LM9830VJDX NSC [National Semiconductor], LM9830VJDX Datasheet - Page 43

• Manufacturer Part Number: LM9830VJDX
• Description: LM9830 36-Bit Color Document Scanner
• Manufacturer: NSC [National Semiconductor]

Stepper Motor Current Controller Block Diagram
CR
CR
DAC code for
DAC code for
TriState Stepper
phase A
phase B
Motor Outputs
8
6
Phase A
Phase B
Invert
Invert
Generator
÷1 to 256
(50MHz)
high time
A
A
CRYSTAL IN
B
B
0/64 to
PWM
63/64
÷64
÷4
CR
CR
CR
3
3
DAC A:
0.125V,
0.191V,
0.353V,
0.462V,
DAC A:
0.125V,
0.191V,
0.353V,
0.462V,
0.500V
0.500V
Comparators need no hysteresis. SR flipflops are set periodi-
cally by pulse from PWM Generator. Flipflops can only be reset
after SR goes low when Reset (comparator output) is high
(V
Reset is level sensitive, not edge sensitive.
SENSE
–
+
+
–
> V
DAC
).
Reset
Reset
Set-Dominant
Set-Dominant
Set
Set
S/R Flipflop
S/R Flipflop
Q
Q
LM9830
SENSE1
SENSE2
A
A
HIGH CURRENT
B
B
GND SENSE
Phase A
Phase B
Stepper
Stepper
1
1
+24V
+24V
Phase A
Phase B
Stepper
Stepper
Optional zener speeds
decay when transistor
up motor current
is off. V
Z
~ 24V