TEA3718SP

TEA3718 Stepper motor driver Features ■ Half-step and full-step mode ■ Bipolar drive of stepper motor for maximum motor performance ■ Built-in protection diodes ■ Wide range of current control 5 to 1500 mA ■ Wide voltage range 10 to 50 V ■ Designed for unstabilized motor supply voltage ■ Current levels can be selected insteps or varied continuously ■ Thermal overload protection ■ Alarm output or pre-alarm output Power DIP 12+2+2 SO20 Multiwatt™ 15 Figure 1. Block diagram Applications Motor winding The TEA3718 is a bipolar monolithic integrated circuit intended to control and drive the current in one winding of a bipolar stepper motor. OUT A OUT B COMPARATOR INPUT Description PHASE The circuits consist of an LS-TTL compatible logic input, a current sensor, a monostable and an output stage with built-in protection diodes. Two TEA3718 ICs and a few external components form a complete control and drive unit for LS-TTL or microprocessor-controlled stepper motor systems. PULSE TIME IN0 IN1 REFERENCE TEA3718 ALARM (TEA3718SP) PRE-ALARM (TEA3718SFP) SENSE RESISTOR Table 1. Device summary Order code Package TM: Multiwatt is a trademark of STMicroelectronics E-TEA3718SDP Power DIP E-TEA3718DP E-TEA3718SFP SO20 E-TEA3718SFPTR SO20 (tape and reel) E-TEA3718SP Multiwatt™ 15 January 2009 Rev 2 1/26 www.st.com 26 Pin connections 1 Pin connections Figure 2. Package pin locations (top views) E-TEA3718SP (Multiwatt 15) 2/26 E-TEA3718SFP (SO20) E-TEA3718DP E-TEA3718SDP (Power DIP 12+2+2) Contents Contents 1 Pin connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2 Device diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4 5 3.1 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2 Recommended operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.3 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Functional blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.1 Alarm output (TEA3718SP, TEA3718DP and TEA3718SDP) . . . . . . . . . 14 4.2 Pre-alarm output (TEA3718SFP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.3 Current reduction in alarm condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.4 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.1 Input logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.2 Phase input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.3 Current sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.4 Single-pulse generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.5 Output stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.6 VSS, VS and VR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Analog control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.7 3/26 Contents 6 7 Application notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 6.1 Motor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 6.2 Unused inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 6.3 Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 6.4 Operating sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 4/26 Device diagrams 2 Device diagrams Figure 3. Detailed block diagram (TEA3718SFP) Figure 4. Detailed block diagram (TEA3718SP) 5/26 Device diagrams Table 2. Pin functions Name Function OUTB Output connection (with pin OUT A). The output stage is a "H" bridge formed by four transistors and four diodes suitable for switching applications. PULSE TIME A parallel RC network connected to this pin sets the OFF time of the lower power transistors. The pulse generator is a monostable triggered by the rising edge of the output of the comparators (toff = 0.69 RT CT). VS(B) Supply voltage input for half output stage GND Ground connection. In SO20 and power DIP these pins also conduct heat from die to printed circuit copper. VSS Supply voltage input for logic circuitry IN1 This pin and pin IN0 are logic inputs which select the outputs of three comparators to set the current level. Current also depends on the sensing resistor and reference voltage. SeeTable 8: Truth table. PHASE This TTL-compatible logic input sets the direction of current flow through the load. A high level causes current to flow from OUT A (source) to OUT B (sink). A Schmidt trigger on this input provides good noise immunity and a delay circuit prevents output stage short circuits during switching. IN0 See IN1 COMPARATOR INPUT Input connected to the three comparators. The voltage across the sense resistor is feedback to this input through the low pass filter RCCC. The lower power transistor are disabled when the sense voltage exceeds the reference voltage of the selected comparator. When this occurs the current decays for a time set by RT CT, Toff = 0.69 RT CT. REFERENCE A voltage applied to this pin sets the reference voltage of the three comparators. Reference voltage with the value of RS and the two inputs IN0 and IN1 determines the output current. VS(A) Supply voltage input for half output stage OUTA See pin OUT B SENSE RESISTOR Connection to lower emitters of output stage for insertion of current sense resistor ALARM When Tj reaches T1 oC the alarm output becomes low (TEA3718SP) PRE-ALARM When Tj reaches T2 oC the pre-alarm output becomes low (T2 5 µs td Turn off delay (see Figure 6 and Figure 7) Tamb = 25oC, dVC/dt > 50 mV/µs) - 1.6 - µs Vsat(alarm) Alarm output saturation voltage IO = 2 mA (Multiwatt) - 0.8 - V Iref Reference input current, VR = 5 V - 0.4 1 mA Power DIP Im = 0.5 A Power DIP Im = 1 A - 1.05 1.35 Multiwatt Im = 0.5 A Multiwatt Im = 1 A - - 1.3 1.7 If(source) = 0.5 A - 1.1 1.5 (1.6) If(source) = 1 A - 1.25 1.7 (1.9) If = 1A - - 5 Power DIP Im = 0.5 A Power DIP Im = 1 A - 1 1.2 Multiwatt Im = 0.5 A Multiwatt Im = 1 A - - If(sink) = 0.5 A If(sink) = 1 A - 1 1.1 Vsat(source) Source diode transistor pair saturation voltage Vf(source diode) Source diode forward voltage Isub Vsat(sink) Vf(sink diode) Substrate leakage current Sink diode transistor pair saturation Sink diode forward voltage 1.2 (1.3) V 1.5 (1.7) V V mA 1.2 (1.3) V 1.3 (1.5) 1.3 1.5 V 1.4 (1.6) V 1.5 (1.9) 1. Vs = Vss = 5 V, ± 5%, Vmm = 10 V to 45V, Tamb = 0 to 70oC (Tamb = 25 oC for TEA3718SFP) unless otherwise specified. 2. Values in parentheses apply only to E-TEA3718SFP and E-TEA3718SFPTR mounted in SO20 package. 10/26 Electrical specifications Figure 8. Sink driver VCE sat against Iout and Tj Figure 9. Lower diode Vf against IOUT and Tj Figure 10. Source driver VCE sat against IOUT and Tj 11/26 Electrical specifications Figure 11. Upper diode Vf against IOUT and Tj Figure 12. Iref against junction temperature Figure 13. Comparator input current against Tj and VC 12/26 Functional blocks 4 Functional blocks Figure 14. Alarm output (TEA3718SP) Figure 15. Pre-alarm output (TEA3718SFP) 13/26 Functional blocks 4.1 Alarm output (TEA3718SP, TEA3718DP and TEA3718SDP) The ALARM output pin becomes low when the junction temperature reaches T ° C. When an alarm condition occurs, parts of the supply voltage (dividing bridge R - RC) is fed to the comparator input pin (Figure 16). Depending on the RC value the behavior of the circuit on an alarm condition is as follows: ● RC > 80 ohms, the output stage is switched off ● RC > 60 ohms, the current in the motor windings is reduced according to the approximate formula: (see also Figure 18 and Figure 19) V CC RC V TH Im = ---------- – ------------------ • -------RS R + RC RS with VTH = threshold of the comparator (VCH, VCM, VCL) R = 700 ohms (typical). For several Multiwatt packages a common detection can be obtained as in Figure 17. Figure 16. Alarm detection for power DIP package 14/26 Functional blocks Figure 17. Common detection for several Multiwatt packages 4.2 Pre-alarm output (TEA3718SFP) When the junction temperature reaches T1° C (typically = 170 ° C) a pre-alarm signal is generated on the PRE-ALARM output pin. Soft thermal protection occurs when function temperature reaches T2 (T2 > T1). 4.3 Current reduction in alarm condition Note: The resistance values given in this section are for the VCH threshold. They should be adjusted when using other comparator thresholds or Vref values. Figure 18. Current reduction in the motor on alarm condition (typical curve) 15/26 Functional blocks Figure 19. Half-current on alarm condition circuit (Vref = 5 V) 4.4 Typical application Figure 20. Typical application circuit 16/26 Functional description 5 Functional description The circuit is intended to drive a bipolar constant current through one motor winding. The constant current is generated through switch mode regulation. There is a choice of three different current levels with the two logic inputs lN0 and lN1. The current can also be switched off completely. 5.1 Input logic If any logic input is left open, the circuit treats it as a high-level input. l Table 8. 5.2 Truth table IN0 IN1 Current level H H No current L H Low current H L Medium current L L Maximum current Phase input The PHASE input pin determines the direction of current flow in the winding, depending on the motor connections. The signal is fed through a Schmidt trigger for noise immunity, and through a time delay in order to guarantee that no short-circuit occurs in the output stage during phase-shift. A high level on the PHASE input causes the motor current flow from OUTA through the winding to OUTB. The lH0 and lH1 input pins select the current level in the motor winding. The values of the different current levels are determined by the reference voltage VR together with the value of the sensing resistor RS. 5.3 Current sensor This part contains a current sensing resistor (RS), a low pass filter (RC, CC) and three comparators. Only one comparator is active at a time. It is activated by the input logic according to the current level chosen with signals IN0 and IN1. The motor current flows through the sensing resistor RS. When the current has increased so that the voltage across RS becomes higher than the reference voltage on the other comparator input, the comparator output goes high, which triggers the pulse generator and its output goes high during a fixed pulse time (toff), thus switching off the power feed to the motor winding, and causing the motor current to decrease during toff. 17/26 Functional description 5.4 Single-pulse generator The pulse generator is a monostable triggered on the positive going edge of the comparator output. The monostable output is high during the pulse time, toff, which is determined by the timing components RT and CT. toff = 0.69 ⋅ RT CT The single pulse switches off the power feed to the motor winding, causing the winding current to decrease during toff. If a new trigger signal should occur during toff, it is ignored. 5.5 Output stage The output stage contains four Darlington transistors and four diodes, connected in an Hbridge. The two sinking transistors are used to switch the power supplied to the motor winding, thus driving a constant current through the winding. Note: It is not permitted to short circuit the outputs. 5.6 VSS, VS and VR The circuit stands any order of turn-on or turn-off the supply voltages VSS and VS. Normal dV/dt values are then assumed. Preferably, VR should track VSS during power on and power off if VS is established. 5.7 Analog control The current levels can be varied continuously if VR is varied with a circuit varying the voltage on the comparator terminal. Figure 21. Power losses against output current 18/26 Application notes 6 Application notes 6.1 Motor selection Some stepper motors are not designed for continuous operation at maximum current. As the circuit drives a constant current through the motor, its temperature might increase excessively both at low and high speed operation. Also, some stepper motors have such high core losses that they are not suited for switch mode current regulation. 6.2 Unused inputs Unused inputs should be connected to proper voltage levels in order to get the highest noise immunity. 6.3 Interference As the circuit operates with switch mode current regulation, interference generation problems might arise in some applications. A good measure might then be to decouple the circuit with a 15 nF ceramic capacitor, located near the package between power line VS and ground. The ground lead between RS, CC and circuit GND should be kept as short as possible. This applies also to the lead between the sensing resistor RS and point S. See Section 4: Functional blocks. 19/26 Application notes 6.4 Operating sequence Figure 22. Principal operating sequence 20/26 Package mechanical data 7 Package mechanical data In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: www.st.com. ECOPACK® is an ST trademark. 21/26 Package mechanical data 22/26 Package mechanical data 23/26 Package mechanical data 24/26 Revision history Revision history Table 9. Document revision history Date Revision Changes 24-Jan-2006 1 Initial release. 21-Jan-2009 2 Document reformatted. Added Figure 1. 25/26 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. 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