Fujitsu ULTIMA90 Maintenance Manual page 159

An internal interrupt is caused to the MPU every step and, when needed, the excitation time and current
specification data are changed to FPGA control the stepping motor.
Figure 5.3.16 shows the space motor drive circuit.
Figure 5.3.16 Space motor drive circuit
The space motor uses a constant current drive circuit as shown in Figure 5.3.16
The constant current drive circuit and drive FET used exclusively for motor driving.
The FPGAstepping motor control circuit outputs SPM0 to SPM3 as phase data.
When the output signal is Hi-Z(H), the FET in the HIC goes on to supply current to the motor phase.
Current I flows to SG2 through resistor R. Voltage level IR for the SG2 when current I flows into resistor R
is compared with the reference voltage in the comparator.
When IR exceeds the reference voltage, the comparator output and phase signal are ANDed in the HIC to
turn off the FET and thereby control flowing current constant.
The reference voltage is generated by pressure division of the resistor as shown in Figure 5.3.16. The
reference voltage is changed at the pressure division resistor by current control signals SPI0-2 from
the motor control circuit, and thus output current is controlled.
[Line feed motor and tractor motor drive circuits]
The 4-phase line feed motor and tractor motor (Uni-polar stepping motor) are controlled by the constant current drive circuit
shown below.
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