INT200

F

1/96

4

General Circuit Operation

One phase of a three-phase brushless

DC motor drive circuit is shown in Figure

4 to illustrate an application of the

INT200/201. The LS IN signal directly

controls MOSFET Q1. The

HSINsignal

causes the INT200 to command the

INT201 to turn MOSFET Q2 on or off as

required. The INT200 will ignore input

signals that would command both Q1

and Q2 to conduct simultaneously,

protecting against shorting the HV+ bus

to HV-.

Local bypassing for the low-side driver

is provided by C1. Bootstrap bias for the

high-side driver is provided by D1 and

C2. Slew rate and effects of parasitic

oscillations in the load waveforms are

controlled by resistors R1 and R2.

The inputs are designed to be compatible

with 5 V CMOS logic levels and should

not be connected to V

power supply sequencing should be

observed. The order of signal application

should be V

HV+. V

low impedance voltage source.

The length of time that the high-side can

remain on is limited by the size of the

bootstrap capacitor. Applications with

extremely long high-side on times

require special techniques discussed in

AN-10.

Figure 6. Using the INT200 and INT201 to Drive a Fluorescent Lamp.

PI-1462-042695

HV+

VDD

12

34

87

65

12

34

87

65

INT201

INT200

OSCILLATOR

FLUORESCENT

LAMP

HV-

Maximum frequency of operation is

limited by power dissipation due to high-

voltage switching, gate charge, and bias

power. Figure 5 indicates the maximum

switching frequency as a function of

input voltage and gate charge. For higher

ambient temperatures, the switching

frequency should be derated linearly.

Figure 5. Switching Frequency versus Gate Charge for a) PDIP and b) SOIC.

100

0

0

100

200

Gate Charge (nC)

200

300

400

VIN = 200 V

VIN = 300 V

VIN = 400 V

SOIC

100

0

0

100

200

Gate Charge (nC)

200

300

400

VIN = 200 V

VIN = 300 V

VIN = 400 V

PDIP