RF3158 Ver la hoja de datos (PDF) - RF Micro Devices
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Fabricante
RF3158 Datasheet PDF : 26 Pages
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RF3158
RF3158 power is ramped up and down through the VRAMP control voltage which in turn controls the collector voltage of the
amplifier stages. The RF signal applied at the RFIN pin must be a constant amplitude signal and should be high enough to sat-
urate the amplifier in the GSM mode. The input power (PIN) range is indicated in the specifications. Power levels below this
range will result in reduced maximum output power and the potential for more variation of output power over extreme condi-
tions. Higher input power is unnecessary and will require more current in the circuitry driving the power amplifier and will
increase the minimum output power of the RF3158.
The saturation detector circuit monitors the VBATT and VCC voltages and adjusts the power control loop to prevent the series-
pass FET regulator from entering saturation. If the VCC regulator were to saturate, the response time would increase dramati-
cally. This is undesirable because the VCC regulator must accurately follow the burst ramp up or ramp down applied to the
VRAMP pin, or the transient spectrum will degrade.
EDGE (Linear) Mode
In EDGE mode, VCC is fixed and the bias currents are controlled by VRAMP. The low band gain is significantly reduced from
GMSK mode in order to improve receive band noise performance. The RF3158 then operates as a linear amplifier where out-
put power is directly controlled by input power. The RF signal applied to the RFIN pin must be accurately controlled to produce
the desired output amplitude and burst ramping. The RFIN power must be maintained so that the amplifier is operating in its
linear region. If the input drive is too high, the amplifier will begin to saturate causing the ACPR and EVM performance to
degrade. The most sensitive of these on the RF3158 is the +/-400kHz offset ACPR. As the amplifier approaches saturation,
this will be the first parameter to show significant degradation.
During production calibration of a system containing the RF3158, the PA gain and other parameters must be determined. After
that, the RF3158 functions as a fixed gain block while the system adjusts input power such that the output from the transmit-
ter meets the desired system specifications.
Since the RF3158 operates as a gain block in EDGE mode, gain variation over extreme conditions must be considered when
determining the output power that a specific input power will produce. Typical Gain versus Temperature is shown in Figure 3.
Special attention must be given to ensure that the output power of the PA does not go higher than the maximum linear output
that the PA can provide with acceptable EVM and ACPR performance.
38.0
37.0
36.0
35.0
34.0
33.0
32.0
31.0
30.0
29.0
28.0
27.0
26.0
-40.0
Typical EDGE Gain over Temperature
High Bias Mode, Average over Frequency
-20.0
Low Band Gain
High Band Gain
0.0
20.0
40.0
60.0
Temperature (°C)
80.0
100.0
Figure 3. EDGE Gain over Temperature
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7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com.
Rev A2 DS070615
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