Datasheet AS2574BP, AS2574BN Datasheet (Austria Mikro Systeme International)

Data Sheet

AS2574B

20 NUMBER ONE TOUCH DIALLER WITH



SERIAL BUS FOR DISPLAY DRIVER

Austria Mikro Systeme International

Key Features

❑ Low operating voltage (2.5V to 5.5V)
❑ Low current consumption (typ. 200 µA in LD mode)
❑ Oscillator using ceramic resonator (681 kHz)
❑ MF level independent of supply voltage
❑ Direct ´wake-up´ from keyboard
❑ Automatic Call Progress by direct memory key
❑ Data protection with 8 digit FIFO
❑ Sliding cursor protocol with comparison
❑ Diode options for different PTT requirements
❑ Automatic pause generation after access code
❑ Temporary MF select via keyboard
❑ 36 digit LNR (Last Number Redial)
❑ 20 memories addressable with direct keys and the

2nd key or indirect with a MEM key

❑ Notepad
❑ Serial interface to display driver AS2590
❑ Consistent, simple and useable procedures
❑ Input for dial tone recognizer

General Description

The AS2574B is an integrated CMOS device for feature
telephones. It is a very versatile LD/MF dialler with serial
interface to a display driver. The device is designed to be
used in a wide variety of applications together with the
companion display driver, AS2590.

The on chip RAM can contain up to 20 memories (each
with maximum 18 digits), a 36 digit Last Number Redial
(LNR) and an 18 digit notepad. Access to the 20 memo­ries is either with direct keys, abbreviated dial code or a
combination of both. The AS2574B provides a unique
feature, Automatic Call Progress (ACP), on all memory
keys, i.e. the circuit automatically seizes the line and
waits for the dial tone and dials the number just by
pressing any of the memory keys (including LNR).

The circuit features 2 different access code procedures
to allow easy use under a PABX. A dial tone input
enables the use of a dial tone recognizer.

Application

High feature telephone sets.

Direct wake-up is an AMS patented
solution providing line seizing with
a telephone, that is entirely
powered from the telephone line,
by pressing a key in a key matrix
connected to a dialler/controller
that is constantly connected to the
line by means of a line voltage
limiter and yet maintaining a high
dc isolation resistance in idle state
(on-hook).

The wake-up feature allows the
user to go off-hook by pressing a
direct memory key or a
loudspeaker key, so-called on­hook dialling or call progress
monitoring, and thereby seize the
line.

Package

Available in 28 pin DIP and PLCC.

La

Lb

E

ENTER

3

2

1

6

5

MODE

ACP

M/B

MS

4

7

*

LS

DISPLAY

R

2ND

9

8

MUTE

#

0

M1

M3
M4 M8

M10MEMM9LNR

Flash

Ground
Loop

M6M5M2

M7

VDD

MS

SDA
SCL

X1

V23

X2

V13

AS2590

BIAS

V

LCD

Vss

DP

ER

R1

VDD

R2

HS

R3

MASK

R4

TONE

DIALLER/CONTROLLER

R5

OSC1

C6
C5

OSC2

C4
C3

TB

C2
C1

AS2574B

CD

MT

Vss
SCL

MR

SDA

LS

32.768kHz

681kHz

SPEECH

LOUDHEARING

HANDSFREE

TONE RINGER

Rev. 1

1

Jan. 1995

Data Sheet

Pin Description

Pin # Pin Node Description

1 OSC2 Oscillator pins for ceramic resonator (681 kHz)
2 OSC1

3 SCL The SCL output is used to clock all data into the display driver
4 SDA The SDA output is used to transfer data into the display driver

5 - 10 C1 - 6 Keyboard columns

11 - 15 R1 - 5 Keyboard rows

16 LS Output for controlling loudhearing and handsfree facilities, active high

(see hook state diagramme)

17 MASK Mask output, active high during pulsing (make and break period, see timing

diagrammes).

18 CD Chip disable input, active low.

When CD is low, the circiut is disabled.
If this pin is pulled to VSS during Off-hook (indicating a disconnect) for more than

2 sec., the circuit is reset*. If the pin is pulled to VSS for less than 2 sec., the
line break is ignored.
* If in ACP or monitor state, reset also means return to idle state.

19 MR Mute output, active high during signalling (see timing diagrammes).

AS2574B

20 MT Transmit mute output, active high when MR is high and when

the Mute key has been activated (see timing diagrammes).

21 ER Earth recall input/output, active high during ER but when forced to VDD,

the flash is enabled.

22 DT Dial tone input.

This input is scanned when invoking ACP or a pause is read in a digit string:

DT pin Function
Open Pause duration 4.1 sec
Low If a high is not detected within 8 sec., the circuit is

reset *

High If the pin is high for > 1.15 sec., the pause is termi-

nated and the dialling continued. Noise immunity > 8 ms

* Reset means that dialling is stopped and the circuit returns to standby.
If the circuit was in ACP state, the reset will also return the circuit to idle state.

23 DP Hook switch control, dial pulse and flash output; low during Idle and break

periods and high during off-hook (see timing diagrammes).

Continues…

Rev. 1

2

Jan. 1995

Data Sheet

Pin Description Continued

Pin # Pin Node Description

24 HS Hook switch input; active high with internal pull-down resistor. Debounce 25 ms.
25 Vss Negative terminal of power supply.
26 TB Tone burst output:

LS high 80 ms burst, 8 sec pause
MT high 80 ms burst, 2 sec pause Only in speech mode
MT+LS high 80 ms burst, 2 sec pause

27 TONE MF tone output.

An on chip reference voltage provides tone levels independent of the
supply voltage.

A dc path from TONE output is needed to accommodate an external voltage
divider for setting the appropriate tone level.

Frequencies:

Frequency (Hz) Key Matrix (Hz) Error (%)

AS2574B

697 row 1
770 row 2

852 row 3

941 row 4
1209 col. 1 ≤ ± 0.7%
1336 col. 2
1477 col. 3
1633 see p. 7

28 Vdd Positive terminal of power supply

Keyboard Layout

COLUMN

123456

1

2

3

ROWS

4

5

123

456

789

*

LS

0

LNR M9

#

ENTER

RECALL

2ND

MUTE

MEM

M1

M2

M3

M4

M10

M5

M6

M7

M8

In off-hook state all keys are
enabled (CD = high)

Enabled only
when off-hook

Enabled also
when ACP is
active (diode 5
inserted)

The keyboard is arranged in a 5 x 6 contact matrix with single pole single throw
contacts (SPST).
Keyboard resistance: Ron < 5 k

Rev. 1

Ω

; Roff > 5 MΩ.

3

Enabled when
CD = high

Jan. 1995

Data Sheet

AS2574B

Power On Reset

The on chip analogue power on reset circuit monitors the
supply voltage (VDD). As long as VDD remains below the
internal reference voltage, V
oscillator is inhibited. When VDD rises above V
signal is generated to assure correct start-up, and the
oscillator is enabled.

The correct start-up/reset condition of the circuit is
guaranteed regardless of the absolute and chronologi­cal rise time of VDD, CD and HS inputs.

(typically 1.2V), the

REF

, a reset

REF

Line Supervision

In off-hook condition the device performs supervision of
the line current disconnects in the following manner:
Line disconnects (CD low) of less than 2 sec. are ignored
and the device continues operation.
Line disconnects of more than 2 sec. cause stop of
dialling and the circuit is switched to standby mode if HS
is high, otherwise the circuit will return to idle mode.

Valid Keys

A valid key is detected from the keyboard by connecting
the appropriate row to the column. This can be done
using an n x m keyboard matrix with single contacts.
Positive and negative edges of each contact are de­bounced. The debounce time is 15 ms.

following procedures revert it to default LD mode:

- pressing R key (all subsequently entered digits are
buffered in FIFO),

- by next On-hook.

Last Number Redial

LNR is a facility that allows resignalling of the last
manually dialled number without keying in all the digits
again. The LNR is repeatable.

A manually entered number is automatically stored in the
LNR RAM. The capacity of the RAM is 36 digits. If a
number greater than 36 digits is entered, the LNR facility
will be inhibited (until new entries < 37 digits) and further
entries will be buffered in FIFO. If more than 18 digits are
entered, the display will show the digit 19 and onwards.

Postdialled digits, i.e. digits manually entered after LNR
has been invoked, are not stored in RAM but buffered in
FIFO.

The current contents of the LNR RAM are overwritten by
new entries.

Memory Dial

An on chip RAM enables the dialler to store up to 20
numbers, each containing a maximum 18 digits/data.

In idle state (on-hook) only the LS key is always valid
independent of the CD pin. When diode 5 is connected,
also the LNR, MEM, and M1 - 9 keys are valid entries
invoking ACP (automatic call progress).

Mute Key

Depressing the Mute key activates and deactivates
(toggle switch) the MT output, when internal mute is
inactive, i.e. when no data is being read from the RAM or
FIFO.

A change of the hook state will release the mute.

Mode Selection

The default mode (LD or MF) can be selected by the
diode option mode (diode 6).

When default LD mode is selected, a temporary change
to MF mode can be invoked by pressing the * key.

When the circuit is in temporary MF mode, each of the

The first 10 memories are accessible with 10 Direct dial
keys (M1 to M10) and another 10 memories (11 - 20) are
accessible by pressing the 2nd key before one of the
Direct dial keys or by pressing the MEM key and a digit
0 - 9 (abbreviated dialling).

Basic store procedure:
1 Press Enter key
2 Key in digits, including access code, pauses and recall

as appropriate (number is stored in LNR RAM)

3 Select location by keeping Enter key depressed while

entering the desired location (M1…M10, 2nd

M1…M10, or MEM 0…9)
4 Release Enter key to finish
5 Continue with 1, 2, 3 and 4 for storing further numbers.
Only the first 18 digits/data will be stored when copying

more than 18 digits/data in a memory.

Rev. 1

4

Jan. 1995

Data Sheet

AS2574B

Recall Function

A recall activation will invoke a flash (timed loop break)
or an earth recall (ER) depending on the ER pin. When
the ER pin is forced to VDD, a flash is executed; and when
ER is open (> 50 kΩ}, an earth recall is executed.

If R is the first entry in a digit string, it will be stored in LNR
RAM.

If the R key is depressed after a digit string has been
dialled out, the recall will not be stored, and subsequently
entered digits will be buffered in the FIFO.

A recall will automatically generate a pause when a recall
is read from a memory and therecall has been stored as
an access code.

A manual invoked earth recall will pull ER high for
minimum 500 ms, but the ER pin is maintained high as
long as the key is depressed.

During auto dial an earth recall is executed with a
duration of 500 ms.

Access Codes

Different access codes (totally up to 18 digit/data inclu­ding spaces) can be stored in one string. Spaces bet­ween the different access codes are entered by pressing
the 2nd # during programming. Each access code can
contain up to 4 digits.

If one or more access codes are stored, the first entered
digit(s) in a digit string read from the RAM will be
compared with the access code(s) and if equal, a pause
is generated.

Pause Generation

Pause introduces a delay in signalling digits strings to
accommodate second and subsequent dial tones.

Automatic pauses are generated:

- during dialling out from memories when the first digit(s)

in the digit string equal the stored access code(s)

(pause depends on DT input).

- when going Off-hook by pressing LNR, MEM, or M1 -

9 (ACP).
Any pause can be terminated (shortened) prior to time

out by pressing the LNR key or a high level on the DT
input.

During ACP a pause time out, i.e. DT kept low for > 8
sec., will return the device to idle state.

Pauses are storable as digits within a string of any of the
memories by pressing 2nd # during programming.
Multiple pause entries can be stored up to the maximum
length of the digit string (18 digits/data). A pause is not
accepted in location 1 of a digit string.

If more pauses have been stored in succession, they can
all be terminated by one depression of the LNR key or a
high level on the DT pin for ≥ 1.15 sec.

Sliding Cursor Procedure

To accommodate redialling (LNR) behind a PABX wi­thout using automatic pause generation (storing access
codes), a sliding cursor protocol is implemented. If new
entries match the previous LNR RAM contents, pressing
the LNR key will dial out the remaining digits.

Example on programming access codes:

ENTER, 9 , 2nd #, 50

Keep

ENTER

Release both
The first access code in this example is 9 and the second

50.

Rev. 1

depressed while pressing

0

If there is an error in matching, the LNR will be inhibited
until next On-hook, and the LNR RAM will contain the
new number.

5

Jan. 1995

Data Sheet

AS2574B

Serial Interface

The AS2574B supports a serial bus. The protocol
defines device that sends data onto the bus as a
transmitter, and the receiving device as the receiver. The
AS2574B is controlling the transfer and hence the
master. The display driver, AS2590, being controlled is
the slave.

Clock and Data Conventions

Data states on the SDA line can change only during SCL

SDA

SCL

START

BIT

Figure 1: Data Transmission

No Symbol/command MSB B3 B2 B1 LSB HEX

10111001C
2 1 0000000

3 2 0010004
4 3 0001002
5 4 1000010
6 5 1010014
7 6 1001012
8 7 0100008

98011000C
10 9 0 1 0 1 0 0A
11 a 0 0 1 1 0 06
12 b 1 0 1 1 0 16
13 c 0 1 1 1 0 0E
14 d 1 1 1 1 0 1E
15 * 1 1 0 0 0 18
16 # 1 1 0 1 0 1A
17 Pause 1 1 0 1 1 1B
18 Temporary MF select 1 1 0 0 1 19
19 Recall 0 0 0 0 1 01

20 LS on 0 0 1 0 1 05
21 LS off 0 0 0 1 1 03

22 MT on 1 0 0 0 1 11
23 MT off 0 1 0 0 1 09
24 2nd on 0 0 1 1 1 07
25 2nd off 1 1 1 1 1 1F
26 Set Clock 0 1 0 1 1 0B
27 Start 0 1 1 0 1 0D
28 Start copy 0 1 1 1 1 0F
29 Start FIFO 1 0 0 1 1 13
30 Start timer 1 0 1 0 1 15
31 Blank all 1 1 1 0 1 1D
32 Test mode 1 0 1 1 1 17

BIT 0 BIT 1 … … BIT 4 STOP BIT

low. SDA state changes during SCL high are reserved
for indicating start and stop conditions (see figure 1).

Start Condition

All commands are preceded by the start condition, which
is a high to low transition of SDA when SCL is high.

Stop Condition

All communications are terminated by a stop condition,
which is low to high transition of SDA when SCL is high.

WORD

GAP

Rev. 1

6

Jan. 1995

Data Sheet

Key Combinations

Key/Key Combination Function Remarks

ENTER Programming

R Flash or ground loop Code no 19

MEM Abbreviated dialling

MUTE Privacy mute Code no 22/23

LS Monitor/Handsfree Code no 20/21

LNR Last Number Redial During execution of a pause the LNR key is used

M1 - 10 Direct memory keys

2nd Second functions Code no 24
2nd, 1 a Code no 11
2nd, 2 b Code no 12
2nd, 3 c Code no 13

AS2574B

to terminate the pause.

2nd, 4 d Code no 14

2nd, * Enter FIFO Code no 29

2nd, # Pause Code no 17

2nd, M1 - 10 Memories 11 - 20

MEM, 0 - 9 Memories 11 - 20

ENTER, Address* Displaying content of Memo

ENTER/Address* Programming Code no 28 when both keys are released

ENTER/# Setting clock Code no 26
2nd, 5 - 9 5 - 9 Code no 6 - 10

2nd, 0 0 Code no 1
2nd, R RECALL Code no 19

2nd, MUTE Privacy MUTE Code no 22/23

ENTER/LNR Clearing LNR Code no 27

ENTER, ENTER Displaying Access code Code no 27

*)

Address

means M1 - 10 keys or 2nd, M1 - 10 or MEM, 0 -9 key combinations.

Rev. 1

7

Jan. 1995

Data Sheet

Diode Options

Option Column Function No diode diode

NoP 1 Number of Pulses Standard NZ

Digit 1 1 9

228
337
446
555
664
773
882
991
01010

FT 2 Flash Time 101.2 ms 600 ms

MS 3 Memory Size 10 20

M/B 4 Make/Break Ratio 33/66 ms 40/60 ms

AS2574B

ACP 5 Automatic Call Progress no yes

MODE 6 Default Signalling Mode MF LD

Columns

123456

Row 5

MODEACPM/BMSFTNoP

System Considerations

The device is intended to be used in telephone instru­ments, that are permanently on-line, i.e. also when on­hook the circuit is connected to the telephone line, but in
standby mode (idle) and hence only drawing a small
leakage current from the line.

This implementation offers new features like electronic
hook switch and call progress monitoring (on-hook
dialling).

Call progress monitoring (CPM) means pressing the LS
key will switch the telephone on from standby (direct
´wake-up´from keyboard) and will present the dialling
tones via a loudspeaker without lifting the handset.

Furthermore, it is also possible to invoke the CPM by
pressing the LNR, MEM or M1 - 9 when the ACP
(Automatic Call Progress) is activated (diode 5).

Procedure Principles

The procedures for utilizing the features of the device are
optimized out of consideration for the human factor
in order to:

- meet the user´s expectations

- be easy to learn and relearn

- not invoke any automatic functions which the user
doesn’t expect

- protect the user from committing critical errors, e.g.
dialling wrong numbers, deleting stored numbers, etc.

- be consistent, simple and usable.

The diode options
are scanned by
POR and low to
high transition on
HS.

Rev. 1

8

Jan. 1995

Data Sheet

Symbols

Idle Standby state, no keys activated

Idle

AS2574B

Manual Dial

Off-hook

On-hook

Lifting handset (HS = High) or pressing LS key

Replacing handset (HS = Low) or repressing LS key

Idle

Idle

Off-hook

Key in

digits

Entries stored

in LNR RAM

Rev. 1

Entries are

dialled out

Speech mode

On-hook

Idle

The last manually dialled number is automatically stored in the LNR RAM.
In LD mode * invokes temporary MF mode and # are ignored.
In MF mode * and # are automatically stored in LNR RAM.

9

Jan. 1995

Data Sheet

Programming/Notepad

During programming
the dial out is inhibited.

Speech mode

Speech mode

or idle

Enter

AS2574B

correction

Key in

an address

Content of selected

memory is displayed

Enter

change

Direct dial

(M1 - 10)

no

Key in

number

Digits are entered

in LNR RAM

Enter

keep Enter
depressed

2nd MEM

Direct dial
(M11 - 20)

Digit 0

(access codes)

Digit 0-9

(M11 - 20)

Rev. 1

release

Access code(s)

are displayed

10 Direct dial keys, a MEM and a 2nd key are available for addressing up to 20 numbers.
Each number can contain up to 18 digits, including recall and pauses.
Programming a new number will automatically clear the previous.
2nd, # has to be pressed between the different access codes.

Enter

stored

Speech mode

Speech mode

or idle

The content of the LNR RAM
is stored in the selected memory.

Code no 28

10

Jan. 1995

Data Sheet

Direct Dial/Abbreviated Dial/Last Number Redial

AS2574B

D

MEM 2nd

Digit 0 - 9

(M11 - 20)

(M11 - 20)

N

HS = High

Direct dial

Idle

Y

Off-hook

Y

D

Diode

3 ?

N

Direct dial

(M1 - 10)

D

LNR

DDD D

Terminate pause

Reset timer

DT high

≥

N

1.15 sec

Pause

4 sec

Y

H

Executing pause

Starting timer

Hi-Z

DT
pin

L

Timer

overflow

Y

N

DIALLING

Y

All digits
dialled ?

Speech mode

Postdialling

available

Pause

N

N

Y

Rev. 1

11

Jan. 1995

Data Sheet

AS2574B

Automatic Call Progress (ACP)

D

Y

MEM

Off-hook

Off-hook

Start timer

Start timer

Time-out

8 sec

N

Digit 0 - 9

(M11 - 20)

D

D

Idle

(Diode 5 inserted)

Y

Diode

3 ?

Direct dial

(M1 - 9)

Off-hook

Off-hook

Start timer

Start timer

N

LNR

Off-hook

Off-hook

Start timer

Start timer

DD

Terminate pause

Reset timer

DT high

≥ 1.15 sec

N

Time-out

8 sec

N

Pause

4 sec

Y

H

Executing pause

Starting timer

Hi-Z

DT
pin

L

Timer

overflow

Y

N

Reset timer

Dialling

Y

All digits
dialled ?

Speech mode

Postdialling

available

Pause

N

Y

Y

N

Rev. 1

12

Jan. 1995

Data Sheet

Privacy Mute

MT output will go low.

AS2574B

(code 23)

Speech mode

Dialling

Change of
hook state

Mute key

Speech mode

MT high

Mute key

Speech mode

(code 22)

(code 23)

MT output will go low.

Rev. 1

13

Jan. 1995

Data Sheet

Temporary MF Select

AS2574B

Speech mode

LD default

*

Speech mode

MF selected

Key in

digits

All further entries are NOT stored in LNR
RAM but buffered in FIFO.
The LNR RAM will contain the number
entered before pressing the * key and
the mode change code.

Recall On-hook

LD default Idle

Key in

digits

LD default

Off-hook

Speech mode

LD default

Rev. 1

14

Jan. 1995

Data Sheet

Setting Clock (in display driver)

Speech mode

Speech mode

or idle

keep Enter

Enter

depressed

keep Enter

keep Enter

depressed

depressed

Press

#

AS2574B

__:__

keep Enter

Enter

depressed

release

Enter

Key in hours

(2 digits)

Key in min.

(2 digits)

Speech mode

Speech mode

or idle

or idle

18:__

18:31

Rev. 1

15

Jan. 1995

Data Sheet

Hook States

AS2574B

1)

Idle

LS

Monitor

P O T

2)

5)

or

Handsfree

LS

P O T

+

Monitor

1) Pressing any unvalid key doesn´t have any effect in Idle state.

2) POT means Plain Ordinary Telephone.

3) Lift handset means HS going high.

4) Replace handset means HS going low.

5) Lifting the handset during ACP will change the hook state to POT, however, the dialling will continue uneffected.

LS

Diode

5 ?

N

Y

M

( )

Dialling

finished

LS

Automatic

Call Progress

(ACP)

Y

On-hook

Off-hook

N

Rev. 1

16

Jan. 1995

Data Sheet

Timing Diagrammes

The timing diagrammes do not show the correct scaling only the sequence.

P.O.T.

< 2 sec. 2 sec.

CD

HS

DP

Whole
keyboard
enabled

AS2574B

Monitor State

CD

LS key

DP

Whole
keyboard
enabled

CD

Diode scanning

2 sec.

< 2 sec. 2 sec.

ιι

ιι

ιι

< 2 sec.

ιι

Rev. 1

LS key

DP

17

ιι

ιι

Jan. 1995

Data Sheet

LD Dialling

Osc

AS2574B

Key entry

MT

MR

Mask

DP

= depending on Mute key
(high when Mute key has been activated, otherwise low)

MF Dialling

Osc

Key entry

2 1

Tidp

Tpre

2 1

Tm

Tb

Tpo

3

Tidp

Tpre

Tho

TbTb

Tpo

MT

MR

Mask

Tone

DP

Tmo

Tho

Ttd Titp

= depending Mute key
(high when Mute key has been activated, otherwise low)

Tmo

Tho

Rev. 1

18

Jan. 1995

Data Sheet

AS2574B

Flash

Osc

Key entry

MT

MR

Mask

DP

GL

Pause

= depending on Mute key
(high when Mute key has been activated, otherwise low)

Ground Loop (GL)

R

T

pre

Tfd

Tpo

T

ho

Osc

Key entry

MT

MR

Mask

DP
GL

Pause

R

Tho

Tgl

Tpre

= depending on Mute key
(high when Mute key has been activated, otherwise low)

Tpo

Rev. 1

19

Jan. 1995

Data Sheet

Automatic Dialling LD (content of LNR is GL, 2, 1 and GL is stored as access code)

Osc

AS2574B

Key entry

MT

MR

Mask

DP
GL

Pause

Automatic Dialling MF (content of LNR is Flash, 1, 2, 3, and Flash is stored as access code)

LNR

Tap

Tpo

= depending on Mute key
(high when Mute key has been activated, otherwise low)

Tidp

Tho

Osc

Key entry

MT

MR

Mask

DP
GL

Tone

Pause

LNR

Tap

Tpo

= depending on Mute key
(high when Mute key has been activated, otherwise low)

Tmo

Rev. 1

20

Jan. 1995

Data Sheet

Electrical Data

Absolute Maximum Ratings

AS2574B

Positive Supply Voltage ...................................................................................................................-0.3V ≤ V

LS

≤ 7V

Input Voltage .......................................................................................................................-0.3V ≤ VIN ≤ VDD + 0.3V

Input Current ................................................................................................................................................± 25 mA

Storage Temperature......................................................................................................................-65°C to +125°C

Electrostatic Discharge (HBM)......................................................................................................................±1000V

Recommended Operating Range

Parameter Symbol Min Typ Max Unit Condition

Operating Temperatur Top - 25 70 °C
Operating Voltage V
Retention Voltage V

DD

DD

2.5 3.0 5.5 V

1.8 5.5 V

Oscillator Frequency Fosc 681 kHz

DC Characteristics

Default conditions: Recommended Operating Range; VDD = 3.0V.

Parameter Symbol Min Typ Max Unit Condition

Supply Current I

DD

Outputs unloaded

Operating except MF 200 250 µA
Operating MF 0.75 1 mA

Data Retention 1 2 µAVDD=1.8V; note1

24µA Note 1

Input Voltage

Low Vil V

SS

High Vih 0.7xV

DD

0.3xV
V

DD

DD

V
V

Input Current

Low Iil 1 µA
High Iih 1 µA

Output Current

Sink Iol 1.5 mA Vol = 0.4V
Source Ioh 1 mA Voh = VDD - 0.4V

Pull-down Resistor

HS Input Rhs 1 MΩ
CD Input Rcd 1 MΩ

Scanning Current DT During Pause

Sink Isl 20 150 µA
Source Ish 20 150 µA

Note 1: Circuit in Idle state (HS = Low and no key activated).

Rev. 1

21

Jan. 1995

Data Sheet

Signalling Characteristics

Defaults conditions: Recommended Operating Range

Parameter Symbol Min Typ Max Unit Condition

Clock Startup Time Ts 5 ms
Key Debounce Time Td 14 18 ms

HS Debounce Time Ths 21 26 ms
CD Reset Delay Time Tr 2 sec

DTMF

Tone Level, High Group Vol - 12.4 - 10.9 - 9.4 dBm RL = 15 kΩ
Preemphasis 2 2.5 2.8 dBm RL = 15 kΩ
Distortion - 26 dBr RL = 15 kΩ, note 3

Tone Duration Ttd 80 82.3 85 ms Note 1
Inter Tone Pause Titp 80 82.3 85 ms Note 1

Tone Rise/Fall Time Ttr 5 ms Note 2

LD

Dial Rate 10 pps ± 5%
Make/Break Period Tm/Tb 33/66 ms ± 5%
(diode option) 40/60 ms ± 5%
Inter Digit Pause Tidp 753 785 ms
Pre Digit Pause Tpre 55 57 ms
Post Digit Pause Tpo 55 57 ms

Flash

Duration Tfd 100 101.2 103 ms No diode 2

600 620 ms With diode 2

AS2574B

Earth Recall Tg

Duration 500 510 ms

Automatic Access Pause Tap

Short 4 4.1 4.2 sec DT = Hi-Z
Long 7.9 8 8.1 sec DT = Low
Termination 1.15 1.2 1.25 sec DT = High

Mute Overhang Tmo 182 200 223 ms
MR/MT Hold Over Tho 18 27 ms

Tone Burst

Frequency Fb 700 800 Hz
Output Level Vtb -13 -11 -9 dBm
Tone Duration Ttb 80 85 ms
Inter Tone Pause (LS) Titb1 7 8 9 sec
Inter Tone Pause (Mute) Titp2 1.8 2 2.2 sec

Time-out Tto 7.7 8 8.2 sec

Note 1: The values are valid during automatic dialling and are minimum values during manual dialling, i.e. the tones will continue

as long as the key is depressed.

Note 2: The rise time is the time from valid key detection (key has been debounced) till the tone amplitude has reached 90 % of its

final value.

Note 3: Relative to high group.

Rev. 1

22

Jan. 1995

Data Sheet

Pin Configuration

28 Pin DIP 28 Pin SOIC

AS2574B

OSC2
OSC1

SCL

SDA

C1
C2
C3

C4
C5

C6
R1
R2
R3
R4

128

Vdd
TONE
TB
Vss
HS
DP

DT
ER

MT
MR

CD
MASK
LS

14 15

R5

OSC1

SCL

SDA

C1
C2
C3
C4
C5
C6

R1

R2
R3
R4

128OSC2

14 15

Vdd
TONE
TB
Vss
HS
DP
DT
ER
MT

MR
CD
MASK

LS

R5

28 Pin PLCC

C1
C2
C3
C4
C5
C6

R1

SDA

R2

SCL

R3

OSC1

R4

OSC2

Vdd

LS

R5

TONE

TB

CD

MASK

Ordering Information

Part number Package

AS2574B P 28 pin DIL
AS2574B N 28 pin PLCC

Vss
HS
DP
DT
ER
MT

MR

Rev. 1

23

Jan. 1995

Data Sheet

AS2574B

Devices sold by Austria Mikro Systeme are covered by the warranty and patent indemnification provisions appearing in its Term of
Sale. Austria Mikro Systeme makes no warranty, express, statutory, implied, or by description regarding the information set forth
herein or regarding the freedom of the described devices from patent infringement. Austria Mikro Systeme 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 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 equipment are specifically
Mikro Systeme for each application.

Copyright  1995, Austria Mikro Systeme International, Schloss Premstätten, 8141 Unterpremstätten, Austria. Trademarks
Registered. 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.

Rev. 1

24

not

recommended without additional processing by Austria

Jan. 1995