LTC1755 Datasheet, PDF (10/12 Pages) Linear Technology – Smart Card Interface

LTC1755
APPLICATIONS INFORMATION
POWER OFF
IDLE
DEACTIVATION
PWR = 0V
PWR = DV_CC
ACTIVE
PWR = DV_CC
PRES ≠ NC/NO
NO
FAULT
FAULT
ALARM
DEACTIVATION
FAULT > 5µs
or
PRES ≠ NC/NO
FAULT
TIMEOUT
1755 F04
Figure 4. LTC1755 State Diagram
State Definitions
IDLE/DEACTIVATION
V_CC, RST, CLK, I/O AUX2, AUX1 = L
READY, ALARM, DATA, AUX2IN, AUX1IN = Z
CARD = PRES ⊕ NC/NO
Once the LTC1755 enters the Idle/Deactivation state the
deactivation sequence begins. The deactivation sequence
will continue until V_CC is discharged to approximately 1V.
An activation command (PWR = 0V) will only be acknowl-
edged once this occurs.
ALARM/DEACTIVATION
Same as Idle/Deactivation except:
ALARM = L
The only possible next state is Idle/Deactivation which is
achieved by disabling the LTC1755 via the PWR pin
(i.e., PWR = DV_CC).
The alarm indication can be cleared by rapidly cycling the
PWR pin. However, a new activation cycle will not begin
until V_CC is or has dropped below approximately 1V.
ACTIVE
V_CC = 3V or 5V (as determined by the 5V/3V pin)
RST = R_IN, CLK = C_IN
I/O, AUX2, AUX1, DATA, AUX2IN, AUX1IN = Ready for
data (after READY becomes low)
CARD = PRES ⊕ NC/NO
ALARM = H
FAULT TIMEOUT
Same as Active except:
The duration of a fault is being measured. If the fault
duration exceeds 5µs then the Alarm/Deactivation state
follows. If the fault duration is less than 5µs, then the
device is returned to the Active state.
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