Peak Detector Timing
The Peak Detector attack time constant is set by the value of the capacitor
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
constant 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
between the PRATE pin and
ground. The interval can be adjusted between 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 receiver RF
amplifiers operate at a nominal 50%-50% duty cycle. In this case, the peri-
od 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 re-
sistor over a range of 0.1 to 1.1 µs using 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 resis-
tor, the RF amplifiers operate at a nominal 50%-50% duty cycle, facilitating
high data rate operation. In this case, the RF amplifiers 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 bandwidth,
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 kilo-
hms.
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.
Receiver Event Timing, 3.0 Vdc, -40 to +85 °C
Event
Turn On to Receive
Sleep to RX
RX to Sleep
AGC Engage
AGE Hold-In
PKDET Attack Time Constant
PKDET Decay Time Constant
PRATE Interval
PWIDTH RFA1
PWIDTH RFA2
PRATE Cycle
PWIDTH High (RFA1 & RFA2)
LPF Group Delay
LPF 3 dB Bandwidth
BBOUT-CMPIN Time Constant
Symbol
t
PR
t
SR
t
RS
t
AGC
t
AGH
t
PKA
t
PKD
t
PRI
t
PW1
t
PW2
t
PRC
t
PWH
t
FGD
f
LPF
t
BBC
Time
3*t
BBC
+ 15 ms
3*t
BBC
10 µs
5 µs
C
AGC
/19.1
C
PKD
/4167
1000*t
PKA
0.1 to 5 µs
0.55 to 1 µs
1.1*t
PW1
0.1 to 1.1 µs
0.05 to 0.55 µs
1750/f
LPF
1445/R
LPF
0.064*C
BBO
Min/Max
max
max
max
max
min
min
min
range
range
range
range
range
max
min
min
Test Conditions
10 ms supply voltage rise time
1 µs CNTRL0/CNTROL 1 rise times
1 µs CNTRL0/CNTROL 1 fall times
1 µs rise time, -30 dBm signal
CAGC in pF, t
AGH
in µs
C
PKD
in pF, t
PKA
in µs
t
PKD
and t
PKA
in µs
low data rate mode
low data rate mode
low data rate mode
high data rate mode
high data rate mode
t
FGD
in µs, f
LPF
in kHz
f
LPF
in kHz, R
LPF
in kilohms
t
BBC
in µs, C
BBO
in pF
Notes
time until receiver operational
time until receiver operational
time until receiver is in power-down mode
RFA1 switches from 35 to 5 dB gain
user selected; longer than t
PKD
user selected
slaved to attack time
user selected mode
user selected mode
user selected mode
user selected mode
user selected mode
user selected
user selected
user selected
Table 1
RF Monolithics, Inc.
Phone: (972) 233-2903
Fax: (972) 387-8148
RFM Europe
Phone: 44 1963 251383
Fax: 44 1963 251510
©1999 by RF Monolithics, Inc. The stylized RFM logo are registered trademarks of RF Monolithics, Inc.
E-mail: info@rfm.com
http://www.rfm.com
RX5001-062805
Page 7 of 10
RFM [ RF MONOLITHICS, INC ]
