MT88E45
Application Circuits
Advance Information
Tx+
Tx-
Microphone
Speaker
Telephone
Hybrid
TIP
TIP
or
Speech IC
(Symbolic)
RING
RING
Rx+
Rx-
R5
R3
R6
R11
R10
MT88E45
D1
R1
C1
R8 C3
V
IN2+
IN2-
GS2
CB2
CB1
Vdd
CD
REF
D2
IN1+
IN1-
R9 C4
R12
D3
R7
GS1
R4
C2 R2
= To Microcontroller
= From Microcontroller
D4
Vss
Vdd
OSC1
OSC2
CB0
Xtal
Vss
C5
C6
(FSK Interface Mode 1 selected)
ST/GT
EST
R13
R14
DCLK
DATA
R15
R15 is required only if both FSK
interface mode 0 and power
down features are used.
C6 should be
connected directly
across Vdd and Vss
pins
DR/STD
D5
Unless stated otherwise, resistors are 1%, 0.1Watt; capacitors are 5%, 6.3V.
For 1000Vrms, 60Hz isolation from Tip to Earth and Ring to Earth:
R1,R2
430K, 0.5W, 5%, 475V min. C1,C2
(e.g. IRC type GS-3)
2n2, 1332V min.
If the 1000Vrms is handled by other methods then this circuit has to meet the FCC Part 68 Type B Ringer requirements:
R1,R2
432K, 0.1W, 1%, 56V min. C1,C2
2n2, 212V min.
Common to both sets of R1,R2:
5V, 0dB gain 3V, -3.5dB gain
R3,R4
R8,R9
R13
34K
464K
825K
C3,C4
C5
C6
2n2
100n
100n, 20%
R5,R10
R6,R11
R7,R12
53K6
60K4
464K
35K7
40K2
309K
R14
R15
226K or 26K1
100K, 20%
D1-D4
D5
Xtal
Diodes. 1N4148 or equivalent
Diode. 1N4148 or equivalent
3.579545MHz, 0.1% crystal
or ceramic resonator
Figure 7 - Application Circuit: Bellcore MEI Compatible Type 2 Telephone
12
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