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AN1673 APPLICATION NOTE

Figure 3. Oscillator Block

Figure 4. Frequency Diagrams

BOOTSTRAP SECTION.

The supply of the high voltage section is obtained by means of a bootstrap circuitry. This solution normally

requires a high voltage fast recovery diode for charging the bootstrap capacitor (fig. 5a). In the device a

patented integrated structure, replaces this external diode. It is realised by means of a high voltage DMOS,

driven synchronously with the low side driver (LVG), with in series a diode, as shown in fig. 5b.

+

S

R

+

+

X4

X8

D03IN1444

0

0

200

400

Cf(pF)

200

400

fmin

(KHz)

Rf=90K

Ω - calc.

Rf=90K

Ω - meas.

Rf=19.9K

Ω - calc.

Rf=19.9K

Ω - meas.

D03IN1442

20

40

60

80

20

40

60

80

100

(KHz)

D98IN891