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MOTOROLA
SEMICONDUCTOR APPLICATION NOTE
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AN1607 ITC122 Low Voltage Micro to Motor Interface
By Bill Lucas and Warren Schultz A MOSFET power stage that is designed to run Brush or Brushless DC motors with input signals from an ASB124 Motion Control Development Board is presented here. It will supply up to 4 amps continuous current from DC bus voltages up to 48 volts.
Figure 1. ITC122 -- Low Voltage Micro to Motor Interface
EVALUATION BOARD DESCRIPTION
A summary of the information required to use ITC122 Low Voltage Micro to Motor Interface boards is presented as follows. A discussion of the design appears under the heading Design Considerations.
Function
The evaluation board shown in Figure 1 is designed to provide a direct interface between microcomputers and fractional horsepower motors. It accepts 6 logic inputs which
control 3 complementary Half-Bridge outputs, and is arranged such that a logic ZERO at the input turns on the corresponding power transistor. This type of configuration is applicable to pulse width modulated (PWM) systems where the PWM signal is generated in a microcomputer, digital signal processor, or other digital system. It is suitable for driving fractional horsepower Brush and Brushless DC motors. In addition to controlling the motor, current sense, temperature sense, and bus voltage feedback are provided. This board is designed to interface directly with Motorola ASB124 motor control development boards.
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Coupled with an ASB124 control board, it completes the link between software development tools and a motor. Its use allows code to be written before hardware design is completed in an environment where mechanical outputs can be seen. The design can also be used as a reference for speeding hardware development.
Electrical Characteristics
The following electrical characteristics apply to operation at 25 degrees Celsius, and unless otherwise specified, B+ = 24 volts.
Table 1. Electrical Characteristics
Characteristic Power Supply Voltage RMS Motor Current -- Two Phases Active -- Three Phases Active Input Current @ VIN = 5 V Min Logic 1 Input Voltage Max Logic 0 Input Voltage Quiescent Current Bus Current Sense Voltage Temperature Sense Voltage Bus Voltage Sense Voltage Power Dissipation -- Two Phases Active -- Three Phases Active Symbol B+ IM 4 5 Iin VIH VIL ICC Isense Vtemp Vbus PDISS 5.5 6.75 Watts Watts 500 2.7 2.0 25 250 .65 50 Amps Amps A Volts Volts mA mV/A Volts mV/V Min 12 Typ Max 48 Units Volts
The above numbers for power dissipation assume still air and no additional heat sinking. Maximum current ratings are based upon applying pulse width modulation signals only to the top inputs, a maximum PWM frequency of 23 KHz, and a
maximum supply voltage of 40 volts. Bonding heat sinks to the back of the board and/or providing air flow will significantly increase both power dissipation and output current ratings.
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Content
Board contents are described by the following schematic and parts list. A pin by pin circuit description follows in the next section. Table 2. Parts List
Designators C11, C2-C4, C8, C9 C5 C6 C7, C10 C1 D1 D2-D10 D11 J1 J2 Q13, Q15, Q17 Q12, Q14, Q16 Q3, Q4, Q6, Q7, Q9, Q10 Q5, Q8, Q11 Q1, Q2 R36 R13, R45 R15, R16 R17 R37-R39, R43 R40-R42, R44 R14 R2, R4, R6, R8, R10, R12 R1, R3, R5, R7, R9, R11 R19, R27, R31 R18, R26, R30 R20, R29, R33 R21, R28, R32 R22, R24, R34 R23, R25, R35 T1 T2 U1 U2, U3 U4, U5 U6 Z1-Z6 Z7 Z8-Z10 No Designator ITC122 Qty. 6 1 1 2 1 1 9 1 1 1 3 3 6 3 2 1 2 2 1 4 4 1 6 6 3 3 3 3 3 3 1 1 1 2 2 1 6 1 3 4 1 Description 1 F Capacitor .1 F Capacitor 220 F .1 F Capacitor .001 F Capacitor LED SOT-23 Schottky Diode SOD-123 SOD-123 Diode 2x7 .1o.c. Jumper Block 2x8 .1o.c. Jumper Block N-Channel Power TMOS FET P-Channel Power TMOS FET Small Signal NPN Transistor Small Signal PNP Transistor Small Signal NPN Transistor .01 Ohm Resistor 1% 1.02K Ohm Resistor 1% 4.7K Resistor 1.8K Resistor 37.4K Ohm Resistor 1% 1.96K Ohm Resistor 1% 24.3K Ohm Resistor 1% 1K Resistor 10K Resistor 820 Ohm Resistor 4.3K Resistor 56 Ohm Resistor 91 Ohm Resistor 270 Ohm Resistor 150 Ohm Resistor 7 Screw Terminal Connector 6 Screw Terminal Connector 5 Volt Regulator Quad NAND Gate MOSFET Driver Dual Rail to Rail Op-Amp Zener Diode SOT-23 Zener Diode SMB Zener Diode SOD-123 Self Stick Rubber Feet Printed Circuit Board 4.7 V 15 V 12 V 1 Watt 1.5 Watt 40 V 30 V Note: 2 Note: 2 Rating 25 V 50 V 63 V 100 V 50 V Manufacturer Digi-Key Digi-Key Digi-Key Sprague Sprague Digi-Key Motorola Motorola Digi-Key Digi-Key Motorola Motorola Motorola Motorola Motorola OHMITE Yageo Yageo Yageo Yageo Yageo Yageo Yageo Yageo Yageo Yageo Yageo Yageo Yageo Yageo Phoenix Contact Phoenix Contact Motorola Motorola Motorola Motorola Motorola Motorola Motorola MKDSN 1,5/7-5,08 MKDSN 1,5/6-5,08 MC78L05ACD MC74HC02D MC34152D MC33202D BZX84C4Z7LT1 P6SMB15AT3 MMSZ5242BT1 Part Number PCS5105CT-ND PCC104BCT-ND P6736-ND 1C105Z5U104M100B PCC102CCT-ND LT-1076-ND MBR0540T1 MMSD1000T1 S2011-36-ND S2011-36-ND MTB36N06V MTB30P06V MMBTA06LT1 MMBTA56LT1 BCP56T1 RW1S5CAR010F
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+5.0 V J1-2 Atop T1 R11 10 K R12 1.0 K Z6 4.7 V +5.0 V J1-4 Abot T1 +5.0 V J1-8 Bbot T1 +5.0 V J1-6 Btop T1 +5.0 V 8 9 11 12 +5.0 V J1-10 Ctop T1 R3 10 K R4 1.0 K Z2 4.7 V +5.0 V MC74HC02 U3 1 7 R31 820 U3 U3 R5 10 K R6 1.0 K Z3 4.7 V R7 10 K R8 1.0 K Z4 4.7 V 8 9 7 MC74HC02 +5.0 V 5 + 6- U6 MC33202 7 AGND J2-4 B+ Z10 12 V Q10 MMBT A06LT1 VCC Q11 MMBT A56LT1 R30 4.3 K Q9 MMBT A06LT1 D10 R33 R32 91 R40 1.96 K 1% R37 37.4 K 1% Pc AGND R34 270 Bout Aout GND 3 5 D6 7 I SENSE J2-15 D7 MC33202 R35 150 18 4 +5.0 V 3 + -2 U6 J2-6 Cbot Q17 MTB36N06V R45 C1 1.02 K 0.001 R13 1.02 K CS+ R36 0.01 W CS- GND 62 Ctop Q16 MTB30P06V C12 0.047 mF +5.0 V U2 12 11 MC74HC02 Z9 12 V Q7 MMBT A06LT1 14 10 R27 820 Q8 MMBT A56LT1 R41 1.96 K 1% U2 13 R26 4.3 K D4 Q6 MMBT A06LT1 D9 R29 62 Btop D5 R9 10 K R10 1.0 K MC74HC02 5 6 Z5 4.7 V 2 U2 4 + C8 1.0 mF 4 Bin Ain GND 3 B+ 270 R25 150 U4 MC34152 Bout Aout 5 D3 7 D2 R24 B+ C10 0.047 mF Q14 MTB30P06V 2 3 MC74HC02 U2 1 Z8 12 V Q4 MMBT A06LT1 R19 820 VCC Q5 MMBT A56LT1 R18 4.3 K R20 Q3 MMBT A06LT1 D8 62 R21 R42 91 1.96 K 1% R39 37.4 K 1% Pa AGND R22 270 R23 150 J2-2 Abot Q13 MTB36N06V Atop B+ Q12 MTB30P06V
T2 Aout
6 VCC
R28 91
T2 Q15 MTB36N06V Bbot Bout
R38 37.4 K 1% Pb
10 MC74HC02 13
3 14 2
T2 Cout
+5.0 V J1-12 Cbot T1 R1 10 K R2 1.0 K Z1 4.7 V GND T1 U3 4 MC74HC02
+
C9 1.0 mF 4 Bin 2 Ain
6
U5 MC34152
5 6
VCC
Figure 2. Schematic
R14 24.3 K
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B+
B+ R15 4.7 K R16 4.7 K Q1 BCP56T1 VCC Z7 15 V Q2 BCP56T1 R43 37.4 K 1% + C6 220 mF C4 1.0 mF C5 C11 0.1 mF 1.0 mF C7 0.1 mF R44 1.96 K 1% AGND GND T1 GND T2 J1-5, 7, 9, 11, 13, 14 T2 Vbus J2-13
U1 MC78L05ACD 8 IN OUT GROUND GND 6, 7 1
+5.0 V
+
C3 1.0 mF
+ C2 1.0 mF
R17 1.8 K D1
+
J2-1, 3, 5, 7, 8, 9, 10, 11
J2-14, 16
AGND Vtemp D11 AGND J2-12
AGND
Figure 3. Schematic
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Pin By Pin Description
Inputs and outputs are grouped into four connectors. Two connectors are provided for inputs, one with screw terminals and the other for ribbon cable. Either can be used, they are wired in parallel. Outputs to the motor, B+, and ground are also supplied on a screw connector. Feedback signals are grouped together on a separate ribbon cable connector. In addition, through-hole pads have been placed immediately adjacent to R36 and D11 for easy access to the current feedback resistor and temperature sensing diode. Ribbon connector PINOUTS are shown in Figure 4.
INPUT
FEEDBACK
+5
1
2
Atop
GND
1
2
Pa
+5
3
4
Abot
GND
3
4
Pb
GND
5
6
Btop
GND
5
6
Pc
GND
7
8
Bbot
GND
7
8
N/C
GND
9
10
Ctop
GND
9
10
N/C
GND
11
12
Cbot
GND
11
12
Vtemp
GND
13
14
GND
Vbus
13
14
AGND
J1
I SENSE
15
16
AGND
TOP VIEW
J2
Figure 4. Connector Pinouts Inputs: Inputs Atop, Abot, Btop, Bbot, Ctop, and Cbot are logic inputs. A logic 0 turns on the input's corresponding output transistor, i.e., a logic 0 on Atop turns on output transistor Atop, etc. Logic levels are standard 5 volt CMOS. Input current is higher, typically 500 A, since each of these inputs is pulled up with a 10K resistor. In the absence of any inputs all output transistors are turned off. If a logic 0 is inadvertently applied to both top and bottom inputs for one phase, i.e., Atop & Abot, the bottom input is locked out and only the top output transistor is turned on. This feature helps protect the bridge from errors that may occur during code development. Motor Outputs: Motor output terminals are labeled Aout, Bout, and Cout. This output configuration can be used to drive a fractional horsepower 3 phase brushless DC motor, a reversible brush DC motor, or 3 brush DC motors unidirectionally. When driving a single brush DC motor, thermal performance is optimized by using Aout and Cout for the motor connections. B+: B+ is the motor power input connection. It is the only supply required. Acceptable input voltage range is 12.0 to 48 VDC. It is located on the output connector. 6 GND: There are multiple ground connections. One of the two grounds on the output connector should be used as the power supply return. Isense: Isense is a current sense feedback voltage that appears on pin 15 of connector J2. It is derived from a .01 ohm low inductance surface mount sense resistor that is in series with the ground return. The voltage across this resistor is amplified with a gain of 25. Isense, therefore, represents motor current with a scale factor of 250 mV/Amp. Since only return current is measured, this output will not detect shorts from the motor outputs to ground. Vbus: Vbus is a bus voltage feedback signal that appears on pin 13 of connector J2. It is derived from a 37.4K/1.96K divider which scales B+ at a ratio of approximately 50 mV per volt. This is an unfiltered and unbuffered signal. Vtemp: A temperature output signal derived from a forward biased diode's VF appears on connector J2 at pin 12. The diode, D11, is mounted such that it measures board temperature adjacent to power transistor Q12. MOTOROLA
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Phase Voltage Feedback: Phase voltage feedback signals Pa, Pb, & Pc are also included on feedback connector J2. They are located on pins 2, 4, and 6. These pins provide motor phase voltages divided down with the same 50 mV/Volt ratio as Vbus. They are also unfiltered and unbuffered signals. connections to an ASB124 control board and a Brushless DC motor. This arrangement can be run stand alone, or the ASB124 can be connected to an MMDS05 for code development. The two boards are designed such that the Drive and Feedback ribbon connectors line up. Ribbon cables are supplied with the ASB124 board. Once they are plugged in it is only a matter of connecting power supply, motor, and Hall sensor leads to get a system up and running.
APPLICATION EXAMPLE
An application example shown in Figure 5 illustrates system
MOTION CONTROL DEVELOPMENT BOARD
LOW VOLTAGE MICRO TO MOTOR INTERFACE
GND 7.5-28 VDC B+ BRUSHLESS MOTOR MOTOROLA ASB124 MOTOROLA ITC122 Aout Bout Cout B+ GND FEEDBACK HALL1 HALL2 HALL3 GND GND +5 12-48 VDC
DRIVE
Figure 5. Application Example
An important application's consideration is pulse width modulation topology. The controller that is shown in Figure 5 pulse width modulates Atop, Btop, & Ctop inputs, and commutates Abot, Bbot, & Cbot. This configuration performs better from a power dissipation standpoint than its more commonly used alternative, namely lower half bridge pulse width modulation with upper half bridge commutation. When the upper half bridge is pulse width modulated, circulating currents flow through the lower rds(on) and lower forward diode voltages of the N-Channel transistors. Since transition times for both P-Channel & N-Channel transistors are approximately the same, high side pulse width modulation is considerably more efficient. With more efficient operation, available output power to the motor is maximized.
DESIGN CONSIDERATIONS
A block diagram that provides an overview of the design is
illustrated in Figure 6. Top and Bottom inputs for each phase are coupled to gate drive circuits through cross coupled NOR gates. This arrangement locks out the bottom input when both inputs for one phase are low, thereby adding robustness for lab use. If all six inputs are low, transistors Atop, Btop, and Ctop are turned on, which brakes the motor. This condition can occur when an ASB124 controller is powered down. The output is a 3 phase bridge that is made from complimentary 30 amp surface mount MOSFET's. Gate drive for the N-Channel transistors is provided by MC33152 MOSFET drivers and for the P-Channels by a discrete circuit. A more detailed view of the gate drive circuits is shown in Figure 7. Both the P-Channel & N-Channel transistors have transition times targeted for approximately 200 nsec. This target allows high enough value gate drive resistors to somewhat soften diode snap, yet produces switching losses that are less than static losses at 23 KHz.
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Atop B+ (12-48 VOLTS)
Atop Btop
Btop Ctop
Ctop
Aout
Bout Abot Abot Cout Bbot Bbot
Cbot
Cbot
GND
Figure 6. Block Diagram
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B+
12 V
5.6 K 62
91
820 Aout
270 MC34152
150
Figure 7. Gate Drive
CONCLUSION
The ITC122 Low Voltage Micro to Motor Interface is part of a motor control tool set that significantly reduces design and
development time. It accepts signals from an ASB124 Motion Control Development Board, and provides a 3 phase power output that is capable of supplying 4 amps from bus voltages up to 48 VDC.
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NOTES
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NOTES
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