u6081b ETC-unknow, u6081b Datasheet - Page 3

• Manufacturer Part Number: u6081b
• Description: Power Control With Duty Cycle Switch
• Manufacturer: ETC-unknow

TELEFUNKEN Semiconductors
Rev. A1, 14-Feb-97
V
V
V
a
The above mentioned threshold voltages are calculated
for the following values given in the data sheet.
V
a
V
V
V
For a duty cycle of 100%, an oscillator frequency, f, is as
follows:
f
Therefore:
f
For a duty cycle of less than 100%, the oscillator
frequency, f, is as follows:
f
whereas
f
+
A selection of different values of C
range of oscillator frequency, f, from 10 to 2000 Hz.
+
1
1
+
+
+
T
Batt
T100
TL
T100
T
TL
,
t
t
= 0.7,
185 Hz
a
100
100
+
+
2
2
2
2
2
= 12 V, I
+
+
and
+
+
Low switching threshold
11.4 V
(7.6 V
High switching threshold (100% duty cycle)
a
( 12 V
( V
( 8 V
( V
High switching threshold (
2
11.4 V
a
3
= 0.67 and
T100
T
t
are fixed constant.
C
S
100
*
*
4
= 4 mA, R
*
I
*
40
osc
= 470 pF
*
3.2 V)
3.2 V )
0.28
4 mA
V
m
V
TL
0.67
A
TL
)
a
+
)
3
3
I
= 0.28.
40
osc
22 nF
+
C
= 150
3.2 V
150
22 nF
C
2
m
2
7.6 V
A
, whereas C
)
)
W
W
and I
4
)
+
2
t
4
,
and C
100% duty cycle)
189 Hz
V
12 V
0.7
osc
Batt
4
+
, provides a
2
[
+
40
C
470 pF
8 V
22 nF
4
m
A
Pins 5 and 6, Short-Circuit Protection and
Current Sensing
1. Short-Circuit Detection and Time Delay, t
The lamp current is monitored by means of an external
shunt resistor. If the lamp current exceeds the threshold
for the short-circuit detection circuit (V
duty cycle is switched over to 100% and the capacitor C
is charged by a current source of 20
external FET is switched off after the cut-off threshold
(V
possible only after a power-on reset. The current source,
I
parasitic currents. The capacitor C
to typ. 0.7 V.
Time delay, t
t
With C
we have
t
+
2. Current Limitation
The lamp current is limited by a control amplifier to pro-
tect the external power transistor. The voltage drop across
an external shunt resistor acts as the measured variable.
Current limitation takes place for a voltage drop of
V
V
occurs only when the short circuit detection circuit has
responded.
After a power-on reset, the output is inactive for an half
oscillator cycle. During this time, the supply voltage
capacitor can be charged so that the current limitation is
guaranteed in the event of a short circuit when the IC is
switched on for the first time.
Pins 7 and 8, Charge Pump and Output
Output, Pin 8, is suitable for controlling a power
MOSFET. During the active integration phase, the supply
current of the operational amplifier is mainly supplied by
the capacitor C
charge is generated by an integrated oscillator
(f
permits a gate voltage supply at a duty cycle of 100%.
dis,
d
d
T1
T1
7
+
+
T5
150 ms.

–V
[
) is reached. Renewed switching on the FET is
ensures that the capacitor C
330 nF
C
400 kHz) and a voltage doubler circuit. This
T2
100 mV.
5
5
@
= 330 nF and V
[
( V
10 mV it is ensured that current limitation
d
@
T5
, is as follows:
( 9.8 V
3
*
(bootstrapping). Additionally, a trickle
0.7 V ) ( I
Owing
*
T5
0.7 V ) 20
= 9.8 V, (I
ch
*
to
I
5
dis
5
U6081B
is discharged by I
)
m
is not charged by
m
ch
A (I
the
A
T2
– I

ch
dis
90 mV), the
– I
) = 20
d
difference
dis
). The
3 (8)
m
dis
A,
5