MSK4224 View Datasheet(PDF) - M.S. Kennedy
Part Name
Description
Manufacturer
MSK4224 Datasheet PDF : 5 Pages
| |||
APPLICATION NOTES
MSK 4224 PIN DESCRIPTIONS
TYPICAL SYSTEM OPERATION
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 75 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
of the module as possible.
OUTPUT A - Is the output pin for one half of the bridge.
Decreasing the input voltage causes increasing duty
cycles at this output.
OUTPUT B - Is the output pin for the other half of the
bridge. Increasing the input voltage 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 an analog input for controlling the PWM
pulse width of the bridge. A voltage lower than Vcc/2
will produce greater than 50% duty cycle pulses out of
OUTPUT A. A voltage higher than Vcc/2 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 MSK4224.
The design Vcc voltage is +12 volts and should have a
good low ESR bypass capacitor such as a tantalum electro-
lytic. 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 direc-
tion 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 re-
quired 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 sepa-
rately. 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 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 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 induc-
tance in the power loop. It is important to design the snub-
ber network to suppress any positive spikes above 70V and
negative spikes below -2V with respect to ground.
3
Rev.- 06/98
Share Link: 