rf3230 RF Micro Devices, rf3230 Datasheet - Page 12

• Manufacturer Part Number: rf3230
• Description: Quad-band Gmsk Txm, 2 Umts Switch Ports
• Manufacturer: RF Micro Devices

RF3230
Overview
The RF3230 is designed for use as the final portion of the transmit section in mobile phones covering the GSM850,
EGSM900, DCS1800, and PCS1900MHz frequency bands in architectures where UMTS pass through ports are required. The
RF3230 is a high power, saturated transmit module containing RFMD’s patented PowerStar® Architecture. The module
includes a multi function CMOS controller, GaAs HBT power amplifier, and pHEMT front end antenna switch. The integrated
power control loop allows a single analog voltage to control output power for GSM PCLs and ramping. This analog voltage can
be driven directly from the transceiver DAC to provide very predictable power control, enabling handset manufacturers to
achieve simple and efficient phone calibration in production.
Additional Features
Current Limiter
During normal use, a mobile phone antenna will be subjected to a variety of conditions that can affect its designed resonant
frequency. This shift in frequency appears as a varying impedance to a power amplifier connected to the antenna. As the
impedance presented to the power amplifier varies, so does the output power and current consumption. If left uncontrolled,
power amplifier current can reach levels that can starve other circuitry, connected to the same supply, of the required voltage
to operate. This can result in a reset or shutdown of the mobile phone. The RF3230 contains an active circuit that monitors the
current and adjusts the internal power control loop to prevent peak current from going above 2.6A. While this current limiter
can limit transmitted power under situations where the antenna is operating at very low efficiency, it is typically more accept-
able for users to have a dropped call than a phone reset.
GMSK Operation
GMSK modulation is a constant RF envelope modulation scheme which encodes information in the phase of the signal and
any amplitude variation is suppressed. Since no information is included in the amplitude of the signal, GMSK transmit is not
sensitive to amplitude non-linearity of the power amplifier, allowing the amplifier to operate in deep class AB or class C satura-
tion for optimum efficiency. The power envelope can be controlled by any one of a number of power control schemes.
During GMSK transmit RF3230 operates as a traditional PowerStar® module. The basic circuit diagram is shown in Figure 1.
The PowerStar® control circuit receives an analog voltage (V
architecture is essentially a closed loop method of power control that is invisible to the user. The V
erence to a high speed linear voltage regulator which supplies the collector voltage to all stages of the amplifier. The base bias
is fixed at a point that maintains deep class AB or class C transistor saturation. Because the amplifier remains in saturation at
any power level, performance sensitivity to temperature, frequency, voltage and input drive level is essentially eliminated,
ensuring robust performance within the ETSI power vs time mask.
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Theory of Operation
RAMP
) which sets the amplifier output power. The PowerStar® I
RAMP
voltage is used as a ref-
DS100406