PCF7936AS/3851/C,1-CT NXP Semiconductors, PCF7936AS/3851/C,1-CT Datasheet - Page 24

• Manufacturer Part Number: PCF7936AS/3851/C,1-CT
• Description: pcf7936as series 32-bit 125 khz read / write security...
• Manufacturer: NXP Semiconductors

NXP Semiconductors
Security Transponder (HITAG2)
7.7 LF Field Power On Reset
When the transponder enters a LF field a rectifier circuitry
becomes operational and the internal transponder supply
voltage (V
exceeds the LF Field Power-On Reset threshold voltage
(V
initialization sequence, see Figure 23.
Subsequently, the transponder is muted and does not
respond to any command prior to termination of the
initialization sequence, t
depends on the basestation configuration, the resonance
circuit properties and the system coupling factor, however,
is small compared with the initialization time typically.
For proper device operation, after a LF Filed Power-On
Reset condition, command execution must commence
within the specified Idle time, t
Otherwise the device may stop command decoding,
disabling any communication with the device. In this case a
2010 May 04
Figure 23. LF field power on reset timing
Figure 24. LF field power on reset setup timing
THR
) the device performs a chip reset and starts its
DD
) develops. As soon as the supply voltage
V
THR
LF field applied
t
START
V
INIT
THR
. The startup time, t
IDLE
, see Figure 23.
LF field OFF
t
INIT
V
V
t
DD
RESET_SETUP
DD
LF field power on reset (POR)
threshold voltage
START
,
24
t
LF Field Power-On Reset has to be applied, in order to
reset and initialize the circuitry. Consequently, the device
would resume WAIT state. As indicated, the Idle time is
specified as the time interval following the initialization
sequence until the last bit of the Command Sequence that
is send to the transponder.
In case one of the Read Only modes is enabled, the device
enters READ ONLY state, if the first two bits of the
START_AUTH command are not being recognized within
the time-out period t
operation commences t
initialization sequence, t
to section 7.5.
In order to force a LF Field Power-On Reset and proper
device initialization at any time, the LF field OFF condition
must be applied for at least t
that the internal device supply voltage, V
the threshold voltage (V
WAIT,SA
t
WAIT,RO
t
LF field power on reset (POR)
threshold voltage
t
Command Sequence
IDLE
READ ONLY Mode
WAIT,SA
THR
INIT
WAIT,RO
), see Figure 24.
, see Figure 23. For details refer
RESET,SETUP
. In this case, Read Only
after termination of the
Product Specification
, in order to ensure
PCF7936AS
t
CONFIDENTIAL
DD
t
, drops below