W
Winfield Hill
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?
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?
