RX5003 Datasheet, PDF (7/11 Pages) RF Monolithics, Inc – 303.825 MHz Hybrid Receiver

Peak Detector Timing
The Peak Detector attack time constant is set by the value of the ca-
pacitor at the PKDET pin. The attack time t_PKA = C_PKD/4167, where
t_PKA is in µs and C_PKD is in pF. The Peak Detector decay time con-
stant t_PKD = 1000*t_PKA.
Pulse Generator Timing
In the low data rate mode, the interval t_PRI between the falling edge
of an ON pulse to the first RF amplifier and the rising edge of the
next ON pulse to the first RF amplifier is set by a resistor R_PR be-
tween the PRATE pin and ground. The interval can be adjusted be-
tween 0.1 and 5 µs with a resistor in the range of 51 K to 2000 K.
The value of the R_PR is given by:
R_PR = 404* t_PRI + 10.5, where t_PRI is in µs, and R_PR is in kilohms
In the high data rate mode (selected at the PWIDTH pin) the re-
ceiver RF amplifiers operate at a nominal 50%-50% duty cycle. In
this case, the period t_PRC from the start of an ON pulse to the first
RF amplifier to the start of the next ON pulse to the first RF amplifier
is controlled by the PRATE resistor over a range of 0.1 to 1.1 µs us-
ing a resistor of 11 K to 220 K. In this case R_PR is given by:
R_PR = 198* t_PRC - 8.51, where t_PRC is in µs and R_PR is in kilohms
In the low data rate mode, the PWIDTH pin sets the width of the ON
pulse to the first RF amplifier t_PW1 with a resistor R_PW to ground (the
ON pulse width to the second RF amplifier t_PW2 is set at 1.1 times
the pulse width to the first RF amplifier in the low data rate mode).
The ON pulse width t_PW1 can be adjusted between 0.55 and 1 µs
with a resistor value in the range of 200 K to 390 K. The value of
R_PW is given by:
R_PW = 404* t_PW1 - 18.6, where t_PW1 is in µs and R_PW is in kilohms
However, when the PWIDTH pin is connected to Vcc through a 1 M
resistor, the RF amplifiers operate at a nominal 50%-50% duty cy-
cle, facilitating high data rate operation. In this case, the RF amplifi-
ers are controlled by the PRATE resistor as described above.
LPF Group Delay
The low-pass filter group delay is a function of the filter 3 dB band-
width, which is set by a resistor R_LPF to ground at the LPFADJ pin.
The minimum 3 dB bandwidth f_LPF = 1445/R_LPF, where f_LPF is in kHz,
and R_LPF is in kilohms.
The maximum group delay t_FGD = 1750/f_LPF = 1.21*R_LPF, where t_FGD
is in µs, f_LPF in kHz, and R_LPF in kilohms.
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