MSK4362_15 Datasheet, PDF (4/9 Pages) M.S. Kennedy Corporation – 75 Volt Motor Supply Voltage

APPLICATION NOTES CONTINUED
BRAKE - is a pin for commanding the output bridge into a motor
BRAKE mode. When pulled low, normal operation commences.
When pulled high, the 3 high side bridge switches turn off and the 3
low side bridge switches turn on, causing rapid deceleration 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
commutation. Logic levels for this input are TTL compatible. It is
internally pulled high.
VOLTAGE REGULATOR POWER DISSIPATION - To figure volt-
age regulator power dissipation and junction temperature, use the
following as an example:
Given:
V+ = 28V, MSK4362 +15V IQ = 90mA, -15V IQ = 40mA.
External Loads: +15V = 25 mA, -15V = 25 mA
-15V Converter Efficiency = 50%
PDISS due to +15V IQ, 90 mA x 13V = 1.17 W
PDISS due to -15V IQ, (40 mA / 0.5) x 13V = 1.04 W
PDISS due to +15V Ext load, 25 mA x 13V = 325 mW
PDISS due to -15V Ext load, (25 mA / 0.5) x 13V = 650 mW
PDISS Total = 1.17 W + 1.04 W + 325 mW+650 mW=3.19W
3.19 W x 9°C/W = 28.7°C RISE above case temperature
Maximum Case Temperature = 150°C - 28.7°C = 121.3°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 5.88 watts. Temperature rise is now 52.9°C
above case temperature, limiting maximum case temperature to
97.1°C. By adding a dropping resistor to lower the +REG IN pin
voltage to 24.1V, the regulator power dissipation is lowered to 2.23
watts. Temperature rise is now 20.1°C above case temperature,
allowing a maximum case temperature all the way to +125°C.
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:
IMPORTANT NOTE ABOUT START UP:
When using the suggested inductor value (47µH) and output capacitor (47µF), the internal DC-DC converter (inverter) requires an input
surge current of approximately 1.5A for 5mS at the -REG IN pin during start up. The +15V supply that is connected to the inverter input
(-REG IN) must be capable of providing the start up surge current or the inverter could latch off into current limit. If the internal regulator is
used to power the inverter, the same requirement applies to the +REG IN supply. As the -15VOUT capacitor value is increased, the pulse
width of the start up current also increases porportionally. Also, since the DC-DC inverter is a basic switcher circuit, the normal operating
DC input current (-REG IN) will always be twice that of the output current (-15VOUT).
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8548-147 Rev. M 1/15