M-88L70 CLARE [Clare, Inc.], M-88L70 Datasheet - Page 6

• Manufacturer Part Number: M-88L70
• Description: 3V DTMF Receiver
• Manufacturer: CLARE [Clare, Inc.]

M-88L70
Figure 4 Single-Ended Input Configuration
6
Figure 6 Timing Diagram
Explanation of Events
(A) Tone bursts detected, tone duration invalid, outputs not
(B) Tone #n detected, tone duration valid, tone decoded
(C) End of tone #n detected, tone absent duration valid,
(D) Outputs switched to high impedance state.
(E) Tone #n + 1 detected, tone duration valid, tone decod-
(F) Acceptable dropout of tone #n + 1, tone absent duration
(G) End of tone #n + 1 detected, tone absent duration valid,
updated.
and latched in outputs.
outputs remain latched until next valid tone.
ed and latched in outputs (currently high impedance).
invalid, outputs remain latched.
outputs remain latched until next valid tone.
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Figure 5 Guard Time Adjustment
Explanation of Symbols
V
ESt
St/GT
Q1 - Q4
StD
OE
t
t
t
t
t
t
t
t
REC
REC
ID
DO
DP
DA
GTP
GTA
IN
DTMF composite input signal.
Early steering output. Indicates detection of
valid tone frequencies.
Steering input/guard time output. Drives
external RC timing circuit.
4-bit decoded tone output.
Delayed steering output. Indicates that valid
frequencies have been present/absent for
the required guard time, thus constituting a
valid signal.
Output enable (input). A low level shifts Q1 -
Q4 to its high impedance state.
Maximum DTMF signal duration not detected
as valid.
Minimum DTMF signal duration required for
valid recognition.
Minimum time between valid DTMF signals.
Maximum allowable dropout during valid DTMF
signal.
Time to detect the presence of valid DTMF
signals.
Time to detect the absence of valid DTMF
signals.
Guard time, tone present.
Guard time, tone absent.
Rev. 1