TDA7703

Function description

Rev 1

9/32

2

Function description

2.1

FM - mixer

The FM image-rejection mixer is optimized for best performance with a passive wide-band

prestage.

The input frequency is downconverted to low IF with high image rejection.

2.2

FM - AGC

The programmable RFAGC senses the mixer input whereas the IFAGC senses the IFADC

input to avoid overload.

The PIN diode driver is able to drive external PIN diodes with a current value as high as

15mA.

The time constant of the FM-AGC is defined by an external capacitor.

2.3

AM - LNA

The AM-LNA is integrated with low noise and high IIP2 and IIP3. The gain of the LNA is

controlled by the AGC. The maximum gain is set with an external resistor, typically 28 dB

with 1.5 k

Ω.

2.4

AM - AGC

The programmable AM-RF-AGC senses the mixer inputs and controls the internal PIN diode

and LNA gain.

First the LNA gain is reduced by about 10dB, then the PIN diodes are activated to attenuate

the signal.

The time constant of the AM-AGC is defined with an external capacitor and programmable

internal currents.

2.5

AM - mixer

The AM mixer converts RF to low IF with high image rejection.

2.6

IF A/D converters

A high performance IQ-IFADC converts the IF-signal to digital IF for subsequent digital

signal processing.