SanDisk SD Card

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Revision 2.2Chapter 3 – SD Card Interface DescriptionSD Card Product Manual3.3.1 Power ProtectionSame as in SD Card Bus Mode.3.4 Electrical InterfaceThe following sections provide valuable information about the electrical interface.3.4.1 Power UpThe power-up of the SD Card bus is handled locally, in each SD Card and in the busmaster.Figure 3-5 Power-up DiagramSupply VoltageLogic working levelV DDmaxBus master supply voltageV DDminValid voltagerange forcommands CMD0,15, 55, andACMD41Valid voltagerange for allother commandsand memoryaccessPower-upTimeSupply Ramp-upTimetimeTimeout value for initialization process = 1 secondInitializationSequenceACMD41N CC ACMD N CC ACMD N CC4141CMD2Initialization delay:the max. of 1 ms,74 clock cyclesand supply rampuptimeOptional repetitions of ACMD1 until nocards respond with busy bit setAfter power up, including hot insertion (i.e., inserting a card when the bus is operating) theSD Card enters the idle state. During this state the SD Card ignores all bus transactionsuntil ACMD41 is received (ACMD command type shall always precede with CMD55).ACMD41 is a special synchronization command used to negotiate the operation voltagerange and to poll the cards until they are out of their power-up sequence. Besides theoperation voltage profile of the cards, the response to ACMD41 contains a busy flag,indicating that the card is still working on its power-up procedure and is not ready foridentification. This bit informs the host that the card is not ready. The host has to wait (andcontinue to poll the cards, each one on his turn) until this bit is cleared. The maximumperiod of power up procedure of single card shall not exceed one second.Getting individual cards, and the entire SD Card system, out of idle state is up to theresponsibility of the bus master. Since the power up time and the supply ramp up timedepend on application parameters such as the maximum number of SD Card s, the buslength and the power supply unit, the host must ensure that the power is built up to theoperating level (the same level which will be specified in ACMD41) before ACMD41 istransmitted.© 2004 SanDisk Corporation 3-6 12/08/04
Revision 2.2Chapter 3 – SD Card Interface DescriptionSD Card Product ManualAfter power up, the host starts the clock and sends the initializing sequence on the CMDline. This sequence is a contiguous stream of logical ‘1’s. The sequence length is themaximum of 1msec, 74 clocks or the supply-ramp-up-time; the additional 10 clocks (overthe 64 clocks after what the card should be ready for communication) is provided toeliminate power-up synchronization problems.Every bus master shall have the capability to implement ACMD41 and CMD1. CMD1 willbe used to ask MultiMediaCards to send their operation conditions. In any case theACMD41 or the CMD1 shall be send separately to each card accessing it through its ownCMD line.3.4.2 Bus Operating ConditionsSPI Mode bus operating conditions are identical to SD Card mode bus operatingconditions. Table 3-4 lists the power supply voltages. The CS (chip select) signal timing isidentical to the input signal timing (see Figure 3-8).Table 3-4Bus Operating Conditions SummaryParameter Symbol Min Max Unit RemarkGeneralPeak voltage on all lines --- -0.3 V DD + 0.3 VAll InputsInput Leakage Current --- -10 10 uAAll OutputsOutput Leakage Current --- -10 10 uAPower Supply Voltage 7Supply Voltage V DD 2.0 3.6 V CMD0, 15, 55,ACMD41 commandsV DD 2.7 3.6 V Except CMD0, 15, 55,ACMD41 commandsSupply voltage differentials(V SS1 , V SS2 )--- -0.3 0.3 VPower-up Time --- --- 250 mS From 0 V to V DD min.3.4.3 Bus Signal Line LoadThe total capacitance, C L , of the clock line in the SD Card bus is the sum of the bus-mastercapacitance (C HOST ), the bus capacitance (C BUS ) itself and the capacitance (C CARD ) of eachcard connected to this line:C L = C HOST + C BUS + N*C CARDWhere N is the number of connected cards. Requiring the sum of the host and buscapacitances not to exceed 30 pF for up to 10 cards, and 40 pF for up to 30 cards, thevalues in Table 3-4 must not be exceeded.7 The current consumption of any card during the power-up procedure must not exceed 10 mA.© 2004 SanDisk Corporation 3-7 12/08/04
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