EVAL6208PD STMicroelectronics

AN1451 APPLICATION NOTE L6208 FULLY INTEGRATED TWO PHASE STEPPER MOTOR DRIVER by Domenico Arrigo, Vincenzo Marano and Thomas Hopkins Modern motion control applications need more flexibility that can be addressed only with specialized IC products. The L6208 is a fully integrated stepper motor driver IC specifically developed to drive a wide range of two phase (bipolar) stepper motors. This IC is a one-chip cost effective solution that includes several unique circuit design features. These features, including a decoding logic that can generate three different stepping sequences, allow the device to be used in many applications including microstepping. The principal aim of this development project was to produce an easy to use, fully protected power IC. In addition several key functions such as protection circuit and PWM current control drastically reduce external components count to meet requirements for many different applications. 1 INTRODUCTION The L6208 is a highly integrated, mixed-signal power IC that allows the user to easily design a complete motor control system for two-phase bipolar stepper motors. Figure 1 shows the L6208 block diagram. The IC inte- grates eight Power DMOS, a centralized logic circuit which implements the phase generation and a constant t PWM current control technique (Quasi-Synchronous mode) for each of the two phases of the motor plus OFF other added features for safe operation and flexibility. Figure 1. L6208 block diagram. V BOOT V BOOT V SA V V BOOT BOOT CHARGE THERMAL V CP PUMP PROTECTION OVER OCD A CURRENT DETECTION OUT1 A OCD B OUT2 A 10V 10V EN GATE LOGIC CONTROL SENSE A HALF/FULL PWM + CLOCK STEPPING ONE SHOT MASKING SEQUENCE MONOSTABLE TIME VREF - RESET SENSE A GENERATION COMPARATOR CW/CCW RC A BRIDGE A V SB VOLTAGE OVER REGULATOR GND CURRENT OUT1 B DETECTION GND OUT2 B SENSE GND GATE B 10V 5V LOGIC VREF GND B RC BRIDGE B B L6208 D01IN1226 October 2003 1/43AN1451 APPLICATION NOTE Table of Contents 1 INTRODUCTION................................................................................................................................1 2 DESIGNING AN APPLICATION WITH L6208 ...................................................................................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 .............................................................................................................6 2.5 Sensing Resistors ....................................................................................................................8 2.6 Charge pump external components.........................................................................................9 2.7 Sharing the Charge Pump Circuitry .......................................................................................10 2.8 Reference Voltage for PWM Current Control.........................................................................11 2.9 Input Logic pins......................................................................................................................12 2.10 EN pin ....................................................................................................................................12 2.11 Programmable off-time Monostable......................................................................................13 2.11.1 Off-time Selection and minimum on-time ........................................................................15 2.11.2 Decay Modes ..................................................................................................................16 2.12 Over Current Protection ........................................................................................................18 2.13 Power Management..............................................................................................................21 2.13.1 Maximum output current vs. selectable devices..............................................................22 2.13.2 Power Dissipation Formulae for different sequences......................................................22 2.14 Choosing the Decay Mode....................................................................................................25 2.15 Choosing the Stepping Sequence.........................................................................................26 2.16 Microstepping........................................................................................................................27 3 APPLICATION EXAMPLE................................................................................................................30 3.1 Decay mode, sensing resistors and reference voltage........................................................30 4 APPENDIX - EVALUATION BOARDS .............................................................................................31 4.1 PractiSPIN..............................................................................................................................31 4.2 EVAL6208N ...........................................................................................................................33 4.2.1 Important Notes................................................................................................................34 4.2.2 Thermal Impedance .........................................................................................................34 4.3 EVAL6208PD.........................................................................................................................38 4.3.1 Important Notes................................................................................................................39 4.3.2 Thermal Impedance .........................................................................................................39 5 REFERENCES.................................................................................................................................43 2/43