5/10

L6574

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.

Timing Section

1

Pre Heat Timing constant

1.15

1.5

1.85

s/

µF

Frequency Shift Timing Constant

0.115

0.15

0.185

s/

µF

Pre Heat Timing Comparator

Threshold

3.3

3.5

3.7

V

Sense OP AMP

6,7

Input Bias current

0.1

µA

Input Offset Voltage

-10

10

mV

5

Ouput Resistance

200

300

Ω

Sink Output Current

0.5

mA

Source Output Current

0.5

mA

6,7

Common Mode Input Range

-0.2

3

V

GBW

Sense Op Amp Gain Band Width

Product

1MHz

Gdc

DC Open Loop Gain

80

dB

Comparators

8,9

Enabling Comparators Threshold

0.56

0.6

0.64

V

Enabling Comparators Hysteresis

20

100

mV

Minimum Pulse lenght

200

ns

ELECTRICAL CHARACTERISTCS (continued)

Symbol

Pin

Parameter

Test Condition

Min.

Typ.

Max.

Unit