SX1230 データシートの表示（PDF） - Semtech Corporation

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SX1230

Integrated Transmitter IC Narrow/wideband 315 MHz, 434 MHz 868 MHz and 915 MHz band Transmitter

Semtech Corporation 

ADVANCED COMMUNICATIONS & SENSING

SX1230

Integrated Transmitter IC

DATASHEET

5.3. The Power Amplifier

A simplified schematic of the dual power amplifiers of the SX1230 is shown in Figure 5. PA 1 comprises a pair of amplifiers:

One dedicated for low power use, LPA, for programmed powers from -18 to -3 dBm: The second for high power use, HPA,

for programmed powers from -2 to 13 dBm. PA 2 is a single high power amplifier and may be used in conjunction with PA 1

to deliver the full 17 dBm of output power.

pa_ramp_rising_time(6:5)

OOK

I/P

Ramp and

Control

LPA

HPA1

PA 1

VR_PA

RFOUT

Match

HPA2

PA 2

Figure 5. Simplified Schematic of the SX1230 Power Amplifier

The mode of operation of the PA’s is determined by the register setting pa_select(1:0) which is configured as shown in

Table 8, below. The output power of the PA is determined by the value of the register pow_val(4:0), with a single PA

enabled the output power is set by:

Pout = –18 dBm + pow_val(4:0)

The default setting for this register is 13 dBm. The expressions for the output power with other combinations of power

amplifier enabled are shown in Table 8. Note also that the power amplifier current limiter, over current protection (OCP),

feature of SX1230 can also limit the output power. To ensure correct operation at 17 dBm ensure that trim_ocp(3:0) is set

to 105 mA (‘1100’).

Table 8 Power Amplifier Mode Selection Truth Table

pa_select(1:0)

Mode

00

invalid

01

PA1 enabled

10

PA2 enabled

11

Dual PA

Power Range

-

-18 to 13 dBm

-

-13 to 17 dBm

Pout Formula

-18 dBm + pow_val(4:0)

-

-13 dBm + pow_val(4:0)

The ramp and power control features of the PA, determine the regulator output voltage which is used to power the

amplifiers, this must be done through an external RF choke.

SX1230, Revision 2 May 2009

©2008 Semtech Corp.

Page 14

www.semtech.com

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