MSK4410_15 Datasheet, PDF (6/8 Pages) M.S. Kennedy Corporation – 55 Volt Motor Supply Voltage

APPLICATION NOTES CONTINUED
TACH RC COMPONENT SELECTION
For a given maximum motor speed, the tach output has a maximum pulse width. For example, if a maximum motor speed of 3000
RPM were desired and the permanet magnet on the rotor of the motor being used has two pairs of poles, each mechanical
revolution would cause each hall effect sensor to deliver two pulses. The three sensors would generate six pulses. The MSK4410
tachometer would generate 12 pulses, one for each rising and falling edge of the sensor pulses. If a maximum motor speed in the
example were desired, this would be 50 revolutions per second. The tachometer will be producing 600 pulses per second or have
a frequency of 600Hz. Therefore, the maximum puse width would have to be less than 1.66 milliseconds. Figure one can be used
to select component values to achieve the desired pulse width.
CURRENT LIMIT ADJUST
FIGURE 1
With the current limit adjust pin (pin 12) left open, the current will be limited to 1 amp ±0.7 amps. If a current limit of more than
1 amp but less than 15 amps is desired, a resistor between the pin and ground can be used to set a different limit. Figure two can
assist in the selection of the resistor value for this purpose.
FIGURE 2
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Rev. E 1/11