AN1625 APPLICATION NOTE

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Table of Contents

1

INTRODUCTION ................................................................................................................................1

2

DESIGNING AN APPLICATION WITH L6235 ...................................................................................3

2.1

Current Ratings ........................................................................................................................3

2.2

Voltage Ratings and Operating Range ....................................................................................3

2.3

Choosing the Bulk Capacitor....................................................................................................5

2.4

Layout Considerations .............................................................................................................5

2.5

Sensing Resistor ......................................................................................................................7

2.6

Charge pump external components .........................................................................................8

2.7

Sharing the Charge Pump Circuitry .........................................................................................9

2.8

Reference Voltage for PWM Current Control.........................................................................10

2.9

Input Logic pins ......................................................................................................................11

2.10

DIAG pin.................................................................................................................................11

2.11

Programmable off-time Monostable .......................................................................................12

2.11.1 Off-time Selection and minimum on-time ........................................................................14

2.11.2 Slow Decay Mode ...........................................................................................................14

2.12

Over Current Detection .........................................................................................................16

2.13

Power Management ...............................................................................................................20

2.13.1 Maximum output current vs. selectable devices..............................................................20

2.13.2 Power Dissipation Formulae ...........................................................................................21

2.14

The decoding logic ................................................................................................................24

2.15

Tacho Output and Speed Loop .............................................................................................25

2.15.1 Static performance - Speed Regulation vs. Resistant Torque: .......................................28

2.15.2 Dynamic performance: ....................................................................................................29

2.15.3 Loop Stability: ..................................................................................................................30

2.15.4 Reference voltage ripple: ................................................................................................30

2.16

Brake.....................................................................................................................................31

3

APPLICATION EXAMPLE................................................................................................................32

4

APPENDIX - EVALUATION BOARDS .............................................................................................34

4.1

PractiSPIN..............................................................................................................................34

4.2

EVAL6235N ...........................................................................................................................35

4.2.1 Important Notes ................................................................................................................36

5

REFERENCES.................................................................................................................................39