DS8023
Smart Card Interface
14 ______________________________________________________________________________________
Smart Card Power Select
The DS8023 supports three smart card V
CC
voltages:
1.8V, 3V, and 5V. The power select is controlled by the
1_8V and 5V/3V signals as shown in Table 3. The 1_8V
signal has priority over 5V/3V. When 1_8V is asserted
high, 1.8V is applied to V
CC
when the smart card is
active. When 1_8V is deasserted, 5V/3V dictates V
CC
power range. V
CC
is 5V if 5V/3V is asserted to a logic-
high state, and V
CC
is 3V if 5V/3V is pulled to a
logic-low state. Care must be exercised when switching
from one V
CC
power selection to the other. If both 1_8V
and 5V/3V are high with CMDVCC high at the same
time, the DS8023 enters stop mode. To avoid acciden-
tal entry into stop mode, the state of 1_8V and 5V/3V
must not be changed simultaneously. A minimum delay
of 100ns should be observed between changing the
states of 1_8V and 5V/3V. See Figure 9 for the recom-
mended sequence of changing the V
CC
range.
