SX1231-31SKB915 Semtech, SX1231-31SKB915 Datasheet - Page 21

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

Specifications of SX1231-31SKB915

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

3.4.5. Modulation Shaping
Modulation shaping can be applied in both OOK and FSK modulation modes, to improve the narrowband response of the
transmitter. Both shaping features are controlled with PaRamp bits in RegPaRamp.
Note
3.4.6. Power Amplifiers
Three power amplifier blocks are embedded in the SX1231. The first one, herein referred to as PA0, can generate up to
+13 dBm into a 50 Ohm load. PA0 shares a common front-end pin RFIO (pin 21) with the receiver LNA.
PA1 and PA2 are both connected to pin PA_BOOST (pin 23), allowing for two distinct power ranges:
When PA1 and PA2 are combined to deliver +17 dBm to the antenna, a specific impedance matching / harmonic filtering
design is required to ensure impedance transformation and regulatory compliance.
All PA settings are controlled by RegPaLevel, and the truth table of settings is given in Table 10.
Table 10 Power Amplifier Mode Selection Truth Table
Notes - To ensure correct operation at the highest power levels, please make sure to adjust the Over Current Protection
3.4.7. Over Current Protection
An over current protection block is built-in the chip. It helps preventing surge currents required when the transmitter is used
at its highest power levels, thus protecting the battery that may power the application. The current clamping value is
controlled by OcpTrim bits in RegOcp, and is calculated with the following formula:
Rev 3 - April 2010
ADVANCED COMMUNICATIONS & SENSING
In FSK mode, a Gaussian filter with BT = 0.3, 0.5 or 1 is used to filter the modulation stream, at the input of the sigma-
delta modulator. If the Gaussian filter is enabled when the SX1231 is in Continuous mode, DCLK signal on pin 10
(DIO1/DCLK) will trigger an interrupt on the uC each time a new bit has to be transmitted. Please refer to section 5.4.2
for details.
When OOK modulation is used, the PA bias voltages are ramped up and down smoothly when the PA is turned on and
off, to reduce spectral splatter.
A low power mode, where -18 dBm < Pout < 13 dBm, with PA1 enabled
A higher power mode, when PA1 and PA2 are combined, providing up to +17 dBm to a matched load.
Pa0On
1
0
0
Other combinations
the transmitter must be restarted if the PaRamp setting is changed, in order to recalibrate the built-in filter.
Limit accordingly in RegOcp.
- If PA_BOOST pin is not used (+13dBm applications and less), the pin can be left floating.
Pa1On
0
1
1
Pa2On
0
0
1
PA0 output on pin RFIO
PA1 enabled on pin PA_BOOST
PA1 and PA2 combined on pin PA_BOOST
Imax
=
45
Mode
+
5 OcpTrim
×
Page 21
(
mA
)
Reserved
-18 to +13 dBm
-18 to +13 dBm
-14 to +17 dBm
Power Range
-18 dBm + OutputPower
-18 dBm + OutputPower
-14 dBm + OutputPower
Pout Formula
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SX1231