8925
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
8925
AND POWER DMOS OUTPUTS
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
AND POWER DMOS OUTPUTS
Data Sheet
26301.30
The A8925CEB is a DMOS three-phase brushless dc motor controller/driver designed for use in Winchester disk drives and other data
storage applications. The power output stages are capable of ±4 A
output currents and have DMOS power outputs with less than 0.25 Ω
r
for low power dissipation. Intrinsic ground clamp and flyback
DS(on)
diodes protect the output drivers when switching inductive loads.
Thermal shutdown circuitry is provided to protect the device from excessive junction temperature.
A transconductance amplifier is used to linearly regulate the load
current and control motor speed. Internal current-sensing circuitry
eliminates the need for external sense resistors. Analog and digital
control circuitry provide complete sequencing of the output drivers as
well as providing brake, disable, and tachometer functions. A FAULT
output flag indicates the presence of an under-voltage condition on the
12 V supply, excessive junction temperature, or an invalid Hall input
combination. The A8925CEB’s commutation logic is compatible with
motors that have digital Hall-effect sensors with 120° of electrical
separation. Internal charge pump circuitry is provided to drive the N-
POWER
GROUND
POWER
GROUND
C
NC
ENABLE
OUT
5
6
4
7
8
9
10
11
12
CHARGE PUMPS
13
14
15
16
17
SUB
18
SENSE
V
19
COMP.
+
20
REFERENCE
LOGIC GROUND
LOGIC SUPPLY
2
3
CC
V
BB
V
22
21
ERROR AMP
LOAD SUPPLY
B
OUT
1
23
BRAKE
POLE
44
43
SEQUENCING
AND CONTROL
25
24
1
H
TACH
CIRCUITRY
NC
A
OUT
NC
424140
27
26
2
NC
H
FAULT
39
38
37
36
35
34
33
32
31
30
29
SUB
28
3
H
Dwg. PP-034
POWER
GROUND
POWER
GROUND
channel DMOS source drivers to their required gate voltages.
ABSOLUTE MAXIMUM RATINGS
AT T
= +25°C
A
Load Supply Voltage, VBB.....................14 V
Output Current, I
Logic Supply Voltage, V
.......................... ±4.0 A
OUT
.....................14 V
CC
Logic Input Voltage Range,
V
................................ -0.3 V to +6.0 V
IN
Package Power Dissipation,
P
......................................... See Graph
D
Operating Temperature Range,
T
..................................... 0°C to +70°C
A
Junction Temperature, T
...............+150°C†
J
Storage Temperature Range,
T
................................ -55°C to +150°C
S
† Fault conditions that produce excessive
DISCONTINUED PRODUCT
junction temperature will activate device thermal
shutdown circuitry. These conditions can be
tolerated, but should be avoided.
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.
— FOR REFERENCE ONLY
The A8925CEB is provided in a 44-lead PLCC power package for
surface-mount applications. The copper batwing provides for maximum allowable package power dissipation in the smallest possible
construction.
FEATURES
■ DMOS Outputs
■ Low r
■ Linear Current Control
■ Internal Commutation Circuitry
■ Internal Current Sensing
■ Thermal Shutdown Circuitry
■ Under Voltage Detection Circuitry
■ Fault Output Flag
■ Power Surface-Mount Package
Always order by complete part number: A8925CEB .
- 0.25 Ω Maximum
DS(on)
8925
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
AND POWER DMOS OUTPUTS
12.5
10
7.5
5.0
2.5
0
ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS
25
ELECTRICAL CHARACTERISTICS AT T
50 75 100 125 150
= +25°C, V
A
R = 6°C/W
θJT
R = 30°C/W
θJA
TEMPERATURE IN °C
CC
= V
Dwg. GP-020B
BB =
12 V
Limits
Characteristic Symbol Test Conditions Min. Typ. Max. Units
Logic Supply Voltage V
Load Supply Voltage V
Supply Current I
Thermal Shutdown T
CC
BB
CC
J
Operating 10 12 14 V
Operating 10 12 14 V
Operating — 30 50 mA
V
= 0 V — 2.0 4.0 mA
ENABLE
— 165 — °C
Output Drivers
Output ON Resistance r
Output Sustaining Voltage V
DS(on)
DS(sus)
Clamp Diode Forward Voltage V
Output Leakage Current I
F
DSX
I
= ±4.0 A, Pulse Test — 0.20 0.25 Ω
OUT
I
= 4.0 A, L = 2 mH 14 —— V
OUT
IF = ±4.0 A — 1.5 2.0 V
V
= 14 V — 10 300 µA
OUT
= 0 V — -10 -300 µA
V
OUT
Control Logic
Logic Input Voltage V
Logic Input Voltage V
Logic Input Current I
V
V
I
IN(0)
IN(1)
IN(0)
IN(1)
IN(0)
IN(1)
ENABLE, POLE ——0.8 V
2.4 ——V
BRAKE ——0.8 V
3.0 ——V
VIN = 0.8 V ——-1.0 µA
VIN = 2.4 V ——1.0 µA
NOTE: Negative current is defined as coming out of (sourcing) the specified device terminal. Continued next page...
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 1990, 1995 Allegro MicroSystems, Inc.
8925
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
AND POWER DMOS OUTPUTS
ELECTRICAL CHARACTERISTICS CONTINUED
Limits
Characteristic Symbol Test Conditions Min. Typ. Max. Units
Logic Output Voltage V
(FAULT, TACH)
OUT(0)
V
OUT(1)
Error Amplifier
Input Bias Current I
Input Offset Voltage V
Input Common-Mode Voltage Range V
Error Voltage Gain A
Unity Gain Bandwidth BW — 1.0 — MHz
Common-Mode Rejection Ratio CMRR — 80 — dB
Power Supply Rejection Ratio PSRR — 50 — dB
IB
OS
IC
VD
Miscellaneous
Current Sense Gain A
Current-Sense Matching — I
Under-Voltage Trip Point V
Hall Input Current I
Hall Input Threshold V
Hall Input Pull-Up Resistance R
IN(0)
I
IN(1)
iCS
CC
IN
PU
I
= 3 mA ——0.8 V
OUT
I
= -50 µA 2.0 ——V
OUT
VCM = 0.01 V — 5.0 10 µA
VCM = 1.0 V — 3.0 5.0 mV
0.01 — 6.0 V
V
/ V
, V
= 1.0 V — 80 — dB
CM
I
OUT
OUT
S OUT
S IN
= -1.0 A 1/1k 1/1.2k 1/1.4k —
= -1.0 A — ±3.0 ±5.0 %
8.0 — 9.5 V
VIN = 0 V — -500 -1000 µA
VIN = 5.0 V — -250 -500 µA
— 3.8 — V
— 25 — kΩ
NOTE: Negative current is defined as coming out of (sourcing) the specified device terminal.
COMMUTATION TRUTH TABLE
Hall Sensor Inputs Outputs
H
1
High Low High High High High High Low Z
High Low Low High High High High Z Low
High High Low High High High Z High Low
Low High Low High High High Low High Z
Low High High High High High Low Z High
Low Low High High High High Z Low High
High High High High High Low Z Z Z
Low Low Low High High Low Z Z Z
X X X Low High X Z Z Z
XXXXLowXLowLowLow
X = Irrelevant
Z = High Impedance
H
2
H
ENABLE BRAKE FAULT OUT
3
OUTBOUT
A
C
8925
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
AND POWER DMOS OUTPUTS
TERMINAL FUNCTIONS
Term. Terminal Name Function
1 OUT
B
2 LOGIC SUPPLY VCC; low-current 12 V supply for the logic.
3 LOGIC GROUND Low-level logic ground.
4 OUT
C
6 ENABLE Active high chip enable.
7–17 POWER GROUND Power ground and thermal heat sink.
18 V
SENSE
19 COMP. Compensation; error amplifier output.
20 REFERENCE V
21 ERROR AMP. Input that controls the current in the load.
22 LOAD SUPPLY VBB; high-current 12 V supply for the voice-coil motor.
23 BRAKE A logic low turns OFF all source drivers and turns ON all sink drivers (shorts the windings to
24 H
26 H
28 H
1
2
3
29–39 POWER GROUND Power ground and thermal heat sink.
40 FAULT A logic low at this output indicates a thermal shutdown, under -voltage fault, or an invalid Hall
42 OUT
A
43 TACH Speed reference output; the H1 Hall input divided by the number of motor poles.
44 POLE Designates four- or eight-pole motor; Low = 4 pole, High = 8 pole.
Power DMOS output.
Power DMOS output.
External precision resistor for sense-FET current.
; voltage input that sets the power output current.
REF
ground).
High-level input from a Hall sensor.
High-level input from a Hall sensor.
High-level input from a Hall sensor.
input combination.
Power DMOS output.
V
SENSE
FUNCTIONAL DESCRIPTION
V
BB
CHARGE
SENSE
AMPLIFIER
I .
OUT
1200
R
3
R
S
REF
1
R
2
R
V
_
-
+
+
ERROR
AMPLIFIER
C
1
COMP.
PUMP
SEQUENTIAL
LOGIC
C
2
OUT
OUT
V
SUB
Dwg. EP-040
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Power Outputs (OUTA, OUTB, and
OUTC). The power outputs of the A8925CEB
are DMOS transistors with a maximum r
DS(on)
of 0.25 Ω. Intrinsic ground clamp and flyback
diodes clamp transient voltage spikes when
switching inductive loads. Internal charge
pump circuitry is used to drive the gates of
the N-channel source drivers to their required
gate voltages.
Current Control. Current in the load is
monitored by an internal sense amplifier that
produces an output current that is approximately one twelve hundredth that of the load
current (see Figure). This current is output to
the V
terminal and develops a voltage
SENSE
Continued next page...
8925
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
AND POWER DMOS OUTPUTS
across RS that equals RS • I
sense voltage (V
erence voltage (V
developed that is gated in by the sequential
control logic to drive the gate of the appropriate output sink transistor. A
transconductance control function is thus realized where I
components C1, C2, R1, R2, and R3 are compensation components used to obtain optimal
response and settling of the current control
loop. Information on how to select these
components is available.
FAULT. The FAULT terminal when low
indicates the presence of one of three fault
conditions:
A) An under-voltage condition
B) An invalid Hall input combi-
C) An excessive device
OUT
on the logic supply. The
trip point for this function is
between 8 and 9.5 volts.
nation … all inputs High or
all inputs Low.
junction temperature. The
thermal shutdown circuitry
disables the output drivers
in addition to forcing the
FAULT output signal low.
) is compared to a ref-
SENSE
) and an error voltage is
REF
= V
• 1200/RS. External
REF
/1200. This
LOAD
HALL INPUTS (H1, H2, H3). The A8925CEB is configured for use
with open-collector Hall-effect devices. Internal 25 kΩ pull up resistors
to 10 volts are connected to these inputs.
ENABLE. The ENABLE terminal when Low puts the device in a
low current consumption, power-down mode. When ENABLE is High
the device is active.
BRAKE. When the BRAKE input goes Low the output source drivers are disabled and the gates of the sink drivers are pulled high and
left floating. This achieves optimum passive braking performance
since the sink power DMOS output drivers are ON until the motor has
fully completed braking. The braking control circuitry operates off the
load supply (VBB) to allow it to remain operational during power loss by
using the back-EMF voltage of the motor as it’s supply.
LOAD SUPPLY (VBB). This terminal is the power supply connection for the power output drivers and braking control circuitry. This terminal should be decoupled with a large-value capacitor to absorb load
currents dumped back into the supply during the de-energization of
motor windings. These currents can cause the supply voltage to exceed the maximum voltage rating of the device if not properly
decoupled. The intrinsic ground clamp and flyback diodes will rectify
the motor’s back-EMF voltage during power loss. In applications were
use of the motor’s back-EMF voltage is desired a series diode should
be used to isolate this terminal from the logic supply (VCC). This is to
avoid dumping the charge back into the supply and therefor clamping
the voltage available from rectification of the motor’s back-EMF
voltage.
LOGIC SUPPLY (VCC). This is the 12 volt supply terminal for the
A8925CEB and powers all circuitry except the power outputs and
brake control circuitry.
TACH and POLE. In order to develop a
low-jitter tachometer signal (TACH) for use in
controlling motor speed, the A8925CEB divides the frequency of the H1 input by the
number of poles in the motor. This eliminates the jitter caused by variations in Halleffect device placement , sensitivity, and
magnet strengths by always changing state
when looking at the same magnet/sensor
pair. The resulting TACH signal changes state
every mechanical revolution of the motor.
The POLE input sets the TACH signal for fourpole motors when Low or eight-pole motors
when High.
LOGIC GROUND. This must be connected to the power ground
terminals in systems that do not use separate power and logic
grounds.
POWER GROUND. Terminals 7 through 17 and 29 through 39
are webbed together and attach to the die mounting area to form a low
thermal resistance path to allow heat to be conducted out of the device. The power dissipation of the package can be further enhanced
by soldering these terminals to a large area of copper foil on the
printed wiring board.
8925
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
AND POWER DMOS OUTPUTS
DIMENSIONS IN INCHES
(for reference only)
28
18
0.319
0.291
0.319
0.291
8.10
7.39
0.021
0.013
0.050
BSC
29
0.032
0.026
0.695
0.685
0.656
0.650
39
40
0.020
MIN
0.180
0.165
DIMENSIONS IN MILLIMETERS
(controlling dimensions)
28
29
0.812
0.661
0.656
0.650
144
0.695
0.685
INDEX AREA
2
17
7
6
Dwg. MA-005-44A in
18
17
MIN
17.65
17.40
16.662
16.510
39
16.662
16.510
144
17.65
17.40
40
8.10
7.39
0.533
0.331
1.27
BSC
0.51
4.57
4.20
NOTES: 1. Webbed lead frame. Leads 7 through 17 and 29 through 39 are internally one piece.
2. Exact body and lead configuration at vendor’s option within limits shown.
3. Lead spacing tolerance is non-cumulative.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
INDEX AREA
2
7
6
Dwg. MA-005-44A mm
8925
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
AND POWER DMOS OUTPUTS
Allegro MicroSystems, Inc. reserves the right to make,
from time to time, such departures from the detail specifications as may be required to permit improvements in the
design of its products.
The information included herein is believed to be
accurate and reliable. However, Allegro MicroSystems, Inc.
assumes no responsibility for its use; nor for any infringements of patents or other rights of third parties which may
result from its use.
8925
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
AND POWER DMOS OUTPUTS
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
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