MT88L70AN1 Zarlink, MT88L70AN1 Datasheet - Page 5

• Manufacturer Part Number: MT88L70AN1
• Description: DTMF RX 3.58MHz CMOS 3V 20-Pin SSOP Tube
• Manufacturer: Zarlink

Specifications of MT88L70AN1

• Package: 20SSOP
• Operating Frequency: 3.58 MHz
• Typical Supply Current: 2 mA
• Typical Operating Supply Voltage: 3 V
• Minimum Operating Supply Voltage: 2.7 V
• Maximum Operating Supply Voltage: 3.6 V

Different steering arrangements may be used to select independently the guard times for tone present (t
tone absent (t
on both tone duration and interdigital pause. Guard time adjustment also allows the designer to tailor system
parameters such as talk off and noise immunity. Increasing t
probability that tones simulated by speech will maintain signal condition long enough to be registered. Alternatively,
a relatively short t
time and immunity to tone drop-outs are required. Design information for guard time adjustment is shown in Figure
4.
Power-down and Inhibit Mode
A logic high applied to pin 6 (PWDN) will power down the device to minimize the power consumption in a standby
mode. It stops the oscillator and the functions of the filters.
Inhibit mode is enabled by a logic high input to the pin 5 (INH). It inhibits the detection of tones representing
characters A, B, C, and D. The output code will remain the same as the previous detected code (see Table 1).
GTA
). This may be necessary to meet system specifications which place both accept and reject limits
REC
with a long t
DO
St/GT
St/GT
V
V
V
ESt
ESt
would be appropriate for extremely noisy environments where fast acquisition
DD
DD
DD
MT88L70
Figure 4 - Guard Time Adjustment
Figure 3 - Basic Steering Circuit
R
R
1
St/GT
1
V
ESt
StD
Zarlink Semiconductor Inc.
DD
C
C
R
1
1
R
2
MT88L70
2
a) decreasing t
t
t
GTP
GTP
b) decreasing t
5
R
=(R
=(R
t
t
GTA
GTP
t
t
REC
GTA
GTA
P
1
C
C
=(RC)In(V
=(RC)In[V
R
R
=(R
=(R
1
1
improves talk-off performance since it reduces the
) In [V
P
) In [V
P
= (R
= (R
P
1
v
C
GTP
C
C
c
1
1
GTA
DD
) In (V
DD
) In (V
1
1
; (t
R
R
DD
DD
2
2
/ (V
/ (V
; (t
) / (R
) / (R
GTP
/(V
/V
DD
DD
GTP
TSt
DD
DD
DD
< t
1
1
-V
-V
)
/ V
/ V
-V
+ R
+ R
> t
GTA
TSt
TSt
TSt
TSt
TSt
GTA
2
2
)]
)
)]
)]
)
)
)
)
)
Data Sheet
GTP
) and