8905
3-PHASE BRUSHLESS DC
MOTOR CONTROLLER/DRIVER
8905
Data Sheet
26301.3
3-PHASE BRUSHLESS DC MOTOR
CONTROLLER/DRIVER WITH BACK-EMF SENSING
The A8905CLB isw a three-phase brushless dc motor controller/
driver for use with CD-ROM or DVD drives. The three half-bridge
outputs are low on-resistance n-channel DMOS devices capable of
driving up to 1.25 A. The A8905CLB 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, diagnostic modes, and others.
LOAD
SUPPLY
C D2
C WD
CST
1
2
V BB
COMMUTATION
DELAY
24
23
C D1
DATA IN
CLOCK
CHIP SELECT
RESET
SERIAL PORT
3
4
5
6
7
22
21
20
19
OUTA
GROUND
GROUND
OUT B
OUT C
CENTERTAP
BRAKE
C RES
ABSOLUTE MAXIMUM RATINGS
at T
A
= +25
°
C
Load Supply Voltage, V
BB
. . . . . .
14 V
Output Current, I
OUT
. . . . . . . .
±
1.25 A
Logic Supply Voltage, V
DD
. . . .
6.0 V
Logic Input Voltage Range,
V
IN
. . . . . . .
-0.3 V to V
DD
+ 0.3 V
Package Power Dissipation,
P
D
. . . . . . . . . . . . . . . .
See Graph
Operating Temperature Range,
T
A
. . . . . . . . . . . . . .
0
°
C to +70
°
C
Junction Temperature, T
J
. . .
+150
°
C†
Storage Temperature Range,
T
S
. . . . . . . . . . . .
-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.
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.
T
C
U Y
D L
O N
R O
P E
D C
E N
U E
IN ER
T F
N E
O R
C R
IS O
D F
—
GROUND
18
GROUND
8
MUX
FLL
17
DATA OUT
9
9
16
OSCILLATOR
APPLICATIONS
s
CD-ROMs
s
DVDs
10
11
VDD
15
14
LOGIC
SUPPLY
INDEX
BOOST
CHARGE
PUMP
12
13
FILTER
FEATURES
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
Dwg. PP-040-1
DMOS Outputs
Low r
DS(on)
Startup Commutation Circuitry
Back-EMF Commutation Circuitry
Serial Port Interface
Frequency-Locked Loop Speed Control
Tachometer Signal Input
Programmable Start-Up Current
Diagnostics Mode
Sleep Mode
Linear Current Control
Internal Current Sensing
Dynamic Braking Through Serial Port
Power-Down Dynamic Braking
System Diagnostics Data Out
Data Out Ported in Real Time
Internal Thermal Shutdown Circuitry
Always order by complete part number, e.g.,
A8905CLB
.
8905
3-PHASE BRUSHLESS DC
MOTOR CONTROLLER/DRIVER
FUNCTIONAL BLOCK DIAGRAM
LOGIC
SUPPLY
15
C D1
24
C D2
2
C ST
4
BRAKE
11
C RES
12
VDD
BOOST
CHARGE
PUMP
1
BRAKE
V
BB
COMMUTATION
LOGIC
LOAD
SUPPLY
OUT A
OUT B
OUTC
OUT A
OUT B
OUT C
CENTERTAP
C WD
10
START-UP
OSC.
BLANK
SEQUENCE
LOGIC
FCOM COMMUTATION
DELAY
5
8
9
3
WATCHDOG
TIMER
INDEX
14
OSC
16
FREQUENCY-
LOCKED LOOP
CHARGE
PUMP
CURRENT
CONTROL
RS
6-7
GROUND
DATA IN
23
SERIAL PORT
MUX
TSD
18-19
GROUND
21
22
20
17
13
CHIP
SELECT
CLOCK
RESET
DATA
OUT
FILTER
Dwg. FP-034-1
ALLOWABLE PACKAGE POWER DISSIPATION in WATTS
2.5
R
θJT
= 6°C/W
2.0
1.5
1.0
R
θJA
= 55°C/W
0.5
0
25
50
75
100
125
150
Dwg. GP-019B
TEMPERATURE in
°C
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 1998 Allegro MicroSystems, Inc.
8905
3-PHASE BRUSHLESS DC
MOTOR CONTROLLER/DRIVER
ELECTRICAL CHARACTERISTICS at T
A
= +25
°
C, V
DD
= 5.0 V
Limits
Characteristic
Logic Supply Voltage
Logic Supply Current
Symbol
V
DD
I
DD
Operating
Operating
Sleep Mode
Load Supply Voltage
Thermal Shutdown
Thermal Shutdown Hys.
Output Drivers
Output Leakage Current
I
DSX
V
BB
= 14 V, V
OUT
= 14 V
V
BB
= 14 V, V
OUT
= 0 V
Total Output ON Resistance
Output Sustaining Voltage
Clamp Diode Forward Voltage
Control Logic
Logic Input Voltage
V
IN(0)
V
IN(1)
Logic Input Current
I
IN(0)
I
IN(1)
DATA Output Voltage
V
OUT(0)
V
OUT(1)
C
ST
Current
I
CST
INDEX, RESET, CLK,
CHIP SELECT, OSC, BRAKE
V
IN
= 0 V
V
IN
= 5.0 V
I
OUT
= 500
µA
I
OUT
= -500
µA
Charging
Discharging
C
ST
Threshold
V
CSTH
V
CSTL
Filter Current
I
FILTER
Charging
Discharging
Leakage, V
FILTER
= 2.5 V
C
D
Current
I
CD
Charging
Discharging
C
D
Current Matching
C
D
Threshold
C
WD
Current
—
V
CD
I
CWD
Charging
I
CD(DISCHRG)
/I
CD(CHRG)
-0.3
3.5
—
—
—
3.5
14
-14
2.1
—
7.0
-7.0
—
14
-26
1.7
—
14
—
—
—
—
—
—
20
-20
2.5
500
10
-10
5.0
22
-35
2.2
2.5
22
1.5
5.3
-0.5
1.0
1.5
—
28
-28
2.9
—
15
-15
—
28
-66
2.3
—
28
V
V
µA
µA
V
V
µA
µA
V
mV
µA
µA
nA
µA
µA
—
V
µA
r
DS(on)
V
DS(sus)
V
F
I
OUT
= 600 MA
V
BB
= 14 V, I
OUT
= I
OUT
(MAX), L = 3 mH
I
F
= 1.0 A
—
—
—
14
—
1.0
-1.0
1.1
—
1.25
300
-300
1.4
—
1.5
µA
µA
Ω
V
V
V
BB
T
J
∆T
J
Operating
Test Conditions
Min.
4.5
—
—
4.5
—
—
Typ.
5.0
7.5
—
—
165
20
Max.
5.5
10
1.5
14
—
—
Units
V
mA
mA
V
°C
°C
Continued next page …
8905
3-PHASE BRUSHLESS DC
MOTOR CONTROLLER/DRIVER
ELECTRICAL CHARACTERISTICS continued
Limits
Characteristic
C
WD
Threshold Voltage
Symbol
V
TL
V
TH
Max. FLL Oscillator Frequency
f
OSC
V
DD
= 5.1 V, T
A
= 25°C
V
DD
= 4.5 V, T
A
= 70°C
I
OUT
(MAX) Accuracy
BRAKE Threshold
Transconductance Gain
Centertap Resistors
Back-EMF Hysteresis
—
V
BRK
g
m
R
CT
—
V
BEMF
- V
CTAP
at
FCOM Transition
I
OUT
= 1 A
Test Conditions
Min.
0.80
2.4
20
—
—
1.4
0.26
5.0
15
-15
Typ.
0.85
2.75
—
10
±20
1.7
0.35
10
25
-25
Max.
0.95
3.0
—
—
—
2.0
0.50
13
40
-40
Units
V
V
MHz
MHz
%
V
A/V
kΩ
mV
mV
SERIAL PORT TIMING CONDITIONS
CHIP SELECT
E
CLOCK
C
DATA
D
C
D
A
B
Dwg. WP-019
A. Minimum CHIP SELECT setup time before CLOCK rising edge ...... 100 ns
B. Minimum CHIP SELECT hold time after CLOCK rising edge ........... 150 ns
C. Minimum DATA setup time before CLOCK rising edge .................... 150 ns
D. Minimum DATA hold time after CLOCK rising edge ........................ 150 ns
E. Minimum CLOCK low time before CHIP SELECT .............................. 50 ns
F. Maximum CLOCK frequency ........................................................... 3.3 MHz
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
8905
3-PHASE BRUSHLESS DC
MOTOR CONTROLLER/DRIVER
TERMINAL FUNCTIONS
Term.
1
2
3
4
5
6-7
8
9
10
11
Terminal Name
LOAD SUPPLY
C
D2
C
WD
C
ST
OUT
A
GROUND
OUT
B
OUT
C
CENTERTAP
BRAKE
Function
V
BB
; the 5 V or 12 V motor supply.
One of two capacitors used to generate the ideal commutation points from the back-EMF
zero-crossing points.
Timing capacitor used by the watchdog circuit to disable the back-EMF comparators
during commutation transients, and to detect incorrect motor position.
Startup oscillator timing capacitor.
Power amplifier output A to motor.
Power and logic ground and thermal heat sink.
Power amplifier output B to motor.
Power amplifier output C to motor.
Motor centertap connection for back-EMF detection circuitry.
Active low turns ON all three sink drivers shorting the motor windings to ground. External
capacitor and resistor at B
RAKE
provide brake delay. The brake function can also be
controlled via the serial port.
External reservoir capacitor used to hold charge to drive the source drivers’ gates. Also
provides power for brake circuit.
Analog voltage input to control motor current. Also, compensation node for internal speed
control loop.
External tachometer input.
V
DD
; the 5 V logic supply.
Clock input for the speed reference counter. Typical max. frequency is 10 MHz.
Thermal shutdown indicator, FCOM, TACH, or SYNC signals available in real time,
controlled by 2-bit multiplexer in serial port.
Power and logic ground and thermal heat sink.
When pulled low forces the chip into sleep mode; clears all serial port bits.
Strobe input (active low) for data word.
Clock input for serial port.
Sequential data input for the serial port.
One of two capacitors used to generate the ideal commutation points from the back-EMF
zero-crossing points.
12
13
14
15
16
17
18-19
20
21
22
23
24
C
RES
FILTER
INDEX
LOGIC SUPPLY
OSCILLATOR
DATA OUT
GROUND
RESET
CHIP SELECT
CLOCK
DATA IN
C
D1
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