UDQ2917 Allegro MicroSystems, UDQ2917 Datasheet - Page 4

• Manufacturer Part Number: UDQ2917
• Description: DUAL FULL-BRIDGE PWM MOTOR DRIVER
• Manufacturer: Allegro MicroSystems

to drive both windings of a bipolar stepper
motor. Output current is sensed and con-
trolled independently in each bridge by an
external sense resistor (R
parator, and monostable multivibrator.
increases in the motor winding and it is
sensed by the external sense resistor until the
sense voltage (V
at the comparator’s input:
ostable which turns off the source driver of
the bridge. The actual load current peak will
be slightly higher than the trip point (espe-
cially for low-inductance loads) because of
the internal logic and switching delays. This
delay (t
motor current will normally decay, circulating
through the ground clamp diode and sink
transistor. The source driver’s off time (and
therefore the magnitude of the current de-
crease) is determined by the monostable’s
external RC timing components, where t
R
200 pF to 500 pF.
winding current (the sense voltage) is again
allowed to rise to the comparator’s threshold.
This cycle repeats itself, maintaining the
average motor winding current at the desired
level.
prevent runaway current control when the
fixed off time (t
circuitry prevents the source driver from being
re-enabled until the load current has decayed
to below the I
T
2917
DUAL FULL-BRIDGE
PWM MOTOR DRIVER
C
The UDN2917EB dual bridge is designed
When the bridge is turned on, current
The comparator then triggers the mon-
When the source driver is re-enabled, the
Special circuitry has been included to
T
within the range of 20 kΩ to 100 kΩ and
d
) is typically 2 µs. After turn-off, the
TRIP
I
TRIP
off
) is set too short. This
SENSE
level.
= V
) reaches the level set
REF
S
/10 R
), internal com-
S
off
=
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
V
I
OUT
PHASE
0
+
–
R S
V
BB
BRIDGE ON
SOURCE OFF
ALL OFF
t
d
Dwg. EP-006-1
t
I
off
TRIP
Dwg. WM-003-1A