SX1235 datasheet(29/104 Pages) SEMTECH

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SX1235

WIRELESS & SENSING

DATASHEET

Rev 1 - December 2012

3.4.4. OOK Modulation

OOK modulation is applied by switching on and off the Power Amplifier. Digital control and smoothing are available to

improve the transient power response of the OOK transmitter.

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.

In FSK mode, a Gaussian filter with BT = 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 SX1232 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.

Note

the transmitter must be restarted if the ModulationShaping setting is changed, in order to recalibrate the built-in

filter.

3.4.6. RF Power Amplifiers

Three power amplifier blocks are embedded in the SX1235. The first one herein referred to as PA0, can generate high

efficiency RF power into a 50 ohm load. The RF power is programmable between -1dBm and +14dBm. PA0 is connected

to pin RFO (pin 22).

PA1 and PA2 are both connected to pin PA_BOOST (pin 23). They can deliver up to +17 dBm in programmable step of 1dB

to the antenna, a specific impedance matching / harmonic filtering design is required to ensure impedance transformation

and regulatory compliance. The RF power is programmable between +2 dBm and +17 dBm. The high power mode allows

to achieve fixed output power of +20 dBm.

Table 12 Power Amplifier Mode Selection Truth Table

Notes - For +20 dBm restrictions of operation, please consult the following section

- To ensure correct operation at the highest power levels, please make sure to adjust the OcpTrim accordingly in

RegOcp.

- If PA_BOOST pin is not used the pin can be left floating.

PaSelect

Mode

Power Range

Pout Formula

PA0 output on pin RFO

-1 to +14 dBm

-1 dBm + OutputPower

PA1 and PA2 combined on pin PA_BOOST

+2 to +17 dBm

+2 dBm + OutputPower

PA1+PA2 on PA_BOOST with high output

power +20dBm settings (see 3.4.7)

+5 to +20 dBm

+5 dBm + OutputPower

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