Transceiver Event Timing
Transceiver event timing is summarized in Table 1. Please refer to this ta-
ble for the following discussions.
Turn-On Timing
The maximum time t
PR
required for the receive function to become opera-
tional at turn on is influenced by two factors. All receiver circuitry will be op-
erational 5 ms after the supply voltage reaches 2.2 Vdc. The BBOUT-
CMPIN coupling-capacitor is then DC stabilized in 3 time constants
(3*t
BBC
). The total turn-on time to stable receiver operation for a 10 ms
power supply rise time is:
t
PR
= 15 ms + 3*t
BBC
The maximum time required for either the OOK or ASK transmitter mode to
become operational is 5 ms after the supply voltage reaches 2.2 Vdc.
Receive-to-Transmit Timing
After turn on, the maximum time required to switch from receive to either
transmit mode is 12 µs. Most of this time is due to the start-up of the trans-
mitter oscillator.
Transmit-to-Receive Timing
The maximum time required to switch from the OOK or ASK transmit mode
to the receive mode is 3*t
BBC
, where t
BBC
is the BBOUT- CMPIN coupling-
capacitor time constant. When the operating temperature is limited to 60
o
C, the time required to switch from transmit to receive is dramatically less
for short transmissions, as less charge leaks away from the
BBOUT-CMPIN coupling capacitor.
Sleep and Wake-Up Timing
The maximum transition time from the receive mode to the power-down
(sleep) mode t
RS
is 10 µs after CNTRL1 and CNTRL0 are both low
(1 µs fall time).
The maximum transition time from either transmit mode to the sleep mode
(t
TOS
and t
TAS
) is 10 µs after CNTRL1 and CNTRL0 are both low
(1 µs fall time).
The maximum transition time t
SR
from the sleep mode to the receive mode
is 3*t
BBC
, where t
BBC
is the BBOUT-CMPIN coupling-capacitor time con-
stant. When the operating temperature is limited to 60
o
C, the time required
to switch from sleep to receive is dramatically less for short sleep times, as
less charge leaks away from the BBOUT- CMPIN coupling capacitor.
The maximum time required to switch from the sleep mode to either trans-
mit mode (t
STO
and t
STA
) is 16 µs. Most of this time is due to the start-up of
the transmitter oscillator.
AGC Timing
The maximum AGC engage time t
AGC
is 5 µs after the reception of a -30
dBm RF signal with a 1 µs envelope rise time.
The minimum AGC hold-in time is set by the value of the capacitor at the
AGCCAP pin. The hold-in time t
AGH
= C
AGC
/19.1, where t
AGH
is in µs and
C
AGC
is in pF.
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.
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
TR3003-070105
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