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NJM3772
DUAL STEPPER MOTOR DRIVER
s 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. s PACKAGE OUTLINE
NJM3772D2
NJM3772FM2
s FEATURES * Dual chopper driver * 1000mA continuous output current per channel * Specially matched to the Dual DAC NJU39610 * Packages DIP22 / PLCC28
s BLOCK DIAGRAM
Phase 1 VR1
C1
V MM1
E1
NJM3772
VCC V
-- + CC
R S
Q M A1 Logic M B1 V BB1
+ --
V BB2 M B2 Logic M A2
RC
+ --
S R
Q
Phase 2
V R2
C2
GND
V MM2
E2
Figure 1. Block diagram
NJM3772
s PIN CONFIGURATIONS
Phase 2
V MM2
GND
GND
GND
GND
MA2
RC 1 C2 2 V R2 3
25 24 23
22 VCC 21 C 1 20 VR1 19 Phase 1 18 GND
28
27
VBB2 5 E2 6 M B2 7 M B1 8 GND 9 E1 10 VBB1 11
26
4
3
2
1
VR2 C2 RC VCC C1 VR1 Phase1
Phase 2 4 GND 5 GND 6 VMM2 7 MA2 8 VBB2
9
NJM3772FM2
22 21 20 19
NJM 3772D2
17 GND 16 VMM1 15 MA1 14 VBB1 13 E 1 12 MB1
MA1 12
GND 13
GND 14
GND 15
GND 16
GND 17
VMM1 18
E 2 10 MB2 11
Figure 2. Pin configurations s PIN DESCRIPTION
PLCC DIP Symbol Description
1-3, 9, 13-17 28 4 5 6 7 8 10 11 12 18 19 20 21
5, 6 GND 17, 18 8 9 10 11 12 13 14 15 16 19 20 21 MA2 VBB2 E2 MB2 MB1 E1 VBB1 MA1 VMM1 Phase1 VR1 C1
22 23 24
22 1 2
VCC RC C2
25 26 27
3 4 7
VR2 Phase2 VMM2
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
s 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
3
Fast Current Decay Slow Current Decay
Time
Figure 3. Output stage with current paths during turn-on, turn-off and phase shift.
NJM3772
s 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 Current Motor output current Logic inputs Analog inputs Temperature Operating junction temperature Storage temperature Power Dissipation (Package Data) Power dissipation at TGND = +25C, DIP and PLCC package Power dissipation at TGND = +125C, DIP package Power dissipation at TGND = +125C, PLCC package
22 7, 16 9, 14 4, 19 2, 21 3, 20 8, 11, 12, 15 4, 19 2, 3, 20, 21
VCC VMM VBB VI VC VR IM II IA Tj TS PD PD PD
0 0 0 -0.3 -0.3 -0.3 -1200 -10 -10 -40 -55 -
7 45 45 6 VCC 7.5 +1200 +150 +150 5 2.2 2.6
V V V V V V mA mA mA C C W W W
s RECOMMENDED OPERATING CONDITIONS
Parameter Symbol Min Typ Max Unit
Logic supply voltage Motor supply voltage Output stage supply voltage Motor output current Junction temperature ** Rise and fall time, logic inputs Oscillator timing resistor ** See operating temperature chapter
VCC VMM VBB IM TJ tr , t f RT
4.75 10 VMM- 0.5 -1000 -20 2
5 15
5.25 40 VMM +1000 +125 2 20
V V V mA C s k
Phase 1 VR1 19 20
C1 21
V MM1 16
E1 13
NJM3772
I CC V V 22
-- + CC CC
Pin no. refers to DIP-package
R S Q 15 Logic 12 M A1 M B1 V BB1 V BB2 M B2 M A2
IM I OL
| V MA - V MB |
t on 50 %
t off
14
15 k +
RT
--
9 11 Logic 8
t VE
RB
I RC
RC
1
+ --
td
S R
Q
V
3 300 pF
CH
VCC CT 4 Phase 2 II I IH I IL IA VI V V
IH
3 V R2
2 C2 IC IA
5, 6, 17, 18 GND
7 V MM2
10 E2
I MM
1 k
t
VA V
R
VCH V
C 820 pF
RC
VE
VM V
MA
V BB
V MM
IL
CC
RS
fs = t + t on off
1
ton D= ton + t off
Figure 4. Definition of symbols
Figure 5. Definition of terms
NJM3772
s ELECTRICAL CHARACTERISTICS
Electrical characteristics over recommended operating conditions, unless otherwise noted. -20C< TJ < 125C
Parameter Symbol Conditions Min Typ Max Unit
General Supply current Total power dissipation Total power dissipation Thermal shutdown junction temperature Turn-off delay 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 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
ICC PD 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. TA = +25C, dVC/dt 50 mV/s, IM = 100 mA. Note 3.
-
60 1.8 1.8 160 1.4
75 2.1 2.2 2.0
mA W W C s
td
VIH VIL IIH IIL VCH VCH,diff IC RR IR
VI = 2.4 V VI = 0.4 V RC = 1 kohm, VR = 2.50 V RC = 1 kohm
2.0 -0.4 430 -10 25.0
450 1 5 0.5 0.6 1.2 0.6 0.8 26.5
0.8 20 470 1 1.0 0.9 700 1.5 0.9 1.1 700 28.0
V V A mA mV mV A kohm mA V A V V V A kHz
TA = +25C VR = 2.50 V 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
fs
CT = 3300 pF, RT = 15 kohm
s THERMAL CHARACTERISTICS
Parameter Symbol Conditions Min Typ Max Unit
Thermal resistance
RthJ-GND RthJ-A RthJ-GND RthJ-A
DIP package DIP package. Note 2 PLCC package PLCC package. Note 2
-
11 40 9 35
-
C/W C/W C/W 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 = +25C 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
s 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.
+5 V V MM R 0.5 22 V 19 Phase 1 20 V 26 Phase 25 V R2 RC 23 +5 V 15 k 3300 pF GND 1, 3, 28, 14, 16, 2, 9, 13, 15, 17, C1 21 E1 10 1 k C2 24 1 k D3 820 pF RS 0.5 GND (VCC ) 820 pF RS 0.5 D4 V MM M B2 E2 6 7
2 R1 CC
+
B
0.1 F
RB
0.5 27 5 V
BB2
10 F
D1 12
A1
D2
18 V
MM1
11 V
BB1
V
MM2
M
M
8
B1
NJM3772
4 M A2
STEPPER MOTOR
D1 - D4 are UF 4001 or BYV 27, t rr 100 ns. Pin numbers refer to PLCC package. GND (V MM)
Figure 6. Typical stepper motor driver application with NJM3772
VCC (+5V)
+ RB 0.5 RB 0.5 D1 D2
V MM
0.1 F 14 25 D0 V DD 12 Sign1 To m P 16 D7 27 28 15 1 7 9 10 DA1 20 VR1 4 Sign
2
10 F
22 V 19 Phase 1
CC
18 V
MM1
11 V
BB1
27 V
MM2
5 V
BB2 MA1
12
MB1
8 4
NJU39610
A0 A1 WR CS RESET V Ref 26 6 DA2 V SS 2 +5 V 15 k 25
NJM3772
MA2
Phase 2 VR2 RC GND 23 1, 2, 3, 9, 28, 13, 14, 15, 16, 17, C1 21
1 k
MB2 E1 10 C2 24
1 k
7
+2.5V
E2 6
D3 D4
STEPPER MOTOR
V MM
3300 pF
820 pF RS 0.5
820 pF RS 0.5
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 m, permits the circuit to operate with 750 mA output current, both channels driving, at ambient temperatures up to 70C. 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 160C. Normal operation is resumed when the temperature has decreased. Operating temperature. The max recommended operating temperature is 125C. 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]
80
28-pin PLCC
70
60
50
40
30
22-pin DIP
5 10 15 20 25 30 35
20
PCB copper foil area [cm 2 ]
PLCC package DIP package
Figure 8. Typical thermal resistance vs. PC Board copper area and suggested layout
NJM3772
s TYPICAL CHARACTERISTICS
PD (W)
3.0
Two channels on. R = 0.68 ohm.
NJM3772
3.0 2.5
PD (W)
NJM3772
Maximum allowable power dissipation [W]
6
5
Batw
2.5 2.0
V MM = 36 V
2.0
4
Am
bie
nt
ing
te
m
pin
pe
3
ra
tu
tem
re
pera
1.5
Two channels on. RB = 0.47 ohm. One channel on. RB = 0.47 ohm.
V MM = 12 V
1.5
ture
V MM = 12 V
1.0
2
1.0 .5
1
.5
R B = 0.68
1.0 1.2
0 0 .20 .40 .60 .80 1.0 1.2
0 -25
0
25
50
75
100
125
150
0
Temperature [C]
PLCC package DIP package All ground pins soldered onto a 20 cm 2 PCB copper area with free air convection.
0
.20
.40
.60
.80
I M (A)
I M (A)
Figure 9. Power dissipation vs. motor current. Ta = 25C
VCE Sat, lt (V)
1.2 1.0 .8 NJM3772
Figure 10. Power dissipation vs. motor Figure 11. Maximum allowable current, both channels on. Ta = 25C power dissipation vs. temperature
Vd (V)
PBL 3772
1.2 1.0
VCE Sat, ut (V)
NJM3772
1.2
R B = 0.47
1.0 .8
TJ =125C .4 .2 TJ =25C
.8
.6
.6
R B = 0.68
.4 .2
.6
.4 .2
0
.20
.40
.60
.80
1.0
1.2
I M (A)
0
.20
.40
.60
.80
1.0
1.2
0
.20
.40
.60
.80
1.0
1.2
I M (A)
I M (A)
Figure 12. Typical lower transistor saturation voltage vs. output current
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.

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