Absolute Maximum Ratings
Load Supply Voltage, V
BB
. . . . . . . . . . . . 15 V
Output Current
1
, I
OUT
. . . . . . . . . . . . . . . . . . . . . ±1.4 A
Peak Output Current (Brake)
2
, I
OUT(BRK)
. ±3.0 A
Period
2
for I
OUT(BRK)
to fall from
±3.0 A to ±1.4 A . . . . . . . . . . . . . . . 800 ms
Logic Supply Voltage, V
DD
. . . . . . . . . . . 7.0 V
Logic Input Voltage Range, V
IN
(continuous) . . . . . . -0.3 V to V
DD
+ 0.3 V
(t
w
<30 ns) . . . . . . . -1.0 V to V
DD
+ 1.0 V
Package Power Dissipation, P
D
. . See Graph
Operating Temperature, T
A
. . . -20°C to +85°C
Junction Temperature
3
, T
J
. . . . . . . . . +150°C
Storage Temperature,T
S
. . . . -55°C to +150°C
1
Output current rating may be restricted to a value
determined by system concerns and factors. These
include: system duty cycle and timing, ambient
temperature, and use of any heatsinking and/or forced
cooling. For reliable operation, the specified maximum
junction temperature should not be exceeded.
2
Peak output current is a transient condition that
occurs during braking when the motor acts as a
generator. The 3 A level is based on the maximum
peak of a sine wave that is damped. The maximum
period between the initial brake being applied and the
current through the drivers falling to 1.4 A should not
exceed 800 ms. See Braking section for more
information.
3
Fault conditions that produce excessive junction
temperature will activate device thermal shutdown
circuitry. These conditions can be tolerated, but should
be avoided.
Data Sheet
26301.5B
The A8904SLB and A8904SLP are three-phase brushless dc motor
controller/drivers designed for applications where accurate control of high-
speed motors is required. The three half-bridge outputs are low on-resistance
n-channel DMOS devices capable of driving up to 1.2 A. The A8904 provides
complete, reliable, self-contained back-EMF sensing, motor startup and
running algorithms. A programmable digital frequency-locked loop speed
control circuit together with the linear current control circuitry provides
precise motor speed regulation.
A serial port allows the user to program various features and modes of
operation, such as the speed control parameters, startup current limit, sleep
mode, direction, and diagnostic modes.
The A8904 is fabricated in Allegro’s BCD (Bipolar CMOS DMOS)
process, an advanced mixed-signal technology that combines bipolar, analog
and digital CMOS, and DMOS power devices. The A8904SLB is provided in
a 24-lead wide-body SOIC batwing package. The A8904SLP is provided in a
thin (<1.2 mm), 28-lead SSOP package with an exposed thermal pad. Each
package type is available in a lead-free version (100% matte tin leadframe).
Features
„ Pin-for-pin replacement for A8902CLBA
„ Startup commutation circuitry
„ Sensorless commutation circuitry
„ Option of external sector data tachometer signal
„ Option of external speed control
„ Oscillator operation up to 20 MHz
„ Programmable overcurrent limit
„ Transconductance gain options: 500 mA/V or 250 mA/V
„ Programmable watchdog timer
„ Directional control
„ Serial Port Interface
„ TTL-compatible inputs
„ System diagnostics data out ported in real time
„ Dynamic braking through serial port or external terminal
3-PHASE BRUSHLESS DC MOTOR
CONTROLLER/DRIVER WITH BACK-EMF SENSING
8904
A8904SLB (SOIC)
Always order by complete part number:
Part Number Package
A8904SLB 24-pin batwing SOIC
A8904SLB-T 24-pin batwing SOIC; Lead-free
A8904SLP 28-pin SSOP with Exposed Thermal Pad
A8904SLP-T 24-pin SSOP with Exposed Thermal Pad; Lead-free