TELEFUNKEN Semiconductors
U4078B
Pin Description
Pin
1, 8
2
Symbol
a , b
Function
a’
b’
1
2
3
4
8
7
6
5
AC ringing signal input
V
B
Output to charging capacitor
(for supply)
V
GND
OSC
ST
B
TH
MS
3
4
TH
MS
Comparator threshold adjustment
input
U4078B
Mode selection: inductive or
opto-coupler mode
5
6
ST
Switching transistor connection
OSC
RC circuit for internal oscillator
input
94 7902 e
7
GND
Ground
Functional Description
The ringing ac signal, supplied by the exchange via lines bridge circuit, the smoothing of the power supply is
a, b, is identified by a comparator circuit. An integrated provided by the external capacitance at Pin 2 (22 nF).
oscillator, generates a 38 kHz clock signal, f
coupled 2:1 divider. With the help of the external RC
circuit, oscillation frequency is set at Pin 6.
PNP-transistor connected at Pin 5 enables the power
transmission (transfer) in inductive or opto-coupler mode,
which is selected at Pin 4. For inductive mode, Pin 4 is
open, whereas for opto-coupler mode, Pin 4 is connected
to GND (Pin 7).
, via a
clock
Pin 3: Comparator Threshold
TH
A
Comparator threshold as regards the ringing voltage
is set at ca. 12.5 V. Switching threshold can be increased or
decreased by connecting a resistance at Pin 3 w.r.t. GND.
Pin 4: Mode Selection
MS
The ringing ac signal transfer (transmission) without
potential loss occurs either via an inductive or opto-coupler
mode. Pin 4 is set to a high state by an internal power source
of 4 µA (approximately). This switches the output (Pin 5)
to an operating state for the inductive mode. In case of
opto-coupler mode, Pin 4 is connected to the ground
(Pin 7).
Pin 1,8: Power Supply – a , b
Pins 1 and 8 connect the circuit with the ac ringing signal
supplied by the exchange via lines
a
and b.
A 1µF decoupling capacitor of 1 µF value together with a
series resistance (1.5 kΩ) protect the circuit from overload
across Pins 1 and 8. The circuit features the following
overload protection across the a , b terminals:
Pin 5: Switching Transistor Connection
An external PNP transistor, whose emitter is at V (Pin 2)
S
1) It can withstand a voltage of 110 V @ 50 Hz for
maximum time of 15 seconds.
potential, serves to control the inductive or opto-coupler
mode by connecting the base of the transistor with Pin 5.
In case of inductive mode, the signal, f
is interrupted
clock
2) Testing of the circuit according to figure 2 does not
destroy the circuit under following conditions:
for the duration of t
= 32/f
, with every transition
pulse
clock
(rise or fall) of the ringing ac signal, f . During the
ring
interruption, the setting at Pin 5 is such that the coil is
critically damped (attenuated), whereas a current of 10 µA
flows when the transistor at Pin 5 is switched on during the
Charging voltage of surge capacitance: V = 2 kV
CS
Pulse shape: 10/700 µs
Pulse sequence: 30 s
No. of surges: 10
following t
up to the next edge of the pulse.
pulse
Polarity change after 5 surges
In case of opto-coupler mode, the external transistor is
switched on for a period of t = 32/f with every flank
pulse
clock
Pin 2: Charging Capacitor
(power supply filtering)
of the pulse of f
.
ring
Pin 5 is at high resistance upto the next edge (flank) of the
After the rectification of the ringing ac signal across the transition pulse of the ringing ac signal.
2
TEMIC [ TEMIC SEMICONDUCTORS ]
