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Participant ipsbiz
Participant
7,097 Views
Registered: ‎12-16-2008

XC9500/XL driving a XR-2203 (related to this topic)

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I recently solved most of my too hot problem (still more than a bit warm....http://forums.xilinx.com/t5/CPLDs/Update-Solved-fairly-certain-XC9500-XL-driving-a-XR-2203-similar/td-p/400199) and could use more info on this.

 

My specific question: Assuming the XC9536 has not been damaged due to emf from relays (driven by XR-2203) on the same 5V line, is there any reason why the XC9536 would get so warm? The XR-2203 requires only ~1.5 mA per channel when activated, so I wouldn't think it was an overdrive issue for the XC9536.

 

Could the problem be related to unprogrammed cells for the XC9536? I don't use much of the XC9536 logic (50% macrocells, 31% function block and 17% registers....nearly 90% I/O, tho). Could it be I need to explicitly "disable" any/all unused blocks or I/O to reduce current draw or eliminate "spurious" oscillations/logic transitions?

 

 Should I go to an XC9536XL w/tristate outputs pulled to +5V for the XR-2203?

 

  Thanks in advance for the help......

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Participant ipsbiz
Participant
8,276 Views
Registered: ‎12-16-2008

Re: XC9500/XL driving a XR-2203 (related to this topic)

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I appreciate the suggestions. Setting low power mode is something I plan to do once I know I have the devices as close as possible to operational "prefection". Setting the unused pins to PGND is not something I have done (nor realized that was a viable option). Will look at that, as well.

 

More specifically to my problem....I went back and discovered I did indeed have a solder short to ground on an output pin. My circuit was working (and, thus I never realized the problem) because I had not yet implemented (externally) that part of the design. Once I corrected the problem, the heat issue seemed to disappear.

 

Thanks again for the help.

 

  Cheers....

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Xilinx Employee
Xilinx Employee
7,090 Views
Registered: ‎08-01-2012

Re: XC9500/XL driving a XR-2203 (related to this topic)

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There are several resons for the XC9536 would get so warm. Few of them are below

 

  • The junction temperature is proportional to power consumption. The power consumption is depends upon design
  • There could some problems like two ooutput signals short
  • There could be some problem in supply rails  etc
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Participant ipsbiz
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7,032 Views
Registered: ‎12-16-2008

Re: XC9500/XL driving a XR-2203 (related to this topic)

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Apologies for so long getting back (priority shift refocused me for the last couple of weeks :( So, to get back to this.... I have checked the +5V (specifically a 5-Volt only design) and they are well within tolerance and there does not appear to be much noise. As for the short suggestion, I use ~ 80% of the I/O and have checked it once (will go back and do it again, especially the unused lines, just because I can). If I had any shorts in the active lines, my circuit wouldn't work at all. In this specific CPLD, the only "clocking" going on is addr and RD/WR lines gen'd by the CPU. There is no oscillation circuit connected to it or any circuits using feedback. Pretty basic and straightforward. It's all address select and latches for setting conditions. The only clocking coming into the device is to a 1/4 selector which then goes to output, but none of that has been connected up yet. Is there something I need to/can do within the CPLD design to prevent excessive power draw (assuming I don't find an external circuit problem. What other things can I look at? You didn't mention it specifically (maybe in the original thread which seems o have been deleted/archived), but based on specs, I can't see any reason why the XC9536 can't drive the XR2203/ULN2003 directly. Or, is there? Thanks in advance.....
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Observer dpollum238
Observer
6,986 Views
Registered: ‎04-11-2008

Re: XC9500/XL driving a XR-2203 (related to this topic)

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Regarding excess power draw - Floating/unconnected inputs can cause to chip to use more power because the input stage can see Lo, Hi, and analog levels that are between valid logic levels.  A floating input could oscillate.  Unused inputs should be tied to GND; or pulled up, via a resistor, to VDD(i.e. 5v), as appropriate.  You can also try putting all unused blocks into low-power mode.  It also wouldn't hurt to connect all unused pins to GND, by setting those pins to "PGND".

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Participant ipsbiz
Participant
8,277 Views
Registered: ‎12-16-2008

Re: XC9500/XL driving a XR-2203 (related to this topic)

Jump to solution

I appreciate the suggestions. Setting low power mode is something I plan to do once I know I have the devices as close as possible to operational "prefection". Setting the unused pins to PGND is not something I have done (nor realized that was a viable option). Will look at that, as well.

 

More specifically to my problem....I went back and discovered I did indeed have a solder short to ground on an output pin. My circuit was working (and, thus I never realized the problem) because I had not yet implemented (externally) that part of the design. Once I corrected the problem, the heat issue seemed to disappear.

 

Thanks again for the help.

 

  Cheers....

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