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LMD18245

www.ti.com

SNVS110E –APRIL 1998–REVISED APRIL 2013

LMD18245 3A, 55V DMOS Full-Bridge Motor Driver

Check for Samples: LMD18245

FEATURES

DESCRIPTION

The LMD18245 full-bridge power amplifier

• DMOS Power Stage Rated at 55V and 3A

incorporates all the circuit blocks required to drive

Continuous

and control current in a brushed type DC motor or

• Low R

DS(ON)

of Typically 0.3Ω per Power

one phase of a bipolar stepper motor. The multi-

Switch

technology process used to build the device

combines bipolar and CMOS control and protection

• Internal Clamp Diodes

circuitry with DMOS power switches on the same

• Low-loss Current Sensing Method

monolithic structure. The LMD18245 controls the

• Digital or Analog Control of Motor Current

motor current via a fixed off-time chopper technique.

• TTL and CMOS Compatible Inputs

An all DMOS H-bridge power stage delivers

• Thermal Shutdown (Outputs Off) at T

= 155°C

continuous output currents up to 3A (6A peak) at

supply voltages up to 55V. The DMOS power

• Overcurrent Protection

switches feature low R

DS(ON)

for high efficiency, and a

• No Shoot-Through Currents

diode intrinsic to the DMOS body structure eliminates

• 15-lead Package

the discrete diodes typically required to clamp bipolar

power stages.

APPLICATIONS

An innovative current sensing method eliminates the

• Full, Half and Microstep Stepper Motor Drives

power loss associated with a sense resistor in series

with the motor. A four-bit digital-to-analog converter

• Stepper Motor and Brushed DC Motor Servo

(DAC) provides a digital path for controlling the motor

Drives

current, and, by extension, simplifies implementation

• Automated Factory, Medical and Office

of full, half and microstep stepper motor drives. For

Equipment

higher resolution applications, an external DAC can

be used.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (30 pages)

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LMD18245 www.ti.com SNVS110E – APRIL 1998 – REVISED APRIL 2013 LMD18245 3A, 55V DMOS Full-Bridge Motor Driver Check for Samples: LMD18245 FEATURES 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.
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LMD18245 SNVS110E – APRIL 1998 – REVISED APRIL 2013 www.ti.com Functional Block and Connection Diagram 15-Lead TO-220 Power Package (NDL) Figure 1. Functional Block Diagram Connection Diagram Figure 2.
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LMD18245 www.ti.com SNVS110E – APRIL 1998 – REVISED APRIL 2013 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 DAC, the comparator triggers the monostable. Pin 3, RC: Monostable timing node. A parallel resistorcapacitor network connected between this node and ground sets the monostable timing pulse at about 1.1 RC seconds.
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LMD18245 SNVS110E – APRIL 1998 – REVISED APRIL 2013 www.ti.com These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.
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LMD18245 www.ti.com SNVS110E – APRIL 1998 – REVISED APRIL 2013 Electrical Characteristics (1) The following specifications apply for VCC = +42V, unless otherwise stated. Boldface limits apply over the operating temperature range, −40°C ≤ TJ ≤ +125°C. All other limits apply for TA = TJ = 25°C. Symbol ICC Parameter Quiescent Supply Current Conditions DAC REF = 0V, VCC = +20V Typical (2) Limit 8 (2) Units (Limits) mA 15 mA (max) 0.4 Ω (max) 0.6 Ω (max) 0.4 Ω (max) 0.6 Ω (max) 1.
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LMD18245 SNVS110E – APRIL 1998 – REVISED APRIL 2013 www.ti.com Electrical Characteristics (1) (continued) The following specifications apply for VCC = +42V, unless otherwise stated. Boldface limits apply over the operating temperature range, −40°C ≤ TJ ≤ +125°C. All other limits apply for TA = TJ = 25°C. Symbol Parameter Conditions Typical (2) Limit (2) Units (Limits) DIGITAL-TO-ANALOG CONVERTER (DAC) Resolution 4 Monotonicity 4 Bits (min) 0.25 LSB (max) 0.
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LMD18245 www.ti.com SNVS110E – APRIL 1998 – REVISED APRIL 2013 Typical Performance Characteristics RDS(ON) vs Temperature RDS(ON) vs Load Current Figure 3. Figure 4. RDS(ON) vs Supply Voltage Current Sense Output vs Load Current Figure 5. Figure 6. Supply Current vs Supply Voltage Supply Current vs Temperature Figure 7. Figure 8.
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LMD18245 SNVS110E – APRIL 1998 – REVISED APRIL 2013 www.ti.com 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 9). The bridge consists of four solid state power switches and four diodes connected in an H configuration. Control circuitry (not shown) monitors the winding current and compares it to a threshold.
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LMD18245 www.ti.com SNVS110E – APRIL 1998 – REVISED APRIL 2013 (e) (f) (g) Figure 9. Chopper Amplifier Chopping States: Full VCC Applied Across the Winding (a) and (d), Shorted Winding (b) and (e), Winding Current Decays During a Change in the Direction of the Winding Current (c) and (f), and the Chopped Winding Current (g) THE LMD18245 CHOPPER AMPLIFIER The LMD18245 incorporates all the circuit blocks needed to implement a fixed off-time chopper amplifier.
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LMD18245 SNVS110E – APRIL 1998 – REVISED APRIL 2013 www.ti.com During actual motor operation there are many variables that can effect the motor winding magnetic behavior and performance. Resonance, eddy currents, friction, motor loading, damping, temperature coefficients of the windings, are only a few. These are all issues that are beyond the scope of the this data sheet. Figure 10.
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LMD18245 www.ti.com SNVS110E – APRIL 1998 – REVISED APRIL 2013 Figure 11. 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 12 ) uses a small fraction of the cells of both upper switches to provide a unique, low-loss means for sensing the load current.
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LMD18245 SNVS110E – APRIL 1998 – REVISED APRIL 2013 www.ti.com THE DIGITAL-TO-ANALOG CONVERTER (DAC) The DAC sets the threshold voltage for chopping at VDAC REF × D/16, where D is the decimal equivalent (0–15) of the binary number applied at M4 through M1, the digital inputs of the DAC. M4 is the MSB or most significant bit. For applications that require higher resolution, an external DAC can drive the DAC REF input.
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LMD18245 www.ti.com SNVS110E – APRIL 1998 – REVISED APRIL 2013 Figure 12. The Source Switches of the Power Bridge and the Current Sense Amplifier 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 at VCC to less than the 60V Absolute Maximum Rating.
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LMD18245 SNVS110E – APRIL 1998 – REVISED APRIL 2013 www.ti.com THERMAL SHUTDOWN Internal circuitry senses the junction temperature near the power bridge and disables the bridge if the junction temperature exceeds about 155°C. When the junction temperature cools past the shutdown threshold (lowered by a slight hysteresis), the device automatically restarts. UNDERVOLTAGE LOCKOUT Internal circuitry disables the power bridge if the power supply voltage drops below a rough threshold between 8V and 5V.
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LMD18245 www.ti.com SNVS110E – APRIL 1998 – REVISED APRIL 2013 The Typical Application Figure 14 shows the typical application, the power stage of a chopper drive for bipolar stepper motors. The 20 kΩ resistor and 2.2 nF capacitor connected between RC and ground set the off-time at about 48 μs, and the 20 kΩ resistor connected between CS OUT and ground sets the gain at about 200 mA per volt of the threshold for chopping.
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LMD18245 SNVS110E – APRIL 1998 – REVISED APRIL 2013 www.ti.com ONE-PHASE-ON FULL STEP DRIVE (WAVE DRIVE) To make the motor take full steps, windings A and B can be energized in the sequence A→B→A*→B*→A→ …, where A represents winding A energized with current in one direction and A* represents winding A energized with current in the opposite direction. The motor takes one full step each time one winding is de-energized and the other is energized.
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LMD18245 www.ti.com SNVS110E – APRIL 1998 – REVISED APRIL 2013 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 1 2 3 4 1 1 2 3 4 1 DIRECTION A DIRECTION B M4 A, M3 A, M2 A, and M1 A M4 B, M3 B, M2 B, and M1 B FORWARD REVERSE BRAKE A = BRAKE B = 0 Figure 15.
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LMD18245 SNVS110E – APRIL 1998 – REVISED APRIL 2013 www.ti.com 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 1 2 3 4 1 1 2 3 4 1 DIRECTION A DIRECTION B FORWARD REVERSE M4 A through M1 A = M4 B through M1 B = 1 BRAKE A = BRAKE B = 0 Figure 16.
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LMD18245 www.ti.com SNVS110E – APRIL 1998 – REVISED APRIL 2013 Top Trace: Phase A Winding Current at 1A/div Bottom Trace: Phase A Sense Voltage at 5V/div Horizontal: 1 ms/div *500 steps/second Figure 17.
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LMD18245 SNVS110E – APRIL 1998 – REVISED APRIL 2013 www.ti.com 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 1 2 3 4 5 6 7 8 1 1 2 3 4 5 6 7 8 1 DIRECTION A DIRECTION B M4 A, M3 A, M2 A, and M1 A M4 B, M3 B, M2 B, and M1 B FORWARD REVERSE BRAKE A = BRAKE B = 0 Figure 18.
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LMD18245 www.ti.com SNVS110E – APRIL 1998 – REVISED APRIL 2013 HALF STEP DRIVE WITH TORQUE COMPENSATION To make the motor take half steps, the windings can also be energized with sinusoidal currents (Figure 19). Controlling the winding currents in the fashion shown doubles the step resolution without the significant torque ripple of the prior drive technique. The motor takes one half step each time the level of either winding current changes.
PAGE 22
LMD18245 SNVS110E – APRIL 1998 – REVISED APRIL 2013 www.ti.com Top Trace: Phase A Winding Current at 1A/div Bottom Trace: Phase B Winding Current at 1A/div Horizontal: 2 ms/div *500 steps/second 1 2 3 4 5 6 7 8 1 1 2 3 4 5 6 7 8 1 DIRECTION A DIRECTION B M4 A, M2 A, M1 A, and M3 B M4 B, M2 B, M1 B, and M3 A FORWARD REVERSE BRAKE A = BRAKE B = 0 90° ELECTRICAL/FULL STEP ÷ 2 MICROSTEPS/FULL STEP = 45° ELECTRICAL/MICROSTEP Figure 19.
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LMD18245 www.ti.com SNVS110E – APRIL 1998 – REVISED APRIL 2013 Table 2. Lookup Table for Half Step Drive with Torque Compensation α |cos(α)| DA DIRECTION A |sin(α)| DB DIRECTlON B | 0° 1 15 1 0 0 1 FORWARD 45° 0.707 11 1 0.707 11 1 ↓ 90° 0 0 0 1 15 1 135° 0.707 11 0 0.707 11 1 180° 1 15 0 0 0 0 ↑ 225° 0.707 11 0 0.707 11 0 REVERSE 270° 0 0 1 1 15 0 | 315° 0.707 11 1 0.
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LMD18245 SNVS110E – APRIL 1998 – REVISED APRIL 2013 www.ti.com Table 3. Lookup Table for Quarter Step Drive with Torque Compensation (1) α |cos(α)| DA DIRECTION A |sin(α)| DB DIRECTION B | 0.0° 1 15 1 0 0 1 FORWARD 22.5° 0.924 14 1 0.383 6 1 ↓ 45.0° 0.707 11 1 0.707 11 1 67.5° 0.383 6 1 0.924 14 1 90.0° 0 0 0 1 15 1 112.5° 0.383 6 0 0.924 14 1 135.0° 0.707 11 0 0.707 11 1 157.5° 0.924 14 0 0.383 6 1 180.0° 1 15 0 0 0 0 202.5° 0.
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LMD18245 www.ti.
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LMD18245 SNVS110E – APRIL 1998 – REVISED APRIL 2013 www.ti.com REVISION HISTORY Changes from Revision D (April 2013) to Revision E • 26 Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
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MECHANICAL DATA NDL0015A TA15A (Rev B) www.ti.
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