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dandvan
2 Posts |
 Posted - 08 May 2003 : 18:42:41
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| I've seen a lot of references to the PCMCIA spec, but have not been able to find a copy of it. Specifically, I'm looking for how much power is supposed to be provided by a PCMCIA slot...per the spec. It looks like the graphics master is only rated to 500 mA at 5V. |
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akidder
1519 Posts |
Posted - 09 May 2003 : 13:34:58
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The PCMCIA standard limits supply current to 500mA per pin, of which there are two on the PCMCIA socket. CompactFlash specification 1.4 limits current to 500mA per socket.
The Graphics Master power ratings are conservative and are primarily rated based on the power transistors we use. We've found that with the exception of a few very high current devices, 802.11, modem and storage cards work well in the Graphics Master, Graphics Client Plus, AGC and Bitsy. Our latest product releases (Bitsy Plus, BitsyX, etc) supply more current than in previous designs.
I've posted some PCMCIA/CF references at topic 947 if you are interested in reading further. I hope this information helps!
-Drew |
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dandvan
2 Posts |
Posted - 09 May 2003 : 16:57:36
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Then what you're saying is that the total power available from the regulator on the Graphics Master should be 1A at 5V? Because that is not what we're seeing in our preliminary tests. We have loaded down this supply (at pins 17 and 51) with a mere 400 mA and noticed a 250 mV drop to 4.75V. The Graphics master will not turn on with a 600 mA load...this falls far short of 1A.
We have also seen turn on problems with the RangeLan2 wireless lan adapter and the Ambicom WL1100B 802.11 card. Both look like power problems. Can you explain to me how the power gets from the 3.3 and 5V that we supply to the PCMCIA card? Do you guys re-regulate or simply go through some sort of FET switch to control power? |
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akidder
1519 Posts |
Posted - 13 May 2003 : 12:07:01
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Hi Dan. We use transistors to enable power to the PCMCIA and CF slot (that's one of the features that gives the sockets their hot-swappable functionality). As you noted in the Graphics Master specifications, we rate the socket at 500mA.
You might be seeing a voltage drop across the transistors, though I would also make sure that you're not losing power through the wiring on the main power supply. Try probing pin 3 of JP1--a good, on-board test point for 5V--to determine the level of the 5V power supply. If 5V is low there as well as on the PCMCIA slot, you might increase the input 5V supply to 5.3V. That would give you a greater margin for PCMCIA/CF devices that drain higher current.
If you are still having issues, please don't hesitate to give me a call at 301.490.4007, extension 122.
Cheers, Drew |
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Microsoft Windows CE
PCMCIA Spec? (power available)
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