+15V - is the low voltage supply for all the internal logic and

isolated supplies which provide power to the gate drivers. A

0.1µF ceramic capacitor in parallel with a 22µF tantalum capaci-

tor is recommended for bypassing the low voltage supply to

GND.

GND - is the low voltage supply return for the +15V. All

bypassing of the +15V should return here. Since the output

section of the hybrid is completely isolated, there are no restric-

tions for potential differences between this GND and any hi-

voltage returns, up to 500V.

AHI,BHI,CHI - are the logic inputs for controlling the switching

of the corresponding hi-side bridge outputs. A logic high will

turn on the corresponding hi-side output. The input levels are

5V CMOS or TTL compatible. If one of these inputs are active

at the same time as the corresponding low-side bridge outputs,

neither output will be allowed to turn on until one of the inputs

is switched low. There will be a deadtime inserted before the

corresponding bridge output is switched in all cases. This pre-

vents simultaneous conduction of the output, shorting high

voltage supply and destroying the bridge.

ALO,BLO,CLO - are the logic inputs for controlling the switching

of the corresponding low-side bridge outputs. A logic high will

turn on the corresponding low-side output. The input levels are

5V CMOS or TTL compatible. If one of these inputs are active

at the same time as the corresponding hi-side bridge outputs,

neither output will be allowed to turn on until one of the inputs

is switched low. There will be a deadtime inserted before the

corresponding bridge output is switched in all cases. This pre-

vents simultaneous conduction of the output, shorting the high

voltage supply and destroying the bridge.

RESET - is an active low logic input for causing all switching to

cease. The input level is 5V CMOS or TTL compatible. Upon

releasing RESET, the outputs will resume after the dead time.

R/C - is the input pin for setting the deadtime of the bridge.

Connecting a resistor between this input and OSC OUT, and a

capacitor to ground will create the time for an internal oscillator.

OSC OUT - is a pin that brings the deadtime oscillator out to be

connected through the timing resistor to R/C. This is not an

output to be used externally, but just for the timing circuit.

AV+,BV+,CV+ - are pins for connecting the tops of each half

bridge to the high voltage supply. Each pin must be connected

individually, as there is no internal connection across the three

half bridges. Proper power supply bypassing must be connected

to these pins and the V- pins as close to the hybrid as possible

for proper filtering.

AV-,BV-,CV- - are pins for connecting the bottoms of each half

bridge to the high voltage supply return. Each pin must be

connected individually, as there is no internal connection across

the three half bridges. Proper power supply bypassing must be

connected to these pins and the V+ pins as close to the hybrid

as possible for proper filtering.

AØ, BØ, CØ - are the pins connecting the 3 phase bridge switch

outputs.

TEMP SENSE - is a pin for measuring the output of a tempera-

ture sensor IC. The case temperature is depicted as a voltage

corresponding to 10mV/°C with 0 volts equating to absolute

zero, 0°K or -273°C.

APPLICATION NOTES

DEADTIME SELECTION

MSK4351 PIN DESCRIPTION

The amount of deadtime required is based on the propagation

delay of the input to actual completion of switching of the output

transistors. Not taking all this into account can possibly allow the

opposite transistor in a half bridge to turn on before the active

transistor can turn off. Excessive current will flow through the

half bridge because this creates a momentary short across the

power supply.

Once all these factors are taken into account, the deadtime can be

determined. Allow sufficient safety factor for changes in compo-

nents over temperature, and variations from system to system in

production.

Deadtime is exactly 8 R/C clock periods. Use the formula:

Max. Clock = 8/Min. Deadtime

For clock operation below 1MHz:

Clock Frequency =

For clock operation above 1MHz:

Clock Frequency =

As an alternative, the R/C pin can be driven directly with an HCMOS

compatible clock up to 24MHz.

PRELIMINARY Rev. A 11/01

3

0.95

0.95

RSENSE+ - is the pin for connecting to the internal sense resistor.

It has a value of 0.003 ohms, 20 watts. AV-,BV- and CV- should

connect to this point for sensing the current at the bottom of the

bridge.

RSENSE- - is the pin for connecting the internal sense resistor to

the high voltage return.

RKELVIN+ - is the pin for connecting to the sense resistor +KELVIN

connection. This is on the same side of the resistor as RSENSE+.

RKELVIN- - is the pin for connecting to the sense resistor -KELVIN

connection. This is on the same side of the resistor as RSENSE-.