Datasheet

- 23 -
datasheet SD Card
Rev. 1.0
MMBTFxxGWBCA-xMExx
5.5 Electrical Interface
The following sections provide valuable information about the electrical interface. See Chapter 6 of the SDA Physical Layer Specifica-
tion, Version 3.00 for more detail information.
5.5.1 Power Up
The power-up of the SD/microSD Card bus is handled locally in each SD Card and in the host
Figure 5-11. Power-up Diagram
Supply voltage
Host supply voltage
Power up time
Supply ramp up time
Initialization sequence
ACMD
41
ACMD
41
ACMD
41
CMD2CMD0 CMD8
N
CC
N
CC
N
CC
Optional repetitons of ACMD41
until no cards are responding
with busy bit set
Time out value for
initialization process = 1Sec
End of first ACMD41 to card ready
time
Initialization delay:
The maximum of
1 msec, 74 clock cycles
and supply ramp up time
V
DD
min
V
DD
max
Valid voltage range for
all commands
.• Power up time is defined as voltage rising time from 0 volt to VDD(min.) and depends on application parameters such as the maximum number of
SD Cards, the bus length and the characteristic of the power supply unit.
• Supply ramp up time provides the time that the power is built up to the operating level (the host supply voltage) and the time to wait until the SD card
can accept the first command,
• The host shall supply power to the card so that the voltage is reached to VDD(min.) within 250ms and start to supply at least 74 SD clocks to the
SD card with keeping CMD line to high. In case of SPI mode, CS shall be held to high during 74 clock cycles.
• After power up (including hot insertion, i.e. inserting a card when the bus is operating) the SD Card enters the idle state. In case of SD host, CMD0 is
not necessary. In case of SPI host, CMD0 shall be the first command to send the card to SPI mode.
• CMD8 is newly added in the Physical Layer Specification Version 2.00 to support multiple voltage ranges and used to check whether the card supports
supplied voltage. The version 2.00 host shall issue CMD8 and verify voltage before card initialization. The host that does not support CMD8 shall supply
high voltage range.
• ACMD41 is a synchronization command used to negotiate the operation voltage range and to poll the cards until they are out of their power-up
sequence. In case the host system connects multiple cards, the host shall check that all cards satisfy the supplied voltage. Otherwise, the host should
select one of the cards and initialize.