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| tea3718 tea3718s stepper motor driver ? half-step and full-step mode bipolar drive of stepper motor for maximum motor performance built-in protection diodes wide range of current control 5 to 1500 ma wide voltage range 10 to 50 v designed for unstabilized motor supply voltage current levels can be selected in steps or varied continuously thermal overload protection alarm output or pre-alarm output (see internal table) description the tea3718 and tea3718s are bipolar monolithic integrated circuits intended to control and drive the current in one winding of a bipolar stepper motor. the circuits consist of an ls-ttl compatible logic input, a current sensor, a monostable and an output stage with built-in protection diodes. two tea3718 or tea3718s and a few external components form a complete control and drive unit for ls-ttl or mi- croprocessor-controlled stepper motor systems. powerdip 12 + 2 + 2 multiwatt-15 tea3718sp (multiwatt-15) tea3718sfp (so-20) tea3718dp tea3718sdp (powerdip 12+2+2) pin connections (top views) ordering numbers : tea3718sdp tea3718dp ordering number : tea3718sp 1/16 so-20 ordering number : tea3718sfp july 2003
block diagram tea3718s block diagram tea3718 tea3718-tea3718s 2/16 pin functions name function out b output connection (with pin outa). the output stage is a "h" bridge formed by four transistors and four diodes suitable for switching applications. 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 ). v s (b) supply voltage input for half output stage gnd ground connection. in so-20l and powerdip these pins also conduct heat from die to printed circuit copper. v ss supply voltage input for logic circuitry in1 this pin and pin in0 are logic inputs which select the outputs of three comparators to set the current level. current also depends on the sensing resistor and reference voltage. see truth table. phase this ttl-compatible logic input sets the direction of current flow through the load. a high level causes current to flow from out a (source) to out b (sink). a schmitt trigger on this input provides good noise immunity and a delay circuit prevents output stage short circuits during switching. in0 see input 1 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 . reference a voltage applied to this pin sets the reference voltage of the three comparators. reference voltage with the value of r s and the two inputs in0 and in1 determines the output current. v s (a) supply voltage input for half output stage out a see pin out b sense resistor connection to lower emitters of output stage for insertion of current sense resistor alarm when t j reaches t1 c the alarm output becomes low (tea3718sp) pre-alarm when t j reaches t2 c the prealarm output becomes low (t2 maximum power dissipation figure 1. r s = 1 w inductance free r c = 470 w c c = 820 pf ceramic r t = 56 k w c t = 820 pf ceramic p = 500 w r 2 = 1 k figure 2. tea3718-tea3718s 5/16 electrical characteristics (v cc = 5v, 5%, v mm = 10v to 45v, t amb = 0 to 70 c (t amb = 25 c for tea3718fp/sfp) unless otherwise specified) symbol parameter min. typ. max. unit i cc supply current - - 25 ma v ih high level input voltage - logic inputs 2 - - v v il low level input voltage - logic inputs - - 0.8 v i ih high level input current - logic inputs - - 20 m a i il low level input current - logic inputs (vi = 0.4v) -0.4 - - ma v ch v cm v cl comparator thershold voltage (vr = 5v) i o = 0 i o = 0 i o = 0 i 1 = 0 i 1 = 0 i 1 = 1 390 230 65 420 250 80 440 270 90 mv mv mv i co comparator input current -20 - 20 m a i off output leakage current (i o = 0, i 1 = 1 t amb = 25 c - - 100 m a v sat total saturation voltage drop (im = 1a) so20/powerdip multiwatt - - - - 2.8 3.2 v v p tot total power disssipation - i m = 1a, f s = 30khz - 3.1 3.6 w t off cut off time (see figure 1 and 2, v mm = 10v, v ton > 5 m s 25 30 35 ms t d turn off delay (see fig. 1 and 2, t amb = 25 c, dvc/dt>50mv/ m s) - 1.6 - m s v sat alarm output saturation voltage - i o = 2ma (multiwatt) - 0.8 - v i ref reference input current, v r = 5v - 0.4 1 ma v sat source diode transistor pair saturation voltage powerdip i m = 0.5a powerdip i m = 1a - - 1.05 1.35 1.2 (1.3) 1.5 (1.7) v v multiwatt i m = 0.5a multiwatt i m = 1a - - - - 1.3 1.7 v v v f diode forward voltage i f = 0.5a i f = 1a - - 1.1 1.25 1.5 (1.6) 1.7 (1.9) v v i sub substrate leakage current i f = 1a - - 5 ma v sat sink diode transistor pair saturation voltage powerdip i m = 0.5a powerdip i m = 1a - - 1 1.2 1.2 (1.3) 1.3 (1.5) v v multiwatt i m = 0.5a multiwatt i m = 1a - - - - 1.3 1.5 v v v f diode forward voltage i f = 0.5a i f = 1a - - 1 1.1 1.4 (1.6) 1.5 (1.9) v v notes: (...) only for tea3718sfp mounted in so-20l package. tea3718-tea3718s 6/16 tea3718-tea3718s 7/16 functional blocks figure a: alarm output (tea3718sp - tea3718dp) figure b: pre-alarm output (tea3718sdp - tea3718sfp) tea3718 tea3718s tea3718-tea3718s 8/16 alarm outputs (tea3718sp - tea3718dp) the alarm output becomes low when the junc- tion temperature reaches t c. when an alarm condition occours, parts of the supply voltage (dividing bridge r - r c ) is fed to the comparator input pin (fig. a) depending of the r c c value the behaviour of the circuit is different on alarm condition: 1) r c > 80 w t the output stage is switched off 2) r c > 60 w t the current in the motor windings is reduced according to the approximate formula: (see also fig. e and f) with v th = threshold of the comparator (v ch , v cm , v cl ) r = 700 w (typical) for several multiwatt packages a common de- tection can be obtained as in fig. d pre-alarm output when the junction temperature reaches t1 c (typ. = 170 c) a prealarm signal is generated. soft thermal protection occours when function temperature reaches t2 (t2 > t1) i m = v th r s - v cc r + r c r c r s figure c: alarm detection for powerdip package figure d: commondetection for several multiwatt package tea3718-tea3718s 9/16 typical application phase b in0b in1b phase a in0a in1a figure e: (typical curve) current reduction in the motor on alarm condition. figure f: (v ref 5v) block diagram for half cur- rent on alarm condition. notes: 1. resistance values given here are for the v ch threshold. they should be adjusted using other comparators threshold or other v ref value. tea3718-tea3718s 10/16 the circuit is intended to drive a bipolar constant cur- rent through one motor winding. the constant current is generated through switch mode regulation. there is a choice of three different current levels with the two logic inputs ln0 and ln1. the current can also be switched off completely. input logic if any of the logic inputs is left open, the circuit will treat it as a high level input. functional description in0 in1 current level h l h l h h l l no current low current medium current maximum current phase - this input determines the direction of cur- rent flow in the winding, depending on the motor connections. the signal is fed through a schmidt- trigger for noise immunity, and through a time delay in order to guarantee that no short-circuit occurs in the output stage during phase-shift. high level on the phase input causes the motor current flow from out a through the winding to out b. l h0 and l h1 - the current level in the motor winding is selected with these inputs. the values of the dif- ferent current levels are determined by the refer- ence voltage v r together with the value of the sens- ing resistor r s . current sensor this part contains a current sensing resistor (r s ), a low pass filter (r c , c c ) and three comparators. only one comparator is active at a time. it is activated by the input logic according to the current level chosen with signals in0 and in1. the motor current flows through the sensing resistor r s . when the current has increased so that the voltage across r s be- comes higher than the reference voltage on the other comparator input, the comparator output goes high, which triggers the pulse generator and its out- put goes high during a fixed pulse time (t off ), thus switching off the power feed to the motor winding, and causing the motor current to decrease during t off . single-pulse generator the pulse generator is a monostable triggered on the positive going edge of the comparator output. the monostable output is high during the pulse time, t off , which is determined by the timing components r t and c t . t off = 0.69 r t c t the single pulse switches off the power feed to the motor winding, causing the winding current to de- crease during t off . if a new trigger signal should occur during t off , it is ignored. output stage the output stage contains four darlington transis- tors 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 con- stant current through the winding. it should be noted however, that it is not permitted to short circuit the outputs. v ss , v s , v r the circuit will stand any order of turn-on or turn-off the supply voltages v ss and v s . normal dv/dt val- ues are then assumed. preferably, v r should be tracking v ss during power- on and power-off if v s is established. analog control the current levels can be varied continuously if v r is varied with a circuit varying the voltage on the comparator terminal. power losses v s output current tea3718-tea3718s 11/16 motor selection some stepper motors are not designed for continu- ous operation at maximum current. as the circuit drives a constant current through the motor, its tem- perature might increase exceedingly both at low and high speed operation. also, some stepper motors have such high core losses that they are not suited for switch mode cur- rent regulation. unused inputs unused inputs should be connected to proper voltage levels in order to get the highest noise immunity. interference as the circuit operates with switch mode current regulation, interference generation problems might arise in some applications. a good measure might then be to decouple the circuit with a 15 nf ceramic capacitor, located near the package between power line v s and ground. the ground lead between r s , c c and circuit gnd should be kept as short as possible. this applies also to the lead between the sensing resistor r s and point s, see functional blocks. application notes principal operating sequence tea3718-tea3718s 12/16 multiwatt15 v dim. mm inch min. typ. max. min. typ. max. a 5 0.197 b 2.65 0.104 c 1.6 0.063 d 1 0.039 e 0.49 0.55 0.019 0.022 f 0.66 0.75 0.026 0.030 g 1.02 1.27 1.52 0.040 0.050 0.060 g1 17.53 17.78 18.03 0.690 0.700 0.710 h1 19.6 0.772 h2 20.2 0.795 l 21.9 22.2 22.5 0.862 0.874 0.886 l1 21.7 22.1 22.5 0.854 0.870 0.886 l2 17.65 18.1 0.695 0.713 l3 17.25 17.5 17.75 0.679 0.689 0.699 l4 10.3 10.7 10.9 0.406 0.421 0.429 l7 2.65 2.9 0.104 0.114 m 4.25 4.55 4.85 0.167 0.179 0.191 m1 4.63 5.08 5.53 0.182 0.200 0.218 s 1.9 2.6 0.075 0.102 s1 1.9 2.6 0.075 0.102 dia1 3.65 3.85 0.144 0.152 outline and mechanical data tea3718-tea3718s 13/16 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 powerdip 16 outline and mechanical data tea3718-tea3718s 14/16 11 0 11 20 a e b d e l k h a1 c so20mec h x 45? so20 dim. mm inch min. typ. max. min. typ. max. a 2.35 2.65 0.093 0.104 a1 0.1 0.3 0.004 0.012 b 0.33 0.51 0.013 0.020 c 0.23 0.32 0.009 0.013 d 12.6 13 0.496 0.512 e 7.4 7.6 0.291 0.299 e 1.27 0.050 h 10 10.65 0.394 0.419 h 0.25 0.75 0.010 0.030 l 0.4 1.27 0.016 0.050 k 0? (min.)8? (max.) outline and mechanical data tea3718-tea3718s 15/16 information furnished is believed to be accurate and reliable. however, stmicroelectronics assumes no responsibility for the co nse- quences of use of such information nor for any infringement of patents or other rights of third parties which may result from i ts use. no li- cense is granted by implication or otherwise under any patent or patent rights of stmicroelectronics. specification mentioned i n this publi- cation are subject to change without notice. this publication supersedes and replaces all information previously supplied. stmi croelectron- ics products are not authorized for use as critical components in life support devices or systems without express written appro val of stmi- croelectronics. the st logo is a registered trademark of stmicroelectronics ? 2003 stmicroelectronics C printed in italy C all rights reserved stmicroelectronics group of companies australia - brazil - canada - china - finland - france - germany - hong kong - india - israel - italy - japan - malaysia - malt a - morocco - singapore - spain - sweden - switzerland - united kingdom - united states. http://www.st.com tea3718-tea3718s 16/16 |
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