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LMD18245T/HALF Datasheet

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LMD18245
3A, 55V DMOS Full-Bridge Motor Driver
General Description
The LMD18245 full-bridge power amplifier incorporates all
the circuit blocks required to drive and control current in a
brushed type DC motor or one phase of a bipolar stepper
motor. The multi-technology process used to build the device
combines bipolar and CMOS control and protection circuitry
with DMOS power switches on the same monolithic struc-
ture. The LMD18245 controls the motor current via a fixed
off-time chopper technique.
An all DMOS H-bridge power stage delivers continuous out-
put currents up to 3A (6A peak) at supply voltages up to 55V.
The DMOS power switches feature low R
efficiency, and a diode intrinsic to the DMOS body structure
eliminates the discrete diodes typically required to clamp
bipolar power stages.
An innovative current sensing method eliminates the power
loss associated with a sense resistor in series with the motor.
A four-bit digital-to-analog converter (DAC) provides a digital
path for controlling the motor current, and, by extension,
simplifies implementation of full, half and microstep stepper
motor drives. For higher resolution applications, an external
DAC can be used.
Functional Block and Connection Diagram
(15-Lead TO-220 Molded Power Package (T) )
© 2006 National Semiconductor Corporation
Features
n DMOS power stage rated at 55V and 3A continuous
n Low R
DS(ON)
n Internal clamp diodes
n Low-loss current sensing method
n Digital or analog control of motor current
n TTL and CMOS compatible inputs
n Thermal shutdown (outputs off) at T
n Overcurrent protection
n No shoot-through currents
n 15-lead TO-220 molded power package
for high
DS(ON)
Applications
n Full, half and microstep stepper motor drives
n Stepper motor and brushed DC motor servo drives
n Automated factory, medical and office equipment
Order Number LMD18245T
See NS Package Number TA15A
DS011878
March 2006
of typically 0.3
per power switch
= 155˚C
J
01187801
www.national.com
Specifications of National Semiconductor LMD18245T/HALF
Operating Supply Voltage (max):
55V
Operating Supply Voltage (min):
12V
Operating Temperature Classification:
Automotive
Package Type:
TO-220

Summary of Contents

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... For higher resolution applications, an external DAC can be used. Functional Block and Connection Diagram (15-Lead TO-220 Molded Power Package (T) ) © 2006 National Semiconductor Corporation Features n DMOS power stage rated at 55V and 3A continuous n Low R DS(ON) ...

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Connection Diagram Pinout Descriptions (See Functional Block and Connection Diagrams) Pin 1, OUT 1: Output node of the first half H-bridge. Pin 2, COMP OUT: Output of the comparator. If the voltage at CS OUT exceeds that provided by the ...

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... Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. DC Voltage at: OUT and OUT 2 CC COMP OUT, RC, M4, M3, M2, M1, BRAKE, DIRECTION, CS OUT, and DAC REF DC Voltage PGND to SGND Continuous Load Current ...

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Electrical Characteristics The following specifications apply for V perature range, 40C T 125C. All other limits apply for T J Symbol Parameter CURRENT SENSE AMPLIFIER Current Sense Offset DIGITAL-TO-ANALOG CONVERTER (DAC) Resolution Monotonicity Total Unadjusted Error Propagation Delay I DAC ...

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Typical Performance Characteristics RDS(ON) vs Temperature RDS(ON) vs Supply Voltage Supply Current vs Supply Voltage RDS(ON) vs Load Current 01187829 01187831 01187833 5 01187830 Current Sense Output vs Load Current 01187832 Supply Current vs Temperature 01187834 www.national.com ...

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Functional Descriptions TYPICAL OPERATION OF A CHOPPER AMPLIFIER Chopper amplifiers employ feedback driven switching of a power bridge to control and limit current in the winding of a motor (Figure 1). The bridge consists of four solid state power switches ...

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Functional Descriptions (a) 01187803 (b) 01187804 (e) 01187807 (f) 01187808 FIGURE 1. Chopper Amplifier Chopping States: Full V and (e), Winding Current Decays During a Change in the Direction of the Winding Current (c) and (f), and the (Continued) Applied ...

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Functional Descriptions THE LMD18245 CHOPPER AMPLIFIER The LMD18245 incorporates all the circuit blocks needed to implement a fixed off-time chopper amplifier. These blocks include: an all DMOS, full H-bridge with clamp diodes, an amplifier for sensing the load current, a ...

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Functional Descriptions (Continued) 01187810 01187811 FIGURE 2. The DMOS H-Bridge 9 www.national.com ...

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Functional Descriptions FIGURE 3. Decay Paths for Initial Winding Current During a Change in the Direction of the Winding Current THE CURRENT SENSE AMPLIFIER Many transistor cells in parallel make up the DMOS power switches. The current sense amplifier (Figure ...

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Functional Descriptions THE DIGITAL-TO-ANALOG CONVERTER (DAC) The DAC sets the threshold voltage for chopping D/16, where D is the decimal equivalent (015) DAC REF of the binary number applied at M4 through M1, the digital inputs of ...

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Applications Information POWER SUPPLY BYPASSING Step changes in current drawn from the power supply occur repeatedly during normal operation and may cause large voltage spikes across inductance in the power supply line. Care must be taken to limit voltage spikes ...

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The Typical Application Figure 7 shows the typical application, the power stage of a chopper drive for bipolar stepper motors. The 20 k and 2.2 nF capacitor connected between RC and ground set the off-time at about 48 µs, and ...

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The Typical Application wave drive. The motor takes one full step at each change of direction of either winding current. Figure 9 shows the wind- Top Trace: Phase A Winding Current at 1A/div Bottom Trace: Phase B Winding Current at ...

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The Typical Application Top Trace: Phase A Winding Current at 1A/div Bottom Trace: Phase B Winding Current at 1A/div Horizontal: 1 ms/div 500 steps/second M4 A through through BRAKE A ...

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The Typical Application HALF STEP DRIVE WITHOUT TORQUE COMPENSATION To make the motor take half steps, windings A and B can be energized in the sequence AB A AB B AB A The motor takes one half ...

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The Typical Application HALF STEP DRIVE WITH TORQUE COMPENSATION To make the motor take half steps, the windings can also be energized with sinusoidal currents (Figure 12). Controlling the winding currents in the fashion shown doubles the step resolution without ...

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The Typical Application cos 0 FORWARD 45 90 135 180 225 REVERSE 270 315 REPEAT FIGURE 13. Lookup Table for Half Step Drive with Torque Compensation www.national.com (Continued DIRECTION 0.707 11 ...

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The Typical Application QUARTER STEP DRIVE WITH TORQUE COMPENSATION Figure 14 shows the winding currents and lookup table for a quarter step drive (four microsteps per full step) with torque compensation. Top Trace: Phase A Winding Current at 1A/div Bottom ...

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Test Circuit and Switching Time Definitions www.national.com 01187828 20 ...

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... BANNED SUBSTANCE COMPLIANCE National Semiconductor manufactures products and uses packing materials that meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no Banned Substances as defined in CSP-9-111S2. ...

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