Calling Line Identifier

FX602

© 1998 Consumer Microcircuits Limited

7

D/602/7

1.5

General Description

1.5.1

Mode Control Logic

The FX602's operating mode and the source of the DET and IRQN outputs are determined by the logic levels

applied to the MODE and ZP input pins;

ZP

MODE

Mode

DET o/p from

IRQN o/p from

0

0

Tone Alert Detect

Tone Alert Signal

Detection

End of Tone Alert Signal.

Ring or Line Polarity

Reversal Detector.

0

1

FSK Receive

FSK Level Detector

FSK Data Retiming [1].

Ring or Line Polarity

Reversal Detector.

1

0

'Zero-Power'

Ring or Line Polarity

Reversal Detector.

Ring or Line Polarity

Reversal Detector.

1

1

'Zero-Power'

Ring or Line Polarity

Reversal Detector.

-

[1] If enabled.

In the 'Zero-Power' modes, power is removed from all of the internal circuitry except for the Ring or Line

Polarity Reversal Detector and the DET and IRQN outputs.

1.5.2

Input Signal Amplifier

This amplifier is used to convert the balanced FSK and Tone Alert signals received over the telephone line to

an unbalanced signal of the correct amplitude for the FSK receiver and Tone Alert Detector circuits.

Figure 3a : Input Signal Amplifier, balanced input configuration

The design equations for this circuit are;

Differential voltage gain VAOP / V(b-a) = R8/R6

R6 = R7 = 470k

Ω

R10 = 160k

Ω

R9 = R8 x R10 / (R8 - R10)

The target differential voltage gain depends on the expected signal levels between the A and B wires and the

FX602's internal threshold levels, which are proportional to the supply voltage.

The FX602 has been designed to meet the applicable specifications with R8 = 470k

rising to 680k

section 1.4 and Fig 3c.