TCA3388 Datasheet, PDF (6/16 Pages) Motorola, Inc – TELEPHONE LINE INTERFACE

TCA3388
DESCRIPTION OF THE CIRCUIT
Concept
With a TCA3388, a microcontroller and a ringer, a basic
telephone set can be built according to the concept depicted
in Figure 1.
In off–hook position, the application is in speech mode.
The line current flows through transistor T2 and supplies the
externals (microcontroller) at the supply point VCC which is
stabilized by the TCA3388. The Vline, Iline characteristic is
adjusted by the external components Z0, Z1, Z21 and R1
which are in a regulator loop, acting on transistor T2. The ac
impedance is generated in a similar way. The handset can be
connected directly to the TCA3388. Via a logic level interface,
the microcontroller drives the TCA3388 to perform the
DTMF/pulse–dialing. The user keyboard has to be connected
to the microcontroller. In on–hook position, a ringing melody
can be generated with a ringer application.
The block diagram of the TCA3388, in Figure 2, shows the
basic blocks of the device plus the essential external
components.
Figure 1. Telephone Concept with TCA3388
Hookswitch
Z1
Z0
Z21
T2
VCC
A/B
Ringer
Handset
TCA3388
R1
Micro
Gnd
Line +
Figure 2. Block Diagram of the TCA3388 with Essential Components
Z2 _C17
Z1
C16
Z0
R19 R20
Z21
DTMF
R12
C20
R6
R9
RXO1
19
RXO2
20
RXI
1
C5 _TXI
2
Mic
Ear
Mute, AGC
Mute, AGC
Mic
7
6
8 10
5
9 16
HYS
HYL CM SAO
LAI
IMP Iref
VCC
DC Mask Generation
AC Termination
Supply–
17
2–4 Wire Conversion
Stabilizer
Line Length AGC
Protection
References _Gnd
18
T2
C7
Micro–Interface
Hook–Detect
PABX
Line
Driver
LAO
T3
4
3
TCA3388
Line –
SAI
DCM HSO PI MUT
11
12
13
14 15
ZDCM
R22
To/From
Microcontroller
R1
6
MOTOROLA ANALOG IC DEVICE DATA