UC1717 UC2717 UC3717 Stepper Motor Drive Circuit FEATURES • Half-step and Full-step Capability • Bipolar Constant Current Motor Drive • Built-in Fast Recovery Schottky Commutating Diodes • Wide Range of Current Control 5-1000mA • Wide Voltage Range 10-45V • Designed for Unregulated Motor Supply Voltage • Current Levels can be Selected in Steps or Varied Continuously • Thermal Overload Protection DESCRIPTION The UC3717 has been designed to control and drive the current in one winding of a bipolar stepper motor. The circuit consists of an LSTTL-compatible logic input, a current sensor, a monostable and an output stage with built-in protection diodes. Two UC3717s and a few external components form a complete control and drive unit for LSTTL or micro-processor controlled stepper motor systems. The UC1717 is characterized for operation over the full military temperature range of -55°C to +125°C, the UC2717 is characterized for -25°C to +85°C, and the UC3717 is characterized for 0°C to +70°C. ABSOLUTE MAXIMUM RATINGS (Note 1) Voltage Logic Supply, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7V Output Supply, VM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45V Input Voltage Logic Inputs (Pins 7, 8, 9). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6V Analog Input (Pin 10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vcc Reference Input (Pin 11) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15V Input Current Logic Inputs (Pins 7, 8, 9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -10mA Analog Inputs (Pins 10, 11) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -10mA Output Current (Pins 1, 15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±1A Junction Temperature, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +150°C Storage Temperature Range, TS . . . . . . . . . . . . . . . . . . -55°C to +150°C BLOCK DIAGRAM 7/95 Note 1: All voltages are with respect to ground, Pins 4,5, 12, 13. Pin numbers refer to DIL-16 package. Currents are positive into, negative out of the specified terminal. Note 2: Consult Packaging Section of Databook for information on thermal limitations and considerations of package. UC1717 UC2717 UC3717 CONNECTION DIAGRAMS DIL-16 (TOP VIEW) J or N Package PLCC-20 (TOP VIEW) Q Package PACKAGE PIN FUNCTION FUNCTION PIN N/C 1 BOUT 2 Timing 3 VM 4 Gnd 5 N/C 6 Gnd 7 VCC 8 I1 9 Phase 10 N/C 11 I0 12 Current 13 VR 14 Gnd 15 N/C 16 Gnd 17 Vm 18 AOUT 19 Emitters 20 RECOMMENDED OPERATING CONDITIONS PARAMETER Supply Voltage, VCC Supply Voltage, VM Output Current. IM Rise Time Logic Inputs, tR Fall Time Logic Inputs, tF Ambient Temperature, TA UC1717 UC2717 UC3717 MIN 4.75 10 20 -55 -25 0 TYP 5 MAX UNITS 5.25 V 40 V 800 mA 2 µs 2 µs 125 85 70 °C °C °C ELECTRICAL CHARACTERISTICS Unless otherwise specified, these specifications apply for VCC = 5V, TA = TJ. PARAMETER Supply Current, ICC High-Level Input Voltage, Pins 7, 8, 9 Low-Level Input Voltage, Pins 7, 8, 9 High-Level Input Current, Pins 7, 8, 9 Low Level Input Current, Pins 7, 8, 9 Comparator Threshold Voltage Comparator Input Current Output Leakage Current Total Saturation Voltage Drop Total Power Dissipation Cut Off Time, tOFF Turn Off Delay, tD Thermal Shutdown Junction Temperature TEST CONDITIONS MIN TYP 2.0 VI = 2.4V VI = 0.4V IO = 0, I1 = 0, VR = 5.0V IO = 1, I1 = 0, VR = 5.0V IO = 0, I1 = 1, VR = 5.0V IO = 1, I1 = 1, TA = +25°C IM = 500mA IM = 500mA, fS = 30kHz IM = 800mA, fS = 30kHz VM = 10V, tON≥ 5µs (See Figure 5 and 6) TA = +25°C; dVc/dt ≥ 50mV/µs (See Figure 5 and 6) -0.4 390 230 65 -20 25 +160 2 420 250 80 1.4 2.9 30 1.6 MAX 25 UNITS mA V 0.8 V 20 µA mA 440 mV 270 mV 90 mV 20 µA 100 µA 4.0 V 2.1 W 3.1 W 35 µs 2.0 µs +180 °C UC1717 UC2717 UC3717 Figure 1 Figure 3: Typical Sink Saturation Voltage vs Output Current Figure 2: Typical Source Saturation Voltage vs Output Current Figure 4: Typical Power Losses vs Output Current FUNCTIONAL DESCRIPTION The UC3717 drive circuit shown in the block diagram includes the following functions: (1) Phase Logic and H-Bridge Output Stage (2) Voltage Divider with three Comparators for current control (3) Two Logic inputs for Digital current level select (4) Monostable for off time generation Input Logic: If any of the logic inputs are left open, the circuit will treat it as a high level input. Phase Input: The phase input terminal, pin 18, controls the direction of the current through the motor winding. The Schmidt-Trigger input coupled with a fixed time delay assures noise immunity and eliminates cross conduction in the output stage during phase changes. A low level on the phase input will turn Q2 on and enable Q3 while a high level will turn Q1 on and enable Q4. (See Figure 7). Figure 5: Connections and Component Values as in Figure 6. across the source transistors. The Schottky diodes allow the current to circulate through the winding while the sink transistors are being switched off. The diodes across the sink transistors in conjunction with the Schottkys provide the path for the decaying current during phase reversal. (See Figure 7). Output Stage: The output stage consists of four Darlington transistors and associated diodes connected in an H-Bridge configuration. The diodes are needed to provide a current path when the transistors are being switched. For fast recovery, Schottky diodes are used PHASE INPUT Low High 3 Q1, Q4 Off On Q2, Q3 On Off UC1717 UC2717 UC3717 Figure 6 I0 0 1 0 1 I1 0 0 1 1 ing causing the current to decay. The time is determined by the external timing components RT and CT as: CURRENT LEVEL 100% 60% 19% Current Inhibit TOFF = 0.69 RTCT If a new trigger signal should occur during TOFF, it is ignored. Current Control: The voltage divider, comparators and monostable provide a means for current sensing and control. The two bit input (I0, I1) logic selects the desired comparator. The monostable controls the off time and therefore the magnitude of the current decrease. The time duration is determined by RT and CT connected to the timing terminal (pin 2). The reference terminal (pin 11) provides a means of continuously varying the current for situations requiring half-stepping and microstepping. The relationship between the logic input signals at pin 7 and 9 in reference to the current level is shown in Table 1. The values of the different current levels are determined by the reference voltage together with the value of the external sense resistor RS (pin 16). Single-Pulse Generator: The pulse generator is a monostable triggered on the positive going edge of the comparator. Its output is high during the pulse time and this pulse switches off the power feed to the motor wind- Note: Dashed lines indicate current decay paths. Figure 7: Simplified Schematic of Output Stage 4 UC1717 UC2717 UC3717 FUNCTIONAL DESCRIPTION (cont.) Overload Protection: The circuit is equipped with a thermal shutdown function, which will limit the junction temperature by reducing the output current. It should be noted however, that a short circuit of the output is not permitted. Operation: When the voltage is applied across the motor winding the current rises linearly and appears across the external sense resistor as an analog voltage. This voltage is fed through a low pass filter RC, CC to the voltage comparator (pin 10). At the moment the voltage rises beyond the comparator threshold voltage the monostable is triggered and its output turns off the sink transistors. The current then circulates through the source transistor and the appropriate Schottky diode. After the one shot has timed out, the sink transistsor is turned on again and the procedure repeated until a current reverse command is given. By reversing the logic level of the phase input (pin 8), both active transistors are being turned off and the opposite pair turned on. When this happens the current must first decay to zero before it can reverse. The current path then provided is through the two diodes and the power-supply. Refer to Figure 7. It should be noted at this time that the slope of the current decay is steeper, and this is due to the higher voltage build up across the winding. For better speed performance of the stepping motor at half step mode, the phase logic level should be changed at the same time the current inhibit is applied. A typical current wave form is shown in Figure 8. Figure 9 The timing diagram in Figure 10 shows the required signal input for a two phase, full step, stepping sequence. Figure 11 shows a one phase, full step, stepping sequence, commonly referred to as wave drive. Figure 12 shows the required input signal for a one phase-two phase stepping sequence called half-stepping. The circuit of Figure 13 provides the signal shown in Figure 10, and in conjunction with the circuit shown in Figure 9, will implement a pulse-to-step two phase, full step, bidirectional motor drive. The schematic of Figure 14 shows a pulse to half step circuit generating the signal shown in Figure 12. Care has been taken to change the phase signal the same time the current inhibit is applied. This will allow the current to decay faster and therefore enhance the motor performance at higher step rates. Figure 8 APPLICATIONS A typical chopper drive for a two phase bipolar permanent magnet or hybrid stepping motor is shown in Figure 9. The input can be controlled by a microprocessor, TTL, LS or CMOS logic. Using the UC3717 to drive the L298 provides a uniquely packaged state-of-the-art high power stepper motor control and drive. See Figure 15. 5 UC1717 UC2717 UC3717 FUNCTIONAL DESCRIPTION (cont.) Figure 10: Phase Input Signal for Two Phase Full Step Drive (4 Step Sequence) Figure 11: Phase and Current-Inhibit Signal for Wave Drive (4 Step Sequence) Figure 12: Phase and Current-Inhibit Signal for Half Stepping (8 Step Sequence) Figure 13: Full Step Bidirectional Two Phase Drive Logic 6 UC1717 UC2717 UC3717 Figure 14: Half-Step, Bidirectional Drive Logic CONSIDERATION which rise in an exponential manner as the frequency or step rate is increased. The power losses can not be calculated by I2R where I is the chopping current level and R the DC resistance of the coil. Actual measurements indicate the effective resistance may be many times larger. Therefore, for 100% duty cycle the current must be limited to a value which will not overheat the motor. This may not be necessary for lower duty cycle operation. Half-Stepping: In the half step sequence the power input to the motor alternates between one or two phases being energized. In a two phase motor the electrical phase shift between the windings is 90 degrees. The torque developed is the vector sum of the two windings energized. Therefore when only one winding is energized the torque of the motor is reduced by approximately 30%. This causes a torque ripple and if it is necessary to compensate for this, the VR input can be used to boost the current of the single energized winding. Interference: Electrical noise generated by the chopping action can cause interference problems, particularly in the vicinity of magnetic storage media. With this in mind, printed circuit layouts, wire runs and decoupling must be considered. 0.01 to 0.1µF ceramic capacitors for high frequency bypass located near the drive package across V+ and ground might be very helpful. The connection and ground leads of the current sensing components should be kept as short as possible. Ramping: Every drive system has inertia and must be considered in the drive scheme. The rotor and load inertia plays a big role at higher speeds. Unlike the DC motor the stepping motor is a synchronous motor and does not change its speed due to load variations. Examining typical stepping motors, torque vs. speed curves indicates a sharp torque drop off for the start-stop without error curve, even with a constant current drive. The reason for this is that the torque requirements increase by the square of the speed change, and the power need increases by the cube of the speed change. As it can be seen, for good motor performance controlled acceleration and deceleration should be considered. Ordering Information UNITRODE TYPE NUMBER UC3717N - 16 Pin Dual-in-line (DIL) "Bat Wing" Package UC1717J - 16 Pin Dual-in-line Ceramic Package UC1717SP - 16 Pin Dual-in-line Hermetic Power Package Iron Core Losses: Some motors, especially the Tin-Can type, exhibit high iron losses mostly due to eddy currents 7 UC1717 UC2717 UC3717 Figure 15: UC3717 with L298 Power Amplifier UNITRODE INTEGRATED CIRCUITS 7 CONTINENTAL BLVD. • MERRIMACK, NH 03054 TEL. (603) 424-2410 • FAX (603)424-3460 8 PACKAGE OPTION ADDENDUM www.ti.com 18-Sep-2008 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty 5962-9474601M2A OBSOLETE LCCC FK 20 TBD Call TI Call TI UC1717J OBSOLETE CDIP J 16 TBD Call TI Call TI Lead/Ball Finish MSL Peak Temp (3) UC1717J883B OBSOLETE CDIP J 16 TBD Call TI Call TI UC1717L883B OBSOLETE LCCC FK 20 TBD Call TI Call TI UC1717SP883B OBSOLETE CDIP J 16 TBD Call TI Call TI UC2717J OBSOLETE CDIP J 16 TBD Call TI Call TI UC3717J OBSOLETE CDIP J 16 TBD Call TI Call TI UC3717N OBSOLETE PDIP N 16 TBD Call TI Call TI UC3717Q OBSOLETE PLCC FN 20 TBD Call TI Call TI UC3717QTR OBSOLETE PLCC FN 20 TBD Call TI Call TI (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. 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