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RF142
Heterojunction Bipolar Transistor Power Amplifier Dual-Band Controller for GSM and PCS Applications
The RF142 Power Amplifier (PA) controller is a highly integrated, monolithic device optimized for use in 900 MHz, 1800 MHz, and 1900 MHz Global System For Mobile communications® (GSM®) and other Time Division Multiple Access (TDMA) applications. The control current output from the RF142 can be used to control the transmit power of a dual or multi-band Heterojunction Bipolar Transistor (HBT) PA. The device consists of two sections: an RF detector, and a gain controller. The RF142, when combined with a PA and a coupler, forms a closed PA control loop, where the PA output power is controlled by a single analog reference voltage, typically supplied by the baseband. The RF142 device package and pin configuration are shown in Figure 1. The signal pin assignments and functional pin descriptions are specified in Table 1. An RF142 block diagram is shown in Figure 2.
Features
• RF PA controller for use with HBT PAs • 50 dB detector dynamic range • Broadband, logarithmic power detector (800 MHz to 2000 MHz) • Logarithmic RF power detector requires no external diodes • Integrator and gain shaping block enhance loop stability and linearity • Three-cell battery operation (2.7 V to 5.0 V) • Standby mode with 20 µA of current consumption • 20-pin Thin Shrink Small Outline Package (TSSOP)
Applications
• Transmit power control for dual or multi-band GSM digital cellular handsets
G ND1 VREF VMP VAPC+ VAPCENABLE RFPC+ RFPCG ND2 VCC1
1 2 3 4 5 6 7 8 9 10
20 19 18 17 16 15 14 13 12 11
VCC2 VPCGSM VPCDCS BAND AUXAUX+ CAPCAP+ NC NC
100774A-1_090700
Figure 1. RF142 Pin Configuration – 20-Pin TSSOP
Data Sheet
Conexant
Proprietary Information and Specifications are Subject to Change
Doc. No. 100774B September 7, 2000
RF142 Table 1. RF142 Signal Description Pin #
1 2 3 4 5 6 7 8 9 10
Power Amplifier Controller
Name
GND1 VREF VMP VAPC+ VAPC– ENABLE RFPC+ RFPC– GND2 VCC1 Ground
Description
Output reference voltage Midpoint voltage for gain shaper Tx power control positive polarity Tx power control negative polarity Device enable (active high) RF input to detector positive polarity RF input to detector negative polarity Ground Power supply
Pin #
11 12 13 14 15 16 17 18 19 20
Name
NC NC CAP+ CAP– AUX+ AUX– BAND VPCDCS VPCGSM VCC2 No connect No connect
Description
Integrator time constant Cap+ Integrator time constant Cap– Aux output + Aux output – Band select. High selects VPCDCS as the output control pin; low selects VPCGSM as the output control pin. 1800 MHz/1900 MHz power amplifier control voltage 900 MHz power amplifier control voltage Vcc for the output stage
BAND
VPCGSM VREF VMP
Gain Shaper
VPCDCS RFPC+ RFPC– VCC2 VCC1 GND
AUX+
Logarithmic Detector Amp 1 Amp 2
DC Bias Circuitry
AUX–
CAP- CAP+
VAPC- VAPC+
ENABLE
C013
Figure 2. RF142 Block Diagram
Technical Description
The RF142 dual-band PA controller is designed to control HBT PAs. It combines the functions of a broadband RF detector and error amplifier/integrator to provide transmit burst control for dual or multi-band HBT PAs. It has two separate dedicated output stages and pins for GSM900MHz PAs and GSM1800/1900 MHz PAs. The device, when connected to dual or multi-band HBT PAs with a coupler, forms a loop to control the transmit power in a dual or multi-band wireless application. The transmit power is controlled by a single balanced analog reference voltage input to the RF142. The RF142 has low power consumption and operates off a three-cell battery pack (2.7 V to 5.0 V). Extremely low standby current of 20 µA maximizes the standby time of a GSM handset. The absolute maximum ratings of the RF142 are provided in Table 2, the operating conditions are specified in Table 3, and electrical specifications are provided in Table 4. Figure 3 shows
2 September 7, 2000
the diagram for a typical application circuit using the RF142 PA controller. Figure 4 shows the package dimensions for the 20pin TSSOP device and Figure 5 provides the tape and reel dimensions. RF Detector. An external RF coupler is required at the PA output to couple the RF output from the PA to the RF logarithmic detector input. The input to the logarithmic detector must be within the range –40 dBm to +10 dBm. The coupled signal is fed to the input of the RF power detector. The output from the detector is a DC voltage that is proportional to the RF power (in dBm) at the RFPC input to the device. The dynamic range of the detector is 50 dB. Integrating Error Amplifier. The integrating error amplifier (Amp2) amplifies and integrates the voltage difference between the detector output and the power control input, VAPC. The integrator time constant is set by the two external capacitors connected from AUX pins to the CAP pins.
Conexant
Proprietary Information and Specifications are Subject to Change
100774A
Power Amplifier Controller
RF142
Gain Shaper. The output of the integrator is fed to.