TYPICAL SYSTEM OPERATION
This is a diagram of a typical application of the MSK 4203. The design Vcc voltage is +12 volts and should have a good low
ESR bypass capacitor such as a tantalum. The analog input can be an analog speed control voltage from a potentiometer, other
analog circuitry or by microprocessor and a D/A converter. This analog input gets pulled by the current control circuitry in the proper
direction to reduce the current flow in the bridge if it gets too high. The gain of the current control amplifier will have to be set to
obtain the proper amount of current limiting required by the system.
Current sensing is done in this case by a 0.1 ohm sense resistor to sense current from both legs of the bridge separately. It is
important to make the high current traces as big as possible to keep inductance down. The storage capacitor connected to the V+
and the hybrid should be large enough to provide the high energy pulse without the voltage sagging too far. A low ESR ceramic
capacitor or large polypropylene capacitor will be required. Mount capacitor as close to hybrid as possible. The connection between
GND and the V+ return should not be carrying any motor current. The sense resistor signal is common mode filtered as necessary
to feed the limiting circuitry for the microprocessor. This application will allow full four quadrant torque control for a closed loop
servo system.
A snubber network is usually required, due to the inductance in the power loop. It is important to design the snubber network to
suppress any positive spikes above 75V and negative spikes below -2V with respect to GROUND.
4
Rev. A 10/02
MSK [ M.S. KENNEDY CORPORATION ]
