U3741BM Datasheet, PDF (12/25 Pages) ATMEL Corporation – UHF ASK RECEIVER IC

U3741BM
Clock Bitcheck
counter
Dem_out
DATA
TXClk
t _ee
Figure 16. Synchronization of the demodulator output
Dem_out
DATA
Enable IC
Lim_min <= CV_Lim < Lim_max
t _ee
tmin1
CV_Lim < Lim_min or CV_Lim >= Lim_max
t _ee
tmin2
Figure 17. Debouncing of the demodulator output
Bitcheck
Dem_out
DATA
Sleep – Mode
Bitcheck – Mode
Receiving mode
tmin2
t _{DATA_L_max}
Figure 18. Steady L state limited DATA output pattern after transmission
After the end of a data transmission the receiver remains
active and random noise pulses appear at Pin DATA. The
edge-to-edge time period t_ee of the majority of these noise
pulses is equal or slightly higher than T_{DATA_min}.
Switching the Receiver Back to Sleep Mode
The receiver can be set back to polling mode via Pin
DATA or via Pin ENABLE.
When using Pin DATA, this pin must be pulled to Low for
the period t1 by the connected µC. Figure 19 illustrates
the timing of the OFF command (see also figure 23). The
minimum value of t1 depends on BR_Range. The
maximum value for t1 is not limited but it is
recommended not to exceed the specified value to
prevent erasing the reset marker. This item is explained
in more detail in the chapter ‘Configuration of the
Receiver’. Setting the receiver to sleep mode via DATA
is achieved by programming bit 1 of the OPMODE
register to be ‘1’. Only one sync pulse (t3) is issued.
The duration of the OFF command is determined by the
sum of t1, t2 and t10. After the OFF command initially the
sleep time T_Sleep elapses. Note that the capacitive load at
Pin DATA is limited. The resulting time constant t
together with an optional extenal pull-up resistor may not
be exceeded to ensure proper operation.
If the receiver is set to polling mode via Pin ENABLE, a
‘L’ pulse (T_Doze) must be issued at that pin. Figure 20
illustrates the timing of that command. After the positive
edge of this pulse the sleep time T_Sleep elapses. The
receiver remains in sleep mode as long as ENABLE is
held to ‘L’. If the receiver is polled exclusively by a µC,
T_Sleep can be programmed to 0 to enable a instantaneous
response time. This command is the faster option than via
Pin DATA at the cost of an additional connection to the
µC.
12 (25)
Preliminary Information
Rev. A1, 15-Oct-98