CURRENT LEVEL

0

0

100%

1

0

60%

0

1

19%

1

1

Current Inhibit

Current Control: The voltage divider, comparators and

monostable provide a means for current sensing and

comparator. The monostable controls the off time and

therefore the magnitude of the current decrease. The

the timing terminal (pin 2). The reference terminal (pin

11) provides a means of continuously varying the cur-

rent for situations requiring half-stepping and micro-

stepping. The relationship between the logic input

signals at pin 7 and 9 in reference to the current level is

shown in Table 1. The values of the different current lev-

els are determined by the reference voltage together

Single-Pulse Generator: The pulse generator is a

monostable triggered on the positive going edge of the

comparator. Its output is high during the pulse time and

this pulse switches off the power feed to the motor wind-

ing causing the current to decay. The time is determined

nored.

Figure 6

UC1717

UC2717

UC3717

Note: Dashed lines indicate current decay paths.

4