M761EB1 ,Dual tone multifrequency generatorStl -TH 0
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MEES@HL
M761E
DUAL TONE MULTIFREQUENCY GENERATOR
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M761EB1
DUAL TONE MULTIFREQUENCY GENERATOR
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7Z7 Miemememgmes
DUAL TONE MULTIFREQUENCY GENERATOR
n 2.4 TO 4 V SUPPLY RANGE
a VERY LOW POWER CONSUMPTION
n ON-CHIP CRYSTAL CONTROLLED OSCILLA-
TOR (fo = 4.433619 MHz) WITH INTEGRATED
FEEDBACK RESISTOR AND LOAD CAPACI-
LOW HARMONIC DISTORTION ( S 2 %)
u FIXED PRE-EMPHASIS ON HIGH-GROUP
u FAST START-UP TIME
I: LOW POWER CONSUMPTION IN STANDBY
n MUTE OUTPUT
tt ONE CONTACT PER KEY
DESCRIPTION
The M761 provides all the tone frequency pairs te-
quired for a DTMF Dialling System. Tones are ob-
tained from an inexpensive TV crystall (fo =
4.433619 MHz) followed by two independent pro-
grammable dividers. The dividing ratio is controlled
by the selected key. Keyboard format is 4 rows x 4
columns and a key is valid when a column and a row
are connected together.
Internal logic prevents the transmission of illegal
tones when more than one key is pressed. If no key
is selected the oscillatorturns off and the linear parts
are strobed to decrease the total power consump-
As any buttom is pressed row and column inputs are
scanned internally, to identify the activated ones.
Electrically, row and column inputs are activated on
high level voltage.
Single tone output cannot be emitted by a "1" an a
row or column only. For single tone emission see
"Single tone procedure".
A debounce output is available to indicate that a key
has been selected. D/A conversion is accomplished
by a capacitive network allowing very low power
consumption, very low distortion and an exceptional
stability of tone level against temperature variations.
The tones are mixed in a resistive network ; a unity
gain amplifier is provided to realize a two pole ac-
tive filter with only four external passive compo-
nents.
November 1988
ORDER CODE : M761EB1
The M761 can be interfaced with the speech circuit
family LS156, LS356, LS656 with MF interface avoi-
ding the need of the common spring set.
The M761 utilizes low voltage CMOS technology
and is available in 18 pin dual in-line plastic
package.
PIN CONNECTION (top view)
t 16 V00
2 17a FILTER IN
Ct 3 15] FILTER OUT
c2[4 15] MUTE om
COLUMNS
csls M761 14 y,
cal 6 13192
N,C. 7 12 M
MIXER our a ll "
DIG.FREt1.
vss 9 IO our
S-3810/2
M761 E
BLOCK DIAGRAM
t Mutt Output
'tr- m Low FREQUENCY CLOCK
o m oscnunon PRESCALER WAHMILE FREm‘ucy ___O(*J
asaoa,- T4 Ccumzn ouwur tiN/f,"""'"'
.L.___.J
(H "" MIgtFt OUIPUI’
H SHIFT stoma R r--,
KEvaonno 'tlr/T H4 Low FREMNCV FIUER Input
CF---. LOGIC “3:50. "lt 'd'fgl',C, fl j
c'-, F. SHIFT a:asrtn r Amine "21T 23:;
i l I l J “W
HIM FREQUENCY
um rnmucucv smb'm
ABLE GENERATOR
L coumsu
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit
l/oo Supply Voltage - 0.5 to + 5.5 V
VI Input Voltage - 0.3 to V00 ' 0.5 V
Ptot Power Dissipation 400 mW
Top Operating Temperature Range - 25 to + 70 °C
Tstg Storage Temperature Range - 55 to + 125 °C
THERMAL DATA
Rthramb Thermal Resistance Junction-ambient Max 100 °C/W
2/9 F StiSIHt3MStltl
7” MHGMLEILWRWUGS
