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 structure. The LMD18245 controls the
motor current via a fixed off-time chopper technique.
An all DMOS H-bridge power stage delivers continuous output currents up to 3A (6A peak)
at supply voltages up to 55V. The DMOS power switches feature low RDS(ON)
for high 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.
