sames
SA2532
1/22
sames
VERSATILE SINGLE CHIP TELEPHONE
4153
SA2532 A/C/U
PDS039-SA2532-001 Rev. C 23-10-1995
FEATURES
n
Speech circuit, LD/MF Dialler and Tone
Ringer on one 28 pin CMOS chip
n
Soft clip to avoid harsh distortion
n
Line Loss Compensation selectable by
pin option
n
Power down mode
n
Versatile applications for different PTT
demands
n
31 digit last number redial
n
Sliding Cursor protocol with comparison
n
2 Flash keys, 100 ms and 280 ms (option
600 ms)
n
Pause key for 3 sec Auto Pause or Wait
Function
n
Ring frequency discrimination
n
Operating range from 13 to 100 mA
(down to 5 mA with reduced perform-
ance)
n
Low noise (max. -72dBmp)
n
Real or Complex impedance on chip pro-
grammable
n
LD/MF switchable dialling
n
On chip MF filter (CEPT CS 203 compat-
ible)
n
3-tone melody generator with selectable
repetition rates
1/22
GENERAL DESCRIPTION
The SA2532 is a CMOS integrated circuit that
contains all the functions needed to form a
high performance electronic telephone.
The device incorporates LD/MF dialling,
melody generation, ring frequency discrimi-
nation and a high quality speech circuit.
A RAM is on chip for a 31 digit last number
redial. The sliding cursor procedure makes
Last Number Redial easy behind a PABX.
The versatility of the circuit is provided by on
chip programmability and a few external com-
ponents. This allows easy adaption to differ-
ent PTT requirements without changing the
PCB of the telephone.
PACKAGE
Available in 28 pin DIP and SOIC
SA2532
HS DP
DR-00975
OSC
C3
C4
RR
14
AGND
STB
LLC
CI
MO
DD
RO2
RO1
LS
V
1
R2
15
R4
R3
C1
C2
M2
MODE
M1
FCI
R1
28
SS
V
CS
RI
LI
2/22
SA2532
sames
PIN DESCRIPTION
Pin#
Symbol
Function
23
M1
Microphone Inputs
24
M2
Differential inputs for the microphone (electret).
3
RO1
Receiver Outputs
2
RO2
These are the outputs for driving a dynamic earpiece with an impedance
of 100 to 300
5
A
GND
Analog Ground
This is the analog ground for the amplifiers.
28
RI
Receive Input
This is the input for the receive signal.
6
STB
Side Tone Balance Input
This is the input for side tone cancellation.
1
LS
Line Current Sense Input
This is the input for sensing the line current.
27
LI
Line Input
This input is used for power extraction and line current sensing.
25
CS
Current Shunt Control Output
This N-channel open drain output controls the external high power shunt
transistor for the modulation of the line voltage and for shorting the line
during make period of pulse dialling.
4
V
DD
Positive Voltage Supply
This is the supply pin for the circuit.
26
V
SS
Negative Power Supply
8
MO
Melody Output
Pulse Density Modulated output of the melody generator for tone ringer. At
high impedance when not active.
21
FCI
Frequency Comparator Input
This is a Schmitt trigger input for ring frequency discrimination. Disabled
during off-hook.
10
HS/DP
Hook Switch Input and Dial Pulse Output
This is an I/O that is pulled high by the hook switch when off- hook. An open
drain pulls it low during break periods of pulse dialling and flash.
11
OSC
Oscillator Input
Oscillator pin for Xtal or ceramic resonator (3.58 MHz).
9
LLC
Line Loss Compensation
Select pin for line loss compensation.
12
RR
Repetition Rate
Select pin for repetition rate of melody.
22
MODE
Signalling Mode Select Input
Mode pin
Function
High
LD default mode, make/break = 33/66 ms
Open
MF only
Low
LD default mode, make/break = 40/60 ms
20
R1
Keyboard Rows
19
R2
18
R3
17
R4
16
C1
Keyboard Columns
15
C2
14
C3
13
C4
7
CI
Complex Impedance Input
Input pin for the capacitor in the complex impedance
sames
SA2532
3/22
FUNCTIONAL DESCRIPTION
Power On Reset
The on chip power on reset circuit monitors the supply voltage (V
DD
). When V
DD
rises above
approx. 1.2V, a power on reset occurs to assure correct start-up and the RAM is cleared.
DC Conditions
The normal operating range is from 13mA to 100 mA. Operating range with reduced
performance is from 5mA to 13mA. In the operating range all functions are operational.
In the line hold range from 0 to 5 mA the device is in a power down mode and the voltage at
LI is reduced to maximum 3.5V.
The dc characteristic (excluding diode bridge and Pulsing transistors) is determined by the
voltage at LI and the resistor R1 as follows:
VLS = VLI + I
Line
.R1
The voltage at LI is 4.5V.
During pulse dialling the speech circuit and other parts of the device not required are in a
power down mode to save current. The CS pin is pulled to V
SS
in order to turn the external
shunt transistor on to keep a low voltage drop at the LS pin during make periods.
AC Impedance
The Characteristic or Output impedance of the SA2532 is set within the IC and adjusted by
Mask Options. Available options are for 600
and 1000
. When the 1000
option is selected
then a capacitor may be added to the circuit at pin CI to add a reactive element and make the
output impedance complex.
Oscillator
All the Timing Functions of the SA2532 are based on a Clock Frequency of 3.58MHz. A crystal
or ceramic resonator of this frequency should be connected to the OSC pin. In practise minor
deviations from the nominal frequency may occur due to the characteristics of the frequency
reference device used and so it is recommended that care is taken in the selection of
components.
In some cases a small value capacitor (
47pF) may have to be connected in parallel with the
Frequency Reference to ensure start-up and/or operation at the nominal frequency.
Speech Circuit
The speech circuit consists of a transmit and a receive path with soft clip, mute, line loss
compensation and side tone cancellation.
Transmit
The gain of the transmit path is 35 dB for M1/M2 to LS (see test circuit figure 5). The
microphone input is differential with an input impedance of 25 k
.
The soft clip circuit limits the output voltage at LI to 2.0V
PEAK
. The attack time is 30s/6dB
and the decay time is 20 ms/6 dB. When mute is active, during dialling or after pressing
the MUTE key, the gain is reduced by > 60 dB.
4/22
SA2532
sames
Receive
The receive input is the differential signal of RI and STB. The gain of the receive path is
2 dB (test circuit figure 5) with differential outputs, RO1/RO2 (0dB on SA2532C/U). When
mute is active during dialling the gain is reduced by > 60dB. During DTMF dialling a MF
comfort tone is applied to the receiver. The comfort tone is the DTMF signal with a level
that is -30dB relative to the line signal.
Side Tone
Side Tone is controlled along with Return Loss by a Double Balance Bridge as shown in
Fig. 1.
Figure 1
Double balance bridge (return loss and side tone) with one common ground
A good side tone cancellation is achieved by using the following equation:
ZBAL =
R5
ZLINE
R1
The side tone cancellation signal is applied to the STB input.
Line Loss Compensation
When Line Loss Compensation is active the gain of the Transmit and Receive amplifiers
are changed by 6dB in accord with the DC conditions as measured at Pins LI and LS.
When the LLC Pin is Low this adjustment in gain occurs over the range I
LINE
= 20 to 50 mA.
When LLC is High the range is 45 to 75mA. Note that these figures apply for R1 = R30
.
When the LLC Pin is open the amplifier gains remain fixed regardless of the Line Current.
O N E C O M M O N G R O U N D
Z
B
A
L
DR-00708
R E T U R N L O S S
LINE
V
Z
R
E
F
S S
R 2
R 1
RI
S I D E T O N E
R 5
S T B
S Y N
LI
sames
SA2532
5/22
Dialling Functions
Valid Keys
The keypad of the SA2532 comprises a maximum of 20 keys (of which 3 have no function).
A Bi-polar scan technique is used so that the 20 keys are scanned in a 4 x 5 matrix using
only 8 pins.
A valid key is detected when one and only one contact closure is detected between a Row
and Column Pin. Key contacts are debounced to avoid incorrect detection.
Dial Mode Selection
The default mode (LD or MF) can be selected by the Mode pin. When default LD mode
is selected, a temporary change to MF can be invoked by pressing the * key. The circuit
will revert to LD by pressing the R (or R2) key or by next on-hook.
When MF mode is selected by the mode pin, the circuit can not be changed temporarily
to LD but will remain in MF.
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.
The current contents of the RAM are overwritten by new entries.
A manually entered number is automatically stored in the LNR RAM. The capacity of the
RAM is 31 digits. If a number greater than 31 digits is entered, the LNR facility will be
inhibited (Until new entries < 32 digits) and further entries will be buffered in a First In First
Out Memory (FIFO).
Post dialled digits, i.e. digits manually entered after LNR has been invoked, are not stored
in RAM but buffered in FIFO.
During dialling, one or more pauses can be inserted by pressing the PAUSE KEY. Each
pause is 3 secs (optionally 6 secs) when inserted within the first 5 digits. Otherwise a Wait
Function will halt dialling until the LNR Key is pressed.
Recall Function
A Recall (R key or R2 key) activation will invoke a Flash (Timed Loop Break).
If Recall is the first entry in a digit string, it will be stored in LNR RAM when digit(s) are
entered after the Recall.
If the recall key is depressed after a digit string has been entered or dialled out, the recall
will not be stored but buffered in the FIFO together with subsequently entered digits.
If pressing the recall key is not followed by digit entries, the LNR RAM remains intact.
After a recall, a 3 second pause will automatically be executed.
Mute Function
The MUTE key is enabled in speech mode only. Depressing the MUTE key mutes the
microphone amplifier. Repressing the MUTE key deactivates the mute (toggle function).
Any key entry overwrites a mute activated by the MUTE key and mute will be deactivated.
When privacy mute is activated a reminder tone is applied to the earpiece every 3
seconds.
6/22
SA2532
sames
Sliding Cursor Procedure
To accommodate easy and uncomplicated redialling (LNR) behind a PABX, a sliding
cursor protocol is implemented. If new entries match the previous RAM contents,
pressing the LNR key will dial out the remaining digits.
If there is an error in matching, the LNR will be inhibited until next on-hook, and the RAM
will contain the new number.
Tone Generator
The tone generator incorporates the DTMF tones and 3 basic frequencies for the tone
ringer.
DTMF Tones
The DTMF Tone Generator creates 12 Tones in compliance with CCITT Recommenda-
tion Q23. Signal levels are altered by Mask Option. High group frequencies have a level
2.6dB higher than those of the Low Group.
Details of the DTMF Tones are:
Low group
Digit 1-2-3
697Hz
(Error = -.074%)
Digit 4-5-6
770Hz
(Error = -.679%
Digit 7-8-9
852Hz
(Error = -.621%)
Digit *-0-#
941Hz
(Error = +.139%)
High group
Digit 1-4-7-*
1209Hz
(Error = +.533%)
Digit 2-5-8-0
1336 Hz
(Error = +.176%)
Digit 3-6-9-#
1477Hz
(Error = -.141%)
Errors are calculated with reference to a base clock of 3.58MHz and at ambient
temperature of 24C. They exclude tolerance errors in the base frequency.
KEYBOARD ARRANGEMENT
Figure 2
DR-00709
R 3
R 4
LNR/CONT.
#
8
9
PAUSE
R 2
R 1
C 1
4
MUTE
C 2
5
1
R
0
R2
*
C 3
6
2
C 4
7
3
sames
SA2532
7/22
Microcontroller Interface
The keypad Row and Column Pins can readily be driven by a Microcontroller Interface. When
configured in this way the SA2532 inputs and dials the corresponding digits in either LD or
DTMF. The LNR store can be used to buffer digits to allow high speed data entry. See
Application Note AN3002A for details.
Tone Ringer
The Tone Ringer of the SA2532 incorporates a Discriminator Circuit and adjustable Melody
Generator
Ring Frequency Discrimination
The Ring Frequency Discriminator assures that only signals with a frequency between
20Hz and 60Hz (option 13 Hz to 60 Hz) are regarded as valid ring signals.
When a valid ring signal is present for 73ms continuously, the melody generator is
activated and remains active as long as the ring signal is present.
Once the melody generator has been started, the ring signal is continuously monitored
and the melody generator is instantly turned on or off according to the momentary
presence of a valid or unvalid ring signal respectively (until next POR or off-hook).
Melody Generator
When a Valid Ring Signal is detected the Melody generator is activated and creates a
ringing Signal comprising 3 frequencies F1 (1065Hz), F2 (1420Hz) and F3 (1734Hz).
These frequencies are repeated in a sequence of 6 time slots constructed by the
frequencies
F1
F2
F3
F1
F2
F3
This sequence is repeated 1, 4, 7 or 10 times per second as indicated by the connection
of the RR Pin to one of the four rows of the keyboard.
8/22
SA2532
sames
TYPICAL APPLICATION
Only the components necessary for presenting the complete functions of the SA2532 are
included.
FIGURE 3
sames
SA2532
9/22
FEATURE PHONE APPLICATION
Only the components necessary for presenting the complete functions of the SA2532 are
included.
FIGURE 4
10/22
SA2532
sames
OPERATING PROCEDURES
Procedure Principles
The procedures for utilizing the features of the SA2532 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
SYMBOLS
sames
SA2532
11/22
Privacy Mute
12/22
SA2532
sames
Temporary MF
FIFO
Pressing any other
key does not
change the state.
EXIT FIFO
sames
SA2532
13/22
TIMING DIAGRAMS
MF Dialling
LD Dialling
LD Dialling with Access Pause
14/22
SA2532
sames
ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings
Positive Supply Voltage ....................................................................................... -0.3V
V
DD
7V
Input current .................................................................................................................. 25mA
Input Voltage (LS) .............................................................................................. -0.3V
V
IN
10V
Input Voltage (LI, CS) ........................................................................................... -0.3V
V
IN
8V
Input Voltage (STB, RI) .............................................................................. -2V
V
VIN
V
DD
+0.3V
Input Voltage (MO) ............................................................................................. -0.3V
V
IN
35V
Digital Input Voltage ................................................................................... -0.3V
V
IN
V
DD
+0.3V
Electrostatic Discharge ................................................................................................... 800V
Storage Temperature ...................................................................................... -65C to +125C
Recommended Operating Conditions
Supply Voltage * (Speech Mode).......................................................................... 4V
V
DD
5V
Oscillator Frequency (Resonator: Murata CSA 3.58M G312AM).......................... 3.58 MHz
Operating Temperature ................................................................................... -25C to +70C
* This voltage is generated internally
DC Characteristics (I
LINE
= 15 mA unless otherwise specified)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
I
DD
Operating Current
Speech mode
3
5
mA
MF dialling
4
mA
LD dialling V
DD
= 2.5V
200
A
Ring mode V
DD
= 2.5V
300
A
I
DDO
Retention Current
Idle mode V
DD
= 2V,
0.05
A
T
AMB
= 25C
V
LI
Line Voltage (default)
13mA
I
LINE
100mA
4.5
V
I
OL
Output Current, Sink
V
OL
= 0.4V
1.5
mA
CS,HS/DP,MO
Flash
sames
SA2532
15/22
AC Characteristics (I
LINE
=15mA;f=800Hz unless otherwise specified)
Symbol Parameter
Conditions
Min
Typ
Max
Units
TX
Transmit
Test Circuit Fig.5
A
TX
Gain (M1/M2)
Z
RL
=600
34
35
36
dB
Z
RL
= 1000
36.5
A
TX/F
Variation with Frequency
f=500Hz to 3.4kHz
0.8
dB
THD
Distortion
V
LI
0.5V
RMS
2
%
V
AGC
Soft Clip Level
V
LI
=
2
V
PEAK
A
SCO
Soft Clip Overdrive
20
dB
t
ATTACK
Attack Time
30
s/6dB
t
DECAY
Decay Time
20
ms/6dB
Z
IN
Input Impedance (M1/M2)
20
k
A
MUTE
Mute Attenuation
Mute activated
60
dB
V
NO
Noise Output Voltage
-72
dBmp
V
FC
Unwanted Frequency
50...300 Hz
-43
dBm
Components
4.3...28 kHz
note 1
above 28 kHZ
-70
dBm
V
IN MAX
Input Voltage Range
Differential
1
V
PEAK
(M1/M2)
Single Ended
0.5
V
PEAK
BJT
Output Driver
V
IN MAX
Input Voltage Range (LI)
2
V
PEAK
V
TX
Dynamic Range
2
V
PEAK
RL
Return Loss Z
RL
= 600
SA2532A
18
dB
Z
RL
= 1000
SA2532C/U
Note 1: -37 dBm at 4.3 kHz and decreasing 12 dB/octave till 28 kHz.
16/22
SA2532
sames
AC Characteristics (cont'd) (I
LINE
= 15 mA;f=800Hz unless otherwise specified)
Symbol Parameter
Conditions
Min
Typ
Max Units
RX
Receive
Test Circuit Fig.5
A
RX
Receive Gain (RO1/RO2) Z
RL
=600
1
2
3
dB
Z
RL
=1000
-0.2
A
RX/F
Variation with Frequency
f=500 Hz to 3.4 kHz
0.8
dB
THD
Distortion
V
RI
0.5V
RMS
2
%
V
AGC
Soft Clip Level
V
RI
=
1
V
PEAK
A
SCO
Soft Clip Overdrive
10
dB
t
ATTACT
Attact Time
V
RI
>0.8V
30
s/6dB
t
DECAY
Decay Time
20
ms/6dB
V
NO
Noise Output Voltage
-72
dBmp
V
FC
Unwanted Frequency
50 Hz...20 kHz
-60
dBm
Components
Z
IN
Input Impedance (RI)
8
k
V
IN RI
Input Voltage Range(RI)
2
V
PEAK
ST
Sidetone
Test Circuit Fig.5
A
ST
Sidetone Cancellation
V
RI
0.5V
RMS
26
dB
V
IN ST
Input Voltage Range (STB)
2
V
PEAK
Z
IN
Input Impedance (STB)
80
k
Keyboard
t
D
Key Debounce Time
15
ms
HS Input
t
HS-L
Low to High Debounce
Going off-hook
15
ms
t
HS-H
High to Low Debounce
Line breaks/on-hook
240
ms
DTMF
F
Frequency deviation
Note 5
-.679
+.533
%
V
MF
MF Tone Level(Low group) Optionally
-12.5
-11
-9.5
dB
-9.5
-8
-6.5
dB
V
L-H
Preemphasis Low to High
2.0
2.6
3.0
dB
THD
Distortion
Note 3
-30
dBr
t
TD
Tone Duration
Note 1
80
82.3
85
ms
t
ITP
Inter Tone Pause
80
82.3
85
ms
sames
SA2532
17/22
AC Characteristics Cont'd
Symbol Parameter
Conditions
Min
Typ
Max
Units
t
TR
Tone Rise Time
Note 2
5
ms
t
TF
Tone Fall Time
Note 2
5
ms
LD
t
DR
Dial Rate
5%
10
pps
t
M/B
Make/Break Period
5%, MODE=low
40.8/61.2
ms
5%, MODE=high
33/66
ms
t
PDP
Pre-Digit Pause
35
ms
t
IDP
Inter Digit Pause
800
840
880
ms
t
MO
Mute Overhang
t
M
t
FD
Flash Duration 1
100
102
ms
Flash Duration 2
SA2532A/C
270
300
ms
Flash Duration 2
SA2532U
600
650
ms
t
PFP
Post Flash Pause
2.9
3.0
3.1
sec.
t
AP
Access Pause Period
SA2532A/U
2.9
3.0
3.1
sec
SA2532C
5.8
6.0
6.2
sec
Tone Ringer
V
MO
Melody Output Level
PDM
t
MD
Melody Delay
10
ms
F1
Frequency 1
1020
1064
1107
Hz
F2
Frequency 2
1363
1420
1477
Hz
F3
Frequency 3
1665
1734
1803
Hz
t
DT
Detection Time
Initial
70
80
ms
t
TO
Detection Time-out
note 4
ms
f
MIN
Min. Detection Frequency
19
20
21
Hz
f
MIN
Min. Detection Frequency
Optionally
12
13
14
Hz
f
MAX
Max. Detection Frequency
58
59
60
Hz
Reminder Tone
V
RT
Level (RO1/RO2)
Relative to LS
-30
dBr
t
RTD
Duration
82.3
ms
t
RTI
Interval
3
sec
Comfort Tone (DTMF)
V
CT
Level (RO1/RO2)
Relative to LS
-30
dBr
18/22
SA2532
sames
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 10% of final value until the tone amplitude has reached
90% of its final value.
Note 3:
Relative to high group.
Note 4:
The FCI circuit is reset by POR and HS/DP pulled high (off-hook). After a reset the
FCI circuit is in a standby state. A positive edge on FCI will start a 73ms timer and
the frequency discrimination is initiated. Whenever a period of the ring signal is
missing, the timer is reset. When a valid ring signal is present for
73ms, the
melody generator is started and is directly controlled by the ring signal. This
condition will remain until a new reset.
Note 5:
This does not include the frequency deviation of the ceramic resonator.
sames
SA2532
19/22
Test Circuit
Figure 5
20/22
SA2532
sames
Ordering Information:
Versions
ZRL
DTMF
R2
Access
Package
(ohm)
Level
Period
Pause
SA2532A P
600
-6/-8dBm
280ms
3s
28 pin DIP
SA2532A S
600
-6/-8dBm
280ms
3s
28 pin SOIC
SA2532C P
1000
-6/-8dBm
280ms
6s
28 pin DIP
SA2532C S
1000
-6/-8dBm
280ms
6s
28 pin SOIC
SA2532U P
1000
-9/-11dBm
600ms
3s
28 pin DIP
SA2532U S
1000
-9/-11dBm
600ms
3s
28 pin SOIC
sames
SA2532
21/22
NOTES:
22/22
SA2532
sames
Disclaimer: The information contained in this document is confidential and proprietary to South African Micro-
Electronic Systems (Pty) Ltd ("SAMES) and may not be copied or disclosed to a third party, in whole or in part,
without the express written consent of SAMES. The information contained herein is current as of the date of
publication; however, delivery of this document shall not under any circumstances create any implication that
the information contained herein is correct as of any time subsequent to such date. SAMES does not undertake
to inform any recipient of this document of any changes in the information contained herein, and SAMES
expressly reserves the right to make changes in such information, without notification,even if such changes would
render information contained herein inaccurate or incomplete. SAMES makes no representation or warranty that
any circuit designed by reference to the information contained herein, will function without errors and as intended
by the designer.
South African Micro-Electronic Systems (Pty) Ltd
P O Box 15888,
33 Eland Street,
Lynn East,
Koedoespoort Industrial Area,
0039
Pretoria,
Republic of South Africa,
Republic of South Africa
Tel:
012 333-6021
Tel:
Int +27 12 333-6021
Fax:
012 333-8071
Fax:
Int +27 12 333-8071
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