A3955SB

Product Summary

The A3955SB and A3955SLB are designed for driving one winding of a bipolar stepper motor in a microstepping mode. The outputs arerated for continuous output currents to±1.5 A and operating voltagesto 50 V. Internal pulse-width modulated (PWM) current control com-bined with an internal three-bit nonlinear digital-to-analog converterallows the motor current to be controlled in full-, half-, quarter-, oreighth-step (microstepping) modes. Nonlinear increments minimizethe number of control lines necessary for microstepping.Microstepping provides for increased step resolution, and reducestorque variations and resonance problems at low speed.
Internal circuitry determines no matter the PWM current-controlcircuitry operates in a slow (recirculating) current-decay mode, fast(regenerative) current-decay mode, or in a mixed current-decay modein which the off time is divided into a period of fast current decay withthe remainder of the fixed off time spent in slow current decay. The combination of user-selectable current-sensing resistor and referencevoltage, digitally selected output current ratio; and slow, fast, or mixedcurrent-decay modes provides users with a broad, variable range of motor control.

Parametrics

The absolute maximum ratings of A3955SB are
(1)Load Supply Voltage, VBB: 50 V;
(2)Output Current, IOUT(Continuous) : ±15 A;
(3)Logic Supply Voltage, VCC: 70 V;
(4)Logic/Reference Input Voltage Range,VIN: -03 V to VCC + 03 V;
(5)Sense Voltage, VS: 10 V;
(6)Package Power Dissipation,PD: See Graph;
(7)Operating Temperature Range,TA: -20°C to +85°C;
(8)Junction Temperature, TJ: +150°C;
(9)Storage Temperature Range,TS:-55°C to +150°C

Features

The features of A3955SB can be summarized as
(1)±1.5 A Continuous Output Current;
(2)50 V Output Voltage Rating;
(3)Internal PWM Current Control;
(4)3-Bit Non-Linear DAC;
(5)Fast, Mixed Fast/Slow, and Slow Current-Decay Modes;
(6)Internal Transient-Suppression Diodes;
(7)Internal Thermal-Shutdown Circuitry;
(8)Crossover-Current and UVLO Protection

Diagrams

<DIV><IMG alt="Allegro-A3955SB- DIP" src="http://www.seekic.com/uploadfile/ic-mfg/20127519497651.jpg" border=0></DIV>