BRAKE - is a pin for commanding the output bridge

into a motor BRAKE mode. When pulled low, nor-

mal operation commences. When pulled high, the

3 high side bridge switches turn off and the 3 low

side bridge switches turn on, causing rapid decel-

eration of the motor and will cease motor operation

until pulled high again. Logic levels for this input

are TTL compatible. It is internally pulled high.

DIS - is a pin for externally disabling the output

bridge. A TTL logic low will enable the bridge and a

TTL logic high will disable it. It is internally pulled

up by a 100 µAmp pullup.

60/120- is a pin for selecting the orientation of the

commutation scheme of the motor. A high state

will produce 60/300 degree commutation, whereas

a low state will produce 120/240 degree commuta-

tion. Logic levels for this input are TTL compatible.

It is internally pulled high.

APPLICATION NOTES CONTINUED

4

VOLTAGE REGULATOR POWER DISSIPATION - To figure volt-

age regulator power dissipation and junction temperature, use

the following as an example:

Given:

V+ = 28V, MSK 4362 +15V IQ = 85mA, -15V IQ = 40mA.

External Loads: +15V = 25 mA, -15V = 25 mA

-15V Converter Efficiency = 50%

3.13 W x 9°C/W = 28.1°C RISE above case temperature

Maximum Case Temperature = 150°C - 28.1°C = 121.9°C

To lower power dissipation in the regulator, a dropping resistor

can be added in series from V+ to the +REG IN pin. Using the

above example, if V+ = 39V and there is no dropping resistor,

total power dissipation rises to about 5.76 watts. Temperature

rise is now 51.8°C above case temperature, limiting maximum

case temperature to 98.2°C. By adding a dropping resistor to

lower the +REG IN pin voltage to 24.1V, the regulator power

dissipation is lowered to 2.19 watts. Temperature rise is now

19.7°C above case temperature, allowing a maximum case tem-

perature all the way to +125°C.

Rev. G 2/05

ALTERNATE REGULATOR CONNECTION OPTIONS

By connecting the regulators in different ways, various capabilities can be obtained.

1.

Higher than 55 volt operation -

For operation at higher than 55 volt motor bus voltages, there are three options available: