Citizen CL-S400DT - Drivers; Motor Driver

Chapter 2 Operating Principles
2-2. Operation of Control Parts
CL-S400DT 2-20
2-2-4. Drivers
(1) Motor driver
This is a driving circuit to drive the “Unit, Motor” (stepping motor). The following figure shows
its simplified circuit. The “Unit, Motor” is driven by a bipolar constant current chopper method.
The exciting method for the “Unit, Motor” is a 1-2 phase method.
When FET (Q20) turns ON, the power to the “Unit, Motor” is supplied. The power supply is
controlled by VMTON signal sent from the FPGA (U11). When VMTON signal is “High”, Q22
turns OFF and FEQ (Q20) turns ON to supply power.
The exciting method for the “Unit, Motor” is determined by PFMD1 and PFMD2 signals sent
from the FPGA (U11). Also, the rotational direction of the “Unit, Motor is determined by PFDIR
signal and “Unit, Motor” turns when a pulse (PFCLK) is fed to pin 14 (STEP) of U15 (Motor
driver).
The digital-to-analog converter (U4) is used to set the drive current for the “Unit, Motor”. Its
output (PFMOTCU) is input to pin 15 (REF) of U15 (Motor driver) for setting the drive current.
Note that if an abnormal temperature is detected and "Alarm System Fail" is displayed on the
LCD as mentioned in “(3) Head temperature sensor”, PFOFF signal sent from the FPGA (U11)
goes “High” and Q2 turns ON. Thus, pin 15 (REF) of U15 (Motor driver) goes “Low” and the
drive current setting value becomes zero. Also, since VMTON signal is set from “High” to “Low”,
FET (Q20) turns OFF and the power supply (VMT) to U15 (Motor driver) is shut off.
24
8
19
14
9
17
VBB1
VBB2
MS1
MS2
STEP
DIR
U15
Motor Driver
1
2
3
4
J5
OUT1A
OUT1B
OUT2A
OUT2B
M
Unit, Motor
18
21
1
22
Q22
DTC114EM
Q20
MCH6342
REF
C95
PFMOTCU
PFMD1
PFMD2
PFCLK
PFDIR
15
ENABLE
2
+24V
R122
R124
VMT
[SA Main PCB]
L: Q20 turns ON to supply
power to the "Unit, Motor".
A4984SES-T
PFENB
12
PFPS
SLEEP
Q2
DTC114EM
R75
U4
D/A Converter
LD
DI
6
7
CK
8
1
SDATA
DACLD
SCLK
BH2220
AO1
AO2
AO3
PFOFF
VMTON
R126
From
U1A
CPU
From
U11
FPGA
From
U11
FPGA
From
U11
FPGA
From
U1A CPU
Motor drive current setting