PBL 3772/1 Dual Stepper Motor Driver

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Cecil Fitzgerald
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1 February 999 PBL 3/ Dual Stepper otor Driver Description The PBL 3/ 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 Ericsson s PBL 3/, but has been designed to generate a minimum amount of power dissipation and can deliver substantially more current to the stepper motor, up to 000 ma continuously per channel. At x 50 ma output current, power dissipation is only. W. The circuit is designed for microstepping applications in conjunction with the matching dual DAC (Digital-to-Analog Converter) PB 390/. A complete driver system consists of these two ICs, a few passive components and a microprocessor for generation of the proper control and data codes required for microstepping. The PBL 3/ contains a clock oscillator, which is common for both driver channels, a set of comparators and flip-flops implementing the switching control, and two output H-bridges. oltage supply requirements are 5 for logic and 0 to 5 for the motor. The close match between the two driver channels guarantees consistent output current ratios and motor positioning accuracy. Key Features Dual chopper driver in a single package. Operation at -0 C 000 ma continuous output current per channel. ery low power dissipation,. W at x 50 ma output current. Close matching between channels for high microstepping accuracy. Specially matched to the Dual DAC PB 390. Plastic -pin batwing DIP package or -pin power PLCC with leadframe for heat-sinking through PC board copper. Phase C E PBL 3/ CC CC S Q Logic A B BB BB B PBL 3/ PBL3/ Logic A C S Q Phase C E -pin PLCC package -pin plastic DIP package Figure. Block diagram.

2 PBL 3/ aximum atings Parameter Pin no. DIL package Symbol in ax Unit oltage Logic supply CC 0 otor supply, 0 5 Output stage supply 9, BB 0 5 Logic inputs, 9 I -0.3 Comparator inputs, C -0.3 CC eference inputs 3, Current otor output current,,, 5 I ma Logic inputs, 9 I I -0 ma Analog inputs, 3, 0, I A -0 ma Temperature Operating junction temperature T J C Storage temperature T S C Power Dissipation (Package Data) Power dissipation at T BW = 5 C, DIP and PLCC package P D 5 W Power dissipation at T BW = 5 C, DIP package P D. W Power dissipation at T BW = 5 C, PLCC package P D. W ecommended Operating Conditions Parameter Symbol in Typ ax Unit Logic supply voltage CC otor supply voltage 0 0 Output stage supply voltage BB otor output current I ma Junction temperature ** T J -0 5 C ise and fall time, logic inputs t r, t f µs Oscillator timing resistor T 5 0 kω ** See operating temperature chapter Phase C E I CC CC PBL 3/ CC 9 0 S Q 3 5 A Pin no. refers to DIL-package A B 5 kw Logic B BB 50 % t on t off T 9 BB Logic B A I I OL t I C C S Q E t d CC pf CH C T 3 5,,, 0 Phase C E I I I I IH I IL I A I C I A I kw IH IL A CH C 0 pf C C C E A BB t on f s= t on t D = off t on t off t Figure. Definition of symbols. Figure 3. Definition of terms.

3 PBL 3/ Electrical Characteristics Electrical characteristics over recommended operating conditions, unless otherwise noted. -0 C< T J < 5 C. ef. Parameter Symbol fig. Conditions in Typ ax Unit General Supply current I CC Note. 0 5 ma Total power dissipation P D =, I = I = 50 ma... W = 0. ohm. Notes, 3,, 5. Total power dissipation P D =, I = 000 ma, I = 0 ma... W = 0. ohm. Notes, 3,, 5. Thermal shutdown junction temperature 0 C Turn-off delay t d 3 T A = 5 C, d C /dt 50 m/µs,..0 µs I = 00 ma. Note 3. Logic Inputs Logic HIGH input voltage IH.0 Logic LOW input voltage IL 0. Logic HIGH input current I IH I =. 0 µa Logic LOW input current I IL I = ma Comparator Inputs Threshold voltage CH C = kohm, = m CH - CH mismatch CH,diff C = kohm m Input current I C -0 µa eference Inputs Input resistance T A = 5 C 5 kohm Input current I = ma otor Outputs Lower transistor saturation voltage I = 50 ma Lower transistor leakage current =, E = = 0, C = CC 00 µa Lower diode forward voltage drop I = 50 ma..5 Upper transistor saturation voltage 3 I = 50 ma. = 0. ohm. Note Upper transistor saturation voltage 3 I = 50 ma. = 0. ohm. Note 3, Upper transistor leakage current BB =, E = = 0, C = CC 00 µa Chopper Oscillator Chopping frequency f s 3 C T = 3300 pf, T = 5 kohm khz Thermal Characteristics ef. Parameter Symbol fig. Conditions in Typ ax Unit Thermal resistance th J-BW DIP package C/W th J-A DIP package. Note 0 C/W th J-BW PLCC package 9 C/W th J-A PLCC package. Note 35 C/W Notes. All voltages are with respect to ground. Currents are positive into, negative out of specified terminal.. All ground pins soldered onto a 0 cm PCB copper area with free air convection, T A = 5 C. 3. Not covered by final test program.. Switching duty cycle D = 30%, f s =.5 khz. 5. External resistors for lowering of saturation voltage. 3

4 PBL 3/ A 3 Phase C C CC C BB 5 E B B 9 E 0 PBL 3/QN 5 C 3 C CC C 0 Phase 3 5 PBL 3/N 0 9 Phase BB 9 Phase A 5 A 3 5 BB 9 BB A E 0 3 E B B Figure. Pin configuration. Pin Description PLCC DIP Symbol Description -3, 9, 5, Ground and negative supply. Note: these pins are used thermally for heat-sinking. 3-, ake sure that all ground pins are soldered onto a suitably large copper ground plane for efficient heat sinking. A otor output A, channel. otor current flows from A to B when Phase 5 9 BB Collector of upper output transistor, channel. For lowest possible power dissipation, connect a series resistor to. See Applications information, External components. 0 E Common emitter, channel. This pin connects to a sensing resistor to ground. B otor output B, channel. otor current flows from A to B when Phase B otor output B, channel. otor current flows from A to B when Phase 0 3 E Common emitter, channel. This pin connects to a sensing resistor to ground. BB Collector of upper output transistor, channel. For lowest possible power dissipation, connect a series resistor to. See Applications information, External components. 5 A otor output A, channel. otor current flows from A to B when Phase otor supply voltage, channel, 0 to 0. and should be connected together. 9 9 Phase Controls the direction of motor current at outputs A and B. otor current flows from A to B when Phase 0 0 eference voltage, channel. Controls the threshold voltage for the comparator and hence the output current. C Comparator input channel. This input senses the instantaneous voltage across the sensing resistor, filtered by an C network. The threshold voltage for the comparator is CH = 0. [], i.e. 50 m at =.5. CC Logic voltage supply, nominally 5. 3 C Clock oscillator C pin. Connect a 5 kohm resistor to CC and a 3300 pf capacitor to ground to obtain the nominal switching frequency of.5 khz. C Comparator input channel. This input senses the instantaneous voltage across the sensing resistor, filtered by an C network. The threshold voltage for the comparator is CH = 0. [], i.e. 50 m at = eference voltage, channel. Controls the threshold voltage for the comparator and hence the output current. Phase Controls the direction of motor current at outputs A and B. otor current flows from A to B when Phase otor supply voltage, channel, 0 to 0. and should be connected together.

5 PBL 3/ Functional Description Each channel of the PBL 3/ consists of the following sections: an output H-bridge with four transistors, capable of driving up to 000 ma continuous current to the motor winding; a logic section that controls the output transistors; an S- flip-flop; and a comparator. The clock-oscillator is common to both channels. Constant current control is achieved by switching the output current to the windings. This is done by sensing the peak current through the winding via a current-sensing resistor, effectively connected in series with the motor winding during the turn-on period. As the current increases, a voltage develops across the sensing resistor, which is fed back to the comparator. At the predetermined level, defined by the voltage at the reference input, the comparator resets the flip-flop, which turns off the output transistors. The current decreases until the clock oscillator triggers the flip-flop, which turns on the output transistors again, and the cycle is repeated. The current paths during turn-on, turnoff and phase shift are shown in figure 5. Note that the upper recirculation diodes are connected to the circuit externally. Applications Information Current control The output current to the motor winding is determined by the voltage at the reference input and the sensing resistor,. Chopping frequency, winding inductance and supply voltage also affect the current, but to much less extent. The peak current through the sensing resistor (and motor winding) can be expressed as: I,peak = 0. ( / ) [A] i.e., with a recommended value of 0. ohm for the sensing resistor, a.5 reference voltage will produce an output current of approximately 90 ma. To improve noise immunity on the input, the control range may be increased to 5 if is correspondingly changed to ohm. External components The PBL 3/ exhibits substantially less power dissipation than most other comparable stepper motor driver ICs on the market. This has been achieved by creating an external voltage drop in series with the upper transistor in the output H-bridge, see figure 5. The voltage drop reduces the collectoremitter saturation voltage of the internal transistor, which can greatly reduce power dissipation of the IC itself. The series resistor, designated, shall be selected for about 0.5 voltage drop at the maximum output current. In an application with an output current of 000 ma (peak), a 0. ohm, / W resistor is the best choice. In low current applications where power dissipation is not a critical factor, the resistor can of course be omitted, and the and BB pins (pins 5,,, ) can all be connected directly to the motor supply voltage. otor Current External recirculation diodes BB 3 3 Fast Current Decay Slow Current Decay Time 5 0. mf CC BB BB C 5 Phase Phase PBL 3/ C E C E A B 3,, kw 3, 9, kw kw, 3,, 5, 3300 pf 0 pf 0 pf,, ( ) CC A B D D3 D D D - D are UF 00 or BY, t 00 ns. rr Pin numbers refer to PLCC package. 0 mf STEPPE OTO ( ) Figure 5. Output stage with current paths during turn-on, turn-off and phase shift. Figure. Typical stepper motor driver application with PBL 3/. 5

6 PBL 3/ Contributing to the low power dissipation is the fact that the upper recirculation diodes in the output H- bridge are connected externally to the circuit. These diodes shall be of fast type, with a t rr of less than 00 ns. Common types are UF00 or BY. A low pass filter in series with the comparator input prevents erroneous switching due to switching transients. The recommended filter component values, kohm and 0 pf, are suitable for a wide range of motors and operational conditions. Since the low-pass filtering action introduces a small delay of the signal to the comparator, peak voltage across the sensing resistor, and hence the peak motor current, will reach a slightly higher level than than what is defined by the comparator threshold, CH, set by the reference input ( CH = 50 m at =.5 ). The time constant of the low-pass filter may therefore be reduced to minimize the delay and optimize low-current perform-ance. Increasing the time constant may result in unstable switching. The time constant should be adjusted by changing the C C value. The frequency of the clock oscillator is set by the T -C T timing components at the C pin. The recommended values result in a clock frequency (= switching frequency) of.5 khz. A lower frequency will result in higher current ripple, but may improve low-current level linearity. A higher clock frequency reduces current ripple, but increases the switching losses in the IC and possibly the iron losses in the motor. If the clock frequency needs to be changed, the C T capacitor value should be adjusted. The recommended T resistor value is 5 kohm. The sensing resistor, should be selected for maximum motor current. The relationship between peak motor current, reference voltage and the value of is described under Current control above. Be sure not to exceed the maximum output current which is 00 ma peak when only one channel is activated. Or recommended output current, which is 000 ma peak, when both channels is activated. otor selection The PBL 3/ is designed for twophase bipolar stepper motors, i.e., motors that have only one winding per phase. The chopping principle of the PBL 3/ is based on a constant frequency and a varying duty cycle. This scheme imposes certain restrictions on motor selection. Unstable chopping can occur if the chopping duty cycle exceeds approximately 50%. See figure 3 for definitions. To avoid this, it is necessary to choose a motor with a low winding resistance and inductance, i.e. windings with a few turns. It is not possible to use a motor that is rated for the same voltage as the actual supply voltage. Only rated current needs to be considered. Typical motors to be used together with the PBL 3/ have (5) CC To mp D0 D A0 A W CS ESET ef DD PB 390/ SS Sign DA Sign DA mf CC BB BB Phase PBL 3/ A B Phase A 5 B C C E C E 3,, 0 5 kw 3, 9, kw kw, 3,, 5, 3300 pf 0 pf 0 pf,, D D3 D D 0 mf STEPPE OTO D - D are UF 00 or BY, t rr = 00 ns Pin numbers refer to PLCC package. Figure. icrostepping system with PB 390/ and PBL 3/.

7 PBL 3/ a voltage rating of to, while the supply voltage usually ranges from to 0. Low inductance, especially in combination with a high supply voltage, enables high stepping rates. However, to give the same torque capability at low speed, a reduced number of turns in the winding must be compensated by a higher current. A compromise has to be made. Choose a motor with the lowest possible winding resistance that still gives the required torque, and use as high supply voltage as possible, without exceeding the maximum recommended 0. Check that the chopping duty cycle does not exceed 50% at maximum current. General Phase inputs. A logic HIGH on a Phase input gives a current flowing from pin A into pin B. A logic LOW gives a current flow in the opposite direction. A time delay prevents cross conduction in the H-bridge when changing the Phase input. Heat sinking. Soldering the batwing ground leads onto a copper ground plane of 0 cm (approx.." x."), copper foil thickness 35 µm, permits the circuit to operate with 50 ma output current, both channels driving, at ambient temperatures up to 0 C. Consult figures, 9, 0 and in order to determine the necessary copper ground plane area for heat sinking at higher current levels. Thermal shutdown. The circuit is equipped with a thermal shutdown function that turns the output off at chip temperatures above 0 C. Normal operation is resumed when the temperature has decreased about 0 C. Operating temperature. The max recommended operating temperature is 5 C. This gives an estimated lifelength of about 5 years at continous drive, A change of ±0 would increase/ decrease the lifelength of the circuit about 5 years. P D (W) Two channels on. = 0. ohm. B PBL 3 Two channels on. = 0. ohm. One channel on. = 0. ohm. B = I (A) Figure. Power dissipation vs. motor current.t a = 5 C. Figure 0. aximum allowable power dissipation vs. temperature aximum allowable power dissipation [W] d () Ambient temperature Temperature [ C] PLCC package DIP package Batwing pin temperature All ground pins soldered onto a 0 cm PCB copper area with free air convection. PBL I (A) Figure. Typical lower diode voltage drop vs. recirculating current. P D (W) = 3 PBL 3 = = 0. Ω I (A) Figure 9. Power dissipation vs. motor current, both channels on.t a = 5 C. CE Sat, lt () T =5 C J PBL 3 T =5 C J I (A) Figure. Typical lower transistor saturation voltage vs. output current. CE Sat, ut () PBL 3 = 0. Ω = 0. Ω I (A) Figure 3. Typical upper transistor saturation voltage vs. output current.

8 PBL 3/ Ordering Information Package Part No. DIP Tube PBL3/NS PLCC Tube PBL3/QNS PLCC Tape & eel PBL3/QNT Thermal resistance [ C/W] PCB copper foil area [cm ] PLCC package DIP package Figure. Typical thermal resistance vs. PC Board copper area and suggested layout. 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. 5-PBL3/ Uen ev. D Ericsson Components AB 999 Ericsson Components AB SE- Kista-Stockholm, Sweden Telephone:

PBL 3774/1. Dual Stepper Motor Driver PBL3774/1. February Key Features. Description PBL 3774/1

PBL 3774/1. Dual Stepper Motor Driver PBL3774/1. February Key Features. Description PBL 3774/1 February 999 PBL 77/ Dual Stepper otor Driver Description The PBL 77/ is a switch-mode (chopper), constant-current driver IC with two channels, one for each winding of a two-phase stepper motor. The circuit