Table 3. Look Up Table up to 32 Microsteps (continued)

7

4

95.7%

29.0%

17

8

94.2%

33.7%

20

9

5

3

2

92.4%

38.3%

23

10

90.4%

42.8%

25

11

6

88.2%

47.1%

28

12

85.8%

51.4%

31

13

7

4

83.1%

55.6%

34

14

80.3%

59.6%

37

15

8

77.3%

63.4%

39

16

74.1%

67.2%

42

17

9

5

3

2

1

70.7%

70.7%

45

18

67.2%

74.1%

48

19

10

63.4%

77.3%

51

20

59.6%

80.3%

53

21

11

6

55.6%

83.1%

56

22

51.4%

85.8%

59

23

12

47.1%

88.2%

62

24

42.8%

90.4%

65

25

13

7

4

38.3%

92.4%

68

26

33.7%

94.2%

70

27

14

29.0%

95.7%

73

28

24.3%

97.0%

76

29

15

8

19.5%

98.1%

79

30

14.7%

98.9%

82

31

16

9.8%

99.5%

84

32

4.9%

99.9%

87

32

17

9

5

0.0%

100.0% 90

Setting the Fixed OFF Time (tOFF)

The current regulation circuit is based on a constant tOFF PWM control. If during the ON phase, the bridge current

exceeds the target ITRIP threshold, the OFF phase begins and the current decays. The OFF phase has a fixed time

duration tOFF.

The tOFF can be configured to a desired value by connecting an external resistor to pin ROFF. When the ROFF pin is

shorted to VDD, the tOFF time is internally set at a fixed value (20μs typical). By connecting an external resistor to the

pin ROFF, the user can configure tOFF as shown in the following equation in which RROFF is an external resistor (in kΩ)

connected from the ROFF pin to GND and KTOFF is an internal constant equal to 0.667μs/kΩ.

tOFF(μs) = RROFF × KTOFF

The tOFF can be programmed from a range of 10μs to 80μs.

Setting the Decay Mode

Two logic input pins allow the user to configure the decay mode during TOFF. The MAX22210 supports slow and mixed

decay mode. An adaptive decay mode is also provided. The adaptive decay mode automatically calculates the optimal

ratio between the slow and fast decay as explained in the Adaptive Decay Mode section.

Table 4 shows the Truth Table for the Decay Mode selection.

MAX22210

36V, 3.8A Stepper Motor Driver

with Integrated Current Sense

and 128 Microstep Indexer

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