U4030B TEMIC Semiconductors, U4030B Datasheet - Page 4

• Manufacturer Part Number: U4030B
• Description: Telephone Speech Circuit
• Manufacturer: TEMIC Semiconductors

Charge Up Circuit
By OFF HOOK the handset, an integrated charge up
circuit provides V
reaches 2.2 V, the charge up circuit is automatically
switched off.
The specifications for the German “Deutsche Telekom”
(speech readiness, start time) will be fulfilled even with
1000
Figure 6 illustrates the transient behavior of the circuit at
I
U4030B
4 (14)
L
= 20 mA.
93 7622 e
93 7623 e
m
Figure 6. Charge up characteristics at I
Figure 5. Typical DC characteristics for various
F at Pin 20.
20
15
10
5
0
0
charge-up
20
D
off
with the whole line current. When V
SWAMP resistors
Line current I
40
time: 50 ms / div
V
L
RDC = 10 k
R
60
swamp
L
( mA )
= 82
80
V
D
W
L
100
68 47
= 20 mA
120
D
Electronic Inductance
The AC resistance ( Rimp 1 k
be much higher than the DC resistance ( 325
being decoupled via an electronic inductance.
The value of L is given by:
L
where
RDC = 10
CVC = 10
R30
RC
L
Transmit
Microphone amplifier
The microphone amplifier of U4030B has symmetrical
inputs ( MIC1 and MIC2 ) with an input resistance of
60 k
with resistances RS1 and RS2 as follows:
G
A low pass function can be realised with CSLP. The
corner frequency is given by:
fC
When the AC level on V
of the microphone is reduced by the limiter function. The
threshold of the limiter is fixed at 5.5 dBm ( typical).
DTMF
The amplification of the DTMF signal is determined by
the ratio of RS1 and RS2 as follows:
G
An external voltage divider is used to adjust the proper
DTMF level at line.
For monitoring the dialing procedure, an attenuated
DTMF signal is sent to the earpiece. The Deutsche Tele-
kom specification is fulfilled with the nominal value of
the transmit and receive gain.
T
D
= V
W
( typical). It has a gain of 29 dB which is adjustable
= CVC
= 30 k
= infinite
= V
= 20 log [ (RS1 / RS2 ) + 1 ] dB
= 1 / ( 2
= 20 log {0.19
= 3 H
MICO
MICO
W
m
F
W
/ V
p
DTMF
/ V
RS1 CSLP )
RDC
( MIC1, MIC2 )
L
[ ( RS1 / RS2 ) + 1 ] }
30 k
is very high, the amplification
W )
W
of the telephone should
|| R
Rev. A2, 27-Jan-98
W ),
the latter