8906
BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR
CONTROLLER/DRIVER WITH BACK-EMF SENSING
LOAD
SUPPLY
C D2
C WD
CST
OUTA
GROUND
GROUND
OUT B
OUT C
CENTERTAP
BRAKE
C RES
1
2
V BB
COMMUTATION
DELAY
24
23
C D1
DATA IN
CLOCK
CHIP SELECT
RESET
GROUND
GROUND
DATA OUT
OSCILLATOR
LOGIC
SUPPLY
SECTOR
DATA
FILTER
Data Sheet
26301.4
SERIAL PORT
3
4
5
6
7
8
9
9
10
11
12
BOOST
CHARGE
PUMP
22
21
20
19
18
The A8906CLB is a bidirectional three-phase brushless dc motor
controller/driver. The three half-bridge outputs are low on-resistance n-
channel DMOS devices capable of driving up to 1 A. The A8906CLB
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, rotational
direction, startup current limit, sleep mode, diagnostic modes, and
others.
The A8906CLB 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
A8906CLB is provided in a 24-lead wide-body SOIC batwing package.
It provides for the smallest possible construction in surface-mount
applications.
MUX
FLL
VDD
17
16
15
14
13
PRELIMINARY INFORMATION
Dwg. PP-040B
FEATURES
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
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.
DMOS Outputs
Low
r
DS(on)
Startup Commutation Circuitry
Back-EMF Commutation Circuitry
Direction Control
Serial Port Interface
Frequency-Locked Loop Speed Control
Sector Data 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
(Subject to change without notice)
March 1, 1999
Always order by complete part number, e.g.,
A8906CLB
.
8906
BIDIRECTIONAL
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
VBB
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
SECTOR
14
DATA
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
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 © 1999 Allegro MicroSystems, Inc.
8906
BIDIRECTIONAL
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 Hysteresis
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
(Source + Sink + R
S
)
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
SECTOR DATA, RESET, CLK,
CHIP SELECT, OSC
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
Filter Threshold
C
D
Current
(C
D1
or C
D2
)
C
D
Current Matching
C
D
Threshold
—
V
CDTH
V
FILTERTH
I
CD
Charging
Discharging
I
CD(DISCHRG)
/I
CD(CHRG)
-0.3
3.5
—
—
—
3.5
-9.0
—
2.25
0.85
-9.0
9.0
—
1.57
-18
32
1.8
2.25
—
—
—
—
—
—
-10
500
2.5
1.0
-10
10
—
1.85
-20
40
2.0
2.5
1.5
5.3
-0.5
1.0
1.5
—
-11
—
2.75
1.15
-11
11
5.0
2.13
-22
48
2.2
2.75
V
V
µA
µA
V
V
µA
µA
V
V
µA
µA
nA
V
µA
µA
—
V
r
DS(on)
I
OUT
= 600 mA
—
—
—
1.0
-1.0
1.0
300
-300
1.4
µA
µA
Ω
V
BB
T
J
∆T
J
Operating
Test Conditions
Min.
4.5
—
—
4.0
—
—
Typ.
5.0
7.5
250
—
165
20
Max.
5.5
10
500
14
—
—
Units
V
mA
µA
V
°C
°C
V
DS(sus)
V
F
V
BB
= 14 V, I
OUT
= I
OUT
(MAX), L = 3 mH
I
F
= 1.0 A
14
—
—
1.25
—
1.5
V
V
Continued next page …
8906
BIDIRECTIONAL
3-PHASE BRUSHLESS DC
MOTOR CONTROLLER/DRIVER
ELECTRICAL CHARACTERISTICS continued
Limits
Characteristic
C
WD
Current
C
WD
Threshold Voltage
Symbol
I
CWD
V
TL
V
TH
Max. FLL Oscillator Frequency
I
OUT
(MAX)
f
OSC
—
V
DD
= 5.0 V, T
A
= 25°C
D3 = 0, D4 = 0
D3 = 0, D4 = 1
D3 = 1, D4 = 0
D3 = 1, D4 = 1
BRAKE Threshold
BRAKE Hysteresis Current
Transconductance Gain
Centertap Resistors
Back-EMF Hysteresis
V
BRK
I
BRKL
g
m
R
CT
—
V
BEMF
- V
CTAP
at
FCOM Transition
V
BRK
= 750 mV
Charging
Test Conditions
Min.
-9.0
0.22
2.25
12
1.0
0.9
0.5
—
1.5
—
0.42
5.0
5.0
-5.0
Typ.
-10
0.25
2.5
—
1.2
1.0
0.6
250
1.75
20
0.50
10
20
-20
Max.
-11
0.28
2.75
—
1.4
1.1
0.7
—
2.0
—
0.58
13
37
-37
Units
µA
V
V
MHz
A
A
A
mA
V
µA
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
8906
BIDIRECTIONAL
3-PHASE BRUSHLESS DC
MOTOR CONTROLLER/DRIVER
TERMINAL FUNCTIONS
Term.
1
2
3
4
5
6-7
8
9
10
11
12
13
14
15
16
17
18-19
20
21
22
23
24
Terminal Name
LOAD SUPPLY
C
D2
C
WD
C
ST
OUT
A
GROUND
OUT
B
OUT
C
CENTERTAP
BRAKE
C
RES
FILTER
SECTOR DATA
LOGIC SUPPLY
OSCILLATOR
DATA OUT
GROUND
RESET
CHIP SELECT
CLOCK
DATA IN
C
D1
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 compara-
tors during commutation transients, and to detect incorrect motor position.
Startup oscillator timing capacitor.
Power amplifier A output to motor.
Power and logic ground and thermal heat sink.
Power amplifier B output to motor.
Power amplifier C output 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.
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. Can use sector or index pulses from disk to provide
precise motor speed feedback to internal frequency-locked loop.
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.
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