SX1231-31SKB915 Semtech, SX1231-31SKB915 Datasheet - Page 24

• Manufacturer Part Number: SX1231-31SKB915
• Description: TVS
• Manufacturer: Semtech

Specifications of SX1231-31SKB915

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 12 Receiver Performance Summary
3.5.3.1. RssiThreshold Setting
For correct operation of the AGC, RssiThreshold in RegRssiThresh must be set to the sensitivity of the receiver. The
receiver will remain in WAIT mode until RssiThreshold is exceeded.
Note
3.5.3.2. AGC Reference
The AGC reference level is automatically computed in the SX1231, according to:
With:
3.5.4. Quadrature Mixer - ADCs - Decimators
The mixer is inserted between output of the RF buffer stage and the input of the analog to digital converter (ADC) of the
receiver section. This block is designed to translate the spectrum of the input RF signal to base-band, and offer both high
IIP2 and IIP3 responses.
In the lower bands of operation (290 to 510 MHz), the multi-phase mixing architecture with weighted phases improves the
rejection of the LO harmonics in receiver mode, hence increasing the receiver immunity to out-of-band interferers.
The I and Q digitalization is made by two 5
gain is not constant over temperature, but the whole receiver is calibrated before reception, so that this inaccuracy has no
impact on the RSSI precision. The ADC output is one bit per channel. It needs to be decimated and filtered afterwards. This
ADC can also be used for temperature measurement, please refer to section 3.5.16 for more details.
The decimators decrease the sample rate of the incoming signal in order to optimize the area and power consumption of
the following receiver blocks.
Rev 3 - April 2010
ADVANCED COMMUNICATIONS & SENSING
NF = 7dB
DemodSnr = 8 dB
RxBw
FadingMargin = 5 dB : Fading margin
AGC Reference [dBm] = -174 + NF + DemodSnr +10.log(2*RxBw) + FadingMargin [dBm]
When AFC is enabled and performed automatically at the receiver startup, the channel filter used by the receiver
during the AFC and the AGC is RxBwAfc instead of the standard RxBw setting. This may impact the sensitivity of
the receiver, and the setting of RssiThreshold accordingly
AgcThresh1 < Pin < AgcThresh2
AgcThresh2 < Pin < AgcThresh3
AgcThresh3 < Pin < AgcThresh4
AgcThresh4 < Pin < AgcThresh5
AgcThresh5 < Pin
: LNA’s Noise Figure at maximum gain
: Single sideband channel filter bandwidth
: SNR needed by the demodulator
Input Power
Pin
Pin < AgcThresh1
th
order continuous-time Sigma-Delta Analog to Digital Converters (ADC). Their
Setting
Gain
G2
G3
G4
G5
G1
G6
Page 24
[dBm]
P
-37
-31
-26
-14
>-6
>0
-1dB
Receiver Performance (typ)
[dB]
NF
13
18
27
36
44
7
[dBm]
IIP3
+13
+20
-18
-15
-8
-1
[dBm]
IIP2
+35
+40
+48
+62
+68
+75
DATASHEET
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SX1231