
U4074B
TELEFUNKEN Semiconductors
Rev. A1, 06-May-96
Preliminary Information
2 (6)
Pin Configuration
14
13
12
11
10
9
8
1
2
3
4
5
6
7
16
15
94 7904 e
NC
TH
2f
A1
A0
DD
V
GND
O2
O1
Mel
NC
VB
DC
V
DC
V
a
b
14
13
12
11
10
9
8
1
2
3
4
5
6
7
V
TH
2f
A1
A0
Mel
V
GND
O2
O1
B
DC
VDC
VDD
94 7903 e
a
b
Pin
1, 14
(1,16)
2 (3)
3 (4)
Symbol
a , b
Function
AC ringing signal input
V
B
TH
Output to charging capacitor
Comparator threshold adjust-
ment input
Output for frequency detection
Digital volume adjustment in-
put
Input for melody signal
DC supply diode connections
4 (5)
5, 6
(6, 7)
7 (9)
8, 9
(10, 11)
10 (12)
11, 12
(13, 14)
13 (15)
(2, 8)
2f
A1, A0
Mel
V
DC
V
DD
O
1
, O
2
Microcomputer supply voltage
Outputs to the transducer
GND
NC
Ground
Not connected
Pin Description
Power supply a and b
,
Pin 1, 14
An ac ringing voltage is supplied to the inputs a and b
via a 0.8 F decoupling capacitor connected in series with
a
2.2 k
. resistor
3.
The circuit possesses the following overload resis-
tance at terminals a and b.The circuit can withstand
a voltage of 110 V with a frequency of 50 Hz at
terminals a and b for a maximum of 15 s.
4.
Testing the circuit with the configuration shown in
figure 2 does not destroy the circuit under the
following conditions.
Charging voltage of surge capacitance: V
cs
= 2 kV
Pulse shape: 10/700 s
Pulse sequence: 30 s
Number of surges: 10
Polarity change after 5 surges
See figure 2.
Smoothing Capacitors,
Pin 2, 10
After rectification of the ac ringing voltage via the
integrated rectifier bridge, the pulsating DC voltage is
smoothed by the external capacitor (22 F to 47 F) at
Pin 2 (3). The charging voltage is restricted to a
maximum of 30 V by an integrated Z-diode. A 47 F
external capacitor of will smooth the regulated supply,
V
DD
, at pin 10 (12).