Datasheet AS2525

Revision 2.1

Page 2 of 27

Pin Description

Pin #

Symbol

Type

Description

1CS2

DO

Chip select signal for external LCD driver circuit or 2 mA LED

If signal is not activated, a pull down resistor (100 k

Ω) is inserted.

2DPn

DO

Digital output that holds the line during off-hook operation or pulls low during break periods

of pulse dialing and flash.

3HF

DI

This is a Schmitt-trigger input that is pulled high to enable handsfree operation.

4HS

DI

This is a Schmitt-trigger input that is pulled high by the hook switch to enable handset or

headset operation.

5

FT1

AI

Analogue input pin for connecting a capacitor for offset cancellation.

6

FT2

AI

Analogue input pin for connecting a capacitor for offset cancellation.

7M4

AI

Differential input for the handsfree microphone (electret).

8M2

AI

Differential input for the handset microphone (electret).

9M3

AI

Differential input for the handsfree microphone (electret).

10

M1

AI

Differential input for the handset microphone (electret).

11

STB

AI

Analogue input for side tone cancellation network.

12

CS

AO

N-channel open drain output to control the external high power shunt transistor for

synthesizing ac- and dc-impedance, modulation of line voltage and shorting the line during

make periods of pulse dialing.

13

Supply

Negative Power Supply.

14

LI

AI

Analogue input used for power extraction and line current sensing.

15

RI

AI

Analogue input for ac-separated receive signal.

16

SS

AO

N-channel open drain output to control the external high power source transistor for

supplying (Vpp) the loudspeaker amplifier in off-hook loudspeaking/handsfree mode.

17

LS

AI

Analogue input for sensing the line current.

18

CI

AI

Analogue input pin for the capacitor to program a complex impedance.