MC34216A Datasheet, PDF (10/20 Pages) Motorola, Inc – PROGRAMMABLE TELEPHONE LINE INTERFACE CIRCUIT WITH LOUDSPEAKER AMPLIFIER

MC34216A
Line +
Line –
Figure 4. DC Part of the Block Diagram of the MC34216A
C16
IMP ⁺
Z1
Z0
2.4 V
CM
+
I2
G
+
HYN
2VBE ≈ 1.4 V
NDC
C12
RX
SAI
+
+
VO1
Z21
SAO
MC34216A
LAI
+
LAO
+
Gnd
VO2
R1
T2
R5
VCC
+
T3
C7
The transfer from Region 2 to 3 occurs at the point VLK,
ILK, which is calculated:
+ ) ) ) VLK Z1 x I2CD 2VBE VCD
+ ^{ǒ ) Ǔ )} ILK
Z21
Z0
x
Z1 x I2CD
2VBE
R1
VO2
VCD
+ ⁾ + ⁾ With : I2CD ^I2C ₂ ^I2D , and VCD
VC ₂ VD _,
[ [ and 2VBE 1.4 V, VO2 1.1 V
When the French or U.K. mask is selected, this transfer
takes place for line currents of 30 mA to 40 mA depending
on the components settings. With the Startup and Low
Voltage mask, the transfer lies outside the normal operating
range with line currents of 90 mA or more. In most
applications, the transfer from Region 1 to 2 takes place for
line currents below 10 mA.
With proper settings, Region 4 is only entered during an
overload condition. In this mode, the power consumption in
the telephone set is limited. In order to detect an overload
condition, the voltage between the Pins LAI and SAO is
monitored. When the voltage difference is larger than the
threshold Vclamp1, the protection is made active. The relation
for the line voltage VLP at this point is given as:
+ ) ) VLP
Z0
Z21
x
Vclamp1
VCD
VO2
When the protection mode is entered, the line current is
reduced to a lower value ILP of:
) ^{ǒ Ǔ} Vclamp2 VO1 – VO2
+ ILP
R1
When the line voltage becomes smaller than VLP, the
overload condition is gone and the MC34216A will leave
Region 4.
The current drawn from the line by the dc part is used to
supply the MC34216A and peripheral circuits. The surplus of
current is sunk away by the voltage stabilizer at Pin VCC
where a reservoir capacitor is connected. The reference for
the circuit is Pin Gnd.
Startup of the application is ensured by an internal startup
circuit. During the startup, the internal registers of the
MC34216A are reset, and the reset Pin RS goes high. This
signals is meant to indicate to the microcontroller that the
programming of the MC34216A can start.
When the line current flows, the hook status output
Pin D/HS goes high. This serves as the information for the
microcontroller that the set is off–hook. When the line current
is no longer present, the pin goes low again. Because the line
current is monitored, and not the line voltage, an interrupt of
the exchange can be recognized.
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MOTOROLA ANALOG IC DEVICE DATA