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austriamicrosystems AG

AS2520 Datasheet Preview

AS2520 Datasheet

Telephone Speech Circuit with Loudhearing and Handsfree

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Preliminary
AS2520/21/20B/21B
Telephone Speech Circuit
with Loudhearing and Handsfree
Austria Mikro Systeme International AG
Key Features
u Line/speech circuit, loudhearing, handsfree and
dc/dc converter on one 28 pin CMOS chip
u Operating range from 13 to 100 mA (down to 5
mA with reduced performance)
u Soft clipping control eliminating harsh distortion
u Volume control of receive signal with squelch and
automatic loop gain compensation
u Line loss compensation pin selectable
u Low noise (max. - 72 dBmp)
u Real or complex impedance adjustable
u NET 4 compatible
u Dynamically controlled voice switching
u Same monitor amplifier for loudhearing, handsfree
and tone ringer
u Very few external components
u Power derived from ring signal by switching
converter during ringing
Typical Application
La
General Description
The AS2520/21/20B/21B are CMOS integrated
circuits that contain all the audio functions needed to
form a high comfort, line-powered telephone.
The devices incorporate line adaptation, speech
circuit, loudhearing and handsfree - all supervised by
the novel voice and power control circuit. A switching
converter is also provided for converting the ring
signal. The interface to a dialler/controller is made
very simple to allow easy adaptation to a telecom
microcontroller.
The AS2520 series incorporate volume control for the
earpiece and the loudspeaker (AS2520 digital with +/-
keys and AS2521 analogue with potentiometer). The
volume control circuit automatically compensates the
loop gain to ensure acoustic stability.
Package
Available in 28 pin SOP and DIP.
Lb
3V
123
456
789
*0 #
DIALLER
µCONTROLLER
LCD DRIVER
TELEPHONE
SPEECH CIRCUIT
WITH
LOUDHEARING,
HANDSFREE,
DC/DC CONVERTER
HSM
HFM
Rev. 5.1
AS2520
Figure 1: Typical Handsfree Telephone Application
Page 1
May 1999




austriamicrosystems AG

AS2520 Datasheet Preview

AS2520 Datasheet

Telephone Speech Circuit with Loudhearing and Handsfree

No Preview Available !

Preliminary
Pin Description
Pin #
Name
1 LS
2 CI
3 RO
4 VDD
5 AGND
6 STB
7 LLC
8 LSI
9 TI
10 RTH
11 CM
12 VPP
13 LO
14 VSSP
15 MT
16 PD
17 LE
18 HS
Rev. 5.1
AS2520/21/20B/21B
Type
AI
AI
AO
Supply
Supply
AI
DI
AO
AI
DI
AI
AO
Supply
AO
Supply
DI
DI
DI
DI
Description
Line Current Sense Input
This input is used for sensing the line current.
Complex Impedance Input
Input pin for the capacitor in the complex impedance.
Receive Output
This is the output for driving a dynamic earpiece with an impedance of 140
to 300 ohm.
Positive Voltage Supply
This is the supply pin for the circuit.
Analogue Ground
This pin is the analogue ground for the amplifiers.
Side Tone Balance Input
This is the input for the side tone cancellation network.
Line Loss Compensation Selection Pin
LLC = VDD: High range
LLC = A : Low range
GND
LLC = VSS: No regulation
-6 dB from 45 mA to 75 mA;
-6 dB from 20 mA to 50 mA;
gain independent of line current;
Loudspeaker Amplifier Input
This is the input for applying the receive signal to the loudspeaker
amplifier.
Tone Input
This switchable input is intended for transmitting DTMF or other signals
like messages on TAMs (Telephone Answering Machines) onto the line in
off-hook conditions and when in ringing mode to apply a PDM signal to the
loudspeaker (see also table 1).
Receive Threshold Input
The sensibility of the receive peak detector can be adjusted by applying
the signal from RO to the RTH input through a voltage divider.
Converter Make Output
This is an output for controlling the external switching converter. It
converts the ring signal into a 4V supply voltage and is activated when PD
= high and HS, LE, MT = low.
Loudspeaker Power Supply
High power supply for the output driver stage.
Output for Loudspeaker
Output pin for an ac coupled 32 (25 to 50 )loudspeaker.
Negative High Power Supply
This pin is the negative high power supply for the loudspeaker amplifier.
Mute Input
Dialling mute input (see also table 1).
MT = V : Tx and Rx channels muted;
DD
MT = VSS: Tx and Rx channels not muted.
Power Down Input
Input for powering down the speech circuit and loudhearing/handsfree
(see table 1).
Loudhearing Enable Input
Input for enabling loudhearing/handsfree, active high (see table 1).
Handset Switch Input
This is an input that is pulled high by the hook switch (handset) or µC
when off-hook (see table 1).
Page 2
May 1999


Part Number AS2520
Description Telephone Speech Circuit with Loudhearing and Handsfree
Maker austriamicrosystems AG
Total Page 14 Pages
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