NJM3772 DUAL STEPPER MOTOR DRIVER ■ GENERAL DESCRIPTION The NJM3772 is a stepper motor driver, which circuit is especially developed for use in microstepping applications in conjunction with the matching dual DAC (Digital-to-Analog Converter) NJU39610. The NJM3772 contains a clock oscillator, which is common for both driver channels, a set of comparators and flip-flops implementing the switching control, and two H-bridges with internal recirculation diodes. Voltage supply requirements are +5 V for logic and +10 to +45V for the motor. Maximum output current is 1000mA per channel. ■ PACKAGE OUTLINE NJM3772D2 NJM3772FM2 ■ FEATURES • Dual chopper driver • 1000mA continuous output current per channel • Specially matched to the Dual DAC NJU39610 • Packages DIP22 / PLCC28 ■ BLOCK DIAGRAM Phase 1 VR1 C1 V MM1 E1 NJM3772 — V VCC CC + R S Q M A1 M B1 Logic V BB1 + V BB2 — M B2 Logic M A2 RC + — Phase 2 Figure 1. Block diagram V R2 C2 S R GND Q V MM2 E2 NJM3772 GND Phase 2 26 GND 1 V MM2 GND 2 27 GND 3 28 MA2 4 ■ PIN CONFIGURATIONS RC 1 22 VCC C2 2 21 C 1 V R2 3 VBB2 5 25 VR2 E2 6 24 C2 Phase 2 4 M B2 7 23 RC GND 5 22 VCC GND 9 21 C1 E1 10 20 VR1 VBB1 11 19 Phase1 VMM1 18 GND 17 GND 16 GND 15 GND 14 MA1 12 NJM3772FM2 GND 13 M B1 8 GND 6 VMM2 7 MA2 8 VBB2 9 E 2 10 MB2 11 20 VR1 19 Phase 1 18 GND NJM 3772D2 17 GND 16 VMM1 15 MA1 14 VBB1 13 E 1 12 MB1 Figure 2. Pin configurations ■ PIN DESCRIPTION PLCC DIP 1-3, 9, 13-17 28 4 5 5, 6 GND 17, 18 Symbol 8 9 MA2 VBB2 6 7 8 10 11 10 11 12 13 14 E2 MB2 MB1 E1 VBB1 12 18 19 15 16 19 MA1 VMM1 Phase1 20 20 VR1 21 21 C1 22 23 22 1 VCC RC 24 2 C2 25 3 VR2 26 4 Phase2 27 7 VMM2 Description Ground and negative supply. Note: these pins are used thermally for heat-sinking. Make sure that all ground pins are soldered onto a suitably large copper ground plane for efficient heat sinking. Motor output A, channel 2. Motor current flows from MA2 to MB2 when Phase2 is HIGH. Collector of upper output transistor, channel 2. For lowest possible power dissipation, connect a series resistor RB2 to VMM2. See Applications information, External components. Common emitter, channel 2. This pin connects to a sensing resistor RS to ground. Motor output B, channel 2. Motor current flows from MA2 to MB2 when Phase2 is HIGH. Motor output B, channel 1. Motor current flows from MA1 to MB1 when Phase1 is HIGH. Common emitter, channel 1. This pin connects to a sensing resistor RS to ground. Collector of upper output transistor, channel 1. For lowest possible power dissipation, connect a series resistor RB1 to VMM1. See Applications information, External components. Motor output A, channel 1. Motor current flows from MA1 to MB1 when Phase1 is HIGH. Motor supply voltage, channel 1, +10 to +40 V. VMM1 and VMM2 should be connected together. Controls the direction of motor current at outputs MA1 and MB1. Motor current flows from MA1 to MB1 when Phase1 is HIGH. Reference voltage, channel 1. Controls the threshold voltage for the comparator and hence the output current. Comparator input channel 1. This input senses the instantaneous voltage across the sensing resistor, filtered by an RC network. The threshold voltage for the comparator is VCH1= 0.18 • VR1 [V], i.e. 450 mV at VR1 = 2.5 V. Logic voltage supply, nominally +5 V. Clock oscillator RC pin. Connect a 15 kohm resistor to VCC and a 3300 pF capacitor to ground to obtain the nominal switching frequency of 26.5 kHz. Comparator input channel 2. This input senses the instantaneous voltage across the sensing resistor, filtered by an RC network. The threshold voltage for the comparator is VCH2= 0.18 • VR2 [V], i.e. 450 mV at VR2 = 2.5 V. Reference voltage, channel 2. Controls the threshold voltage for the comparator and hence the output current. Controls the direction of motor current at outputs MA2 and MB2. Motor current flows from MA2 to MB2 when Phase2 is HIGH. Motor supply voltage, channel 2, +10 to +40 V.VMM1 and VMM2 should be connected together. NJM3772 ■ FUNCTIONAL DESCRIPTION Each channel of the NJM3772 consists of the following sections: an output H-bridge with four transistors, capable of driving up to 1000 mA continuous current to the motor winding; a logic section that controls the output transistors; an S-R 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 RS, 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 VR, 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, turn-off and phase shift are shown in figure 3. Note that the upper recirculation diodes are connected to the circuit externally. External recirculation diodes V MM 1 RB V BB 2 3 RS Motor Current 1 2 Fast Current Decay 3 Time Slow Current Decay Figure 3. Output stage with current paths during turn-on, turn-off and phase shift. NJM3772 ■ ABSOLUTE MAXIMUM RATINGS Parameter Pin no. DIP package Symbol Min Max Unit Voltage Logic supply Motor supply Output stage supply Logic inputs Comparator inputs Reference inputs 22 7, 16 9, 14 4, 19 2, 21 3, 20 VCC VMM VBB VI VC VR 0 0 0 -0.3 -0.3 -0.3 7 45 45 6 VCC 7.5 V V V V V V Current Motor output current Logic inputs Analog inputs 8, 11, 12, 15 4, 19 2, 3, 20, 21 IM II IA -1200 -10 -10 +1200 - mA mA mA Temperature Operating junction temperature Storage temperature Tj TS -40 -55 +150 +150 °C °C Power Dissipation (Package Data) Power dissipation at TGND = +25°C, DIP and PLCC package Power dissipation at TGND = +125°C, DIP package Power dissipation at TGND = +125°C, PLCC package PD PD PD - 5 2.2 2.6 W W W Symbol Min Typ VCC VMM VBB IM TJ tr , t f RT 4.75 10 VMM- 0.5 -1000 -20 2 ■ RECOMMENDED OPERATING CONDITIONS Parameter Logic supply voltage Motor supply voltage Output stage supply voltage Motor output current Junction temperature ** Rise and fall time, logic inputs Oscillator timing resistor 5 15 Max Unit 5.25 40 VMM +1000 +125 2 20 V V V mA °C µs kΩ ** See operating temperature chapter Phase 1 VR1 19 20 C1 V MM1 E1 21 16 13 NJM3772 CC CC 22 | V MA – V MB | Pin no. refers to DIP-package — V V I CC + R S Q Logic 15 M A1 12 M B1 14 V BB1 t on t off 50 % 15 k Ω + RT — Logic I RC RC 1 + — S R 9 V BB2 11 M B2 8 M A2 t IM I OL VE Q RB 3 300 pF td V CH VCC CT 4 Phase 2 II I IH 3 V R2 I IL 2 5, 6, 17, 18 7 C2 GND V MM2 10 E2 I MM IC IA IA VI 1 kΩ t V IH V IL VA VCH V V R RC VM V 820 pF MA C CC Figure 4. Definition of symbols VE RS V BB V MM 1 fs = t + t on off ton D= ton + t off Figure 5. Definition of terms NJM3772 ■ ELECTRICAL CHARACTERISTICS Electrical characteristics over recommended operating conditions, unless otherwise noted. -20°C< TJ < 125°C Parameter Symbol Conditions General Supply current Total power dissipation ICC PD Total power dissipation PD Note 4. VMM = 12 V, IM1= IM2= 750 mA. RB = 0.68 ohm. Notes 2, 3, 4, 5. VMM = 12 V, IM1 = 1000 mA, IM2 = 0 mA. RB = 0.47 ohm. Notes 2, 3, 4, 5. Thermal shutdown junction temperature Turn-off delay td Logic Inputs Logic HIGH input voltage Logic LOW input voltage Logic HIGH input current Logic LOW input current Comparator Inputs Threshold voltage | VCH1 - VCH2 | mismatch Input current Reference Inputs Input resistance Input current VIH VIL IIH IIL VCH VCH,diff IC RR IR Motor Outputs Lower transistor saturation voltage Lower transistor leakage current Lower diode forward voltage drop Upper transistor saturation voltage Upper transistor saturation voltage Upper transistor leakage current Chopper Oscillator Chopping frequency fs Min Typ Max Unit - 60 1.8 75 2.1 mA W - 1.8 2.2 W - 160 1.4 2.0 °C µs 2.0 -0.4 - 0.8 20 - V V µA mA 430 -10 450 1 - 470 1 mV mV µA TA = +25°C VR = 2.50 V - 5 0.5 1.0 kohm mA IM = 750 mA VMM = 41 V, VE = VR = 0 V, VC = VCC IM = 750 mA IM = 750 mA. RB = 0.68 ohm. Note 5 IM = 750 mA. RB = 0.47 ohm. Note 3, 5 VMM VBB = 41 V, VE = VR = 0 V, VC = VCC - 0.6 1.2 0.6 0.8 - 0.9 700 1.5 0.9 1.1 700 V µA V V V µA 25.0 26.5 28.0 kHz Min Typ Max Unit TA = +25°C, dVC/dt ≥ 50 mV/µs, IM = 100 mA. Note 3. VI = 2.4 V VI = 0.4 V RC = 1 kohm, VR = 2.50 V RC = 1 kohm CT = 3300 pF, RT = 15 kohm ■ THERMAL CHARACTERISTICS Parameter Thermal resistance Symbol Conditions RthJ-GND DIP package - 11 - °C/W RthJ-A DIP package. Note 2 - 40 - °C/W RthJ-GND PLCC package - 9 - °C/W RthJ-A PLCC package. Note 2 - 35 - °C/W Notes 1. All voltages are with respect to ground. Currents are positive into, negative out of specified terminal 2. All ground pins soldered onto a 20 cm2 PCB copper area with free air convection, TA = +25°C 3. Not covered by final test program 4. Switching duty cycle D = 30%, fs = 26.5 kHz 5. External resistors RB for lowering of saturation voltage NJM3772 ■ APPLICATIONS INFORMATION Current control The output current to the motor winding is determined by the voltage at the reference input and the sensing resistor, RS. 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: IM,peak = 0.18 • ( VR / RS ) [A] i.e., with a recommended value of 0.47 ohm for the sensing resistor RS, a 2.5 V reference voltage will produce an output current of approximately 960 mA. To improve noise immunity on the VR input, the control range may be increased to 5 V if RS is correspondingly changed to 1 ohm. V MM +5 V R RB 0.1 µ F + 0.5 Ω 22 V 18 V CC 0.5 Ω 11 MM1 V 27 V BB1 10 µF B D1 5 V MM2 M BB2 19 12 A1 Phase 1 20 M V R1 NJM3772 26 Phase D2 8 B1 4 M A2 2 25 V R2 RC 23 1, 3, 28, 14, 16, +5 V 15 kΩ 3300 pF 7 M B2 GND E1 C1 21 2, 9, 13, 15, 17, C2 10 1 kΩ E2 STEPPER MOTOR 6 24 1 kΩ D3 820 pF RS 820 pF RS 0.5 Ω D4 V MM D1 - D4 are UF 4001 or BYV 27, t rr ≤ 100 ns. 0.5 Ω Pin numbers refer to PLCC package. GND (VCC ) GND (V MM) Figure 6. Typical stepper motor driver application with NJM3772 VCC (+5V) V MM + RB 0.1 µF RB 10 µF 0.5 Ω 0.5 Ω D1 22 14 25 D0 V V DD 12 19 10 20 Sign1 To mP +2.5V 16 D7 27 28 15 1 7 9 CC 11 V MM1 27 V BB1 MM2 5 V BB2 MA1 12 Phase 1 DA1 MB1 VR1 NJU39610 A0 A1 WR CS RESET V Ref 18 V D2 4 26 6 25 NJM3772 MA2 Phase 2 Sign 2 VR2 DA2 V SS MB2 RC GND 23 2 +5 V 15 kΩ 3300 pF 1, 2, 3, 9, 28, 13, 14, 15, 16, 17, C1 21 E1 10 C2 8 4 7 STEPPER MOTOR E2 24 6 1 kΩ 1 kΩ 820 pF 820 pF D3 RS RS 0.5 Ω 0.5 Ω D4 V MM D1 - D4 are UF 4001 or BYV 27, t rr 100 ns Pin numbers refer to PLCC package. Figure 7. Microstepping system with NJU39610 and NJM3772 NJM3772 External components The NJM3772 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 3. The voltage drop reduces the collector-emitter saturation voltage of the internal transistor, which can greatly reduce power dissipation of the IC itself. The series resistor, designated RB , shall be selected for about 0.5 V voltage drop at the maximum output current. In an application with an output current of 1000 mA (peak), a 0.47 ohm, 1 /2 W resistor is the best choice. In low current applications where power dissipation is not a critical factor, the RB resistor can of course be omitted, and the VMM and VBB pins (pins 5, 11, 18, 27) can all be connected directly to the motor supply voltage VMM. 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 trr of less than 100 ns. Common types are UF4001 or BYV27. A low pass filter in series with the comparator input prevents erroneous switching due to switching transients. The recommended filter component values, 1 kohm and 820 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, VCH , set by the reference input VR (VCH = 450 mV at VR= 2.5 V). The time constant of the low-pass filter may therefore be reduced to minimize the delay and optimize low-current performance. Increasing the time constant may result in unstable switching. The time constant should be adjusted by changing the CC value. The frequency of the clock oscillator is set by the RT-CT timing components at the RC pin. The recommended values result in a clock frequency (= switching frequency) of 26.5 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 CT capacitor value should be adjusted. The recommended RT resistor value is 15 kohm. The sensing resistor RS, should be selected for maximum motor current. The relationship between peak motor current, reference voltage and the value of RS is described under Current control above. Be sure not to exceed the maximum output current which is 1200 mA peak when only one channel is activated. Or recommended output current, which is 1000 mA peak, when both channels is activated. NJM3772 Motor selection The NJM3772 is designed for two-phase bipolar stepper motors, i.e., motors that have only one winding per phase. The chopping principle of the NJM3772 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 5 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 NJM3772 have a voltage rating of 1 to 6 V, while the supply voltage usually ranges from 12 to 40 V. 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 40 V. Check that the chopping duty cycle does not exceed 50% at maximum current. Phase inputs. A logic HIGH on a Phase input gives a current flowing from pin MA into pin MB. 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 20 cm2 (approx. 1.8" x 1.8"), copper foil thickness 35 µm, permits the circuit to operate with 750 mA output current, both channels driving, at ambient temperatures up to 70°C. Consult figures 8, 9, 10 and 11 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 160°C. Normal operation is resumed when the temperature has decreased. Operating temperature. The max recommended operating temperature is 125°C. This gives an estimated lifelength of about 5 years at continuous drive, A change of ±10° would increase/decrease the lifelength of the circuit about 5 years. Thermal resistance [°C/W] 28-pin PLCC 80 70 60 50 40 30 22-pin DIP 20 5 10 15 20 25 30 35 PCB copper foil area [cm 2 ] PLCC package DIP package Figure 8. Typical thermal resistance vs. PC Board copper area and suggested layout NJM3772 ■ TYPICAL CHARACTERISTICS PD (W) PD (W) NJM3772 3.0 Maximum allowable power dissipation [W] NJM3772 6 3.0 Two channels on. R = 0.68 ohm. 5 2.0 V MM = 36 V Am bie 4 nt te m pe ra tu tem 3 pera re 1.5 Two channels on. RB = 0.47 ohm. 1.0 1.0 .5 1 .5 .40 .60 .80 1.0 1.2 0 0 .20 .40 .60 .80 1.0 0 25 50 75 100 125 150 Temperature [°C] 1.2 PLCC package DIP package I M (A) I M (A) All ground pins soldered onto a 20 cm 2 PCB copper area with free air convection. Figure 10. Power dissipation vs. motor Figure 11. Maximum allowable current, both channels on. Ta = 25°C power dissipation vs. temperature Figure 9. Power dissipation vs. motor current. Ta = 25°C VCE Sat, lt (V) 0 -25 R B = 0.68 Ω V MM = 12 V .20 2 V MM = 12 V One channel on. RB = 0.47 ohm. 0 ture 1.5 0 pin 2.0 ing 2.5 Batw 2.5 Vd (V) NJM3772 PBL 3772 1.2 1.2 1.2 1.0 .8 1.0 .8 .6 .8 .6 1.0 VCE Sat, ut (V) NJM3772 R B = 0.47 Ω .6 .2 .4 0 .20 .40 R B = 0.68 Ω TJ =25¡C TJ =125¡C .4 .60 .80 1.0 1.2 I M (A) Figure 12. Typical lower transistor saturation voltage vs. output current .2 .4 .2 0 .20 .40 .60 I M (A) .80 1.0 1.2 0 .20 .40 .60 .80 1.0 1.2 I M (A) Figure 13. Typical lower diode voltage Figure 14. Typical upper transistor drop vs. recirculating current saturation voltage vs. output current The specifications on this databook are only given for information , without any guarantee as regards either mistakes or omissions. The application circuits in this databook are described only to show representative usages of the product and not intended for the guarantee or permission of any right including the industrial rights.