LS656 Ver la hoja de datos (PDF) - STMicroelectronics
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LS656 Datasheet PDF : 15 Pages
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LS656
ELECTRICAL CHARACTERISTICS (continued)
Symbol
Parameter
Test Conditions
MULTIFREQUENCY SYNTHESIZER INTERFACE
VDD MF Supply Voltage Stand by and S2 in (b)
Operation
IDD MF Supply Current Stand by
Operation
S2 in (b)
MF Amplifier Gain
fMF in = 1kHz, VMF in = 80mV
VI
DC Input Voltage Level (pin 14) VMF in = 80mV
RI
Input Impedance (pin 14)
VMF in = 80mV
d
Distortion
Starting Delay Time
VMF in = 150mVp, IL > 17mA
Muting Threshold Voltage (pin3) Speech Operation
MF Operation
Muting Stand by Current (pin 3) )
Muting Operating Current (pin 3) S2 in (b)
Min. Typ. Max. Unit Fig.
2.4 2.5 2.7 V
–
0.5
mA –
2
mA –
15
17 dB 4
VDD
x 0.3
V
–
60
kΩ –
4
%
4
5 ms –
1
V
–
1.6
V
–
– 10 µA –
+ 10 µA –
CIRCUIT DESCRIPTION
1. DC Characteristic
The fig. 5 shows the DC equivalent circuit of the
LS656.
A fixed amount Io of the total available current IL is
drained for the proper operation of the circuit. The
value of Io can be programmed externally by chang-
ing the value of the bias resistor connected to pin 4
(see block diagram).
The minimum value of Io is 7.5 mA.
The voltage Vo = 37 V of the shunt regulator is in-
dependent of the line current.
The shunt regulator (2) is controlled by a tempera-
ture compensated voltage reference (1) (see the
Figure 5 : Equivalent DC Load to the Line.
block diagram).
Fig. 6 shows a more detailed circuit configurationof
the shunt regulator.
ThedifferenceIL-Io flowsthrough the shunt regulator
being Ib negligible. Ia is an internal constant current
generator ; hence Vo = VB + Ia . Ra = 3.7 V.
The VL, IL characteristic of the device is therefore
similar to a pure resistance in series to a battery.
It is important to note that the DC voltage at pin 5 is
proportional to the line current (V5 = V7 + VB = (IL -
Io) R3 + VB).
The DC characteristic of the LS656 is shown in
fig. 7.
5/15
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