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PBL3717A april 1993 stepper motor driver . full step - half step - quarter step operating mode . bipolar output current up to 1 a . from 10 v up to 46 v motor supply voltage . low saturation voltage with inte- grated bootstrap . built in fast protection diodes . externally selectable current level . output current level digitally or analogue controlled . thermal protection with soft inter- vention powerdip 12 + 2 + 2 (plastic package) order code : PBL3717A description the PBL3717A is a monolithic ic which controls and drives one phase of a bipolar stepper motor with chopper control of the phase current. current levels may be selected in three steps by means of two logic inputs which select one of three current compara- tors. when both of these inputs are high the device is disabled. a separate logic input controls the direc- tion of current flow. a monostable, programmed by an external rc net- work, sets the current decay time. the power section is a full h-bridge driver with four internal clamp diodes for current recirculation. an external connection to the lower emitters is available for the insertion of a sensing resistor. two PBL3717As and few external components form a complete stepper motor drive subsystem. the raccomended operating ambient temperature ranges is from 0 to 70 c. the PBL3717A is supplied in a 12 + 2 + 2 lead pow- erdip package. pin connection (top view) 1/11
pin functions n name function 1 utput b output connection (with pin 15). the output stage is a "h" bridge formed by four transistors and four diodes suitable for switching applications. 2 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 (t off = 0.69 r t c t ). 3 supply voltage b supply voltage input for half output stage see also pin 14. 4 ground ground connection. with pins 5, 12 and 13 also conducts heat from die to printed circuit copper. 5 ground see pin 4. 6 logic supply supply voltage input for logic circuitry 7 input 1 this pin and pin 9 (input 0) are logic inputs which select the outputs of the three comparators to set the current level. current also depends on the sensing resistor and reference voltage. see truth table. 8 phase this ttl-compatible logic input sets the direction of current flow through the load. a high level causes current to flow from output a (source) to output b (sink). a schmitt trigger on this input provides good noise immunity and a delay circuit prevents output stage short circuits during switching. 9 input 0 see input 1 (pin 7) . 10 comparator input input connected to the three comparators. the voltage across the sense resistor is feedback to this input through the low pass filter r c c c . 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 r t c t , t off = 0.69 r t c t . 11 reference a voltage applied to this pin sets the reference voltage of the three comparators, this determining the output current (also thus depending on r s and the two inputs input 0 and input 1). 12 ground see pin 4. 13 ground see pin 4. 14 supply voltage a supply voltage input for half output stage. see also pin 13. 15 output a see pin 1. 16 sense resistor connection to lower emitters of output stage for insertion of current sense resistor truth table input 0 (pin 9) input 1 (pin 7) h l h l h h l l no current low current medium current high current PBL3717A 2/11
block diagram absolute maximum ratings symbol parameter value unit v s power supply voltage 50 v v ss logic supply voltage 7 v v i logic input voltage 6 v v c comparator input v ss v r reference input voltage 15 v i o output current (dc operation) 1.2 a t stg storage temperature C 55 to + 150 c t j operating junction temperature 150 c thermal data symbol parameter value unit r th j-case thermal resistance junction-pins 11 c/w r th j-amb thermal resistance junction-ambient* 40 c/w * soldered on a 35 m thick 20 cm 2 p.c. board copper area. PBL3717A 3/11
electrical characteristics (refer to the test circuit v s = 36v, v ss = 5v, t amb = 25 o c unless otherwise specified) symbol parameter test conditions min. typ. max. unit v s supply voltage (pin 3, 14) 10 46 v v ss logic supply voltage (pin 6) 4.75 5.25 v i ss logic supply current (pin 6) 7 15 ma i r reference input current (pin 11) v r = 5v 0.75 1 ma logic inputs v il input low voltage (pins 7, 8, 9) 0.8 v v ih input high voltage (pin 7, 8, 9) 2 v ss v i il low voltage input current (pins 7, 8, 9) v i = 0.4v pin 8 pins 7, 9 C 100 C 400 m a m a i ih high voltage input current (pins 7, 8, 9) v i = 2.4v 10 m a comparators v cl comparator low threshold voltage (pin 10) v r = 5v i o = l i 1 = h 66 78 90 mv v cm comparator medium threshold voltage (pin 10) v r = 5v i o = l i 1 = h 236 251 266 mv v ch comparator high threshold voltage (pin 10) v r = 5v i o = l i 1 = h 396 416 436 mv i c comparator input current (pin 10) 20 m a t off cutoff time r t = 56k w c t = 820pf 25 35 m s t d turn off delay (see fig. 2) 2 m s i off output leakage current (pins 1, 15) i o = h i 1 = h 100 m a source diode-transistor pair v sat saturation voltage (pins 1, 15) i m = C 0.5a (see fig. 2) conduction period recirculation period 1.7 1.1 2.1 1.35 v v sat saturation voltage (pins 1, 15) i m = C 1a (see fig. 2) conduction period recirculation period 2.1 1.7 2.8 2.5 v i lk leakage current v s = 46 v 300 m a v f diode forward voltage i m = C 0.5a i m = C 1a 1 1.3 1.25 1.7 v v i slk substrate leakage current when clamped i m = C 0.5a i m = C 1a 2 5 ma ma sink diode-transistor pair v sat saturation voltage (pins 1, 15) i m = 0.5a i m = 1a 1.1 1.6 1.35 2.3 v v i lk leakage current v s = 46v 300 m a v f diode forward voltage i m = 0.5a i m = 1a 1.1 1.4 1.5 2 v v PBL3717A 4/11
figure 1 : test and application circuit figure 2 : waveforms with ma regulating (phase = 0) PBL3717A 5/11
figure 3 : two phase bipolar stepper motor driver figure 4 : p.c. board and component layout of the circuit of fig. 3 (1 : 1 scale) PBL3717A 6/11
figure 5 : input and output sequences for half step and full step operation application informations figure 3 shows a typical application in which two PBL3717A control a two phase bipolar stepper mo- tor. programming the logic inputs i 0 and i 1 set at three different levels the amplitude of the current flowing in the motor winding according to the truth table of page 2. a high level on the "phase" logic input sets the direction of that current from output a to output b ; a low level from output b to output a. it is recommended that unused inputs are tied to pin 6 (v ss ) or pin 4 (gnd) as appropriate to avoid noise problem. the current levels can be varied continuously by changing the ref. voltage on pin 11. control of the motor the stepper motor can rotate in either directions ac- cording to the sequence of the input signals. it is possible to obtain a full step, a half step and a quar- ter step operation. full step operation both the windings of the stepper motor are ener- gized all the time with the same current i ma = i mb . i 0 and i 1 remain fixed at whatever torque value is re- quired. calling a the condition with winding a energized in one direction and a in the other direction, the se- quence for full step rotation is : ab ? ab ? ab ? a b etc. for the rotation in the other direction the sequence must be reserved. in the full step operation the torque is constant each step. half step operation power is applied alternately to one winding then both according to the sequence : ab ? b ? ab ? a ? ab ? b ? a b ? a etc. like full step this can be done at any current level ; the torque is not constant but it is lower when only one winding is energized. a coil is turned off by setting i 0 and i 1 both high. PBL3717A 7/11
l ? 1 10 lm c ? 4 10 - 10 l quarter step operation it is preferable to realize the quarter step operation at full power otherwise the steps will be of very ir- regular size. the extra quarter steps are added to the half steps sequence by putting one coil on half current accord- ing to the sequence. ab ? a 2 b ? b ? a _ _ 2 b ? ab ? a b 2 ? a etc. motor selection as the PBL3717A provides constant current drive, with a switching operation, care must be taken to se- lect stepper motors with low hysteresis losses to prevent motor over heat. l -c filter to reduce emi and chopping losses in the motor a low pass l -c filter can be inserted across the out- puts of the PBL3717A as shown on the following pic- ture. figure 6 : source saturation voltage versus output current (recircuit period) figure 7 : source saturation voltage versus output current (conduction period) figure 9 : comparator threshold versus junction temperature figure 8 : sink saturation voltage versus output current PBL3717A 8/11
mounting instructions the r th j-amb of the pbl 3717a can be reduced by soldering the gnd pins to a suitable copper area of the printed circuit board or to an external heatsink. the diagram of fig. 11 shows the maximum dissipa- ble power p tot and the r th j-amb as a function of the side " a " of two equal square copper areas having a thichkness of 35 m (see fig. 10). figure 10 : example of p.c. board copper area which is used as heatsink figure 11 : max. dissipable power and junction- ambient thermal resistance versus size "a" PBL3717A 9/11
powerdip16 package mechanical data dim. mm inch min. typ. max. min. typ. max. a1 0.51 0.020 b 0.85 1.40 0.033 0.055 b 0.50 0.020 b1 0.38 0.50 0.015 0.020 d 20.0 0.787 e 8.80 0.346 e 2.54 0.100 e3 17.78 0.700 f 7.10 0.280 i 5.10 0.201 l 3.30 0.130 z 1.27 0.050 PBL3717A 10/11
information furnished is believed to be accurate and reliable. however, sgs-thomson microelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of t hird part ies which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of sgs-thomson microelectronics. specifica- tions mentioned in this publication are subject to change without notice. this publication supersedes and replaces all information pre- viously supplied. sgs-thomson microelectronics products are not authorized for use as critical comp onents in life support dev ices or systems without express written approval of sgs-thomson microelectronics. ? 1994 sgs-thomson microelectronics - all rights reserved sgs-thomson microelectronics group of companies australia - brazil - france - germany - hong kong - italy - japan - korea - malay sia - malta - morocco - the netherlands - s ingapore - spain - sweden - switzerland - taiwan - thaliand - united kingdom - u.s.a. PBL3717A 11/11

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