Conexant RF142 Datasheet

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.

GND1

VREF

VMP

1

2

3

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

20

19

18

VCC2

VPCGS M

VPCDCS

VAPC+

VAPC-

ENABLE

RFPC+

RFPC-

GND2

VCC1

4

5

6

7

8

9

10

Figure 1. RF142 Pin Configuration – 20-Pin TSSOP

17

16

15

14

13

12

11

100774A-1_090700

BAND

AUX-

AUX+

CAP-

CAP+

NC

NC

Data Sheet Conexant Doc. No. 100774B
Proprietary Information and Specifications are Subject to Change September 7, 2000

RF142 Power Amplifier Controller

Table 1. RF142 Signal Description

Pin # Name Description Pin # Name Description

1 GND1 Ground 11 NC No connect

2 VREF Output reference voltage 12 NC No connect

3 VMP Midpoint voltage for gain shaper 13 CAP+ Integrator time constant Cap+

4 VAPC+ Tx power control positive polarity 14 CAP– Integrator time constant Cap–

5 VAPC– Tx power control negative polarity 15 AUX+ Aux output +

6 ENABLE Device enable (active high) 16 AUX– Aux output –

7 RFPC+ RF input to detector positive polarity 17 BAND

8 RFPC– RF input to detector negative polarity 18 VPCDCS 1800 MHz/1900 MHz power amplifier control voltage

9 GND2 Ground 19 VPCGSM 900 MHz power amplifier control voltage

10 VCC1 Power supply 20 VCC2 Vcc for the output stage

BAND

Band select. High selects VPCDCS as the output control
pin; low selects VPCGSM as the output control pin.

VREF

VMP

AUX+

AUX–

Gain Shaper

Amp 1

CAP-

Amp 2

CAP+

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

VAPC- VAPC+

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.

Logarithmic

Detector

DC Bias

Circuitry

ENABLE

VPCGSM

VPCDCS

RFPC+
RFPC–

VCC2
VCC1
GND

C013

2 Conexant 100774A
September 7, 2000 Proprietary Information and Specifications are Subject to Change

Power Amplifier Controller RF142

Gain Shaper. The output of the integrator is fed to the gain
shaping circuit that drives the gain control input of the external
RF PA. The midpoint voltage of the PA control voltage VPC, is
determined by the VMP input. The VMP input is obtained by
connecting a resistor divider to the 2.4 V reference output,
VREF. The integrator in the integrating error amplifier is used to
stabilize the loop.

The maximum voltage obtainable on VPCGSM and VPCDCS is
generally 1 V below VCC2 (pin 20). Therefore, it may be more
desirable to use a higher voltage than VCC.

Output Stages. Each of the two output stages is dedicated to a
frequency band: one for GSM900MHz and one for
GSM1800/PCS1900 MHz. The selection of the output stage is
determined by the BAND select signal. A high signal selects the
VPCDCS as the output pin and a low signal selects VPCGSM

Table 2. Absolute Maximum Ratings

Parameter Minimum Maximum Units

Storage Temperature –40 +125 °C

Supply Voltage –0.3 5.0 V

Power Dissipation -- 500 mW

Input Voltage Range –0.3 Vcc V

as the output pin. When either output is inactive, its residual
output level is extremely low to ensure that the inactive PA is
completely off.

DC Bias Block. The DC bias block provides voltage bias to the
whole chip, which may be put in standby mode using the
ENABLE digital input control pin (pin 6). The ENABLE pin is
compatible with TTL levels. When the ENABLE pin is driven
high, the device is enabled.

Electro-Static Discharge (ESD) Sensitivity

The RF142 is a static sensitive electronic device. Do not operate
or store it near strong electrostatic fields. Take proper ESD
precautions.

Table 3. RF142 Recommended Operating Conditions

Parameter Minimum Typical Maximum Units

Supply Voltage (Vcc) 2.7 3.6 4.8 V

Operating Temperature –30 +25 +85

°C

Table 4. RF142 Electrical Characteristics (1 of 2)

(TA = 25 °°°°C, Vcc = 3.6 V)

Parameter Symbol Test Condition Min Typ Max Units

Detector frequency range f 800 2000 MHz

Detector monotonic dynamic range 50 dB

Detector gain 15 mV/dB

Detector stability

Detector non-linearity error

VAPC common mode range 1.35 V

VAPC differential range

VAPC input impedance ZVAPC 20//5

VREF VREF 2.2 2.4 2.6 V

GSM Maximum Control Voltage VPCGSM

DCS Maximum Control Voltage VPCDCS

Maximum input power and over temperature range.
Minimum input power and over temperature range.

RFPC ± from –40 dBm to +8 dBm

Band <= 0.8 V
Ivpcgsm <= 75 mA

Band >= 1.90 V
Ivpcdcs <= 50 mA

±1

Vcc-1.1 Vcc-1.0 Vcc-0.9 V

Vcc-1.1 Vcc-1.0 Vcc-0.9 V

±0.5

±3

± 2

Vp-p

dB
dB

dB

kΩ//pF

100774A Conexant 3

Proprietary Information and Specifications are Subject to Change September 7, 2000