Datasheet

MTS62C19A
DS22260C-page 8  2010-2013 Microchip Technology Inc.
3.0 FUNCTIONAL DESCRIPTION
The circuit is designed to drive the two windings of a
bipolar stepper motor, and can be divided in two identi-
cal channels (channel 1 and channel 2) and protection
circuitry for overtemperature and undervoltage. The
functionality of a channel and protection circuitry is
presented in the following sections.
3.1 Power Bridge Operation
Each motor winding is driven by an H-type bridge
consisting of two N and two P transistors that allow the
current to flow in both winding directions depending on
the value of the PHASE signal (Table 3-1). The
H-bridge can be set in five configurations that are
related to the digital inputs PHASE, I0 and I1 and to the
current sensed. These configurations are shown in
Table 3-2.
FIGURE 3-1: Power Bridge Control (PHASE = H/forward).
Legend: a) Bridge ON, b) Source OFF, c) All OFF/Coasting
Note: For PHASE = L/Reverse, invert A and B in drawings.
V
LOAD
Pb
Pa
H
H
L
L
Nb
Na
SENSE
OUTA
OUTB
V
LOAD
Pb
Pa
H
H
L
L
Nb
Na
SENSE
OUTA
OUTB
V
LOAD
Pb
Pa
H
H
L
L
Nb
Na
SENSE
OUTA
OUTB
R
S
R
S
R
S
a)
b)
c)
TABLE 3-1: CURRENT DIRECTION CONTROL
Phase Output Current
L Current flows from OUTxB to OUTxA
H Current flows from OUTxA to OUTxB
TABLE 3-2: POWER BRIDGE GATE CONTROL TRUTH TABLE
I0I1 PHASE Overi T
OFF
Case/Mode gna gpa gnb gpb
00/01/10 1 0 0 Forward ON L LHH
00/01/10 1 x 1 Forward OFF L H H H
00/01/10 0 0 0 Reverse ON H HLL
00/01/10 0 x 1 Reverse OFF H HLH
11 x x x No Current/
Coasting
LHLH
Legend: Bold = Active MOS Transistors, Overi = Overcurrent flag, T
OFF
= Channel T
OFF
State Flag