U4030B Datasheet, PDF (3/14 Pages) TEMIC Semiconductors – Telephone Speech Circuit

U4030B
Circuit Description
Reference for all descriptions is figure 9, unless otherwise
specified.
Power Supply
DC characteristic
The power supply stage determines the voltage/ current
characteristic of the circuit. The DC-slope is adjusted to
100 W. A resistor connected from Pin 2 to Pin 14 may be
used to reduce the line voltage ( figure 2 ).
16
300 W and the maximum output current is 300 mA. The
V_M-pin is virtual ground for the receiving amplifier.
6
I_L = 50 mA
4
19 mA
24 mA
2
12
RC = ∞
8
RC = 100 kW
4
V (MIC) = 10 mV_eff
0
0
4
8
12
16
20
93 7620 e
Supply current I_D ( mA )
Figure 3. Supply voltage, V_D
RDC = 10 kW
0
2
0
20
40
60
80 100
93 7619 e
I_L ( mA )
Figure 2. DC characteristics
1
V_L = ( 0.0033 I_DC + I_OFFSET ) ( R30 || RC) + VRS +
IRDC RDC
with:
I_OFFSET
VRS
R30
IDC
= 150 mA
= 150 mV
= 30 kW
= I_L - ( 750 mA + 0.023 I_L )
V_D
An unregulated voltage, V_D, is generated to supply the
internal and external circuits. The maximum voltage at
this pin is limited by an internal Z-diode to a value of
6.2 V. The available output current is shown in figure 3.
V_M
The supply voltage for an electret microphone is derived
from V_D (see figure 4). The output resistance is set to
0
3
93 7621 e
4
5
6
Supply voltage V_D ( mA )
Figure 4. Electret microphone supply, V_M
Swamp
Line current which is not used for internal and external
circuits is converted into heat via resistance Rswamp in
order to prevent the IC from thermal destruction at high
line currents.
The speech circuit will be high ohmic when the voltage
at SWAMP reaches 6 V. Typical characteristics for
various resistors are shown in figure 5.
Rev. A2, 27-Jan-98
3 (14)