A3966SLBTR-T Allegro, A3966SLBTR-T Datasheet - Page 6

• Manufacturer Part Number: A3966SLBTR-T
• Manufacturer: Allegro

6
Load Current Regulation. Due to internal logic and
switching delays (t
slightly higher than the I
blanking time, limit the minimum value the current control
circuitry can regulate. To produce zero current in a
winding, the ENABLE terminal should be held high,
turning off all output drivers for that H-bridge.
Logic Inputs. A logic high on the PHASE input results
in current flowing from OUT
A logic low on the PHASE input results in current flowing
from OUT
(t
spikes that can occur when switching the PHASE input.
output drivers of that H-bridge. This results in a fast
current decay through the internal ground clamp and
flyback diodes. A logic low on the ENABLE input turns
on the selected source and sink driver of that H-bridge.
applications that require a fast current-decay PWM. If
external current-sensing circuitry is used, the internal
current-control logic can be disabled by connecting the
R
resistor divider from V
internally divided down by 4 to set up the current-com-
parator trip-voltage threshold. The reference input voltage
range is 0 to 2 V.
Output Drivers. To minimize on-chip power dissipation,
the sink drivers incorporate a Satlington structure. The
Satlington output combines the low V
saturated transistor and the high peak-current capability of
a Darlington (connected) transistor. A graph showing
typical output saturation voltages as a function of output
current is on the next page.
codt
T
3966
DUAL FULL-BRIDGE
PWM MOTOR DRIVER
C
A logic high on the ENABLE input turns off all four
The ENABLE inputs can be pulse-width modulated for
The REFERENCE input voltage is typically set with a
T
) of approximately 1 µs prevents cross-over current
terminal to ground.
B
to OUT
d
), the actual load current peak will be
A
. An internally generated dead time
CC
TRIP
. This reference voltage is
value. These delays, plus the
A
to OUT
FUNCTIONAL DESCRIPTION (continued)
CE(sat)
B
of that H-bridge.
features of a
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
Miscellaneous Information. Thermal protection
circuitry turns off all output drivers should the junction
temperature reach +165 °C (typical). This is intended
only to protect the device from failures due to excessive
junction temperatures and should not imply that output
short circuits are permitted. Normal operation is resumed
when the junction temperature has decreased about 15°C.
quency, variable duty cycle PWM technique. As a result,
the current-control regulation may become unstable if the
duty cycle exceeds 50%.
ground trace I
should have a separate return to the ground terminal of
the device. For low-value sense resistors, the I x R drops
in the printed-wiring board can be significant and should
be taken into account. The use of sockets should be
avoided as their contact resistance can cause variations in
the effective value of R
decoupled with an electrolytic capacitor (47 µF recom-
mended) placed as close to the device as physically
practical. To minimize the effect of system ground I x R
drops on the logic and reference input signals, the system
ground should have a low-resistance return to the load
supply voltage.
the amount of ripple current. A lower frequency will
result in higher current ripple, but reduced heating in the
motor and driver IC due to a corresponding decrease in
hysteretic core losses and switching losses respectively.
A higher frequency will reduce ripple current, but will
increase switching losses and EMI.
The A3966 current control employs a fixed-fre-
To minimize current-sensing inaccuracies caused by
The LOAD SUPPLY terminal, V
The frequency of the clock oscillator will determine
R
drops, each current-sensing resistor
S
.
BB
, should be