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Preliminary Data Sheet
AS2504
(R)
Austria Mikro Systeme International AG
Cordless telephone, answering machine line interface
General Description
AS2504 is a CMOS integrated circuit that incorporates DC and AC line adaptation (DCmask and synthesised AC-impedance of 1000) as well as a speech circuit with softclipping, line loss compensation and Rxvolume control. It shall act as an a/b-line powered or auxiliarily powered device, which is controlled by a CPU.
Key Features

Analogue line interface and speech circuit for a/b terminals on a 28-pin CMOS-IC 2 balanced transmit inputs 3 unbalanced transmit inputs 2 buffered single ended receive outputs (RL>150) 1 auxiliary single ended receive output (RL>10k) Low noise (max. -72dBmp) Soft clipping to avoid harsh distortion Operating range from 15mA to 100mA (down to 5mA with reduced performance) Line loss compensation selectable by pin option Real and complex impedance selectable by external components Side tone adaptation selectable by external components Digital controls input for mode selection Rx volume control
Application
Cordless base stations, answering machines, a/b-line or auxiliary powered telephone sets.
Package
Available in 28 pin SOIC
Block Diagram
1/12
August 1998
Preliminary Data Sheet
AS2504
Pin description
Pin # 7 5 6 13 3 Symbol LS LI RI STB CS Function
Line Current Sense Input
Input for sensing the line current
Line Input
Input used for power extraction and line current sensing
Receive Input
Input for ac-separated receive signal
Side Tone Balance Input
Input for side tone cancellation network
Current Shunt Control Output N-channel open drain output to control the external high power shunt transistor for synthesising AC- and DC-impedance, modulation of line voltage and shorting the line during make periods of pulse dialling Complex Impedance Input
Input pin for the capacitor to program a complex impedance
14 25
CI MASK
MASK
Input pin to set circuit into power down mode during e.g. LD-dialling. During MASK=HIGH, CS-pin is internally shorted to ground.
26
LLC
Line Loss Compensation Select Pin
45mA-75mA 20mA-50mA None --> VDD --> AGND --> VSS
11
VDD
Voltage Drain Drain
Positive Power Supply, for external circuitry t.m. 4.0mA@IL=20mA and 4.0mA@IL=20mA
4 12 2 1 28 27 24 23
VSS AGND M1 M2 M3 M4 ATI1 ATI2
Voltage Source Source
Negative Power Supply
Analogue Ground
Special ground for the internal amplifiers
Microphone Input 1
Differential input for the microphone (electret)
Microphone Input 2
Differential input for the microphone (electret)
Microphone Input 3
Differential input for the microphone (electret)
Microphone Input 4
Differential input for the microphone (electret)
Auxiliary Transmit Input 1
RI >= 25k
Auxiliary Transmit Input 2
RI >= 100k
2/12
August 1998
Preliminary Data Sheet
AS2504
Pin # 15 8
Symbol ATI3 ROH1
Function
Auxiliary Transmit Input 3
RI >= 100k
Receive Output to Handset 1
Output for driving a dynamic earpiece with an impedance from 150 to 300 (max. 0.7Vp)
9
ROH2
Receive Output to Handset 2
Output for driving a dynamic earpiece with an impedance from 150 to 300 (max. 1.4Vp)
10 16
ARO1 VOL
Auxiliary Receive Output 1
RL > 10k (max. 1.4Vp)
VOLume
Input pin for increasing (= connect to VIN >= VDD-0.3V) or decreasing (= connect to VIN <= VSS+0.3V) the Rx volume. The idle state is between VSS+1.4V < VIN < VDD-1.4V. Max rise time 50ns, max fall time 50ns, min pulse width 1us
22 21 18 17 20 19
HSS RX0 AUX0 AUX1 TX0 TX1
HandSet or HeadSet / bit Digital input to select the ROH1 or ROH2 signal output path Receive 0 / bit Digital input to select a signal path Auxiliary 0 / bit
Digital input to select a signal path
Auxiliary 1 / bit Digital input to select a signal path Transmit 0 / bit Digital input to select a signal path Transmit 1 / bit Digital input to select a signal path

3/12
August 1998
Preliminary Data Sheet
AS2504
Functional Description
Modes of operation There are 3 possible modes: Idle Mode: AS2504 is disconnected from the a/b-line (= no line current) and VDD is not supplied by auxiliary power. All internal circuits are powered down. Input of digital control signals is not possible. Line Power Mode: AS2504 is connected to the a/b-line and VDD is generated by the internal power extraction. The speech circuit is powered up. The line interface circuit is functional (DC-mask and AC-impedance are synthesised). Input of digital control signals is possible. Aux. Power Mode: AS2504 is disconnected from the a/b-line (= no line current) and VDD is supplied by auxiliary power. The speech circuit is powered up. The line interface circuit is not functional (DC-mask and AC-impedance). Input of digital control signals is possible.
The DC characteristic is determined by the voltage at LI-pin and a 30 resistor between LI- and LS-pin. It can be calculated by the following equation: VLS = VLI + ILine * 30. The t.m. voltage at the LI-pin is 4.5V. The calculation leads to the following DC resistances: 330 to 75 at line currents from 15mA to 100mA. With a HIGH at the MASK-pin, the speech circuit and other parts of the device, which are not needed for operation, are in power down mode in order to save current. The CS-pin is pulled to Vss to turn the external shunt transistor fully on. This guarantees a low voltage drop (<1V) at the LI-pin during make periods of pulse dialling or flash.
2/4 wire conversion AS2504 has a built-in dual Wheatstone bridge with one common ground. This provides a maximum of independence of AC-impedance and side tone from each other. One can adapt side tone without changing the AC-impedance.
Start-up in Line Power Mode As soon as AS2504 is supplied with line current, the external Vdd capacitor will be charged up via the LI- and VDD-pin. After the Vdd voltage has reached the operating level of 2V, the line interface circuit and the selected signal path of the speech circuit is switched on. This off-hook status is signalled to the internal logic via the LS-pin (voltage level sensitive).
AC-impedance The AC-impedance of AS2504 is set to t.m. 1000. With the external capacitor at CI-pin it can be programmed complex. With an external resistor of approx. 1.5k connected to the LSpin it can be programmed to 600. ZAC(syn) = 33 * 30.
Side Tone Start-up in Aux. Power Mode As soon as AS2504 is supplied with auxiliary power at the VDD-pin, the selected signal path of the speech circuit is switched on. The line interface circuit (DC-mask and AC-impedance) is not functional. This on-hook status is signalled to the internal logic via the LS-pin (voltage level sensitive). A good sidetone cancellation can be achieved by using the following equation: ZBAL/ZLINE = 10
Transmit path The gain of the M1/M2 --> LS is set to 37dB. The input is differential with an impedance of 20k. The soft clip circuit limits the output voltage at LS to 2Vp. The attack time is 30s/6dB and the decay time is 20ms/6dB. The gain of the M3/M4 --> LS is set to 43dB. The input is differential with an impedance of 10k. The soft clip circuit limits the output voltage at LS to 2Vp. The attack time is 30s/6dB and the decay time is 20ms/6dB. 4/12 August 1998
DC conditions The normal operating mode is from 15mA to 100mA. An operating mode with reduced performance is from 5mA to 15mA. In the line hold range from 0mA to 5mA the device is in a power down mode and the voltage at LI is reduced to a maximum of 3.5V
Preliminary Data Sheet
AS2504
Rx volume control The gain of the ATI1 --> LS is set to 6dB. The input is unbalanced with an impedance of 25k. There is no softclipping. The gain of the ATI2 --> LS is set to 20dB. The input is unbalanced with an impedance of 100k. There is no softclipping. The volume control is available for LS --> ROH1 and LS --> ROH2. It can be decreased by 6dB and increased by 8dB in 2dB steps from the default levels as described in the last paragraph. It remains in the pre-set position as long as VDD does not decrease less than 2.2V
Intercom path The gain of the ATI3 --> ROH1 is set to 6dB. The input is unbalanced with an impedance of 100k. There is no softclipping. The gain of the ATI3 --> ROH2 is set to 12dB. The input is unbalanced with an impedance of 100k. There is no softclipping. The gain of the M1/M2 --> ARO1 is set to 23dB. The input is differential with an impedance of 20k. The soft clip circuit limits the output voltage at ARO1 to 0.4Vp. The attack time is 30s/6dB and the decay time is 20ms/6dB. The gain of the M3/M4 --> ARO1 is set to 29dB. The input is differential with an impedance of 10k. The soft clip circuit limits the output voltage at ARO1 to 0.4Vp. The attack time is 30s/6dB and the decay time is 20ms/6dB.
Line Loss Compensation The line loss compensation is a pin option. When it is activated, the transmit and receive gains for both I/O's are decreased by 6dB at line currents from 20mA to 50mA when the LLC-pin is connected to AGND and from 45mA to 75mA when the LLC-pin is connected to VDD. The line loss compensation is deactivated when LLC-pin is connected to VSS.
Digital interface The selection of the available signal paths must be set via the digital control pins. The following modes are possible:
HSS: bit 0 1 0 1
RX0: bit 0 0 1 1
LS --> ROH1 LS --> ROH2 ATI3 --> ROH1 ATI3 --> ROH2
Receive path The gain of the LS --> ROH1 receive path is set to 3dB. The receive input is the differential signal of RI and STB. The soft clip circuit limits the output voltage at ROH1 to 0.7Vp. It prevents harsh distortion and acoustic shock. There is volume control and LLC for this path. The gain of the LS --> ROH2 receive path is set to 9dB. The receive input is the differential signal of RI and STB. The soft clip circuit limits the output voltage at ROH2 to 1.4Vp. It prevents harsh distortion and acoustic shock. There is volume control and LLC for this path. The gain of the LS --> ARO1 receive path is set to 3dB. The receive input is the differential signal of RI and STB. There is no softclipping, no LLC and no volume control for this path.
AUX0: bit 1 0 0 1 0
AUX1: bit 1 1 1 0 0
HSS: bit X 0 1 X X
MUTE M1/M2 --> ARO1 M3/M4 --> ARO1 LS --> ARO1 MUTE
TX0: bit 0 0 0 1 1
TX1: bit 0 0 1 0 1
HSS: bit 0 1 X X X
M1/M2 --> LS M3/M4 --> LS ATI1 --> LS ATI2 --> LS MUTE
5/12
August 1998
Preliminary Data Sheet
AS2504
Typical Application
6/12
August 1998
Preliminary Data Sheet
AS2504
Electrical characteristics
Electrical charateristics are measured with the Test Circuit application. Typical mean values will not be tested.
Absolute maximum ratings Positive Supply Voltage Input Current Input Voltage (LS) Input Voltage (LI, CS) Input Voltage (STB, RI) Digital Input Voltage Electrostatic Discharge (HBM 1.5k-100pF) Storage Temperature -0.3V <= VDD <= 7V 25mA -0.3V <= Vin <= 12V -0.3V <= Vin <= 8V -2V <= Vin <= VDD+0.3V -0.3V <= Vin <= VDD+0.3V 1000V -65C to +125C
Recommended operating conditions Supply Voltage (generated internally) Operating Temperature 4V <= VDD <= 5V -25C to +70C
DC characteristics ILine=15mA w/o operation of any additional external circuitry, unless other specified Symbol Parameter IDD VLI IOL VIL VIH Operating Current Line Voltage Output Current, Sink CS VOL=0.4V Digital Input Voltage LOW Pins HSS,RX0,TX0, TX1,AUX0,AUX1 VSS 0.8 VDD 1 0.2 VDD VDD mA V V Conditions Speech Mode MASK=H, VDD=2.5V 15mA<=ILINE<=100mA 4.2 Min Typ 3 300 4.5 Max 5 4.8 Units mA A V
Digital Input Voltage HIGH Pins HSS,RX0,TX0, TX1,AUX0,AUX1
7/12
August 1998
Preliminary Data Sheet
AS2504
Transmit characteristics V ILine=15mA f=800Hz, unless other specified Symbol Parameter AM1/2TX Transmit Gain M1/M2 --> LS AM3/4TX Transmit Gain M3/M4 --> LS AAT1X AAT2X Transmit Gain ATI1 --> LS Transmit Gain ATI2 --> LS Variation with frequency Distortion Unwanted Freq. Comp. Soft Clip Level M1/M2 --> LS at LS Soft Clip Level M3/M4 --> LS at LS Soft Clip Overdrive M1/M2 - M3/M4 Attack time Decay time Conditions ZAC(syn)=1000 ZAC(syn)=1000 ZAC(syn)=1000 ZAC(syn)=1000 f = 500Hz ... 3.4kHz VLS=0.25VRMS f = 200Hz ... 20kHz 2.0 2.0 20 30 20 20 10 25 100 60 differential TAMP=25C ZAC(syn)=1000 18 0.5 1 -71 Min +36.0 +42.0 +5.0 +19.0 Typ +37.5 +43.5 +6.5 +20.5 0.8 2 -60 Max +39.0 +45.0 +8.0 +22.0 Units dB dB dB dB dB % dBm VP VP dB
s/6dB ms/6d B
ATX
THD VUFC VAGC1 VAGC2 ASCO tattack tdecay
ZIN-M1/2 Input Impedance M1/M2 ZIN-M3/4 Input Impedance M3/M4 ZIN-ATI1 Input Impedance ATI1 ZIN-ATI2 Input Impedance ATI2 AMUTE VINmax VNO RL Mute Attenuation M1/2 - M3/4 Input Voltage Range M1/2 - M3/4 Noise Output Voltage LS Return Loss Temp. Variation
k k k k dB Vp dBmp dB /C
ZAC/C
8/12
August 1998
Preliminary Data Sheet
AS2504
Intercom characteristics ILine=15mA f=800Hz, unless other specified Symbol Parameter AM1/2IX AM3/4IX AAT3IX AAT4IX Intercom Gain M1/M2 --> ARO1 Intercom Gain M3/M4 --> ARO1 Intercom Gain ATI3 --> ROH1 Intercom Gain ATI3 --> ROH2 Conditions Min +21.5 +27.2 +4.5 +10.5 Typ +23.0 +28.7 +6.0 +12.0 100 Max +24.5 +30.2 +7.5 +13.5 Units dB dB dB dB k
ZIN-ATI3 Input Impedance ATI3
Receive characteristics ILine=15mA f=800Hz, unless other specified Symbol Parameter AHRX AAR1X AAR1X Receive Gain LS --> ROH1 Receive Gain LS --> ROH2 Receive Gain LS --> ARO1 Variation with frequency Volume control range Distortion ROH1-ROH2 Distortion ARO1 Unwanted Freq. Comp. Soft Clip Level ROH1 Soft Clip Level ROH2 Soft Clip Overdrive ROH1/2 Attack time Decay time Noise Output Voltage ROH1/2 - ARO1 Input Imp. RI Input Voltage Range RI TAMP=25C 8 2 VLS=0.25VRMS VLS=0.25VRMS f = 200 ... 20kHz 0.7 1.4 10 30 20 -71 Conditions ZAC(syn)=1000 ZAC(syn)=1000 ZAC(syn)=1000 f=500Hz to 3.4kHz Min +1.0 +7.0 +0.7 Typ +2.5 +8.5 +2.2 0.8 -6/+8 2 3 -60 Max +4.0 +10.0 +3.7 Units dB dB dB dB dBr % % dBm VP VP dB
s/6dB ms/6d B
ARX
AVOL THD THD VUFC VAGC VAGC ASCO tattack tdecay VNO ZIN-RI VINmax
dBmp k Vp
9/12
August 1998
Preliminary Data Sheet
AS2504
Symbol Parameter ZIN-STB VINmax ST RL Input Imp. STB Input Volt. Range STB Sidetone Return Loss Temp. Variation
Conditions
Min
Typ 80 2
Max
Units k Vp dB
VRI<=0.25VRMS ZAC(syn)=1000
24 18 0.5
ZAC/C
dB /C
Test circuit
10/12
August 1998
Preliminary Data Sheet
AS2504
Packaging
The device is available in the packages outlined below (not to scale). For exact mechanical package dimensions please see AMSAG packaging information.
28-pin plastic SOIC (suffix T)
Max. Body Length Max. Body Width Pitch
18.1mm / 713mil 7.6mm / 300mil 1.27mm / 50mil
Pin-out
1 2 3 4 5 6 7 8 9 10 11 12 13 14
- - - - - - - - - - - - - -
M2 M1 CS VSS LI RI LS ROH1 ROH2 ARO1 VDD AGND STB CI
M3 M4 LLC MASK ATI1 ATI2 HSS RX0 TX0 TX1 AUX0 AUX1 VOL ATI3
- - - - - - - - - - - - - -
28 27 26 25 24 23 22 21 20 19 18 17 16 15
Marking
YYWWAAA AS2504 Austria
YY WW AAA
year of production calendar week of production AMSAG assembly ID
11/12
August 1998
Preliminary Data Sheet
AS2504
Ordering information
Number AS2504 T Package SO28 Description
plastic small outline package - 28 leads (suffix T)
Devices sold by Austria Mikro Systeme Int. AG are covered by the warranty and patent idemnification provisions appearing in its Term of Sale. Austria Mikro Systeme Int. AG makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the decribed devices from patent infringement. Austria Mikro Systeme Int. AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior to designing this product into a system, it is necessary to check with Austria Mikro Systeme Int. AG for current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equiment are specifically not recommended without additional processing by Austria Mikro Systeme Int. AG for each application. Copyright (c) 1997-98, Austria Mikro Systeme International Int. AG, Schloss Premstaetten, 8141 Unterpremstaetten, AustriaEurope. Trademarks Registered (R). All rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished here by Austria Mikro Systeme Int. AG is believed to be correct and accurate. However, Austria Mikro Systeme Int. AG shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential damag es, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of Austria Mikro Systeme Int. AG rendering of technical or other services.
Headquarters
Austria Mikro Systeme International Int. AG Schlo Premstatten 8141 Unterpremstatten, Austria-Europe Tel: +43 (0)3136 500-0 Fax: +43 (0)3136 52501, 53650 email: info@vertical-global.com http://www.vertical-global.com
France
124 Avenue de Paris F-94300 Vincennes Tel:+33 (0)1 4374 0090 Fax: +33 (0)1 4374 2098
Germany (south)
Stefan-George-Ring 19 D-81929 Munchen Tel: +49 (0)89 993 558-0 Fax: +49 (0)89 993 558-66
Germany (nord)
Am Seestern 8 D-40547 Dusseldorf Tel: +49 (0)211 536 02-0 Fax: +49 (0)211 536 02-50
Hong Kong
21/F., 1 Des Voeux Road West Sheung Wan, Hong Kong Tel: +852 2524 2738 Fax: +852 2868 4155
Italy
Piazzale Lugano 9 I-20158 Milano Tel: +39 02 3932 1022 Fax: +39 02 3932 3087
Spain
Parc Tecnologic del Valles E-08290 Cerdanyola/Barcelona Tel: +34 (0)93 582 4470 Fax: +34 (0)93 582 4471
Sweden (Scandinavia)
Sjoangsvagen 7 S-19272 Sollentuna Stockholm Tel: +46 (0)8 7549 395 Fax: +46 (0)8 7544 544
United Kingdom
Coliseum Business Centre Watchmoor Park Camberley, Surrey England GU15 3YL Tel: +44 (0)1276 233 99 Fax: +44 (0)1276 293 53
USA
Suite 460 20863 Stevens Creek Blvd. Cupertino, CA 95014 Tel: +1 408 865 1217 Fax: +1 408 865 1219
Austria Mikro Systeme Int. AG is represented by distributors in the following countries. Please contact your nearest regional sales office for the distributor's address: China, India, Japan, Korea, Singapore, Taiwan
Application support
Please contact your local sales office or your distributor
12/12
August 1998

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