RF3196 Ver la hoja de datos (PDF) - RF Micro Devices
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RF3196 Datasheet PDF : 16 Pages
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RF3196
Theory of Operation
Overview
Building on previous generations of PowerStar® modules, the RF3196 has integrated Power Control with additional features
such as VBATT tracking, and a power flattening circuit that reduces power and current variation into mismatch conditions.
Theory of Operation
The type of power control used in the RF3196 is a closed loop method that regulates the collector voltage of the amplifier while
the stages are held at a constant bias. As the required output power is decreased from full power down to minimum PCLs, the
collector voltage is also decreased. This process is repeatable and enables the user to implement a single point calibration,
thereby increasing production by saving valuable time in the factory. The basic circuit is shown below in Figure 1.
VBATT
VRAMP
-
+
3 dB BW
300 kHz
-
+
H(s)
Saturation
Detector
VCC
RF IN
RF OUT
Figure 1. Power Control Circuit
TX ENABLE
Output power does not vary due to supply voltage under normal operating conditions if VCC is sufficiently lower than VBATT. Reg-
ulating the collector voltage to the PA essentially eliminates voltage sensitivity. This covers most cases where the PA will be
operated. However, as the battery discharges and approaches its lower voltage range, the maximum output power from the PA
will also drop slightly. In this case it is important to decrease VRAMP to prevent the power control circuitry from inducing switch-
ing transients. These transients occur as a result of the control loop slowing down and not regulating power in accordance with
VRAMP..
In the RF3196, is a VBATT tracking circuit that reduces the level of VRAMP as the battery voltage decreases. The limiter is inte-
grated into the CMOS controller and requires no additional input from the user. In the circuit, a feedback loop is implemented
that compares VBATT to VCC and produces a correction so that VRAMP is decreased. This prevents the switch transistor from
being driven into saturation and inducing switching transients.
In addition to the VBATT tracking circuit, the RF3196 has an integrated power flattening circuit that reduces the amount of cur-
rent variation when a mismatch is presented to the output of the PA. When a mismatch is presented to the output of the PA, its
output impedance is varied and could present a load that will increase output power. As the output power increases, so does
current consumption. The current consumption can become very high if not monitored and limited. The power flattening circuit,
like the VBATT tracking circuit, is also integrated onto the CMOS controller and requires no input from the user.
Rev A2 DS071207
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com.
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