MSK4221 Datasheet, PDF (3/5 Pages) List of Unclassifed Manufacturers – 75 VOLT 8 AMP MOSFET H-BRIDGE PWM MOTOR DRIVER/AMPLIFIER

APPLICATION NOTES
MSK 4221 PIN DESCRIPTIONS
VCC - Is the low voltage supply for powering internal
logic and drivers for the lowside and highside MOSFETS.
The supplies for the highside drivers are derived from
this voltage.
V+ - Is the higher voltage H-bridge supply. The
MOSFETS obtain the drive current from this supply pin.
The voltage on this pin is limited by the drive IC. The
MOSFETS are rated at 100 volts. Proper by-passing to
GND with sufficient capacitance to suppress any volt-
age transients, and to ensure removing any drooping
during switching, should be done as close to the pins
on the module as possible.
OUTPUT A - Is the output pin for one half of the bridge.
Increasing the duty cycle of the input causes increas-
ing duty cycles at this output.
VREF OUT - Is a pin providing a resistor divider net-
work dividing Vcc voltage down to be used as a de-
fault reference level input for the INPUT signal thresh-
old. It is set up primarily to be used as a TTL threshold.
To use, just connect VREF OUT to VREF IN. VREF
OUT is bypassed internally with a capacitor.
VREF IN - Is a pin provided to allow the user to tailor
the INPUT threshold to their particular logic level re-
quirements. In a default configuration, VREF IN gets
connected to VREF OUT for TTL threshold level require-
ments.
TYPICAL SYSTEM OPERATION
OUTPUT B - Is the output pin for the other half of the
bridge. Decreasing the duty cycle of the input causes
increasing duty cycles at this output.
RSENSE A - Is the connection for the bottom of the A
half bridge. This can have a sense resistor connection
to the V+ return ground for current limit sensing, or
can be connected directly to ground. The maximum
voltage on this pin is ±2 volts with respect to GND.
RSENSE B - Is the connection for the bottom of the B
half bridge. This can have a sense resistor connection
to the V+ return ground for current limit sensing, or
can be connected directly to ground. The maximum
voltage on this pin is ±2 volts with respect to GND.
GND - Is the return connection for the input logic and
Vcc.
INPUT - Is digital input for controlling the PWM pulse
width of the bridge. A duty cycle higher than 50% will
produce greater than 50% duty cycle pulses out of
OUTPUT A. A duty cycle lower than 50% will produce
greater than 50% duty cycle pulses out of OUTPUT B.
DISABLE - Is the connection for disabling all 4 output
switches. DISABLE high overrides all other inputs.
When taken low, everything functions normally. An
internal pullup to Vcc will keep DISABLE high if left
unconnected.
HEN - Is the connection for enabling the high side out-
put switches. When taken low, HEN overrides other
inputs and the high side switches remain off. When
HEN is high everything functions normally. An internal
pullup to Vcc will keep HEN high if left unconnected.
IN
This is a diagram of a typical application of the MSK 4221.
The design Vcc voltage is +12 volts and should have a good
low ESR bypass capacitor such as a tantalum electrolytic.
The input will be a pulse width modulated digital signal from
a microcontroller, DSP or other microprocessor. A 50% duty
cycle input will cause zero average current through the load.
A smaller duty cycle input will cause increasing average cur-
rent in one direction, a larger duty cycle input will cause in-
creasing average current in the other direction. 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 the common source of the
bridge together. It is important to make the high current
traces as big as possible to keep inductance down. The stor-
age capacitor connected to the V+ and the module 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 the
capacitor as close to the module 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 mi-
croprocessor. This application will allow full four quadrant
torque control for a closed loop servo system.
A snubber network is usually required, due to the induc-
tance in the power loop. It is important to design the snub-
ber network to suppress any positive spikes above 75V and
negative spikes below -2V with respect to ground.
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Rev. C 6/00