RF3158PCBA-41X RFMD [RF Micro Devices], RF3158PCBA-41X Datasheet - Page 16

• Manufacturer Part Number: RF3158PCBA-41X
• Description: QUAD-BAND GSM/EDGE/GSM850/EGSM900 /DCS/PCS POWER AMPLIFIER MODULE
• Manufacturer: RFMD [RF Micro Devices]

RF3158
RF3158 power is ramped up and down through the V
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 (P
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 V
pass FET regulator from entering saturation. If the V
cally. This is undesirable because the V
V
EDGE (Linear) Mode
In EDGE mode, V
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.
16 of 26
Figure 3. EDGE Gain over Temperature
RAMP
pin, or the transient spectrum will degrade.
CC
is fixed and the bias currents are controlled by V
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at ([phone] or [e-mail].
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
CC
regulator must accurately follow the burst ramp up or ramp down applied to the
-20.0
BATT
High Bias Mode, Average over Frequency
Typical EDGE Gain over Temperature
and V
0.0
CC
RAMP
regulator were to saturate, the response time would increase dramati-
CC
Temperature (°C)
IN
20.0
voltages and adjusts the power control loop to prevent the series-
control voltage which in turn controls the collector voltage of the
) range is indicated in the specifications. Power levels below this
40.0
RAMP
60.0
. The low band gain is significantly reduced from
Low Band Gain
High Band Gain
80.0
100.0
Rev A2 DS070615