February 1999 PBL 377 17/1 60 V Stepper Motor Drive Circuit Description Key Features PBL 377 17/1 is a bipolar monolithic circuit intended to control and drive the current in one winding of a stepper motor. 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 with built-in protection diodes. Two PBL 377 17/1 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 modes. * Switched mode bipolar constant current drive. * Wide range of current control 5 - 1200 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. P B L 37 71 7/ 1 * Built-in recirculation diodes. VMM VCC Time Delay Phase 1 1 1 I1 L B /1 P 17 7 37 Schmitt Trigger 16-pin plastic batwing DIP VMM MA MB I0 VR & & & 1 & + - 1 Output Stage + - Current Sensor C Figure 1. Block diagram. 7/1 L PB Monostable t = 0.69 * R * C T T off + - GND 28-pin plastic PLCC package * 1 77 3 PBL 377 17/1 T 20-pin SO wide batwing package E * To be released 1 PBL 377 17/1 Maximum Ratings Parameter Pin no. Voltage * Symbol Min Max Unit Logic supply 6 VCC 0 7 V Motor supply 3, 14 VMM 0 60 V Logic inputs 7, 8, 9 VI -0.3 6 V Comparator input 10 VC -0.3 VCC V Reference input 11 VR -0.3 15 V Motor output current 1, 15 IM -1200 +1200 Logic inputs 7, 8, 9 II -10 mA Analog inputs 10, 11 IA -10 mA Operating junction temperature TJ -40 +150 C Storage temperature TS -55 +150 C Symbol Min Typ Max Logic supply voltage VCC 4.75 5 5.25 V Motor supply voltage VMM 10 55 V Motor output current IM -1000 +1000 mA Operating junction temperature TJ -20 +125 C Rise time logic inputs tr 2 s Fall time logic inputs tf 2 s Current mA Temperature * refers to DIL package Recommended Operating Conditions Parameter I I I I I CC I IH IL Phase 8 I 7 I IA 1 V CC V 6 14 Schmitt Trigger Time Delay MM 0 1 11 & & 1 & CC V V IH VA Output Stage V V Monostable t = 0.69 * R * C off T T + - 4, 5, GND 12, 13 Current Sensor 10 IC C PBL 377 17/1 2 16 T E 1 k Pin no. refers to DIL package IA R VC VCH 820 pF CC 2 I OL MB - IL IM 1 + V R Figure 2. Definition of symbols. MA 1 + - VI MM 9 & V V 15 VR MM 3 1 1 Unit C VE 820 pF 56 k 1 R T C T R S M MA V MM PBL 377 17/1 Electrical Characteristics Electrical characteristics over recommended operating conditions. unless otherwise noted -20C TJ +125C. CT = 820 pF, RT = 56 kohm. Parameter Ref. Symbol fig. Conditions Min Typ Max Unit 25 mA fs = 28 kHz, IM = 500 mA, VMM = 36 V Note 2, 4. fs = 28 kHz, IM = 800 mA, VMM = 36 V Note 3, 4. 1.4 1.7 W 2.8 3.3 W Ta = +25C, dVC/dt 50 mV/s. 0.9 1.5 General Supply current ICC Total power dissipation PD Turn-off delay 2 td 3 Thermal shutdown junction temperature s C 170 Logic Inputs Logic HIGH input voltage VIH 2 Logic LOW input voltage VIL 2 2.0 Logic HIGH input current IIH 2 VI = 2.4 V Logic LOW input current IIL 2 VI = 0.4 V V 0.8 20 -0.4 V A mA Reference Input Input resistance RR Ta = +25C 6.8 kohm Comparator Inputs Threshold voltage VCH 2 VR = 5.0 V, I0 = I1 = LOW 400 415 430 mV Threshold voltage VCM 2 VR = 5.0 V, I0 = HIGH, I1 = LOW 240 250 265 mV Threshold voltage VCL 2 VR = 5.0 V, I0 = LOW, I1 = HIGH 70 80 90 mV Input current IC 2 A -20 Motor Outputs Lower transistor saturation voltage 2 IM = 500 mA IM = 800 mA 0.9 1.1 1.2 1.4 V V Lower diode forward voltage drop 2 IM = 500 mA IM = 800 mA 1.2 1.3 1.5 1.7 V V Upper transistor saturation voltage 2 IM = 500 mA IM = 800 mA 1.0 1.2 1.25 1.5 V V Upper diode forward voltage drop 2 IM = 500 mA IM = 800 mA 1.0 1.2 1.25 1.45 V V Output leakage current 2 I0 = I1 = HIGH, Ta = +25C 100 A 3 VMM = 10 V, ton 5 s 31 35 s Typ Max Monostable Cut off time toff 27 Thermal Characteristics Parameter Ref. Symbol Fig. Conditions Thermal resistance Rthj-c DIL package. Min 11 Unit C/W Rthj-a 16 DIL package. Note 2. 40 C/W Rthj-c PLCC package. 9 C/W Rthj-a 16 PLCC package. Note 2. 35 C/W Rthj-c SO package 11 C/W Rthj-a SO package 40 C/W 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. DIP 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 GND 6 PBL 377 17/1SO GND 4 15 GND GND 5 14 GND GND 7 VCC 8 VCC 6 12 C Phase 10 11 I 0 13 GND V MM GND GND GND GND N/C N/C 2 1 28 27 26 25 N/C MA 6 24 V R E 8 12 GND 11 V R 23 C N/C 7 PBL 377 17/1QN I1 7 10 C Phase 8 9 I0 22 N/C 21 I 0 GND 9 20 Phase M B 10 T 11 13 V R I1 9 PBL 377 17/1N N/C 5 19 I1 V CC 18 GND 5 16 GND 14 V MM VMM 3 GND 17 17 GND 15 M A GND 16 GND 4 T 2 GND 15 18 V MM GND 14 VMM 3 16 E MB 1 19 M A V MM 12 T 2 3 20 E GND 13 MB 1 4 PBL 377 17/1 Figure 3. Pin configurations. Pin Description DIP SO PLCC* Symbol Description 1 1 10 MB Motor output B, Motor current flows from MA to MB when Phase is high. 2 2 11 T 3,14 3,18 12,4 VMM Clock oscillator. Timing pin connect a 56 k resistor and a 820 pF in parallel between T and Ground. Motor supply voltage, 10 to 60 V. VMM pins should be wired together on PCB. 4,5, 12,13 4,5,6,7,14 15,16,17 1,2,3,9,13, 14,15,16,17 28 GND 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. 6 8 18 VCC Logic voltage supply normally +5 V. 7 9 19 I1 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%. 8 10 20 Phase 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. 9 11 21 I0 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%. 10 12 23 C Comparator input. This input senses the instaneous voltage across the sensing resistor, filtered through a RC Network. 11 13 24 VR Reference voltage. Controls the threshold voltage of the comparator and hence the output current. Input resistance: typically 6.8k 20%. 15 19 6 MA Motor output A, Motor current flows from MA to MB when Phase is high. 16 20 8 E Common emitter. Connect the sence resistor between this pin and ground. * To be released 4 PBL 377 17/1 Functional Description The PBL 377 17/1 is intended to drive a bipolar constant current through one motor 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: * Input logic * Current sense * Single-pulse generator * Output stage | V MA - V MB | t off t on 50 % t VE td V CH t 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. 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. I1 L H L Single-pulse generator L H H H 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. Medium level 60% Low level Overload protection I0 Motor current 20% Zero current 0% 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 * 0.083) / RS [A], at 100% level im = (VR * 0.050) / RS [A], at 60% level im = (VR * 0.016) / RS [A], at 20% level The motor current can also be continuously varied by modulating the voltage reference input. ton ton + t off Current sensor 100% L 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= Figure 4. Definition of terms. The current sensor contains a reference voltage divider and three comparators for measuring each of the selectable 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 comparator triggers the single-pulse generator. Only one comparator at a time is activated by the input logic. Half- and full-step operation is possible. High level 1 fs = t + t on off toff = 0.69 * RT * CT 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. Output stage The output stage contains four transistors and four diodes, connected in an H-bridge. 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. Operation When a voltage VMM is applied across the motor winding, the current rise follows the equation: im = (VMM / R) * (1 - e-(R * t ) / L ) R = Winding resistance L = Winding inductance t = time (see figure 6, arrow 1) 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). After the monostable has timed out, the current has decayed and the analog voltage across the sensing resistor is below the comparator threshold level. 5 PBL 377 17/1 The sinking transistor then closes and the motor current starts to increase again, The cycle is repeated until the current is turned off via the logic inputs. By reversing the logic level of the phase input (pin 8), both active transistors are turned off and the opposite pair turned on after a slight delay. When this happens, the current must first decay to zero before it can reverse. This current decay is steeper because the motor current is now forced to circulate back through the power supply and the appropriate sinking transistor protection diode. This causes higher reverse voltage build-up across the winding which results in a faster current decay (see figure 6, arrow 4). For best speed performance of the stepper motor at half-step mode operation, the phase logic level should be changed at the same time the currentinhibiting signal is applied (see figure 2). 2 1 200 mA/div 1 ms/div 0 3 100 s/div RS Figure 5. Motor current (IM ), Vertical : 200 mA/div, Horizontal: 1 ms/ div, expanded part 100 s/div. 1 2 3 Fast Current Decay Figure 6. Output stage with current paths for fast and slow current decay. Phase shift here gives fast current decay Phase shift here gives 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 Applications Information Half step position Stand by mode at 20 % Half step mode at 100 % Motor selection Some stepper motors are not designed for continuous operation at maximum current. As the circuit drives a constant 6 Time Slow Current Decay 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 17/1 can be reduced by soldering the ground pins to a suitable copper ground plane on the printed circuit board (see figure 16) or by applying an external heatsink type V7 or V8, see figure 15. The diagram in figure 14 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 500 mA, heatsinking is recommended to assure optimal reliability. The diagrams in figures 13 and 14 can be used to determine the required heatsink of the circuit. In some systems, forced-air cooling may be available to reduce the temperature rise of the circuit. Motor Current Figure 7. Principal operating sequence. Full step mode at 60 % PBL 377 17/1 11 6 3, 14 STEPPER MOTOR V V V 1 8 CC MM M Phase R B 7 I 9 1 PBL 377 17/1 I M 15 0 A T GND C E Phase A I 1A I 0A 2 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. VMM VCC (+5 V) 4, 5 10 12, 13 56 k 16 Interference 1 k V V (+5 V) CC 6 11 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 VR 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. 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. 1 820 pF 820 pF MM 3, 14 V V V 1 8 CC MM M Phase R B 7 I 1 PBL 377 17/1 9 I M 15 0 A Phase B I 1B I 0B T GND 2 C E 4, 5 10 12, 13 56 k 16 Pin no refers to DIL package 1 k 820 pF 820 pF 1 Figure 8. Typical stepper motor driver application with PBL 377 17/1. VSat (V) VSat (V) 1.8 1.8 1.6 1.6 1.4 1.4 Tj = 125 C 1.2 1.2 1.0 Tj = 25 C .8 .8 .6 .6 .4 .4 Unused inputs should be connected to proper voltage levels in order to obtain the highest possible noise immunity. 0 0 .20 .40 .60 .80 1.0 0 .20 .40 Figure 9. Typical source saturation vs. output current. .80 1.0 Figure 10. Typical sink saturation vs. output current. VF (V) VF (V) 1.8 1.8 1.6 1.6 1.4 .60 I M (A) I M (A) 1.4 Tj = 25C 1.2 1.0 1.0 Tj = 125C .8 .6 .6 .4 .4 .2 .2 0 .20 .40 Tj = 25C 1.2 .8 0 Unused inputs Tj = 125C .2 .2 0 Tj = 25C 1.0 .60 .80 1.0 I M (A) Figure 11. Typical lower diode voltage drop vs. recirculating current. 0 Tj = 125C 0 .20 .40 .60 .80 1.0 I M (A) Figure 12. Typical upper diode voltage drop vs. recirculating current. Ramping 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. VCC , VMM 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 from being generated by the motor. 7 PBL 377 17/1 Analog control As the current levels can be continuously controlled by modulating the VR input, limited microstepping can be achieved. 5 4.0 W ith St av 4 B V8 (3 7. he k( 5 C/ W ) C 40 C 5 7. (2 2.0 sin 7 at 3 ) /W /W 2 ) 1.0 1 0 er PC V er av 3.0 St Sensor resistor PD (W) ith W 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 figure7, to obtain a switching frequency above the audible range. Switching frequencies above 40 kHz are not recommended because the current regulation can be affected. PD (W) 0 .20 .40 .60 .80 0 1.0 I M (A) 50 Figure 13. Typical power dissipation vs. motor current. The RS resistor should be of a noninductive type, power resistor. A 1.0 ohm resistor, tolerance 1%, is a good choice for 415 mA max motor current at VR = 5V. Figure 14. Allowable power dissipation vs. ambient temperature. 33,5 m m 18,5 m m 11,6 mm 38,5 mm Thepeak motor current, im , can be calculated by using the formulas: im = (VR * 0.083) / RS [A], at 100% level im = (VR * 0.050) / RS [A], at 60% level im = (VR * 0.016) / RS [A], at 20% level Ordering Information Package DIP Tube PLCC Tube SO Tube SO Tape & Reel mm 38.0 mm 38.0 Part No. PBL 377 17NS *PBL 377 17QNS PBL 377 17SOS PBL 377 17SOT Figure 15. Heatsinks, Staver, type V7 and V8 by Columbia-Staver UK. * To be released 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. These products are sold only according to Ericsson Components' general conditions of sale, unless otherwise confirmed in writing. 16-pin DIP 80 70 60 50 Specifications subject to change without notice. 1522-PBL 377 17/1 Uen Rev.B (c) Ericsson Components AB 1999 20-pin SO 40 30 5 10 15 20 25 30 35 PCB copper foil area [cm2 ] Ericsson Components AB SE-164 81 Kista-Stockholm, Sweden Telephone: +46 8 757 50 00 8 150 100 TAmb (C) PLCC package DIP and SO package Figure 16. Copper foil used as a heatsink. 28-pin PLCC