Atmel ATA5283 - Manual (Page 6)

6
4598H–AUTO–03/07
ATA5283
Figure 3-5. Turn Off Delay Time (t
off
) versus Antenna Q-Factor
3.5 Data Output
The data output N_DATA outputs the demodulated and digitized LF signal according to the
envelope of the antenna input signal. In the standby mode the N_DATA output is disabled and
set to level 1. It is enabled by the wake-up signal and it outputs 1 level if the IC detects the car-
rier signal and a 0 level during the gaps (see
Figure 3-1 on page 3 ).
As the circuit does not check the received data (except the preamble), it is up to the user to
choose the kind of encoding (pulse distance, Manchester, bi-phase...) wanted.
3.6 Wake-up Signal
The wake-up signal (N_WAKEUP) indicates that the ATA5283 has detected the end of a pream-
ble signal and has left the standby mode. It can be used as a wake-up or a chip select signal for
an external device (see
Figure 3-1 on page 3 ).
After a preamble is detected the first valid gap (Start Gap) sets the N_WAKEUP output to low
and enables the data output N_DATA. The N_WAKEUP holds the low level until the IC is reset
to the standby mode by a reset signal.
3.7 Reset
The IC is reset either by the internal POR circuit during a power on sequence or by a high pulse
at the RESET pin. After the reset all internal counters are in the initial state and the IC is in the
standby listen mode.
The POR circuit generates a reset while the supply voltage V
DD
is below the power on reset
threshold V
POR
and release the function of the IC if V
DD
exceeds this threshold.
A high signal at the RESET pin resets the complete circuit. If the IC is activated a reset signal is
necessary to activate the standby listen mode.
The RESET pin can also be used to hold the IC in a power down state. In this state the IC is out
of operation and the current consumption is below the standby current.
Note: The RESET pin is high impedance CMOS input. To avoid floating effects like undefined input
states and malfunctions it should not be open.
0 50 40 30 20 10
Q-factor
180
100
60
80
0
20
40
160
120
140
200
max.
min.
typ.
t off
(µs)
f
field
= 125 kHz