AN2839 Application note L6228 fully-integrated two-phase stepper motor driver Introduction Modern motion control applications need more flexibility, which can only be addressed with specialized IC products. The L6228 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 circuitry and PWM current control, drastically reduce the number of external components to meet requirements for many different applications. The L6228 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 L6228 block diagram. The IC integrates eight Power DMOSs, a centralized logic circuit that implements the phase generation and a constant t PWM current control technique OFF (quasi-synchronous mode) for each of the two phases of the motor, plus other added features for safe operation and flexibility. Figure 1. L6228 block diagram 9 %227 9 %227 9 6 9 9 %227 %227 &+ 5*( 7+(50 / 9 &3 3803 3527(&7,21 29(5 2& &855(17 (7(&7,21 2& % 9 9 (1 7( * /2*,& &21752/ 6(16( + /) )8// 3:0 &/2&. 67(33,1* 21( 6+27 0 6.,1* 6(48(1&( %/( 021267 7,0( 95() 5(6(7 6(16( 7,21 *(1(5 25 7 5 &203 &: &&: 5& %5, *( 9 6% *( 7 92/ 29(5 25 7 5(*8/ *1 &855(17 % (7(&7,21 *1 % 6(16( *1 7( * % 9 9 /2*,& *1 95() % 5& %5, *( % % / - V September 2009 Doc ID 15104 Rev 1 1/40 www.st.com 287 287 287 287 Contents AN2839 Contents 1 Designing an application with L6228 . 4 1.1 Current ratings 4 1.2 Voltage ratings and operating range 4 1.3 Choosing the bulk capacitor 6 1.4 Layout considerations . 7 1.5 Sensing resistors 9 1.6 External components for the charge pump . 10 1.7 Sharing the charge pump circuitry 11 1.8 Reference voltage for PWM current control . 12 1.9 Input logic pins . 13 1.10 EN pin . 13 1.11 Programmable off time monostable . 14 1.11.1 Off time selection and minimum on time 16 1.11.2 Decay modes . 16 1.12 Overcurrent protection . 18 1.13 Power management . 21 1.13.1 Maximum output current versus selectable devices . 23 TM 1.13.2 Power dissipation and thermal analysis with PractiSPIN software 23 1.14 Choosing the decay mode 24 1.15 Choosing the stepping sequence . 25 1.16 Microstepping 27 2 Application example 29 Appendix A Demonstration board . 31 TM A.1 PractiSPIN . 31 A.2 L6228N evaluation with EVAL6208N . 32 A.2.1 Important notes 32 A.3 EVAL6228QR 34 References . 38 Revision history 39 2/40 Doc ID 15104 Rev 1