M54678FP Mitsubishi Electronics America, Inc., M54678FP Datasheet - Page 4

• Manufacturer Part Number: M54678FP
• Description: 2-phase Stepper Motor Driver
• Manufacturer: Mitsubishi Electronics America, Inc.

APPLICATION DIRECTIONS
(1) Ph input, En input determines output function.
(2) Vref (reference voltage)
(3) Current comparator
(4) Oscillating circuit
(5) Spike current cancellation circuit
(6) Phase delay circuit
(7) Rs terminal and S terminal
(8) Voltage stabilizer circuit
Z : High impedance
Output current level is controlled by Vref voltage.
Under VRS (current sensing resistor voltage) > Vref (reference
voltage) condition, the current comparator switches, fip-flop is
reset and output circuit is set to off.
Frequency of PWM operation synchronize with Fref terminal
frequency.
If you change frequency of PWM operation, please change
capacitor value of Fref terminal.
This IC is designed oscillating frequency to be 30kHz when
capacitor = 390pF is connected to Fref terminal. Oscillating
frequency is inversely proportional to capacitor value. When
capacitor value become half, Oscillating frequency will be two
times.
This IC includes Spike cancellation circuit to prevent the failure
function of current comparator by influence of this spike current.
Thus, current comparator don’t function during approximately
2 S from the moment of output transistor is set to on.
This IC includes Phase delay circuit to prevent output through
current at Ph switching time.
Four output transistors of H bridge don’t function during
approximately 3 S at Ph switching time.
Difference of current sensing that caused by wiring resistance
of board (wiring resistance between RS terminal and current
sensing resistor) can be prevented by connecting S terminal
(plus input of current comparator) to current sensing resistor as
close as possible.
This IC includes voltage stabilizer circuit. (3.5volts output). Vref
reference voltage can be generated by resistance potential
dividing from constant voltage output terminal (Regout). Current
capability of constant voltage output terminal is I source =
+1mA, I sink = -0.1mA
*: 1 or 2
Ph*
H
H
L
L
En*
H
H
L
L
Out*
H
Z
Z
L
Out*B
H
L
Z
Z
(9) Setting of output current
*If Vcc, Tj and manufacturing dispersion are considered,
dispersion of Ib will vary maximum 5mA
(minimum = 5mA, maximum = 15mA)
Since output circuit of this IC consists of NPN type transistor,
current flow through the motor coil (Iout) becomes
approximately 20mA (typical value) smaller than current flow
through the current sensing resistor (IRS) by influence of the
base current (Ib) of transistor.
Thus, please consider this current when you set up output
current.
MA
OFF
MITSUBISHI <CONTROL / DRIVER IC>
ON
2-PHASE STEPPER MOTOR DRIVER
RS
Iout
VM
ON
MB
M54678FP
OFF
Iout = IRS - Ib
Ib = 10mA (Typ.)
V
CC