L6574
ELECTRICAL CHARACTERISTCS
(continued)
(V
S
= 12V; V
BOOT
-V
OUT
= 12V; T
amb
= 25°C)
Symbol
Pin
Parameter
Test Condition
Min.
Typ.
Max.
Unit
Timing Section
k
pre
k
fs
V
thpre
Sense OP AMP
l
ib
V
io
R
out
I
out +
I
out -
V
ic
GBW
Gdc
Comparators
V
the
V
hy
e
t
pulse
8,9
Enabling Comparators Threshold
Enabling Comparators Hysteresis
Minimum Pulse lenght
0.56
20
200
0.6
0.64
100
V
mV
ns
6,7
5
6,7
Input Bias current
Input Offset Voltage
Ouput Resistance
Sink Output Current
Source Output Current
Common Mode Input Range
Sense Op Amp Gain Band Width
Product
DC Open Loop Gain
V
out
= 0.2V
V
out
= 4.5V
-10
200
0.5
0.5
-0.2
1
80
3
0.1
10
300
µA
mV
Ω
mA
mA
V
MHz
dB
1
Pre Heat Timing constant
Frequency Shift Timing Constant
Pre Heat Timing Comparator
Threshold
C
pre
= 330nF
C
pre
= 330nF
1.15
0.115
3.3
1.5
0.15
3.5
1.85
0.185
3.7
s/µF
s/µF
V
High/Low Side Driving Section:
High and low side driving sections provide the proper drive to the external power MOSFET. A high sink/
source driving current (450/250 mA typical) ensures fast switching times when a size 4 external power
MOSFET needs to be driven.
Bootstrap Section:
A patented integrated bootstrap section replaces an external bootstrap diode. This section together with
a bootstrap capacitor provides the bootstrap voltage to drive the high side power MOSFET. This function
is achieved using a high voltage DMOS driver which is driven synchronously with the low side external
power MOSFET.
For a safe operation, current flow into the Vboot pin is inhibited, even though ZVS operation may not be
ensured.
Timing Section:
To set the proper preheat time (tpre=kpre*Cpre) for the bulb, a capacitor is connected to the Cpre pin
which is charged with a fixed current. During tpre, the output is switching at fpre (see Oscillator Section).
When the tpre expires, the Cpre capacitor is discharged and then recharged with a different current. This
sets a second time interval tsh (0.1 times the selected preheat time tpre) during which frequency shifting
from fpre to fing is performed to ensure lamp ignition.
5/10
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