LS656AD1 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
LS656AD1 Datasheet PDF : 15 Pages
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LS656
Figure 16 : External Mute Function.
a) with multifrequency
b) without multifrequency
In addition to the above mentioned applications, different values for the external components can be used
in order to satisfy different requirements.
The following table (refer to the application circuit of fig. 10) can help the designers.
Component
R1
R2
R3
R4
R5
R6
R7-R7’
R8
C1
C2
C3
C4
C5
C6-C7
C8
C9
Value
30Ω
330Ω
30Ω
13kΩ
2.2kΩ
6.8kΩ
100Ω
200Ω
10µF
47nF
82nF
15nF
0.33µF
1000pF
100µF
1 µF
Purpose
Bridge Resistors
Line Current
Sensing Fixing DC
Characteristic
Bias Resistor
Balance Network
Receiver
Impedance Matching
Microphone
Impedance Matchin
Regulator AC
byPass
Matching to a
Capacitive Line
Receiving Gain
Flatness
Balance Network
DC Filtering
RF byPass
Receiving Output
DC Decoupling
Receiving Input DC
Decoupling
Note
R1 controls the receiving gain. When high current values are
allowed, R1 must be able to dissipate up to 1 W.
The Ratio R2/R1 fixes the amount of signal delivered to the line. R1
helps in fixing the DC characteristics (see R3 note).
The relationships involving R3 are :
ZML
=
(20
R3//ZB)
+
R1,
GS
=
K
⋅
ZL//ZML
R3
and
VL = (IL – IO) (R3 + R1) + V0 ; V0 = 3.7V
Without any problem it is possible to have a ZML ranging from 600
up to 900Ω. As far as the power dissipation is concerned, see R1
note.
The suggested value assures the minimum operating current. It is
possible to increase the supply current by decreasing R4 (they are
inversely proportional), in order to achieve the shifting of the AGC
starting point. (see fig. 16). After R4 changement, so
It’s possible to change R5 and R6 values in order to improve the
matching
to
different
lines
;
in
any
case
:
ZL
ZB
=
R1,
R2
ZB
=
R5
+
R6//XC4
R7 and R7’, must be equal ; the suggested value is good for
matching to dynamic capsule ; there is no problem in increasing and
decreasing (down to 0Ω) this value. A DC decoupling must be
inserted when low resistance levels are used to stop
A value greater than 10 µF gives a system start time too high for
low current line during MF operation ; a lower value gives an
alteration of the AC line impedance at low frequency.
C2 changes with the characteristics of the transmission line.
C3 depends on balancing and line impedance versus frequency.
See note for R5, R6.
The C5 range is from 0.1 µF to 0.47 µF. The lowest value is ripple
limited, the higher value is starting up time limited.
See note for R7, R7.
12/15
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