SD Card, miniSD Card, hot swap. 50k card detect, power switch..
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From: Winfield Hill on 31 Mar 2010 13:04 With respect to SD Cards and miniSD Cards, as described in the engineering documents at the SD Association's website, http://www.sdcard.org/developers/tech/sd_apps/ and the OEM Product Manual, Version 2.2, June, 2007. Document No. 80-36-00497 These cards have 50k pullup resistor on pin 1, which they suggest you use for card detect, see page 24. But they also suggest a MOSFET power switch, with a delayed turn-on, page 26. This is a hot swap issue, since when the SD card is unpowered, you can't check the 50k pullup to see if a card has been plugged in. "Most card connectors have a card detect switch that signals the SD host when the card is inserted. After the host is aware of the card insertion, it turns on the FET switch to apply power to card's VDD pin. Once the card is inserted and all card pins are making contact, there is a delay before the FET switch is turned on." I see there are up to three physical switches. Hmm, then what's the 50k pullup for? -- Thanks, - Win |