A2919(2010) 데이터 시트보기 (PDF) - Allegro MicroSystems
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A2919 Datasheet PDF : 8 Pages
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A2919
Dual Full-Bridge PWM Motor Driver
LOGIC CONTROL OF OUTPUT CURRENT
Two logic level inputs (l and I ) allow digital selection of
0
1
the motor winding current at 100%, 67%, 41%, or 0% of the
maximum level per the table. The 0% output current condition
turns off all drivers in the bridge and can be used as an output
enable function.
CURRENT-CONTROL TRUTH TABLE
l0
I1
Output Current
L
L
VREF/10 RS = 100% ITRIP
H
L
VREF/15 RS = 67% ITRIP
L
H
VREF/24.4 RS = 41% ITRIP
H
H
0
These logic level inputs greatly enhance the implementation of
μP-controlled drive formats.
During half-step operations, l and l allow the μP to control the
0
1
motor at a constant torque between all positions in an eight-step
sequence. This is accomplished by digitally selecting 100%
drive current when only one phase is on and 67% drive current
when two phases are on. Logic highs on both l0 and l1 turn off all
drivers to allow rapid current decay.
During quarter-step operation, I0 and I1 allow the μP to
control the motor position in a sixteen-step sequence. This is
accomplished by digitally selecting drive current as shown in the
table (for one quadrant of operation). Logic highs on both I and
0
I1 turn off all drivers to allow rapid current decay.
The logic control inputs can also be used to select a reduced
current level (and reduced power dissipation) for ‘hold’
conditions and/or increased current (and available torque) for
start-up conditions.
QUARTER-STEPPING CURRENT CONTROL
Phase 1
Current Level
Phase 2
Current Level
100%
0%
100%
41%
67%
67%
41%
100%
0%
100%
GENERAL
The PHASE input to each bridge determines the direction
motor winding current flows. An internally generated deadtime
(approximately 2 μs) prevents crossover currents that can occur
when switching the PHASE input.
All four drivers in the bridge output can be turned off between
steps (l0 = l1 ž 2.4 V) resulting in a fast current decay through
the internal output clamp and flyback diodes. The fast current
decay is desirable in half-step and high-speed applications. The
PHASE, l , and I inputs float high.
0
1
Varying the reference voltage (VREF) provides continuous control
of the peak load current for micro-stepping applications.
Thermal protection circuitry turns off all drivers when the
junction temperature reaches +170°C. It is only intended
to protect the device from failures due to excessive junction
temperature and should not imply that output short circuits are
permitted. The output drivers are re-enabled when the junction
temperature cools to +145°C.
The A2919 output drivers are optimized for low output
saturation voltages—less than 1.8 V total (source plus sink) at
500 mA. Under normal operating conditions, when combined
with the excellent thermal properties of the batwing package
design, this allows continuous operation of both bridges
simultaneously at 500 mA.
TRUTH TABLE
PHASE
H
L
OUTA
H
L
OUTB
L
H
Allegro MicroSystems, Inc.
5
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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