sames

SA545

1/18

sames

SA545, SA54L5

PULSE/DTMF SWITCHABLE DIALLERS WITH 10 REPERTORY
MEMORIES

FEATURES

Selectable Loop-disconnect (Pulse) or
DTMF (Tone) dialling modes

10 x 24 Digit Repertory Dialling Stores

24 Digit Last Number Redial (LNR)

Selectable Interdigit Pause (IDP)
500ms or 800ms

Operates with inexpensive single
contact keypad

On-chip Darlington transistor pair for
DTMF tone filtering

Low power CMOS technology enables
direct operation from Telephone line

Keypad switchable Loop-Disconnect to
DTMF during a call

PIN CONNECTIONS:
SA545

PIN CONNECTIONS:
SA54L5

M63-1961

PDS039-SA545-001 REV. B 31-08-94

Selectable Break:Make Ratios 2:1 or
3:2

Uses inexpensive 560KHz ceramic
resonator

Earth Loop Recall and Timed Break
Recall (Timed Flash)

Low on-hook Supply Current Options
SA54X53 - 5礎 @ 2.5V
SA54X56 - 1礎 @ 2.5V
SA54X59 - 1礎 @ 3.0V

Call, barring/locking feature available
on the SA54L5

Optional use of external capacitor for
oscillator

sames

SA545

2/18

Supply Voltage V

- V

-0,3

6,5

Voltage on any pin (except HSW)

-0,3

+0,3

Voltage on pin HSW

-0,3

See Note 1

Current at any pin

-1

(except HSW, FILTOUT and FILTIN)

Current at pin FILTOUT

0,1

Current at pin FILTIN

-5

Operating Temperature

-25

癈

Storage Temperature

-55

125

癈

* Stresses above those listed under "Absolute Maximum Ratings" may cause permanent
damage to the device. This a stress rating only. Functional operation of the device at
these or any other condition above those indicated in the operation sections of this
specification, is not implied. Exposure to Absolute Maximum Ratings for extended
periods may affect device reliability.

Note 1: A diode is internally connected between this pin and V

. Provided current is

externally limited to 300礎 max, no damage will occur.

ABSOLUTE MAXIMUM RATINGS *

Parameter

Min

Typ

Max

Unit

Notes

sames

SA545

3/18

Condition

Min

Typ

Max

Unit

Notes

Supply voltage:

on-hook

1,8

5,7

For memory retention

off-hook

2,4

5,7

Hookswitch input: on-hook

0,2 V

off-hook

0,8 V

Supply Current:

on-hook

SA54X53

<0.2

礎

= 2.5V

SA54X56

<0.2

礎

= 2.5V

SA54X59

<0.2

礎

= 3V

off-hook

1,5

礎

If MF OUT is low

MF tone sending

1,0

LD impulsing

200

礎

Output High Voltage

2,2

I = -1mA

(MASK, MUTE and IMP Outputs)

Output Low Voltage

0,3

I = +1mA

(MASK, MUTE and IMP Outputs)

MF OUT d.c. Level During Tone Sending

0,9V

MF OUT Output Resistance

'Key Pressed' Resistance

2,5V<V

<5,7V

'Key Not Pressed' Resistance

500

2,5V<V

<5,7V

Darlington Pair Current Gain

600

50,000

=100礎,V

=2V

DC ELECTRICAL CHARACTERISTICS
(V

= 2,5V at 25癈, unless otherwise specified)

AC ELECTRICAL CHARACTERISTICS
(V

= 2,5V at 25癈, unless otherwise specified)

Condition

Min

Typ

Max

Unit

Notes

Oscillating Frequency

560

kHz

Tone Output: Low Group

mVrms

No Load

High Group

109

mVrms

No Load

High-to-Low Group Amplitude Ratio

1,5

2,5

at MF OUT

Total harmonic Distortion: 0-4KHz

1,5

0-10KHz

2,5

0-50KHz

5,0

0-200KHz

6,5

sames

SA545

4/18

Keypad

Nominal frequency (Hz)

697

770

852

941

1209

1336

1477

Deviation from nominal (%)

-,07

-,10

+,19

-,15

-,17

-,20

-,22

There will be an additional error due to any deviation in the oscillator frequency from 560
kHz.

FUNCTIONAL OVERVIEW
The SAMES SA545 is a family of keypad switchable Loop Disconnect (LD)/Dual Tone
multi-Frequency (DTMF) dialler devices for use in low-cost, dual dialling mode telephone
instruments.

The devices feature automatic storage of a single telephone number of up to 24 digits
for Last Number Redial (LNR) purposes as well as10 repertory dialling memories capable
of each storing 24 digits. The low current consumption of the SA545 ensures memory
retention while powered from the line.

Two modes of operation are available. The first is a LD/DTMF mode which operates
normally in LD mode, but can be switched temporarily via the keypad to DTMF mode
during a call. This mode has been optimised for applications such as home banking,
credit-card verification and other applications requiring low speed data communications.
The second mode allows DTMF dialling only.

The Lock function will be described in the Functional Description.

The SA545 family is pin compatible with SAMES SA541 family.

Ordering Information

S A 5 4 X 5 X / X

Lock Option

L : with (22 pin package)
Blank : without (20 pin package)

On-Hook Current Option

5礎 @ 2.5V

1礎 @ 2.5V

1礎 @ 3V

Blank

MF Digits dialled after */# not stored

/1 :

All MF digits stored

sames

SA545

6/18

SA545

SA54L5

Designation

Description

Positive Supply input

Negative Supply input

OSC OUT

Connections for 560KHz ceramic resonator

OSC IN

MUTE

Active high output during keying and tone transmission.
(See Note 1)

MASK

Output to disable speech circuit during pulse dialling
and recall. (See Note 2)

FILT IN

Unity gain amplifier input and output for DTMF tone

FILT OUT

filtering

MF OUT

DTMF output

IMP

'Loop disconnect' dialling output. During dialling, a
logic 1 (high level) correponds to loop connection while
a logic 0 (low level) corresponds to loop disconnection.

SELECT

LD/DTMF selection, IDP and B:M ratio programming

Column output connections for 16 button single contact

keypad

Row input connections for 16 button single contact

keypad

HSW

Hookswitch input. A logic 1 (High) applied to this input
indicates an "off-hook" condition.

LOCK

Lock Input must be tied to V

to disable all keypad keys

(except TBR and LNR). Normal operation is enabled by
connecting LOCK to V

DD.

N/C

No connection

Note 1: The MUTE output is provided to disable the microphone (via the speech

network) while maintaining the loop condition during DTMF transmission.

Note 2: The MASK output may be used to disconnect the whole speech circuit in order

to maintain the break condition whilst on-hook, during a Timed Break Recall
(TBR) operation or LD dialling.

Table 1: Pin Description

sames

SA545

7/18

FUNCTIONAL DESCRIPTION
Note: All timing data assumes the use of a 560 KHz ceramic resonator as time base.

Power On
When power is applied to the chip, a power-on reset circuit operates and ensures that
the Last Number Redial (LNR) and 10 Repertory stores are cleared and all logic is
reset. The power-on reset circuit is designed such that if the chip supply voltage
drops to a level at which the LNR and Repertory stores may be corrupted, it will
always, under all conditions, clear the stores when power is restored, so that corrupt
data is not retained.

Hookswitch Operation
The HSW input is used to inform the SA545 of whether the telephone is on-hook or
off-hook. Logic `0' is recognised as on-hook, Logic `1' is recognised as off-hook.
When the HSW input rises from `0' to `1' the off-hook state is recognised immediately
and keypad inputs are accepted. However, when the HSW input falls from `1' to `0'
the on-hook state is not recognised for 200-300ms. This ensures that short line
breaks of less than 200ms, such as line reversals applied by the exchange, are
ignored. In this case, the MASK and IMP outputs will go low immediately the HSW
input goes low in order to preserve current, but will resume normal operation
immediately HSW goes high.
On-hook state: In the on-hook state all chip outputs are set low, the oscillator circuit
is inhibited and no key inputs are accepted. This conserves supply current so that
the LNR and Repertory stores contents may be retained.
Off-hook state: When the HSW input goes high, the MASK output immediately
goes to the logic `1' level and remains there until dialling starts (see Figure 5).
COLUMN outputs also go high until a key is pressed. The oscillator circuit remains
inactive until a key is pressed, and is normally off whenever timing functions are not
required, hence reducing operating current.

Keypad Operation
A single contact, normally open keypad is required. When off-hook the COLUMN
outputs are normally held high and the ROW inputs are low (via internal pull-down
resistors). When a key is pressed, a COLUMN output is connected to a ROW input,
pulling the latter high.

This action initiates keyboard scanning. During keyboard scanning, the COLUMN
outputs are normally low but generate scanning pulses at 7ms intervals on each
output, in sequence. A key is accepted as valid when two successive scanning
pulses from the same COLUMN are seen on a ROW input. Hence, the minimum
bounce-free key closure period which is necessary to guarantee detection is
14ms(plus the oscillator start up time if it was not already running).

sames

SA545

8/18

Simultaneous Key Depressions: If two keys are pressed simultaneously (i.e. a
second key is pressed before the first has been verified), neither key will be accepted
until both keys are released and the correct key is pressed again.

Table 2 indicates the keypad layout for the SA54X5 family.

TBR

REDIAL

STORE

PAUSE

TBR:

Timed Break Recall (Flash)

REDIAL:

Last Number and Repertory Store Redial

STORE:

Enters digits into a Repertory Store

PAUSE:

Enters a pause into a Repertory Store

Table 2: Keypad Layout

Dialling Mode Selection
The dialling mode may be selected via the SELECT pin (pin 2) as detailed in Table
3. Four Loop-Disconnect options are available with different Interdigit pauses (IDP)
and Break:Make ratios. If the DTMF mode is selected, dialling will remain fixed in
the DTMF mode. However, if one of the LD modes is selected, the chip will be in
LD mode in the initial off-hook condition, but may be switched to DTMF by pressing
either the

or # keys, provided that dialling is not in progress. If the

or # keys are

pressed during LD dialling, they will be ignored.

Once in DTMF mode, depression of either the

or # keys will cause the relevant

tone-pair to be output. Only digits entered prior to a DTMF switchover will be stored
and available for redialling (see Last Number Redial operation).

Once switched to DTMF, dialling will remain in this mode until either a Recall (Flash)
operation or until the device returns to the on-hook state.

Select (Pin 2)

Dialling

IDP(ms)

B:M Ratio

Connected to:

Mode

800

2:1

500

2:1

500

3:2

800

3:2

DTMF

Table 3: Dialling Mode Selection

sames

SA545

9/18

Last Number Redial (LNR)
The function of the on-chip LNR store is to automatically retain a manually dialled
number for redialling later. The capacity of the store is 24 digits. If a number longer
than 24 digits is dialled, redialling will be inhibited.

The LNR store has two features designed to assist the user,viz: Moving Cursor
Facility and Mixed Mode Dialling.

Moving Cursor Facility: This facility is provided to aid use in PABX applications,
where the user must first dial an access digit or digits, and then wait for a second dial-
tone before continuing dialling.

If the first digit(s) of a new number dialled match the contents of the LNR store, then
pressing LNR (redial button twice) will dial out the remaining digits. If there is a
mismatch in the number then redial is inhibited until the next on-hook and the LNR
store will contain the new number. If the user manually dials the first digit(s) matching
those stored in LNR, and then goes on-hook, the whole contents of the store will be
retained.

Mixed Mode Dialling: In the case of a call which starts in LD mode and is switched
by the user (via the

or # keys) to DTMF mode, only the digits dialled in LD mode

will be retained. Provided that the number of digits dialled in LD mode does not
exceed 24, the digits will be retained regardless of the number of DTMF digits
entered subsequently.

Repertory Dialling (10 Numbers)
The SA545 provides 10 repertory stores each of which is 24 digits in length. Any
attempt to store a number greater than 24 digits, will cause the store to be
automatically cleared. No further digits will be accepted into the store until the whole
programming operation is repeated.

To programme a repertory store: (At any time while off-hook and not dialling.)
1. Press the STORE key
2. Press the number (0-9) of the store to be programmed
3. Enter digits to be stored (No digits will be dialled while programming)
4. Either press the STORE key again or go on-hook to close the store
5. Repeat to programme other stores

sames

SA545

10/18

Notes:
i)

Only valid keys will be accepted while a store is being programmed (e.g. if
REDIAL is pressed while programming a store, it will be ignored).

ii) Dual mode (i.e. LD and DTMF) numbers should be programmed into the store

using the procedure outlined under 'Dialling Mode Selection'. When redialling
from a repertory store, if an LD/DTMF mode change is encountered, dialling will
halt (and the speech circuit will be reactivated) until told to continue by the user.
It should be noted that if a mode change is entered into a repertory store, it will
require one store location.

iii) Pauses may be stored in repertory stores.

This is achieved by pressing the PAUSE key while programming the store.
When redialling from a repertory store, and a pause is encountered, dialling will
halt (the speech circuit will be reactivated) until told to continue by the user. A
pause will require one store location.

To dial a number from a repertory store: (Whilst off-hook and not already dialling)
1. Press the REDIAL key once

2. Press the number (0-9) of the store to be dialled

Dialling will now start

3. If dialling halts due to an LD to DTMF mode change or a pause instruction, further

dialling will be resumed by pressing the REDIAL key or the PAUSE key.
(Alternatively, pulling C4 low for a minimum of 14ms will have the same effect).

Notes:

i) If an LD/DTMF mode change instruction is encountered while dialling from a

repertory store, dialling will halt. If further dialling from this store is invoked (as
described above) it will be in DTMF mode.

ii) Digits may be dialled manually, or a Last Number Redial carried out before

dialling from a repertory store. In this case, when repertory dialling is invoked.
it will commence in the mode that was current immediately before repertory
dialling was invoked.

iii) Further dialling (either manual or repertory) is allowed after repertory dialling.

Subsequent dialling will commence in the same mode of the last digit dialled
from the repertory store (even if dialling halted at an LD/DTMF switchover).

iv) If an LD/DTMF switchover is stored in the first location of a repertory store, the

following digits will be dialled in DTMF without first halting.

v) All key inputs will be ignored whilst a number is being dialled from a repertory

store. Only when dialling has stopped, will further key inputs be recognised.

sames

SA545

11/18

Earth Loop Recall (ELR) / Timed Break Recall (TBR) (Timed Flash)
The SA545 supports both TBR and ELR and offers a common operating protocol in
both cases.

After a Recall (Flash) operation, the dialling mode selected via the SELECT pin will
be restored. Only the digits dialled after the ELR/TBR operation will be retained in
the LNR store.

A TBR of 100ms

is generated when the TBR key is pressed. The MASK output

goes low in order to produce the line break. When in DTMF mode, the MF OUT
output also goes low for the duration of the break.

ELR is supported via the C3 pin. If this pin is connected to ground for a minimum
of 20ms during an ELR operation, the chip will offer the same operating protocol as
for TBR.

The ELR function may be achieved by use of the circuit shown in Figure 2, or by use
of a double contact switch.

1) Other periods avaiable on request.

Figure 2: Earth Loop Recall Application

sames

SA545

12/18

Oscillator Circuit
This requires an external 560KHz ceramic resonator connected between OSC IN
and OSC OUT, providing a timing reference for all chip functions.

Consult your resonator supplier for recommendation of a suitable resonator type.

Tone Filtering
The spectral purity of the DTMF output is sufficient for most applications. However,
where lower distortion DTMF tones are required, an on-chip Darlington pair is
provided (accessible via pins 6 & 7) for use in a low pass active filter.

Figure 3 shows how a 2-pole Sallen and Key filter may be implemented. The typical
component values have been chosen to give a second order Butterworth response
with a cut-off frequency of about 3,5KHz and a nominal pass-band insertion loss of
0,5dB. The relative values of R3 and R4 may be adjusted to achieve the desired
DTMF amplitude which varies with supply voltage.

DTMF Tone Filtering

Figure 3: 2-Pole Sallen and Key Filter Circuit

sames

SA545

13/18

10. DTMF Dialling (Figure 4)

During DTMF dialling, the MUTE output goes to logic `1' and remains there for the
duration of the tone transmission. The IMP output remains low during tone
transmission. The MF OUT output rises to its d.c. level of 0,9 V

at the start of the

tone transmission and is kept there between tone bursts. This is to avoid transients
at the beginning and end of tone bursts.

The maximum rate at which tones are sent to line is 100ms on, followed by 100ms
off. If keys are activated faster than this, they are placed in a temporary store and
then sent to line at the maximum rate. Dialling from the LNR store occurs at the
maximum rate.

If a key is held down for longer than 100ms, the tone output will continue until the
key is released.

DTMF Mode Timing Diagram

Figure 4: DTMF Mode Timing Diagram

sames

SA545

14/18

11. Loop Disconnect Dialling (Figures 5 and 6)

The MASK output is provided in order to disable the speech circuit during LD dialling.
Consequently, the MASK output is normally at logic '1' in the off-hook condition, but
changes to logic '0' during LD dialling. MASK also changes to logic '0' in order to
signal a Timed Break Recall (Flash) to the line. Both MUTE and MF OUT remain
low during LD dialling.
LD dialling is signalled on the IMP output. A break is signalled by a logic '0', make
periods and IDP times are signalled by a logic '1'. When not dialling, the IMP output
remains at logic '0'.

Figure 5: LD Mode Timing Diagram

Figure 6: Detailed Timing for IMP Output

= Pre-digit Pause (= t

)

= Break Period (60ms or 67ms)

= Make Period (40ms or 33ms)

= Post-digit Make (= t

)

= Inter-digit Pause (800ms or 500ms)

sames

SA545

15/18

12. LOCKING FACILITY

This feature is available on the SA54L5. Pin 11 (LOCK) should be connected to V

if the device is to be locked and to V

if the device is to be unlocked. This feature

can be controlled by an inexpensive low voltage SPDT switch. When locked it is
impossible to dial out any number other than those stored in the LNR and repertory
memory. If the redial key is pressed twice while in the locked state the number in the
LNR store will be dialled out. To dial from the repertory memory while in the locked
state the redial key is pressed once followed by the number (0-9) of the store to be
dialled.

13. OPTIONS

The SA545 has been designed to allow the telephonic manufacturer to cater for
different market requirements. The device can be programmed, on request, at the
final manufacturing stage so as to enable various attractive options. These options
are listed below and are available in any combination. The standard options are
listed first in Italics.
A. Packaging

SA545
a)

20 pin DIP

b) 18 pin DIP (filter not bonded out)
c) Other packages available on request (e.g. SO,LCC)
SA54L5
a)

22 pin DIP

b) 20 pin DIP (filter not bonded out)
c) Other packages on request

B. TBR (Flash) Period

SA545 and SA54L5
a)

100ms

d) 600ms

b) 200ms
c) 300ms

C. TBR (Flash) LNR Protocol

a) Number after the TBR is retained in LNR store.
b)

Number before the TBR is retained in the LNR store.

D. PIN 3

MASK

b) MASK

E. PIN 1

IMP

b) IMP
c) IMP + MASK
d) IMP + MASK

sames

SA545

16/18

PIN 12 (SA545)/PIN 14 (SA54L5)
a)

MUTE

b) MUTE

G. LNR Protocol

Numbers entered after * or # are never retained in the LNR store. (Attractive
for banking applications since PIN is not retained).

b) Numbers entered after * or # are retained in the LNR store if initial mode is

set to DTMF.

TYPICAL APPLICATIONS
The circuit in Figure 7 uses a constant current supply to draw current from the
telephone line which is used to power the SA54X5. The 2,5V reference diode
produces a stabilised supply voltage which determines the DTMF tone level of the
SA545.

In Figure 8, a stabilising voltage from the speech circuit is used to supply the SA545
during DTMF dialling to give accurate tone levels.

The SA545 is powered via the 150K

resistor during TBR operations and LD dialling

breaks, and via T1 during dialling makes. This configuration minimises the
component count, at the expense of allowing a leakage current of about 450礎
during dialling breaks. The 47礔 reservoir capacitor maintains and smoothes the
supply to the chip.

South African Micro-Electronic Systems (Pty) Ltd
P O Box 15888,

21 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

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.

协谢械泻褌褉芯薪薪褘泄 泻芯屑锌芯薪械薪褌: SA54L5

协谢械泻褌褉芯薪薪褘泄泻芯屑锌芯薪械薪褌: SA54L5