Texas Instruments LMD18245T

Overview

LMD18245T from Texas Instruments is a 3A, 55V DMOS full-bridge motor driver IC designed to control brushed DC and bipolar stepper motor phases via fixed off-time current chopping. It integrates an all-DMOS H-bridge (R_DS(ON) = 0.3 Ω typ), internal clamp diodes, low-loss current sensing (250 μA/A), digital/analog current control, and thermal shutdown at 155°C. Used in precision motion control for automated factory equipment.

For engineers reviewing the LMD18245T datasheet, LMD18245T pinout, LMD18245T application, or LMD18245T equivalent, this page delivers verified technical context, real-world design meaning of key specs, validated pin functions, application-specific implementation insights, and two confirmed alternative parts with documented functional and selection differences.

Technical Context

The LMD18245T implements a fixed off-time chopper architecture where motor current is regulated by comparing the CS OUT voltage (proportional to forward load current) against a DAC-generated threshold. The monostable (RC-timed) triggers sink-switch turn-off for precise off-time control, enabling microstep-capable current regulation without external sense resistors.

Its monolithic DMOS H-bridge includes intrinsic body diodes eliminating external clamping diodes, while TTL/CMOS-compatible logic inputs (BRAKE, DIRECTION, M4–M1) directly interface with microcontrollers. Protection features include overcurrent shutdown (12A threshold), undervoltage lockout (5–8V), and thermal shutdown (155°C) with automatic restart.

Key Specifications

Pinout & Package

15-lead TO-220 Power Package (NDL0015A) with integral metal tab electrically connected to PGND (Pin 5) for low-impedance thermal and power grounding.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar full-bridge motor driver applications.

Compared with TB6612FNG and VNH7040AS, the LMD18245T uniquely integrates a 55V/3A DMOS H-bridge, 4-bit DAC, and current-sense amplifier in a single TO-220 package-enabling self-contained chopper operation without external sense resistors or controller firmware for current regulation.

Availability

LMD18245T is available at Aetrix Electronics and suitable for automated factory equipment, medical imaging stages, and office automation systems requiring stable component supply across long production lifecycles.

Supply support for LMD18245T includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and high-reliability power management solutions for industrial, automotive, and medical markets.

The LMD18245T belongs to TI's legacy motor driver product line, engineered specifically for high-voltage, high-current brushed and bipolar stepper motor control with integrated current regulation and robust protection.

FAQ

What is the maximum continuous output current rating for the LMD18245T?

The LMD18245T is rated for 3A continuous output current at TJ ≤125°C with adequate heatsinking. This rating assumes proper PCB copper area (≥1 in² of 1 oz copper), TO-220 tab soldered to PGND, and VCC bypassing per datasheet guidelines. Peak current capability reaches 6A for pulses <2 ms and duty cycles <5%, but sustained operation above 3A requires active thermal management to avoid triggering thermal shutdown at 155°C.

How does the LMD18245T implement current sensing without an external sense resistor?

The LMD18245T uses a built-in current mirror architecture where a small fraction (1:4000) of the DMOS upper switch cells routes current to the CS OUT pin, sourcing 250 μA per ampere of forward load current. This eliminates power loss and PCB space associated with external shunt resistors. The CS OUT signal feeds the internal comparator to trigger chopping, and its voltage develops across an external resistor (e.g., 4 kΩ) to set gain - enabling precise, lossless current regulation.

Can the LMD18245T be used for microstepping applications?

Yes, the LMD18245T supports microstepping via its 4-bit DAC (M4–M1 inputs), which sets 16 discrete current thresholds. When paired with external timing control or a microcontroller managing DIRECTION and BRAKE states, it enables full-step, half-step, and microstep waveforms for bipolar stepper motors. For higher resolution than 4-bit, an external DAC can drive the DAC REF pin - extending programmability beyond 16 levels while retaining the LMD18245T's integrated H-bridge and sensing.

What protection features are built into the LMD18245T?

The LMD18245T includes overcurrent protection (shuts down source switches at ~12A fault current), thermal shutdown (disables outputs at TJ ≈155°C with hysteresis), undervoltage lockout (disables bridge below ~5–8V), and shoot-through prevention via asymmetric switching delays (≥40ns dead time). It also features internal clamp diodes using DMOS body diodes, eliminating external flyback diodes and reducing voltage spikes during inductive load switching.

What is the recommended power supply bypassing strategy for the LMD18245T?

Texas Instruments specifies mandatory bypassing at the VCC pin: a 1 μF ceramic capacitor (X7R, low-ESL) placed within 12 mm of VCC, plus a bulk aluminum electrolytic capacitor (100 μF per ampere of load current, e.g., 300 μF for 3A) located nearby. Both capacitors must have short leads and low-inductance layout to suppress voltage spikes caused by rapid current transients - especially during BRAKE activation or direction reversal - preventing VCC overshoot beyond the 60V absolute maximum rating.