Page 694 - Mechatronics with Experiments

680 MECHATRONICS
current sense resistors for each phase (pins REF, SENSA, SENSB). The output stages
control the phase currents via terminals OUTA, OUTA∖, OUTB, OUTB∖ of the IC chip.
Notice that this IC drive is capable of controlling only FULL and HALF step modes and
does not support the microstepping mode. For driving step motors which will require power
dissipation more than 20 W, an external heat sink must be added to the FET power transistor
stage.

Example: Bipolar Integrated Circuit (IC) Drive for Step Motors The
LM18293 (by National Semiconductor) integrates two H-bridges on the chip with 1 A
continuous (2 A peak) current capacity per channel. Therefore, it can be used to drive a
two-phase bipolar step motor (Figure 8.56). It can also be used to drive two separate DC
brush motors bidirectionally. The maximum DC supply voltage is 36 V. A separate enable
pin (ENABLE1 and ENABLE2) controls one of the two H-bridges. If the ENABLE pins

Winding L2

V IN1

V IN2

Winding L2

FIGURE 8.56: Integrated circuit drive chip
(LM18293 by National Semiconductor) for
bipolar step motors or brush-type DC
motors. Source: Texas Instruments.