February 1999 PBL 377 70/1 High Performance Stepper Motor Drive Circuit Description Key Features PBL 377 70/1 is a bipolar monolithic circuit intended to control and drive the current in one winding of a stepper motor. It is a high power version of PBL 377 17/1 and special care has been taken to optimize the power handling capability without suffering in reliability. The circuit consists of a LS-TTL compatible logic input stage, a current sensor, a monostable multivibrator and a high power H-bridge output stage. The circuit is pin-compatible with the PBL 3717/2 industry-standard driver. Two PBL 377 70/1 and a small number of external components form a complete control and drive unit for LS-TTL or microprocessor-controlled stepper motor systems. * Half-step and full-step operation. * Switched mode bipolar constant current drive * Wide range of current control 5 -1800 mA. * Wide voltage range 10 - 60 V. * Designed for unstabilized motor supply voltage. * Current levels can be selected in steps or varied continuously. * Thermal overload protection. VMM 1 1 1 I1 B L Phase 37 7 Time Delay P Schmitt Trigger VMM 70 /1 VCC MA MB I0 & & & 1 & + 1 Output Stage - PB Monostable t = 0.69 * R * C off T T + - PBL 377 70/1 Current Sensor C Figure 1. Block diagram. 0/1 77 7 L3 + - GND L B /1 P 70 7 37 VR T E 16-pin plastic batwing DIP 28-pin plastic PLCC package* 20-pin SOIC-package * To be released 1 PBL 377 70/1 Maximum Ratings Parameter Pin no. (refers to DIP) Symbol Min Max Unit Voltage Logic supply Motor supply Logic inputs Comparator input Reference input 6 3, 14 7, 8, 9 10 11 VCC VMM VI VC VR 0 0 -0.3 -0.3 -0.3 7 60 6 VCC 15 V V V V V Current Motor output current Logic inputs Analog inputs 1, 15 7, 8, 9 10, 11 IM II IA -1800 -10 -10 +1800 mA mA mA Tj Ts -40 -55 +150 +150 C C Temperature Operating junction temperature Storage temperature Recommended Operating Conditions Parameter Symbol Min Typ Max Unit Logic supply voltage Motor supply voltage Motor output current Operating junction temperature Rise time logic inputs Fall time logic inputs VCC VMM IM Tj tr tf 4.75 10 -1500 -20 5 5.25 55 +1500 +125 2 2 V V mA C s s I I CC V CC I I I IH IL Phase 8 I 7 I IA 1 0 VR V 14 3 Schmitt Trigger Time Delay 1 1 1 9 11 & & 1 & 1 + - CC VI V V IH VA 4,5, 12,13 V Monostable t = 0.69 * R * C off T T Current Sensor IC PBL 377 70/1 10 2 16 C T E 1 k Pin no. refers to DIL package IA R VC VCH 820 pF CC B V + - IL I OL Output Stage - GND 2 M IM 1 + V R Figure 2. Definition of symbols. MA 15 & V MM MM 6 I V MM C VE 820 pF 56 k 1 R T C T R S M MA V MM PBL 377 70/1 Electrical Characteristics Electrical characteristics over recommended operating conditions. CT = 820 pF, RT = 56 kohm. Parameter Ref. Symbol fig. Conditions General Supply current ICC Total power dissipation PD 2 Turn-off delay td 3 Thermal shutdown junction temperature Logic Inputs Logic HIGH input voltage Logic LOW input voltage Logic HIGH input current Logic LOW input current VIH VIL IIH IIL 2 2 2 2 Analog Inputs Comparator threshold voltage Comparator threshold voltage Comparator threshold voltage Input current VCH VCM VCL IC 2 2 2 2 Motor Outputs Lower transistor saturation voltage Upper transistor saturation voltage Output leakage current toff VMM = 20 to 40 V, I0 = I1 = HIGH. VMM = 20 to 40 V, I0 = I1 = LOW, fs = 23 kHz fs = 28 kHz, IM = 1000mA, VMM = 36 V Note 2, 4. fs = 24 kHz, IM = 1000mA, VMM = 12 V Note 2, 4. fs = 28 kHz, IM = 1300m A, VMM = 36 V Note 3, 4. fs = 28 kHz, IM = 1500mA, VMM = 36 V Note 3, 4. Ta = +25C, dVC/dt 50 mV/s. 3 Typ Max Unit 30 48 40 65 mA mA 1.9 2.3 W 1.7 2.1 W 2.7 3.2 W 3.5 W 2.5 170 2.0 VI = 2.4 V VI = 0.4 V VR = 5.0 V, I0 = I1 = LOW VR = 5.0 V, I0 = HIGH, I1 = LOW VR = 5.0 V, I0 = LOW, I1 = HIGH 0.8 20 -0.4 400 240 70 -20 VMM = 10 V, ton 5 s s C V V A mA 415 250 80 430 265 90 mV mV mV A 0.5 0.8 1.3 1.5 1.1 1.3 0.8 1.3 1.6 1.8 1.3 1.6 100 V V V V V V A 27 31 35 s Min Typ Max Unit IM = 1000mA IM = 1300, A IM = 1000mA IM = 1300m A IM = 1000 A IM = 1300mA I0 = I1 = HIGH, Ta = +25C Lower diode forward voltage drop Monostable Cut off time Min Thermal Characteristics Parameter Thermal resistance Ref. Symbol Fig. Conditions RthJ-BW DIL package. RthJ-A 15 DIL package. Note 2. RthJ-BW PLCC package. RthJ-A 15 PLCC package. Note 2. RthJ-BW SO package 11 40 9 35 11 C/W C/W C/W C/W C/W RthJ-A 40 C/W SO package Notes 1. All voltages are with respect to ground. Currents are positive into, negative out of specified terminal. 2. All ground pins soldered onto a 20 cm2 PCB copper area with free air convection. Ta = +25C. 3. DIL package with external heatsink (Staver V7) and minimal copper area. Typical RthJ-A = 27.5C/W. Ta = +25C. 4. Not covered by final test program. 3 15 14 VMM GND GND 4 13 GND GND 7 14 VCC 8 13 VR I1 9 12 Phase 10 11 GND GND 5 PBL 377 70/1N 12 GND N/C N/C 28 27 26 MA 6 24 V R N/C 7 23 C GND E 8 GND GND 9 PBL 377 70/1QN 21 I 0 M B 10 VCC 6 11 VR C I1 7 10 C I0 Phase 8 9 I0 22 N/C 20 Phase T 11 19 I1 V CC 18 16 VMM 3 25 N/C GND 17 GND 6 PBL 377 70/1SO GND N/C 5 GND 16 GND 5 MA GND 17 15 GND GND 4 T 2 1 VMM E GND 15 18 16 GND VMM 3 MB 1 2 MA GND 14 19 V MM T 2 3 E V MM 12 20 GND 13 MB 1 4 PBL 377 70/1 Figure 3. Pin configurations. Pin Description SOIC DIP PLCC* Symbol Description 1 2 1 2 10 11 MB T 3, 18 4-7, 14-17 8 9 3,14 4-5, 12-13 6 7 4,12 1-3,9, 13-17,28 18 19 VMM GND 10 8 20 Phase 11 9 21 I0 12 10 23 C 13 11 24 VR 19 20 15 16 6 8 MA E Motor output B, Motor current flows from MA to MB when Phase is high. Clock oscillator. Timing pin connect a 56 k resistor and a 820 pF in parallel between T and Ground. Motor supply voltage, 10 to 55 V. Pin 3(12) and pin 14(4) should be wired together. Ground and negative supply. Note these pins are used for heatsinking. Make sure that all ground pins are soldered onto a suitable large copper ground plane for efficient heat sinking. Logic voltage supply normally +5 V. Logic input. It controls, together with the I0 input, the current level in the output stage. The controlable levels are fixed to 100, 60, 20, 0%. Controls the direction of the motor current of MA and MB outputs. Motor current flows from MA to MB when the phase input is high. Logic input. It controls, together with the I1 input, the current level in the output stage. The controlable levels are fixed to 100, 60, 20, 0%. Comparator input. This input senses the instaneous voltage across the sensing resistor, filtered through an RC Network. Reference voltage. Controls the threshold voltage of the comparator and hence the output current.Input resistance: typically 6.8 k 20%. Motor output A, Motor current flows from MA to MB when Phase is high. Common emitter. Connect the Sence resistor between this pin and ground. * To be released 4 VCC I1 PBL 377 70/1 Functional Description | V MA - V MB | The PBL 377 70/1 is intended to drive a bipolar constant current through one winding of a 2-phase stepper motor. Current control is achieved through switched-mode regulation, see figure 5 and 6. Three different current levels and zero current can be selected by the input logic. The circuit contains the following functional blocks: t off t on 50 % t VE td V CH * Input logic * Current sense * Single-pulse generator * Output stage t 1 fs = t + t on off Input logic Phase input. The phase input determines the direction of the current in the motor winding. High input forces the current from terminal MA to MB and low input from terminal MB to MA. A Schmitt trigger provides noise immunity and a delay circuit eliminates the risk of cross conduction in the output stage during a phase shift. Half- and full-step operation is possible. Current level selection. The status of I0 and I1 inputs determines the current level in the motor winding. Three fixed current levels can be selected according to the table below. D= ton ton + t off Figure 4. Definition of terms. current levels. The motor current is sensed as a voltage drop across the current sensing resistor, RS, and compared with one of the voltage references from the divider. When the two voltages are equal, the compara-tor triggers the single-pulse generator. Only one comparator at a time is activated by the input logic. Single-pulse generator Overload protection The circuit is equipped with a thermal shut-down function, which will limit the junction temperature. The output current will be reduced if the maximum permissible junction temperature is exceeded. It should be noted, however, that it is not short circuit protected. Operation When a voltage VMM is applied across the motor winding, the current rise follows the equation: 0 I 1 100% L L Medium level 60% H L The pulse generator is a monostable multivibrator triggered on the positive edge of the comparator output. The multivibrator output is high during the pulse time, toff , which is determined by the timing components RT and CT. Low level 20% L H toff = 0.69 * RT * CT t 0% H H The single pulse switches off the power feed to the motor winding, causing the winding to decrease during toff . If a new trigger signal should occur during toff , it is ignored. (see figure 6, arrow 1) Motor current High level Zero current I The specific values of the different current levels are determined by the reference voltage VR together with the value of the sensing resistor RS. The peak motor current can be calculated as follows: im = (VR * 0.080) / RS [A], at 100% level The motor current can also be continuously varied by modulating the voltage reference input. Current sensor The current sensor contains a reference voltage divider and three comparators for measuring each of the selectable Output stage The output stage contains four transistors and two diodes, connected in an H-bridge. Note that the upper recirculation diodes are connected to the circuit externally. The two sinking transistors are used to switch the power supplied to the motor winding, thus driving a constant current through the winding. See figures 5 and 6. im = (VMM / R) * (1 - e-(R *t)/L ) R = Winding resistance L = Winding inductance = time The motor current appears across the external sensing resistor, RS, as an analog voltage. This voltage is fed through a low-pass filter, RCCC, to the voltage comparator input (pin 10). At the moment the sensed voltage rises above the comparator threshold voltage, the monostable is triggered and its output turns off the conducting sink transistor. The polarity across the motor winding reverses and the current is forced to circulate through the appropriate upper protection diode back through the source transistor (see figure 6, arrow 2). 5 PBL 377 70/1 After the monostable has timed out, the current has decayed and the analog voltage across the sensing resistor is below the comparator threshold level. The sinking transistor then turns on and the motor current starts to increase again, The cycle is repeated until the current is turned off via the logic inputs. When both I1 and I0 are high, all four transistors in the output H-bridge are turned off, which means that inductive current recirculates through two opposite free-wheeling diodes (see figure 6, arrow 3). this method of turning off the current results in a faster current decay than if only one transistor was turned off and will therefore improve speed performance in half-stepping mode. External recirculation diodes 200 mA/div 2 1 1 ms/div 0 100 s/div 3 Figure 5. Motor current (IM ), Vertical : 200 mA/div, Horizontal: 1 ms/div, expanded part 100 s/div. RS Motor Current Heatsinking The junction temperature of the chip highly effects the lifetime of the circuit. In high-current applications, the heatsinking must be carefully considered. The Rthj-a of the PBL 377 70/1 can be reduced by soldering the ground pins to a suitable copper ground plane on the printed circuit board (see figure 14) or by applying an external heatsink type V7 or V8, see figure 14. The diagram in figure 13 shows the maximum permissible power dissipation versus the ambient temperature in C, for heatsinks of the type V7, V8, or a 20 cm2 copper area respectively. Any external heatsink or printed circuit board copper must be connected to electrical ground. For motor currents higher than approx 600 mA, some form of heatsinking is recommended to assure optimal reliability. The diagrams in figures 12 and 13 can be used to determine the required heatsinking of the circuit. In some systems, forced-air cooling may be available to reduce the temperature rise of the circuit. Applications Information 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 can increase, both at low- and highspeed operation. Some stepper motors have such high core losses that they are not suited for switched-mode operation. 6 1 2 3 Fast Current Decay Time Slow Current Decay Figure 6. Output stage with current paths for fast and slow current decay. I 0A I 1A Ph A Ph B I 0B I 1B I MA 100% 60% -20% -60% -100% I MB 100% 60% 20% -60% -100% Full step position Half step position Stand by mode at 20 % Half step mode at 100 % Figure 7. Principal operating sequence. Full step mode at 60 % PBL 377 70/1 11 8 Phase A I 1A I 0A V Phase R 7 I 9 1 I 0 T 6 3, 14 V V MM CC PBL 377 70/1 GND 2 In order to minimize electromagnetic interference, it is recommended to route MA and MB leads in parallel on the printed circuit board directly to the terminal connector. The motor wires should be twisted in pairs, each phase separately, when installing the motor system. VMM VCC (+5 V) C M B STEPPER MOTOR 1 M 15 A E 4, 5 10 12, 13 56 k 16 1 k V (+5 V) CC V 11 6 Unused inputs 1 820 pF 820 pF Unused inputs should be connected to proper voltage levels in order to obtain the highest possible noise immunity. MM 3, 14 Ramping V V V 8 1 CC MM M Phase R B 7 I 1 9 PBL 377 70/1 I M 15 0 A Phase B I 1B I 0B T GND 2 C E 4, 5 10 12, 13 56 k Diodes are UF 4001 or BYV27 t100ns 16 1 k 820 pF 820 pF A stepper motor is a synchronous motor and does not change its speed due to load variations. This means that the torque of the motor must be large enough to match the combined inertia of the motor and load for all operation modes. At speed changes, the requires torque increases by the square, and the required power by the cube of the speed change. Ramping, i.e., controlled acceleration or deceleration must then be considered to avoid motor pull-out. 1 Pin no refers to DIL package Figure 8. Typical stepper motor driver application with PBL 377 70/1. VSat (V) VF (V) 1.8 1.8 1.6 1.6 1.4 1.4 Tj = 125 C 1.2 1.0 Tj = 25 C .8 .8 .6 .6 .4 .4 .2 .2 0 .20 .40 .60 .80 1.0 I M (A) VSat (V) 1.8 1.6 1.4 Tj = 25 C 1.0 .8 Tj = 125 C .6 .4 .2 0 0 .20 .40 .60 Tj = 125C 0 .20 .40 .60 .80 1.0 I M (A) Figure 9. Typical source saturation vs. output current. 1.2 0 The supply voltages, VCC and VMM, can be turned on or off in any order. Normal dv/dt values are assumed. Before a driver circuit board is removed from its system, all supply voltages must be turned off to avoid destructive transients being generated by the motor. Tj = 25C 1.2 1.0 0 VCC , VMM .80 1.0 I M (A) Figure 10. Typical sink saturation vs. output current. Figure 11. Typical lower diode voltage drop vs. recirculating current. Interference As the circuit operates with switchedmode current regulation, interferencegeneration problems can arise in some applications. A good measure is then to decouple the circuit with a 0.1 F ceramic capacitor, located near the package across the power line VMM and ground. Also make sure that the VRef input is sufficiently decoupled. An electrolytic capacitor should be used in the +5 V rail, close to the circuit. The ground leads between RS, CC and circuit GND should be kept as short as possible. This applies also to the leads connecting RS and RC to pin 16 and pin 10 respectively. Switching frequency The motor inductance, together with the pulse time, toff, determines the switching frequency of the current regulator. The choice of motor may then require other values on the RT, CT components than those recommended in figure 6, to obtain a switching frequency above the audible range. Switching frequencies above 40 kHz are not recommended because the current regulation can be affected. Analog control As the current levels can be continuously controlled by modulating the VR input, limited microstepping can be achieved. Sensor resistor The RS resistor should be of a noninductive type power resistor. A 0.5 ohm 7 PBL 377 70/1 resistor, tolerance 1%, is a good choice for 800 mA max motor current at VR = 5V. The peak motor current, im , can be calculated by using the formula: PD (W) VMM = 36 V 3.0 4.0 V8 (3 5 C/ W ) 5 7. 40 C (2 2.0 k( V7 1.5 sin er 7. he av B at C/ W /W ) ) VMM = 12 V 1.0 1.0 .5 0 0 0 .50 1.0 1.5 50 Figure 13. Allowable power dissipation vs. ambient temperature. 33,5 m m Part No. 18,5 m m 11,6 mm 38,5 mm PBL 377 70/1NS PBL 377 70/1SOS PBL 377 70/1SOT PBL 377 70/1QNS PBL 377 70/1QNT mm 38.0 mm 38.0 Figure 14. Heatsinks, Staver, type V7 and V8 by Columbia-Staver UK. Thermal resistance [C/W] 90 Information given in this data sheet is believed to be accurate and reliable. However no responsibility is assumed for the consequences of its use nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Ericsson Components AB. These products are sold only according to Ericsson Components' general conditions of sale, unless otherwise confirmed in writing. 80 16-pin DIP 70 60 50 40 20-pin SO 30 5 Specifications subject to change without notice. 1522-PBL 377 70/1/1 Uen Rev.B (c) Ericsson Components AB. 1999 10 15 20 25 30 35 PCB copper foil area [cm2 ] PLCC package DIP package 28-pin PLCC Figure 15. Copper foil used as a heatsink. Ericsson Components AB SE-164 81 Kista-Stockholm, Sweden Telephone: +46 8 757 50 00 8 150 100 TAmb (C) I M (A) Ordering Information DIP Tube SO Tube SO Tape & Reel PLCC Tube PLCC Tape & Reel er PC St 3.0 Figure 12. Typical power dissipation vs. motor current. Package St ith Recirculation diodes must be connected across each motor terminal and the supply voltage, VMM. The anodes shall be connected to the motor terminals and the cathodes to the VMM voltage. Ultra-fast recovery diodes should be used for maximum performance and reliability. ith av 2.5 2.0 External recirculation diodes W W im = (VR * 0.080) / RS [A], at 100% level PD (W)