MT88L70
V
DD
C
1
DTMF
Input
R
1
IN+
IN-
R
2
GS
V
Ref
INH
PDWN
OSC1
X-tal
OSC2
V
SS
C
2
MT88L70
V
DD
St/GT
ESt
StD
Q4
Q3
Q2
Q1
TOE
NOTES:
R
1
, R
2
= 100 kΩ
±1%
R
3
= 300 kΩ
±1%
C
1
,C
2
= 100 nF
±5%
X-tal = 3.579545 MHz
±0.1%
V
DD
= 3.0V + 20% / -10%
R
3
Figure 6 - Single-Ended Input Configuration
the input pins are connected as shown in Figure 6
with the op-amp connected for unity gain and V
Ref
biasing the input at 1/2V
DD
. Figure 5 shows the
differential configuration, which permits the
adjustment of gain with the feedback resistor R
5
.
Crystal Oscillator
The internal clock circuit is completed with the
addition of an external 3.579545 MHz crystal and is
connected as shown in Figure 6 (Single-ended Input
Configuration).
Applications
A single-ended input configuration is shown in Figure
6. For applications with differential signal inputs the
circuit shown in Figure 5 may be used.
4-27
MITEL [ MITEL NETWORKS CORPORATION ]
