A8925: Three-Phase Brushless DC Motor Controller/Driver with Linear Current Control and Power DMOS Outputs

8925
41 NC
40 FAULT
43 TACH
42 OUT
A
1 OUTB
44 POLE
LOGIC GROUND
LOGIC SUPPLY
2
V
CC
3
NC
4 OUT
C
6
5
ENABLE
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
AND POWER DMOS OUTPUTS
POWER
GROUND
39
7
POWER
GROUND
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
rDS(on) for low power dissipation. Intrinsic ground clamp and flyback
diodes protect the output drivers when switching inductive loads.
Thermal shutdown circuitry is provided to protect the device from excessive junction temperature.
T
C
U
Y
D
L
O
N
R
P EO
D
C
E
N
U
E
N R
I
T
E
F
N
E
O
R
C
S
R
I
D FO
—
38
9
37
10
36
CHARGE PUMPS
8
13
CIRCUITRY
35
SEQUENCING
12
AND CONTROL
11
34
33
14
15
31
16
30
+
29
POWER
GROUND
3
27
28
H
NC
26
2
H
25
NC
24
1
H
23
SUB
BRAKE
21
ERROR AMP
LOAD SUPPLY
19
20
REFERENCE
VSENSE
18
SUB
22
V
BB
17
COMP.
POWER
GROUND
32
Dwg. PP-034
ABSOLUTE MAXIMUM RATINGS
AT TA = +25°C
Load Supply Voltage, VBB ..................... 14 V
Output Current, IOUT .......................... ±4.0 A
Logic Supply Voltage, VCC ..................... 14 V
Logic Input Voltage Range,
VIN ................................ -0.3 V to +6.0 V
Package Power Dissipation,
PD ......................................... See Graph
Operating Temperature Range,
TA ..................................... 0 °C to +70°C
Junction Temperature, TJ ............... +150°C†
Storage Temperature Range,
TS ................................ -55°C to +150°C
† Fault conditions that produce excessive
junction temperature will activate device thermal
shutdown circuitry. These conditions can be
tolerated, but should be avoided.
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 Nchannel DMOS source drivers to their required gate voltages.
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 DS(on) - 0.25 Ω Maximum
Linear Current Control
Internal Commutation Circuitry
Internal Current Sensing
Thermal Shutdown Circuitry
Under Voltage Detection Circuitry
Fault Output Flag
Power Surface-Mount Package
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.
Always order by complete part number: A8925CEB .
Data Sheet
26301.30
8925
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
AND POWER DMOS OUTPUTS
12.5
T
R θJ
/W
°C
=6
ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS
8925
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
AND POWER DMOS OUTPUTS
10
7.5
5.0
R
2.5
θJA = 3
0°C
/W
0
25
50
75
100
TEMPERATURE IN °C
125
150
Dwg. GP-020B
ELECTRICAL CHARACTERISTICS AT TA = +25°C, VCC = VBB = 12 V
Limits
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Logic Supply Voltage
VCC
Operating
10
12
14
V
Load Supply Voltage
V BB
Operating
10
12
14
V
Supply Current
ICC
Operating
—
30
50
mA
VENABLE = 0 V
Thermal Shutdown
TJ
—
—
2.0
165
4.0
—
mA
°C
IOUT = ±4.0 A, Pulse Test
—
0.20
0.25
Ω
IOUT = 4.0 A, L = 2 mH
14
—
—
V
VF
IF = ±4.0 A
—
1.5
2.0
V
IDSX
VOUT = 14 V
—
10
300
µA
VOUT = 0 V
—
-10
-300
µA
ENABLE, POLE
—
—
0.8
V
2.4
—
—
V
—
—
0.8
V
3.0
—
—
V
Output Drivers
Output ON Resistance
Output Sustaining Voltage
Clamp Diode Forward Voltage
Output Leakage Current
rDS(on)
VDS(sus)
Control Logic
Logic Input Voltage
VIN(0)
VIN(1)
Logic Input Voltage
VIN(0)
BRAKE
VIN(1)
Logic Input Current
IIN(0)
VIN = 0.8 V
—
—
-1.0
µA
IIN(1)
VIN = 2.4 V
—
—
1.0
µA
NOTE: Negative current is defined as coming out of (sourcing) the specified device terminal.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 1990, 1995 Allegro MicroSystems, Inc.
Continued next page...
8925
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
AND POWER DMOS OUTPUTS
ELECTRICAL CHARACTERISTICS CONTINUED
Limits
Characteristic
Symbol
Logic Output Voltage
(FAULT, TACH)
Test Conditions
Min.
Typ.
Max.
Units
VOUT(0)
IOUT = 3 mA
—
—
0.8
V
VOUT(1)
IOUT = -50 µA
2.0
—
—
V
IIB
VCM = 0.01 V
—
5.0
10
µA
Input Offset Voltage
VOS
VCM = 1.0 V
—
3.0
5.0
mV
Input Common-Mode Voltage Range
VIC
0.01
—
6.0
V
Error Voltage Gain
AVD
—
80
—
dB
Unity Gain Bandwidth
BW
—
1.0
—
MHz
Common-Mode Rejection Ratio
CMRR
—
80
—
dB
Power Supply Rejection Ratio
PSRR
—
50
—
dB
Error Amplifier
Input Bias Current
VS OUT / V S IN , V CM = 1.0 V
Miscellaneous
Current Sense Gain
AiCS
IOUT = -1.0 A
1/1k
1/1.2k
1/1.4k
—
Current-Sense Matching
—
IOUT = -1.0 A
—
±3.0
±5.0
%
Under-Voltage Trip Point
VCC
8.0
—
9.5
V
Hall Input Current
IIN(0)
VIN = 0 V
—
-500
-1000
µA
IIN(1)
VIN = 5.0 V
—
-250
-500
µA
Hall Input Threshold
VIN
—
3.8
—
V
Hall Input Pull-Up Resistance
RPU
—
25
—
kΩ
NOTE: Negative current is defined as coming out of (sourcing) the specified device terminal.
COMMUTATION TRUTH TABLE
Hall Sensor Inputs
Outputs
H1
H2
H3
High
High
High
Low
Low
Low
Low
Low
High
High
High
Low
High
Low
Low
Low
High
High
High
High
High
High
High
High
High
High
High
High
High
High
High
Low
X
High
Low
X
High
Low
X
High
High
Low
X
X
X
X
X = Irrelevant
Z = High Impedance
ENABLE BRAKE FAULT
OUT A
OUT B
OUT C
High
High
High
High
High
High
High
High
Z
Low
Low
Z
Low
Z
High
High
Z
Low
Z
Low
Low
Z
High
High
High
High
High
Low
Low
X
Z
Z
Z
Z
Z
Z
Z
Z
Z
Low
X
Low
Low
Low
8925
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
AND POWER DMOS OUTPUTS
TERMINAL FUNCTIONS
Term.
Terminal Name
1
OUTB
Function
Power DMOS output.
2
LOGIC SUPPLY
VCC; low-current 12 V supply for the logic.
3
LOGIC GROUND
Low-level logic ground.
4
OUT C
6
ENABLE
7–17
POWER GROUND
Power DMOS output.
Active high chip enable.
Power ground and thermal heat sink.
18
VSENSE
External precision resistor for sense-FET current.
19
COMP.
Compensation; error amplifier output.
20
REFERENCE
VREF ; voltage input that sets the power output current.
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
24
H1
High-level input from a Hall sensor.
26
H2
High-level input from a Hall sensor.
A logic low turns OFF all source drivers and turns ON all sink drivers (shorts the windings to
ground).
28
H3
29–39
POWER GROUND
High-level input from a Hall sensor.
40
FAULT
42
OUTA
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 ground and thermal heat sink.
A logic low at this output indicates a thermal shutdown, under -voltage fault, or an invalid Hall
input combination.
Power DMOS output.
FUNCTIONAL DESCRIPTION
V BB
CHARGE
PUMP
SENSE
AMPLIFIER
I OUT
.
VSENSE
1200
OUT
R3
SEQUENTIAL
LOGIC
R1
C1
RS
_VREF
++
ERROR
AMPLIFIER
OUT
C2
V
R2
Power Outputs (OUT A, OUTB, and
OUTC). The power outputs of the A8925CEB
are DMOS transistors with a maximum rDS(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.
COMP.
SUB
Dwg. EP-040
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 VSENSE terminal and develops a voltage
Continued next page...
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
8925
3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER
WITH LINEAR CURRENT CONTROL
AND POWER DMOS OUTPUTS
across RS that equals RS • ILOAD /1200. This
sense voltage (VSENSE) is compared to a reference voltage (VREF ) and an error voltage is
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 IOUT = V REF • 1200/R S. External
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
on the logic supply. The
trip point for this function is
between 8 and 9.5 volts.
B)
An invalid Hall input combination … all inputs High or
all inputs Low.
C)
An excessive device
junction temperature. The
thermal shutdown circuitry
disables the output drivers
in addition to forcing the
FAULT output signal low.
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.
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.
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)
18
28
29
17
0.032
0.026
0.319
0.291
0.695
0.685
0.021
0.013
0.656
0.650
0.319
0.291
0.050
INDEX AREA
BSC
39
7
40
0.020
44
1
2
6
0.656
0.650
MIN
0.695
0.685
0.180
0.165
Dwg. MA-005-44A in
DIMENSIONS IN MILLIMETERS
(controlling dimensions)
18
28
29
17
0.812
0.661
8.10
7.39
17.65
17.40
0.533
0.331
16.662
16.510
8.10
7.39
INDEX AREA
1.27
BSC
7
39
40
0.51
MIN
4.57
4.20
44
1
2
6
16.662
16.510
17.65
17.40
Dwg. MA-005-44A mm
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
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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