Data Sheet

LJ1269HC
Rev1.0 Page 33 Web: www.ljelect.com
As shown on Figure 15, a standard AFC sequence uses the result of the FEI to correct the LO frequency and align both local
oscillators. W hen the optimized AFC is enabled (AfcLowBetaOn=1), the receiver‟s LO is corrected by “FeiValue +
LowBetaAfcOffset”.
When the optimized AFC routine is enabled, the receiver startup time can be computed as follows (refer to section 4.2.3):
TS_RE_AGC&AFC (optimized AFC) = Tana + 4.Tcf + 4.Tdcc + 3.Trssi + 2.Tafc + 2.Tpllafc
3.4.16. Temperature Sensor
W hen temperature is measured, the receiver ADC is used to digitize the sensor response. Most receiver blocks are disabled,
and temperature measurement can only be triggered in Standby or Frequency Synthesizer modes.
The response of the temperature sensor is -1°C / Lsb. A CMOS temperature sensor is not accurate by nature, therefore it
should be calibrated at ambient temperature for precise temperature readings.
Figure 15. Temperature Sensor Response
It takes less than 100 microseconds for the LJ1269HC to evaluate the temperature (from setting TempMeasStart to 1 to
TempMeasRunning reset).
3.4.17. Timeout Function
The LJ1269HC includes a Timeout function, which allows it to automatically shut-down the receiver after a receive sequence
and therefore save energy.
 Timeout interrupt is generated TimeoutRxStart x 16x Tbit after switching to RX mode if RssiThreshold flag does not raise
within this time frame
 Timeout interrupt is generated TimeoutRssiThresh x 16 x Tbit after RssiThreshold flag has been raised.
This timeout interrupt can be used to warn the companion processor to shut down the receiver and return to a lower power
mode.
Sub GHz FSK/OOK Transceiver Module DATASHEET