7 Appendix

L9942

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Fast decay can be seen as switching the bridge in opposite direction, if it is compared to ON

state before. The load current control at HS switch is not used, but the comparator is still active.

The reference value is changed to overcurrent limit and a shortage to ground or now between

the outputs too will result in a signal. The internal filter time of at least 4 us will inhibit the signal

in many applications. Then you can use the mode “auto decay without any delay time“ (On

Section 5.1 on page 21 mode 100). On page 34 you can find in the lower part of Figure 3 the

phase counter values, when fast decay as only part of mixed decay is used and the shortages

can be detected during a longer time. After this it is signalised in register 7 as overcurrent in HS

switch (e.g. in

Figure 17 HSA1).

Figure 15. Stall Detection

0 1 2 3 45 67 876 5 432 1 0 12 3 4 56 7 8 765 4 3 2 1

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

012 3 456 7 8 76 5 4 32 1 0 123 4 5 67

87 6 5 4 3 2 1

Current Driver A

Current Driver B

STEP Signal

Adress of Current

Profile Entry

Phase Counter

Micro Stepping Mode: DIR=0

01 23 45 67 87 6 5 43 2 1 0 1 23 45 6 7 8 7 6 5 4 3 2 1

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

0 123 4 5 67 876 5 4 3 21 01 23 45 67

87 65 43 21

Current Driver A

Current Driver B

Micro Stepping Mode: DIR=1

0

Adress of Current

Profile Entry

Time

PWM activ detection

Load Current Rising During High Speed

PWM activ

counter

Stall

Threshold

Stall

Threshold

Activ

sampling and

threshold

Activ

sampling and

threshold

PWM activ

counter

PWM activ detection

PWM activ detection

Counter value is above threshold value.

bit6

bit7

D7

D6

D5

D4

D3

D2

D1

D0

Register 4

bit5

bit6

bit7

Reg3

Register 5

bit5

bit6

bit7

Stall

Time

Threshold

16us *

No

Stall Signal

012 345 67 8 7 65 43 21 0 1 23 4 5 67 8 7 6 5 4 3 2 1

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

0 1 23 45 67 8 7 65 4 3 21 0 1 2 3 4 5 67

876 543 21

Current Driver A

Current Driver B

STEP Signal

Adress of Current

Profile Entry

Phase Counter

Micro Stepping Mode: DIR=0

0 1 23 4567 8 76 5 4321 0 1 2 3 4 5 678 7 6 5 4 3 2 1

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

0 1 2 3 4567 8 7 6 5 4 3 210 1 2 3 4 5 67

8 7 65 4321

Current Driver A

Current Driver B

Micro Stepping Mode: DIR=1

0

Adress of Current

Profile Entry

Time

PWM activ detection

PWM activ

counter

Stall

Threshold

Stall

Threshold

Activ

sampling and

threshold

Activ

sampling and

threshold

PWM activ

counter

PWM activ detection

PWM activ detection

Stall Signal

Stall Signal

Load Current Rising During Low Speed or Stall

Counter value is below threshold value.