usb mass storage ref design: sd card standby mode -

usb mass storage ref design: sd card standby mode

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Author	Topic: usb mass storage ref design: sd card standby mode
jcastillo New Member	posted August 25, 2010 10:33 AM When a read/write is performed on the sd card, a pulse of current is used. Afterwards, the sd card goes into a "standby" state where it pulls minimal current. Does anyone know if the sd card does this automatically or if the firmware sends it a command? IP: Logged
Tsuneo Member	posted August 25, 2010 10:52 PM Both on SD bus and SPI bus, no bus clock drops the SD card into energy-saving mode. Tsuneo IP: Logged
jcastillo New Member	posted August 26, 2010 08:38 AM Thanks for the reply. How long after bus clk stops does the sd card wait before going into standby mode? Is there a link you can provide? IP: Logged
Tsuneo Member	posted August 26, 2010 10:03 AM Nowadays, major SD card manufacturers don't open the datasheets of their SD card to web. Ask to each SD card manufacturer. Here is an excerpt from San Disk SanDisk SD Card Product Manual (ProductManualSDCardv2.2final.pdf) 1.10 Automatic Sleep Mode A unique feature of the SanDisk SD Card is automatic entrance and exit from sleep mode. Upon completion of an operation, the card enters the sleep mode to conserve power if no further commands are received in less than five milliseconds (ms). The host does not have to take any action for this to occur. However, in order to achieve the lowest sleep current, the host needs to shut down its clock to the card. In most systems, the SD card is in sleep mode except when the host is accessing it, thus conserving power. When the host is ready to access the card in sleep mode, any command issued to it will cause it to exit sleep, and respond. 2.4 Typical Card Power Requirements Sleep: 250 uA Max Read: 65 mA Max Write: 75 mA Max 2.5 System Performance Sleep to Ready: 1 ms (typ), 2 ms (max) Tsuneo [This message has been edited by Tsuneo (edited August 26, 2010).] IP: Logged
jcastillo New Member	posted August 26, 2010 10:25 AM Thanks for the response. Greatly appreciated! IP: Logged

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