PBL 3774/1 February 1999 PBL 3774/1 Dual Stepper Motor Driver Key Features Description • Dual chopper driver in a single package. The PBL 3774/1 is a switch-mode (chopper), constant-current driver IC with two chan- nels, one for each winding of a two-phase stepper motor. The circuit is similar to • Operation at -40 °C. Ericsson´s PBL 3771/1 and PBL 3772/1. While all Dual stepper motor drivers are • 1000 mA continuous output current optimized for microstepping applications, the PBL 3774/1 is equipped with a TTL level per channel. compatible Disable input to simplify half-stepping operation. The circuit is well suited for microstepping applications together with the matching • Low power dissipation, 2.6 W at dual DAC (Digital-to-Analog Converter) PBM 3960/1. A complete driver system 2 x 750 mA output current. consists of these two ICs, a few passive components and a microprocessor for generation of the proper control and data codes required for microstepping. • Close matching between channels for In full/halfstepping applications, Ericsson Component’s PBD 3517/1 can be used as high microstepping accuracy. a phase generator (translator) to derive the necessary signals for the PBL 3774/1. • Specially matched to the Dual DAC The PBL 3774/1 contains a clock oscillator, which is common for both driver PBM 3960. channels, a set of comparators and flip-flops implementing the switching control, and two output H-bridges. • Plastic 22-pin batwing DIP package Voltage supply requirements are +5 V for logic and +10 to +45 V for the motor. or 28-pin power PLCC package with The close match between the two driver channels guarantees consistent output lead-frame for heatsinking through current ratios and motor positioning accuracy. PC board copper. E Phase Dis V C 1 1 1 R1 1 PBL 3774/1 – V V CC CC R Q + S M A1 M Logic B1 V MM1 + V MM2 – M B2 Logic M A2 RC S Q + R – 28-pin PLCC package Phase Dis V C GND E 2 2 2 2 R2 22-pin plastic DIL package Figure 1. Block diagram. 1 PBL3774/1 PBL 3774/1 Maximum Ratings Parameter Pin no. [DIL-package] Symbol Min Max Unit Voltage Logic supply 22 V 07 V CC Motor supply 9, 14 V 045 V MM Logic inputs 4, 7, 16, 19 V -0.3 6 V I Comparator inputs 2, 21 V -0.3 V V C CC Reference inputs 3, 20 V -0.3 7.5 V R Current Motor output current 8, 11, 12, 15 I -1200 +1200 mA M Logic inputs 4, 7, 16, 19 I -10 mA I Analog inputs 2, 3, 20, 21 I -10 mA A Temperature Operating Junction temperature T -40 +150 °C J Storage temperature T -55 +150 °C S Power Dissipation (Package Data) Power dissipation at T = +25°C, DIP and PLCC package P 5W BW D Power dissipation at T = +125°C, DIP package P 2.2 W BW D Power dissipation at T = +125°C, PLCC package P 2.6 W BW D Recommended Operating Conditions Parameter Symbol Min Typ Max Unit Logic supply voltage V 4.75 5 5.25 V CC Motor supply voltage V 10 40 V MM Motor output current I -1000 +1000 mA M Operating Junction temperature T - 20 +125 °C J Rise and fall time, logic inputs t , t 2 μs r f Oscillator timing resistor R 2 1520kΩ T E Phase Dis V C 1 1 R1 1 1 19 16 20 21 13 PBL 3774/1 – V I V CC CC CC 22 R Q + | V – V | S MA MB M 15 A1 M Logic 12 B1 V 14 MM1 t t on off 15 kW + I 50 % 9 V MM MM2 R T – M 11 B2 I I M OL Logic M 8 A2 I RC RC 1 t S Q + R V – t d E 3 300 pF V CC V C CH T 42 7 3 5, 6, 17, 18 10 Phase Dis 2 V C GND E 2 R2 2 2 I I I I IH IL I C I I I R A A V V V 1 kW M I CH V V V R V V C V MA MM t IH A C E V V 820 pF IL R t 1 on f = C R D = C S s t + t + t on off t on off Figure 2. Definition of symbols. Figure 3. Definition of terms. 2 PBL 3774/1 Electrical Characteristics Electrical characteristics over recommended operating conditions unless otherwise noted, - 20°C ≤ T ≤ +125°C. J Ref. Parameter Symbol fig. Conditions Min Typ Max Unit General Supply current I 2 Note 4. 60 75 mA CC Total power dissipation P V = 12 V, I = I = 750 mA. 2.6 2.9 W D MM M1 M2 Notes 2, 3, 4. Total power dissipation P V = 12 V, I = 1000 mA, I = 0 mA. 2.6 2.9 W D MM M1 M2 Notes 2, 3, 4. Thermal shutdown junction temperature 160 °C Turn-off delay t 3T = +25°C, dV /dt ≥ 50 mV/μs. 1.4 2.0 μs d A C I = 100 mA. Note 3. M Logic Inputs Logic HIGH input voltage V 2 2.0 V IH Logic LOW input voltage V 2 0.8 V IL Logic HIGH input current I 2V = 2.4 V 20 μA IH I Logic LOW input current I 2V = 0.4 V -0.4 mA IL I Comparator Inputs Threshold voltage V 2R = 1 kohm, V = 2.50 V 430 450 470 mV CH C R | V - V | mismatch V 2R = 1 kohm 1 mV CH1 CH2 CH,diff C Input current I 2 -10 1 μA C Reference Inputs Input resistance R 2T = +25°C 5 kohm R A Input current I 2V = 2.5 V 0.5 1.0 mA R R Motor Outputs Lower transistor saturation voltage 10 I = 750 mA 0.6 0.9 V M Lower transistor leakage current 2 V = 41 V, V = V = 0 V, V = V 700 μA MM E R C CC Lower diode forward voltage drop 11 I = 750 mA 1.2 1.5 V M Upper transistor saturation voltage 12 I = 750 mA. 1.1 1.4 V M Upper transistor leakage current 2 V = 41 V, V = V = 0 V, V = V 700 μA MM E R C CC Chopper Oscillator Chopping frequency f 3C = 3300 pF, R = 15 kohm 25.0 26.5 28.0 kHz s T T Thermal Characteristics Ref. Parameter Symbol fig. Conditions Min Typ Max Unit Thermal resistance Rth DIP package. 11 °C/W J-BW Rth 13 DIP package. Note 2. 40 °C/W J-A Rth PLCC package. 9 °C/W J-BW Rth 13 PLCC package. Note 2. 35 °C/W J-A Notes 1. All voltages are with respect to ground. Currents are positive into, negative out of specified terminal. 2 2. All ground pins soldered onto a 20 cm PCB copper area with free air convection, T = +25°C. A 3. Not covered by final test program. 4. Switching duty cycle D = 30%, f = 26.5 kHz. s 3 PBL 3774/1 RC 1 22 V CC C 2 21 C 2 1 V 3 20 R2 V R1 V 5 25 V R2 Phase 4 19 Phase MM2 2 1 E 6 24 C 2 2 GND 5 18 GND M 7 23 RC B2 PBL GND 6 17 GND 8 22 V M B1 CC PBL 3774/1QN 3774/1N GND 9 21 C 1 Dis 2 7 16 Dis 1 E 10 20 V R1 1 M 8 15 M V A2 A1 11 19 Phase MM1 1 V 9 14 V MM2 MM1 E 10 13 E 2 1 11 12 M M B2 B1 Figure 4. Pin configuration. Pin Description PLCC DIP Symbol Description 1-3, 9, 5, 6 GND Ground and negative supply. Note: these pins are used thermally for heat-sinking. Make sure that all 13-17 17, 18 ground pins are soldered onto a suitably large copper ground plane for efficient heat sinking. 28 48M Motor output A, channel 2. Motor current flows from M to M when Phase is HIGH. A2 A2 B2 2 59V Motor supply voltage, channel 2, +10 to +40 V.V and V should be connected together. MM2 MM1 MM2 610 E Common emitter, channel 2. This pin connects to a sensing resistor R to ground. 2 S 711 M Motor output B, channel 2. Motor current flows from M to M when Phase is HIGH. B2 A2 B2 2 812 M Motor output B, channel 1. Motor current flows from M to M when Phase is HIGH. B1 A1 B1 1 10 13 E Common emitter, channel 1. This pin connects to a sensing resistor R to ground. 1 S 11 14 V Motor supply voltage, channel 1, +10 to +40 V. V and V should be connected together. MM1 MM1 MM2 12 15 M Motor output A, channel 1. Motor current flows from M to M when Phase is HIGH. A1 A1 B1 1 18 16 Dis Disable input (TTL level compatible) for channel 1. When HIGH, all four output transistors are turned off, 1 which results in a rapidly decreasing output current to zero. 19 19 Phase Controls the direction of motor current at outputs M and M . Motor current flows from M to M when 1 A1 B1 A1 B1 Phase is HIGH. 1 20 20 V Ref. voltage, channel 1. Controls the threshold voltage for the comparator and hence the output current. R1 21 21 C Comparator input channel 1. This input senses the instantaneous voltage across the sensing resistor, 1 filtered by an RC network. The threshold voltage for the comparator is V = 0.18 • V [V], i.e. 450 mV CH1 R1 at V = 2.5 V. R1 22 22 V Logic voltage supply, nominally +5 V. CC 23 1 RC Clock oscillator RC pin. Connect a 15 kohm resistor to V and a 3300 pF capacitor to ground to obtain CC the nominal switching frequency of 26.5 kHz. 24 2 C Comparator input channel 2. This input senses the instantaneous voltage across the sensing resistor, 2 filtered by an RC network. The threshold voltage for the comparator is V = 0.18 • V [V], i.e. 450 mV at CH2 R2 V = 2.5 V. R2 25 3 V Ref. voltage, channel 2. Controls the threshold voltage for the comparator and hence the output current. R2 26 4 Phase Controls the direction of motor current at outputs M and M . Motor current flows from M to M when 2 A2 B2 A2 B2 Phase is HIGH. 2 27 7 Dis Disable input (TTL level compatible) for channel 2. When HIGH, all four output transistors are turned off, 2 which results in a rapidly decreasing output current to zero. 4 M 12 4 M A1 A2 GND 13 3 GND GND 14 2 GND GND 15 1 GND GND 16 28 GND Dis GND 17 27 2 Dis 18 26 Phase 1 2 PBL 3774/1 External components Functional Description Applications Information For the device to function properly, four Each channel of the PBL 3774/1 Current control external free-wheeling diodes must be consists of the following sections: an connected, as in figure 6. The diodes The output current to the motor is de- output H-bridge with four transistors, should be of fast type with a reverse termined by the voltage at the reference capable of driving up to 1000mA recovery time of less than 100 ns. Com- input and value of sensing resistor, R . continuous current to the motor winding; S monly used types are UF4001 or Chopping frequency, winding induc- a logic section that controls the output BYV27. tance and supply voltage also affect the transistors; an S-R flip-flop; and a A low pass filter in series with the com- current, but to much less extent. The comparator. The clock-oscillator is parator input prevents erroneous switch- output current can be switched off com- common to both channels. ing due to switching transients.The pletely by a HIGH input level at the Dis- Constant current control is achieved recommended filter component values, 1 able input (Dis1 and Dis2 for respective by switching the output current to the kohm and 820 pF, are suitable for a wide channels). When Disable goes HIGH, all windings. This is done by sensing the range of motors and operational four transistors in the output stage are peak current through the winding via a conditions. switched off, and the output current resistor, R , effectively connected in S Since the lowpass filtering action in- rapidly drops to zero (“fast current series with the motor winding during the troduces a small delay of the signal to decay” – see figure 5). turn-on period. As the current increases, the comparator, peak voltage across the The peak motor current through the a voltage develops across the resistor, sensing resistor, and hence the peak sensing resistor and the motor winding and is fed back to the comparator. At motor current, will reach a slightly higher can be expressed as: the predetermined level defined by the level than what is defined by the voltage at the reference input V , the I = 0.18 • ( V / R ) [A] R M,peak R S comparator threshold, V , set by the CH comparator resets the flip-flop, turning A 2.5 V reference voltage and a 0.47 reference input V (V = 450 mV at V = R CH R off the output transistors. The current ohm sensing resistor will produce an out- 2.5 V). decreases until the clock oscillator put current level of approximately 960 The time constant of the low-pass fil- triggers the flip-flop, turning on the mA. ter may therefore be reduced to output transistors, and the cycle is To improve noise immunity at the V minimize the delay and optimize low- R repeated. input, the voltage control range can be current performance. Increasing the time The current paths during turn-on, turn- increased to 5 V if R is correspondingly constant may result in unstable switch- S off and phase shift are shown in figure 5. changed (for example to 1ohm for 900 ing. The time constant should be Note that the upper recirculation diodes mA max output current). adjusted by changing the C value. C are connected to the circuit externally. V +5 V MM External recirculation diodes + V MM 1 0.1 mF 10 mF D1 D2 22 11 5 2 V VV 12 CC MM1 MM2 M 19 A1 Phase 1 18 Dis 1 M 8 B1 20 V R1 PBL 3774/1 4 26 M Phase A2 2 3 27 Dis 2 7 25 M B2 V R2 RC GND C E C E 2 STEPPER 11 2 R S MOTOR 23 10 24 6 1, 2, 21 Motor Current 1 kW 1 kW 15 kW 3, 9, +5 V D3 D4 13, 14, V MM 15, 16, 3300 pF 820 pF 820 pF 17, 28. R R S S D1 - D4 are UF 4001 or 1 2 3 BYV 27, t £ 100 ns. 0.68 W 0.68 W rr GND (V ) CC Pin numbers refer to PLCC package. Fast Current Decay Time Slow Current Decay Figure 5. Output stage with current paths Figure 6. Typical stepper motor driver application with PBL 3774/1. during turn-on, turn-off and phase shift. 5 Batwing pin temperature Ambient temperature PBL 3774/1 The frequency of the clock oscillator P (W) D is set by the R -C timing components at T T the RC pin. The recommended values V result in a clock frequency (= switching Ref 3.0 frequency) of 26.5 kHz. A lower +5 V frequency will result in higher current 1.2 kΩ ripple, but may improve low-current 2.0 level linearity. A higher clock frequency V and R1 V on reduces current ripple, but increases the R2 PBL 3774 switching losses in the IC and possibly 10 nF 10 kΩ 1.2 kΩ 2.2 kΩ increased iron losses in the motor. If the 1.0 70 % current clock frequency needs to be changed, level the C capacitor value should be T adjusted. The recommended R resistor GND T 0 value is 15 kohm. 0 0.20 0.40 0.60 0.80 The sensing resistor R , should be I (A) S M selected for maximum motor current. The relationship between peak motor Figure 7. Reduction of reference voltage Figure 8. Power dissipation vs. motor current, reference voltage and the value at the V pin of PBL 3774/1. current,T = 25°C. R A of R is described under Current control S above. Be sure not to exceed the V (V) CE Sat maximum output current which is Maximum allowable power dissipation [W] 6 1200mA peak when only one channel is activated. Or recommended output 1.2 5 current, which is 1000mA peak, when both channels is activated. 1.0 4 Motor selection 0.8 3 The PBL 3774/1 is designed for two- 0.6 phase bipolar stepper motors, i.e. 2 motors that have only one winding per 0.4 phase. 1 0.2 The chopping principle of the PBL 3774/1 is based on a constant 0 0 -25 0 25 50 75 100 125 150 frequency and a varying duty cycle. This 0 0.20 0.40 0.60 0.80 Temperature [°C] scheme imposes certain restrictions on I (A) M PLCC package All ground pins soldered onto a motor selection. Unstable chopping can 2 20 cm PCB copper area with DIP package free air convection. occur if the chopping duty cycle exceeds approximately 50%. See figure Figure 9. Maximum allowable continuous Figure 10. Typical lower transistor 3 for definitions. To avoid this, it is power dissipation vs. temperature. saturation voltage vs. output current. necessary to choose a motor with a low winding resistance and inductance, i.e. windings with a few turns. V (V) V (V) d, ld CE Sat It is not possible to use a motor that is rated for the same voltage as the actual supply voltage. Only rated current 1.2 1.2 needs to be considered. Typical motors 1.0 1.0 to be used together with the PBL 3774/1 have a voltage rating of 1 to 6 V, while 0.8 0.8 the supply voltage usually ranges from 12 to 40 V. 0.6 0.6 Low inductance, especially in 0.4 combination with a high supply voltage, 0.4 enables high stepping rates. However, 0.2 0.2 to give the same torque capability at low speed, the reduced number of turns in 0 0 the winding of the low resistive, low 0 0.20 0.40 0.60 0.80 0 0.20 0.40 0.60 0.80 inductive motor must be compensated I (A) M I (A) M by a higher current. A compromise has to be made. Choose a motor with the Figure 11. Typical lower diode voltage Figure 12. Typical upper transistor lowest possible winding resistance and drop vs. recirculating current. saturation voltage vs. output current. 6 One channel on One channel on One channel on Two channels on PBL 3774/1 control of the motor´s shaft position. expectancy and reliability of the mecha- inductance, that still gives the required One disadvantage with the half-step nical system. torque, and use as high supply voltage Modifying the current levels must be mode is the reduced torque in the half as possible, without exceeding the step positions, in which current flows done by bringing the reference voltage maximum recommended 40 V. Check through one winding only. The torque in up (or down) from its nominal value that the chopping duty cycle does not this position is approximately 70 % of the correspondingly. This can be done by exceed 50% at max. current. full step position torque. using DACs or simple resistor divider General networks, as shown in figure 7. Modified half-step mode.The torque The PBL 3774/1 is designed to handle variations in half step mode will be elimi- Phase inputs. A logic HIGH on a Phase nated if the current is increased about about 1.4 times higher current in one input gives a current flowing from pin M A 1.4 times in the halfstep position. A channel on mode, for example 700 mA into M . A logic LOW gives a current flow B constant torque will further reduce per winding in the full-step position, and in the opposite direction. A time delay 1000 mA in the half-step position. resonances and mechanical noise, prevents cross conduction in the H- resulting in better performance, life bridge when changing the Phase input. Heat sinking. Soldering the batwing ground leads onto a copper ground Thermal resistance [°C/W] 80 2 plane of 20 cm (approx. 1.8" x 1.8"), copper foil thickness 35 μm, permits the 70 circuit to operate with 650 mA output current, both channels driving, at 60 ambient temperatures up to 70°C. Consult figures 8, 9 and 13 in order to 50 determine the necessary copper ground plane area for heat sinking at higher 40 current levels. 30 Thermal shutdown. The circuit is equipped with a thermal shutdown func- 20 tion that turns the output off at tempera- 510 15 20 25 30 35 tures above 160°C. Normal operation is 2 PCB copper foil area [cm ] resumed when the temperature has PLCC package DIP package decreased about 20 °C. Programming Figure 13. Typical thermal resistance vs. PC Board copper area and suggested layout. Figure 14 shows the different input and output sequences for full-step, half-step Phase 1 and modified halfstep operations. Full-step mode. Both windings are Dis 1 energized at all the time with the same current, I = I . To make the motor take M1 M2 Phase 2 one step, the current direction (and the magnetic field direction) in one phase is Dis 2 reversed. The next step is then taken when the other phase current reverses. V R1 The current changes go through a 140% 100% sequence of four different states which equal four full steps until the initial state V R2 is reached again. 140% 100% Half-step mode. In the half-step mode, the current in one winding is brought to I MA1 zero before a complete current reversal 140% 100% is made. The motor will then have taken two half steps equalling one full step in –100% rotary movement. The cycle is repeated, –140% but on the other phase. A total of eight I MA2 states are sequenced until the initial 140% 100% state is reached again. Half-step mode can overcome –100% potential resonance problems. Resonan- –140% ces appear as a sudden loss of torque at Full step mode Half step mode Modified half step mode one or more distinct stepping rates and must be avoided so as not to loose Figure 14. Stepping modes. 7 PBL 3774/1 Ordering Information Package Part No. DIP Tube PBL 3774NS PLCC Tube PBL 3774QNS PLCC Tape & Reed PBL 3774QNT 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. Specifications subject to change without notice. 1522-PBL 3774/1 Uen Rev. E © Ericsson Components AB 1999 Ericsson Components AB SE-164 81 Kista-Stockholm, Sweden Telephone: +46 8 757 50 00 8