ts34118 Taiwan Semiconductor Company, Ltd. (TSC), ts34118 Datasheet - Page 16
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ts34118
Manufacturer Part Number
ts34118
Description
Voice Switched Speakerphone Circuit
Manufacturer
Taiwan Semiconductor Company, Ltd. (TSC)
Datasheet
1.TS34118.pdf
(20 pages)
TS34118
Design Equations
This is the general equation defining the microphone voltage necessary to switch comparator C1 when a received
signal V
numbers for Equation 6 yields:
To switch comparator C2, currents I2 and I4 need to be determined. With sound applied to the
microphone, a voltage V
Since G
Comparator C2 switches when I4=I2. I4 is defined by:
Setting I4=I2, and combining the above equations results in:
This equation defines the line voltage at Tip/Ring necessary to switch comparator C2 in the presence of a microphone
voltage. The highest V
Equation 10 yields:
At idle, where the gain of the two attenuators is –20dB (0.1V/V), Equations 6 and 10 yield the same result:
Equations 7, 11 and 12 define the thresholds for switching, and are represented in the following graph:
V
I2 =
I4 =
V
V
V
M
L
L
M
L
HA
=840V
=0.024V
= V
= 0.52V
is present. The highest V
is the differential gain of the hybrid amplifiers, it is divided by two to obtain the voltage V2 applied to R2.
V
V
R4
R2
M
M
L
×
M
(or V
L
L
>
R4
R2
ª
« ¬
G
G
HR
MA
u
M
(Equation 7)
(Equation 12)
L
=0.0019 V
u
M
>
occurs when the circuit is in the transmit mode (G
G
u
is creased by the microphone, resulting in a current I2 into TLI1:
G
>
G
G
MA
FO
Figure 10. Basic Block Diagram For Design Purpos
HR
TX
u
@
u
u
G
L
)
M
G
G
TX
occurs when the receive attenuator is at maximum gain (+6.0dB). Using the typical
2
FO
HA
u
u
º
» ¼
G
2
HA
@
@
16-20
(Equation 11)
(Equation 8)
(Equation 9)
(Equation 10)
TX
= +6.0dB). Using the typical numbers for
2004/09 rev. B