UDQ2916B-T ALLEGRO [Allegro MicroSystems], UDQ2916B-T Datasheet - Page 5

• Manufacturer Part Number: UDQ2916B-T
• Description: DUAL FULL-BRIDGE PWM MOTOR DRIVER
• Manufacturer: ALLEGRO [Allegro MicroSystems]

5
a ect the ability to properly regulate the current when
PWM CURRENT CONTROL
drive both windings of a bipolar stepper motor. Output
current is sensed and controlled independently in each
bridge by an external sense resistor (R
parator, and monostable multivibrator.
the motor winding and it is sensed by the external sense
resistor until the sense voltage (V
set at the comparator’s input:
turns OFF the source driver of the bridge. The actual
load current peak will be slightly higher than the trip point
(especially for low-inductance loads) because of the
internal logic and switching delays. This delay (t
typically 2 µs. After turn-o , the motor current decays,
circulating through the ground-clamp diode and sink
transistor. The source driver’s OFF time (and therefore
the magnitude of the current decrease) is determined by
the monostable’s external RC timing components, where
t = R
100 pF to 1000 pF.
the current chopping above the audible range (< 46 µs)
and long enough to properly regulate the current. Be-
cause only slow-decay current control is available, short
o times (< 10 µs) require additional e orts to ensure
proper current regulation. Factors that can negatively
using short o times include: higher motor-supply volt-
age, light load, and longer than necessary blank time.
current (the sense voltage) is again allowed to rise to the
comparator’s threshold. This cycle repeats itself, main-
taining the average motor winding current at the desired
level.
result in high turn-ON current peaks. This peak (appear-
ing across R
ing in erroneous current control or high-frequency
oscillations. An external R
to further delay the action of the comparator. Depending
on load type, many applications will not require these
external components (SENSE connected to E).
o
2916
DUALFULL -BRIDGE
MOTORDRIVER
The xed-o time should be short enough to keep
The UDN2916B/EB/LB dual bridges are designed to
When the bridge is turned ON, current increases in
The comparator then triggers the monostable which
When the source driver is re-enabled, the winding
Loads with high distributed capaci-tances may
T
C
T
within the range of 20 k Ω to 100 k Ω and
S
I
) will attempt to trip the comparator, result-
TRIP
= V
REF
/ 10 R
C
C
S
C
time delay should be used
SENSE
) reaches the level
S
), internal com-
APPLICATIONS INFORMATION
d
) is
115 Northeast
Worcester, Massachusetts 01615-0036 [phone]
V
I
OUT
P HAS E
Box 15036
0
+
–
PWM OUTPUT CURRENT WAVE FORM
LOAD CURRENT PATHS
R S
t
d
V
B B
B R IDG E ON
S OUR C E OF F
ALL OF F
t
I
o
T R IP
Dwg. E P -006-1
Dwg. WM-003-1A