RF142

Power Amplifier Controller

2

Conexant

100774A

September 7, 2000

Proprietary Information and Specifications are Subject to Change

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

Band select. High selects VPCDCS as the output control

pin; low selects VPCGSM as the output control pin.

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

C013

Gain Shaper

Logarithmic

Detector

Amp 1

RFPC+

VPCGSM

VPCDCS

RFPC–

VAPC- VAPC+

CAP- CAP+

Amp 2

AUX–

AUX+

VREF

VMP

ENABLE

BAND

VCC2

VCC1

GND

DC Bias

Circuitry

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

the diagram for a typical application circuit using the RF142 PA

controller. Figure 4 shows the package dimensions for the 20-

pin 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.