SX1239IMLTRT Semtech, SX1239IMLTRT Datasheet - Page 33

• Manufacturer Part Number: SX1239IMLTRT
• Description: IC, RF RECEIVER, 1.02GHz, QFN-24
• Manufacturer: Semtech

Specifications of SX1239IMLTRT

• Applications: Wireless Sensor Networks, Automated Meter Reading, Home And Building Automation
• Receiving Current: 16mA
• Data Rate: 300Kbps
• Modulation Type: FSK, OOK
• Sensitivity Dbm: -120dBm
• Rohs Compliant: Yes
• Rf Ic Case Style: QFN
• No. Of Pins: 24
• Sensitivity (dbm): -120dBm
• Supply Voltage Range: 1.8V To 3.6V
• Operating Temperature Range: -40°C To +85°C
• Lead Free Status / Rohs Status: Supplier Unconfirmed

4.3. Listen Mode
The circuit can be set to Listen mode, by setting ListenOn in RegOpMode to 1 while in Standby mode. In this mode,
SX1239 spends most of the time in Idle mode, during which only the RC oscillator runs. Periodically the receiver is woken
up and listens for an RF signal. If a wanted signal is detected, the receiver is kept on and the data is demodulated.
Otherwise, if a wanted signal hasn't been detected after a pre-defined period of time, the receiver is disabled until the next
time period.
This periodical Rx wake-up requirement is very common in low power applications. On SX1239 it is handled locally by the
Listen mode block without using uC resources or energy.
The simplified timing diagram of this procedure is illustrated in Figure 17.
4.3.1. Timings
The duration of the Idle phase is given by t
by t
programmed in the configuration registers via the serial interface.
Both time periods t
configuration register and are calculated as follows:
where ListenResolX is the Rx or Idle resolution and is independantly programmable on three values (64us, 4.1ms or
262ms), whereas ListenCoefX is an integer between 1 and 255. All parameters are located in RegListen registers.
The timing ranges are tabulated in Table 13 below.
Table 13 Range of Durations in Listen Mode
Rev 3 - Jan 2011
ADVANCED COMMUNICATIONS & SENSING
ListenRx
. t
ListenRx
ListenRx
includes the wake-up time of the receiver, described in section 4.2.1. This duration can be
Figure 17. Listen Mode Sequence (no wanted signal is received)
and t
t
ListenRx
ListenResolX
Rx
ListenIdle
01
10
11
t
ListenX
(denoted t
ListenIdle
t
ListenIdle
( ListenCoef = 1 )
=
Min duration
ListenCoef
. The time during which the receiver is on and waits for a signal is given
4.1 ms
0.26 s
64 us
ListenX
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Idle
in the following text) are fixed by two parameters from the
X
⋅
Listen
( ListenCoef = 255 )
Re
Max duration
solX
16 ms
1.04 s
67 s
t
ListenRx
Rx
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SX1239
time