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Unformatted text preview: 1. REF & SENSE : The coupled pins specify a current limit of the chip by ?? = where V ref is the voltage input into pin REF and R s is the resistance connected to pin SENSE, and I so is the base drive offset current. By setting V ref to Vcc and grounding SENSE we disable the current limit function. BRAKE: It uses back-emf to dynamically brake the motor by enabling two sink transistors (NPN). By setting this pin high we disable the brake function. MODE: It selects the current decay mode (fast or slow) in forward, reverse and brake if the current has reached the specified current limit. It also tells the chip to stand by or sleep while the chip is disabled. By grounding it we make the chip stand by when not driving the motor. 2. Since the ENABLE pin is active LOW, and the other side of the switch is connected to one pin of an OR gate, the switch must be connected to GND to turn the motor amplifier on. Besides, pin 4.2 needs also to be low to turn on the amplifier. pin 4....
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- Fall '08