RF3140PCBA-41X 데이터 시트보기 (PDF) - RF Micro Devices
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RF3140PCBA-41X Datasheet PDF : 16 Pages
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RF3140
Talk time and power management are key concerns in transmitter design since the power amplifier has the highest current
draw in a mobile terminal. Considering only the power amplifier’s efficiency does not provide a true picture for the total system
efficiency. It is important to consider effective efficiency which is represented by ηEFF. (ηEFF considers the loss between the PA
and antenna and is a more accurate measurement to determine how much current will be drawn in the application). ηEFF is
defined by the following relationship (Equation 2):
m
∑ PN – PIN
ηEFF
=
n----=-----1-----------------------
PDC
⋅
100
(Eq.
2)
Where Pn is the sum of all positive and negative RF power, PIN the input power and PDC is the delivered DC power. In dB the for-
mula becomes (Equation 3):
P----P---A----+-----P----L---O---S---S
-P---I--N-
ηEFF
=
1----0------------1---0-------------–-----1---0----1--0--
VBAT ⋅ IBAT ⋅ 10
(Eq.
3)
Where PPA is the output power from the PA, PLOSS the insertion loss, PIN the input power to the PA and PDC the delivered DC
power.
The RF3140 improves the effective efficiency by minimizing the PLOSS term in the equation. A directional coupler may introduce
0.4dB to 0.5dB loss to the transit path. To demonstrate the improvement in effective efficiency consider the following exam-
ple:
Conventional PA Solution at F=1785MHz:
PPA = +33.5 dBm
PIN = +3 dBm
PLOSS = -0.4 dB
VBAT = 3.5 V
IBAT = 1.16 A
RF3140 Solution:
ηEFF = 50.3%
PPA = +33.5 dBm
PIN = +3 dBm
PLOSS = 0 dB
VBAT = 3.5 V
IBAT = 1.16 A
hEFF = 55.16%
The RF3140 solution improves effective efficiency by 5%.
Output power does not vary due to supply voltage under normal operating conditions if VRAMP is sufficiently lower than VBATT.
By regulating the collector voltage to the PA the voltage sensitivity is essentially eliminated. This covers most cases where the
PA will be operated. However, as the battery discharges and approaches its lower power range the maximum output power
from the PA will also drop slightly. In this case it is important to also decrease VRAMP to prevent the power control from inducing
switching transients. These transients occur as a result of the control loop slowing down and not regulating power in accor-
dance with VRAMP.
10 of 16
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 A9 DS060217
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