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Ordering number : EN4867A
Thick Film Hybrid IC
STK6712BMK4
Unipolar Fixed-Current Chopper-Type 4-Phase Stepping Motor Driver
Overview
The STK6712BMK4 is a unipolar fixed-current choppertype 4-phase stepping motor driver hybrid IC (HIC) which uses a MOSFET power device. The excitation sequence signal is active low.
Package Dimensions
unit: mm 4129
[STK6712BMK4]
Applications
* Serial printer, line printer, and laser beam printer (LBP) paper feed and carriage motor drivers * PPC scanner and LBP paper feed drivers * XY plotter pen drivers * Industrial robot applications, etc.
Features
* This IC has the features of the STK6712BMK3, plus a simultaneous input prevention circuit that protects the IC from any malfunction of the excitation signal. * Self-excitation design means chopping frequency is determined by motor L and R. Supports chopping at 20 kHz or higher. * Very low number of external components required. * Wide operating supply voltage range (V CC1 = 18 to 42V) * Excitation sequence signal is active low, and is TTL level for direct interfacing to the microcomputer and gate array. * The unipolar design enables use as a driver for hybrid, PW, or VR type stepping motors. * Supports W1-2 phase operation, with a dual Vref pin.
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TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110-8534 JAPAN
O1895HA (OT)/N0794TH (OT) No. 4867-1/10
STK6712BMK4
Specifications
Maximum Ratings at Ta = 25C
Parameter Maximum supply voltage 1 Maximum supply voltage 2 Maximum phase current Substrate temperature Junction temperature Storage temperature Repeated avalanche resistance Symbol VCC1 max VCC2 max IOH max Tc max Tj max Tstg Ear max No input signal No input signal per phase, R/L = 5 , 10 mH, 0.5 s 1 pulse, VCC input Conditions Ratings 52 7 2.5 105 150 -40 to +125 38 Unit V V A C C C mJ
Allowable Operating Ranges at Ta = 25C
Parameter Supply voltage 1 Supply voltage 2 Phase driver voltage resistance Phase current Symbol VCC1 VCC2 VDSS IOH max Duty 50% With input signal With input signal Conditions Ratings 18 to 42 4.75 to 5.25 (min) 120 (max) 1.7 Unit V V V A
Junction Thermal Resistance
Parameter Power FET Symbol j-c Conditions Ratings 13.5 Unit C/W
Electrical Characteristics at Tc = 25C, VCC1 = 36 V, VCC2 = 5 V
Parameter Output saturation voltage Output current (average) Pin current dissipation (average) FET diode voltage TTL input ON voltage TTL input OFF voltage Switching time Symbol VST Io ave ICC2 Vdf VIH VIL tON tOFF Conditions RL = 23 , VIN = 0.8 V R/L = 3.5 /3.8 mH, VIN = 0.8 V per phase Load, R = 3.5 , L = 3.8 mH, VIN = 0.8 V per phase Idf = 1.0 A Input voltage when F1, 2, 3, 4 ON Input voltage when F1, 2, 3, 4 OFF RL = 24 , VIN = 0.8 V RL = 24 , VIN = 0.8 V 100 0.2 2.0 0.8 0.45 min typ 1.1 0.50 15 1.2 max 1.5 0.55 25 1.8 Unit V A mA V V V ns s
Note: With constant voltage power supply.
Internal Equivalent Circuit
No. 4867-2/10
STK6712BMK4 Sample Application Circuit
Output current waveform when phases are held (locked)
Measure output current values in this state.
Note: For reference, when IOH 1.1 A, RO1 = 6.8 k and RO2 = 390 . RO2 IOH = K x R 1 + R 2 x VCC2/R7
O O
K 1.3 R7 = R8 0.33 3% To reduce noise during motor hold, it is possible to mount CO1 0.01 F and CO2 = 100-200 pF. Normally these are not required. STK6712BMK4 Circuit Operation
Fig. 1 STK6712BMK4 Internal Equivalent Circuit
No. 4867-3/10
STK6712BMK4 The operation for a 4-phase dual-excitation example is described below. The STK6712BMK4 equivalent circuit is given in Fig. 1. The circuit consists of the phase drivers, the comparator, the PWM excitation select and the current detect resistance. In Fig. 1 oA is input with low, and oA with high. When Q1 goes on, the +pin of IC1 (comparator) goes low, making IC1 output S low also. A winding current iON through Q1 increases as: iON = VCC1 - VSAT R (1 - e - L t ) ........................................................................................................... (1)
R
L: motor winding inductance R: Sum of winding resistance and current detect resistance For this reason, pin voltage VR7 at source resistor R7 increases, and when the VRO2 voltages of pin 8 and RO2 are equal output A goes high, and Q1 turns off. The inverse voltage VTP is as: RO2 VTP = Vref = R 1 + R 2 x VCC2.......................................................................................................... (2) O O In general stepping motor coils use BIFALAR windings, so the energy stored in L1 is generated by L2, at which time the current in L2 is iOFF. iOFF conduction continues until the charges of capacitors C1 and C2 on R3 and R4 pins (EC) equal VRO2. When they are equal, output S inverts and becomes low. Motor winding current iON again rises to VRO2 level. This motor current on/off (constant current chopping) is repeated. This waveform is illustrated on the next page.
STK6712BMK4 Basic Circuit
No. 4867-4/10
STK6712BMK4 Waveform Timing Charts
Fig. 2 Control Logic Timing Chart 1. 2-phase excitation
No. 4867-5/10
STK6712BMK4 2. 1-2 phase excitation
STK6712BMK4 Excitation Circuit Setting Output Current The motor output current waveform is shown to the right. Output current IOH can be set by the user by adjusting the voltage of pin 9 (11). The computation equation is indicated below. RO 2 Vref = R 1 + R 2 x VCC2...............................(3) O O IOH K x Vref RS ...............................................(4) Fig. 3 Output Motor Current Waveform
RS: Internal current detect resistance (0.33 3%) K: 1.1 to 1.2 (correction for actual measurement) Power down can be accomplished by reducing the synthetic impedance by connecting a resistance in parallel to RO2. The motor output current variation range can be set for the range of: IOH = 0.2 A to 1.7 A Fig. 4 Vref Peripheral Circuit
but when set to IOH = 0.2 A or lower note that the HIC GND pattern will be one-point earth with respect to the power supply. If earth is poor, there may be no motor current when IOH = 0.2 A. We recommend a motor inductance usage range of L = 1 mH to 10 mH.
No. 4867-6/10
STK6712BMK4 Determining Chopping Frequency The STK6713BMK4 uses constant current for self-excitation. The IOH tOFF time is set to about 14 s, and the tON time can be expressed as: L In ( R + 0.88 L: R: VCC: IOH: VCC - ( IOH e
- R t L OFF R - tOFF VCC + 0.88 (1 - e L )) (R + 0.88) R ) ............................ (5) VCC - (R + 0.88) IOH
tON
-
Motor winding inductance Motor resistance Motor supply voltage Output current
As a result, the chopping frequency is 1 1 F t +t = t + 14 x 10-6 (Hz) ................................................................................................ (6) ON ON OFF However, note that when the following conditions exist the value for F will change. VCC + 0.88 -L 14 x 10-6 In ( I x R + V + 0.88 ) = tOFF2 ............................................................................. (7) R OH CC tOFF tOFF1 + tOFF2 = 14 x 10-6 + tOFF 1 F = t + 14 x 10-6 + t 2 (Hz)........................................................................................................ (8)
ON OFF
Because the STK6712BMK4 is self-exciting there will be minor variation in motor inductance during motor revolution. Final design verification is required in an actual model. Thermal Radiation Design The HIC radiator plate size is dependent on the motor output current IOH (A), motor electrical characteristics, excitation mode, and excitation input signal clock frequency fclock (Hz). The thermal resistance for the radiator can be determined from the following expression. c - a = Tc max - Ta (C/W).................................................................................................................. (9) Pd
Tc max = HIC substrate temperature (C) Ta = set internal temperature (C) Pd = HIC internal mean power dissipation (W)
No. 4867-7/10
STK6712BMK4 With a 2.00 mm aluminum radiation plate, the required area can be determined from Fig. 6. Note that substrate temperature will vary widely with set internal air temperature, and therefore the rear side of the HIC (the aluminum plate side) must always be kept below the maximum temperature of 105C.
Fig. 5 HIC Internal Mean Power Dissipation Pd
Fig. 6
The internal mean power dissipation of the STK6712BMK4 is primarily due to the current control device, the regenerating current diode, the current detect resistance and the predriver circuit. Loss in each excitation mode is: 2 phase excitation Pd2EX (Vst + Vdf) fclock fclock IOHt2 + IOH (Vst x t1 + Vdf x t3) 2 2 ..................................... (10) 3IOHt2 1-2 phase excitation Pd1 - 2EX (Vst + Vdf) 8 3I fclock + OH fclock (Vst x t1 + Vdf x t3) 3 ..................................... (11) Vst: RON voltage drop + R7 (R8) output voltage Vdf: FET internal diode + R7 (R8) output voltage fclock:Input clock (reference frequency before frequency divider) t1, t2 and t3 are the time modes for the waveform indicated below. t1: Time for winding current to rise to set current t2: Time for constant current chopping region t3: Time from end of phase input signal until inverse current regeneration is complete.
Fig. 7 Motor Output Current Waveform (model)
No. 4867-8/10
STK6712BMK4 R + 0.88 -L In (1 - x IOH) .............................................................................................. (12) VCC R + 0.88 VCC + 0.88 -L In ( I * R + V + 0.88 ) ...................................................................................................... (13) R OH CC VCC : L: R: IOH : Motor supply voltage (V) Motor inductance (H) Motor internal resistance () Motor output current peak (A)
t1 t3
The chopping frequency F and t2 for each excitation mode are: 2 phase excitation F = fclock/2, t2 = (1/F) - (t1 + t3).......................................................................... (14)
1-2 phase excitation F = 3fclock/8, t2 = (1/F) - t1.................................................................................. (15) fclock: 4-phase divider input oscillation frequency The characteristic diagrams (typ) for IOH and Vst, and IOH and Vdf are given in Figs. 8 and 9.
Fig. 8 STK6712BMK4 No Thermal Radiation Range (example) An example of STK6712BMK4 use in the no-fin state is indicated below.
Fig. 9
Conditions: * Motor supply voltage VCC1 = 30 V, stepping motor: Electrical characteristics 3.5 mH/o, 3.5 /o * Excitation: 2-phase * Input clock frequency 500 Hz = fclock * HIC ambient temperature Ta = 25C, natural convection * HIC rear substrate temperature Tc = 105C saturation * Motor output current IOH = 1.4 A At this time, the HIC permissible loss can be calculated as: Maximum loss: Pd max = Tc max - Ta 105 - 25 = = 3.4 (W)........................................................ (16) c - a 23
No. 4867-9/10
STK6712BMK4 From these conditions and expressions (12), (13) and (14): t1 = 0.183 ms t2 = 3.670 ms t3 = 0.147 ms Referring to Figs. 8 and 9, each value for Vst and Vdf is determined by expression (10) as follows : Pd2EX = (Vst + Vdf) fclock fclock IOHt2 + IOH (Vst x t1 + Vdf x t3).......................................... (17) 2 2
= 3.08 + 0.14 = 3.22 (W) From expression (9), Tc is calculated as: Tc = Pd2EX x c - a + Ta = 3.22 x 23 + 25 99.1 (C).......................................................................... (18) This is only one example, and because convection and other air movements around the HIC will not match mathematical modelling verification with an actual model is essential. Motor hold noise countermeasures The STK6712BMK4 executes constant current chopping outside the audible range. During motor hold the current hold is outside the range of audible frequencies, but for motors of sizes 30 to 40 mm square (when seen from the shaft direction) with inductance of about 15 mH, there are cases where the output noise is converted to low-frequency noise. In this case, addition of the following components will essentially eliminate such audible noise.
Fig. 10 Motor Hold Noise Countermeasure
s No products described or contained herein are intended for use in surgical implants, life-support systems, aerospace equipment, nuclear power control systems, vehicles, disaster/crime-prevention equipment and the like, the failure of which may directly or indirectly cause injury, death or property loss. s Anyone purchasing any products described or contained herein for an above-mentioned use shall: Accept full responsibility and indemnify and defend SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors and all their officers and employees, jointly and severally, against any and all claims and litigation and all damages, cost and expenses associated with such use: Not impose any responsibility for any fault or negligence which may be cited in any such claim or litigation on SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors or any of their officers and employees jointly or severally. s Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for volume production. SANYO believes information herein is accurate and reliable, but no guarantees are made or implied regarding its use or any infringements of intellectual property rights or other rights of third parties. This catalog provides information as of October, 1995. Specifications and information herein are subject to change without notice. No. 4867-10/10

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