UDQ2936-120 Allegro MicroSystems, UDQ2936-120 Datasheet - Page 6

• Manufacturer Part Number: UDQ2936-120
• Description: 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
• Manufacturer: Allegro MicroSystems

logic and power outputs to drive three-phase brushless dc
motors.
ended linear or digital Hall-effect devices (HEDs). Internal
pull-up resistors allow for direct use with open-collector digital
HEDs. The H
120° electrical separation. At any one step in the logic sequenc-
ing, one half-bridge driver is sourcing current, one driver is
sinking current, and one driver is in a high-impedance state (see
Truth Table).
drivers and turns off the three source drivers, essentially
shorting the motor windings to ground. During braking, the
back-electromotive force generated by the motor produces a
current that dynamically brakes the motor. Depending upon the
rotational velocity of the motor, this current can approach the
locked rotor current level (which is limited only by the motor
winding resistance). During braking, the output current-
limiting circuitry is disabled and care should be taken to ensure
that the back-EMF generated brake current does not exceed the
maximum rating (3 A peak) of the sink drivers and ground
clamp diodes.
output states, thus reversing the direction of the motor. Chang-
ing the direction of a rotating motor produces a back-EMF
current similar to when braking the motor. The load current
should not be allowed to exceed the maximum rating (±3 A
peak) of the drivers.
2 µs prevents potentially destructive crossover currents that can
occur when changing direction or braking.
modulating the source drivers with a preset hysteresis format.
Load current through an external sense resistor (R
stantly monitored. When the current reaches the set trip point
(determined by an external reference voltage or internal
default), the source driver is disabled. Current recirculates
through the ground clamp diode, motor winding, and sink
driver. An internal constant-current sink reduces the trip point
(hysteresis). When the decaying current reaches this lower
threshold, the source driver is enabled again and the cycle
repeats.
2936
3-PHASE BRUSHLESS
DC MOTOR
CONTROLLER/DRIVER
The UDN2936W-120 power driver provides commutation
The UDN2936W-120 is designed to interface with single-
The commutation logic provides decoding for HEDs with
A logic low on the BRAKE pin turns on the three sink
Changing the logic level of the DIRECTION pin inverts the
An internally generated dead time (t
Motor current is internally controlled by pulse-width
-120
n
inputs have 2.5 V thresholds.
d
) of approximately
S
) is con-
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
or internal defaults can be used. With V
point is internally set at 300 mV with 7.5% hysteresis. Load
current is then determined by the equation:
and peak current are set with external resistors according to the
equations:
current. The chopping frequency is a function of circuit
parameters including load inductance, load resistance, supply
voltage, hysteresis, and switching speed of the drivers.
ing currents of up to ±2 A and startup currents to ±3 A (see
cautions above regarding braking and changing of motor
direction). Internal power ground-clamp and flyback diodes
protect the outputs from the voltage transients that occur when
switching inductive loads. All devices also feature thermal
protection circuitry. If the junction temperature reaches
+165°C, the thermal shutdown circuitry turns off all output
drivers. The outputs are re-enabled when the junction cools
down to approximately +140°C. This protection is only
intended to protect the device from failures due to excessive
junction temperature or loss of heat sinking and should not
imply that output short circuits are permitted.
wiring board should utilize a heavy ground plane. For optimum
performance, the drivers should be soldered directly into the
board. The power supply should be decoupled with an electro-
lytic capacitor (>10 µF) as close as possible to the device
supply pin (V
be easily replaced with a UDN2936W-120 by inserting an
inverter (two resistors and a 2N3904 or 2N2222) between the
H
the figure on the next page. If an extra inverter is available, be
certain that a pull-up for the Hall sensor is provided.
2
Hall sensor and pin 8 of the UDN2936W-120, as shown in
Thresholds and hysteresis can be set with external resistors,
With V
Percentage hysteresis is a fixed value independent of load
The UDN2936W-120 outputs are rated for normal operat-
As with all high-power integrated circuits, the printed
threshold voltage (V
THS
load trip current (I
BB
hysteresis percentage = R
< 3.0 V, the threshold, hysteresis percentage,
).
I
TRIP
THS
= 0.3 /R
) = V
TRIP
The original UDN2936W can
) = V
REF
S
H
THS
x R
THS
/50 V
T
> 3.0 V, the trip
/10 R
/(R
REF
H
S
+ R
T
)