A3955Full-Bridge PWM Microstepping Motor DriverDescription (continued) Internal circuit protection includes thermal shutdown with hysteresis, and a 16-lead plastic SOIC with internally fused pins (suffix ‘LB’). transient-suppression diodes, and crossover-current protection. For both package styles, the thermally enhanced pins are at ground Special power-up sequencing is not required. potential and need no electrical isolation. Both packages are lead The A3955 is supplied in a choice of two power packages; a 16-pin (Pb) free, with leadframe plating 100% matte tin. dual-in-line plastic package with copper heat-sink tabs (suffix ‘B’), Selection GuidePart NumberPackingPackage A3955SB-T 16-pin DIP with exposed thermal tabs 25 per tube A3955SLBTR-T 16-pin SOICW with internally fused pins 1000 per reel Absolute Maximum RatingsCharacteristicSymbolNotesRatingUnits Load Supply Voltage VBB 50 V Logic Supply Voltage VCC 7.0 V Logic/Reference Input Voltage Range VIN –0.3 to VCC + 0.3 V Sense Voltage VS 1.0 V Output current rating may be limited by duty cycle, ambient temperature, and heat sinking. Under any set of conditions, do Output Current, Continuous IOUT ±1.5 A not exceed the specifi ed current rating or a junction tempera- ture of 150 ° C. Package Power Dissipation PD See graph W Operating Ambient Temperature TA Range S –20 to 85 ºC Fault conditions that produce excessive junction temperature Maximum Junction Temperature TJ(max) will activate the device’s thermal shutdown circuitry. These 150 ºC conditions can be tolerated but should be avoided. Storage Temperature Tstg –55 to 150 ºC Thermal CharacteristicsCharacteristicSymbolTest Conditions*ValueUnits B Package, single-layer PCB, 1 in.2 2-oz. exposed copper 43 ºC/W Package Thermal Resistance, Junction R to Ambient θJA LB Package, 2-layer PCB, 0.3 in.2 2-oz. exposed copper each 67 ºC/W side Package Thermal Resistance, Junction R to Tab θJT 6 ºC/W *Additional thermal information available on Allegro website. 4 R = 6.0°C/W θJT 3 SUFFIX 'B', R = 43°C/W θJA 2 1 SUFFIX 'LB', R = 67°C/W θJA 0 25 50 75 100 125 150 ALLOWABLE PACKAGE POWER DISSIPATION (W) TEMPERATURE IN °C Allegro MicroSystems, Inc. 2 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com