The newer FMC12xs are supporting VAdj down to 1.3V.


The boards you are trying to use were shipped in January 2011 at a time VC707 was not even existing.


The only solution is to purchase new boards or to stick with ML605.


Best Regards,
Arnaud

peiyk June 29, 2014, 11:22 PM (#2)

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I am so sorry that I don't have too much time. Physically, Could you give me a solution, such as using wires to give another power supply to FMC1_VIO_B_M2C(1.8V)

arnaudNL June 30, 2014, 05:52 AM (#3)

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Dear Sir,


I am sorry but I don't have any solution to get your 4 years old board on a last year's carrier board.


Use ML605 or purchase a FMC126 r2 hardware.


Best Regards,
Arnaud

arnaudNL July 02, 2014, 07:35 AM (#4)

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This topic is being closed because the issue is considered as resolved by 4DSP. Feel free to create a new topic for any further inquiries.