Data Sheet AS2540

Revision 3.1

Page 3 of 18

Pin #

Symbol

Function

25

OSC

Input for ceramic resonator 3.58MHz.

Recommended type: Murata CSA 3.58MG312AM or compatible

12

AGND

Special ground for the internal amplifiers

26

RXD

Schmitt trigger input to serial interface

27

TXD

Open drain output from serial interface

20

21

R1

R2

Keyboard

22

23

24

C1

C2

C3

Keyboard

10

ROT

Output for driving a transformer with an ac impedance larger than 10k

Ω

1TIT

Single ended input for transformer

9ROH

Output for driving a dynamic earpiece with an impedance from 150

Ω to 300Ω

13

14

M2

M1

Differential inputs for the microphone (electret)