INT200
General Circuit Operation
One phase of a three-phase brushless
DCmotordrivecircuitisshowninFigure
4 to illustrate an application of the
INT200/201. The LS IN signal directly
controlsMOSFETQ1. TheHS INsignal
causes the INT200 to command the
INT201toturnMOSFETQ2onoroffas
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-.
should be VDD, logic signals, and then
HV+. VDD should be supplied from a
low impedance voltage source.
Maximum frequency of operation is
limitedbypowerdissipationduetohigh-
voltage switching, gate charge, and bias
power. Figure 5 indicates the maximum
switching frequency as a function of
inputvoltageandgatecharge. Forhigher
ambient temperatures, the switching
frequency should be derated linearly.
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.
400
400
PDIP
SOIC
V
V
V
= 200 V
= 300 V
= 400 V
V
V
V
= 200 V
= 300 V
= 400 V
IN
IN
IN
IN
IN
IN
Local bypassing for the low-side driver
isprovidedbyC1. Bootstrapbiasforthe
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.
300
200
100
0
300
200
100
0
Theinputsaredesignedtobecompatible
with 5 V CMOS logic levels and should
notbeconnectedtoVDD. NormalCMOS
power supply sequencing should be
observed. Theorderofsignalapplication
0
100
Gate Charge (nC)
200
0
100
Gate Charge (nC)
200
Figure 5. Switching Frequency versus Gate Charge for a) PDIP and b) SOIC.
HV+
8
7
6
5
FLUORESCENT
LAMP
INT201
1
8
2
3
4
V
DD
7
6
5
4
INT200
HV-
1
2
3
OSCILLATOR
PI-1462-042695
Figure 6. Using the INT200 and INT201 to Drive a Fluorescent Lamp.
F
1/96
4
POWERINT [ Power Integrations ]
