NTE1885 Integrated Circuit Module, 4 Phase Stepping Motor Driver, 1.75A Features: Low heat generation due to constant current chopper system. Functions of pause action and power down. Able to be used in any stepping motor of hybrid typ, P.M. type, V.R. type. Inverter buffer provides direct drive, for 4 phase dual excitation. Built in sensing power resistors for load current. Protection elements for flyback voltage are included. Absolute Maximum Ratings: (T = +25C unless otherwise specified) A Supply Voltage, V (Quiescent) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50V CC Phase Peak Current, I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1A OH Operating Case Temperature, T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +105C C Junction Temperature, T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +150C j Storage Temperature Range, T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 to +125C stg Recommended Operating Conditions: (T = +25C Unless othrwise specified) A Supply Voltage Range, V 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22V to 45V CC Phase Peak Current, I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5A OH Operating Characteristics: (T = +25C, V 1 = 36V, V 2 = 5V Unless otherwise specified) A CC CC Parameter Symbol Test Conditions Min Typ Max Unit Diode Forward Voltage V I = 0.3A 1.5 1.8 V df1 f V I = 0.5A 1.2 1.6 V df2 f Output Saturation Voltage V R = 12 , V = GND, 1.2 1.6 V sat1 L in V 1 = 22V CC V R = 21 , V = GND, 2.3 3.0 V sat2 L in V 1 = 36V CC Output Current I 0.98 1.05 1.12 A O1 OSC Frequency f 24 (Fixed OSC) kHz Thermal Resistance TR1, TR6 8.0 C/W jc (Note 1) TR2, TR3, TR4, TR5 13.5 Note 1. From Junction of each transistor or diode to substrateDescription of Operation: Constant Current Chopper Drive a) When the phase drive input is activated, the motor winding current increases. At a predetermined current (the rated current of the motor), the applied voltage of the winding begins to be switched ONOFF to maintain a constant current. This is the constantcurrent chopper drive by PWM offering a higher efficiency (30% under a cer- tain condition) than a constantvoltage drive, but causing relatively large noise due to the switch- ing operation. The PWM method consists of selfexcitation and separate excitation methods. For the separate excitation, an oscillator is required, as PWM is externally conducted. The self excita- tion method has a simpler circuit, not requiring an oscillator, but using the resistance and induc- tance of the motor winding instead. b) When a voltage several times larger than the rated voltage is applied to the motor, a change in the winding currents occurs. The time when the currents reach 63.2% of the rated current (I ) O shows a higherspeed response with regard to the rise of the winding current and acts as a time constant for the RL series network with the rated applied voltage. c) Without a constant current circuit, over current will ramp up to a constant value, so that a constant current chopper drive is needed. The chopping is conducted below the constant value, so that the winding resistance and the rated current must satisfy the following equation: V V CC sat I < O R Where R: Winding resistance per a phase of the motor + R 1 E V :V + V sat sat1 sat2 With an increase in winding inductance, the flyback energy is increased and, when transistors for eachphase drive are OFF, the power loss is increased. Considering b) and c), the following motor is recommended: Motor specification (4phase unipolar stepping motor) Rated current: 1.0 0.5A/phase Winding resistance: 10 /phase Inductance: 1 10mH/phase Chopper Operation (Note: TRs are internal transistors used for reference purposes Ds are inter- nal protection diodes and Ls represent the motor windings) The operation for a unipolar 2phase excitation a of 4phase stepping motor is described as: When a HighLevel input and a LowLevel input are applied to Pin5 (phase A) and Pin6 (phase A) respectively, TR2 is turned ON. Since one terminal of 1/2 IC1 (comparator) is at GND potential, the comparator output (point A becomes High), turning ON TR7. This also causes TR1 to be turned ON and the current in the winding increases as shown by the equation: V V(sat) CC t/ i = (l ) R Where : = L/R time constant L: Winding inductance per phase R: Winding resistance per phase plus emitter resistance, etc. also V := V + V sat sat1 sat2 V :V (sat) of chopper transistors (TR1, 6) sat1 CE V :V (sat) of phasedrive transistors (TR2, 3, 4, 5) and V (Diodes, internal) sat2 CE d