AH285
HALL-EFFECT SMART FAN MOTOR CONTROLLER
Description
The AH285 is a single-chip solution for driving two-coil
brushless direct current (BLDC) fans and motors. The device
includes a Hall-effect sensor, dynamic offset correction and
two complementary open-drain output drivers with internal
Zener diode protection.
To help protect the motor coils, the AH285 provides Rotor
Lock Protection which shuts down output drives if rotor lock is
detected. The device automatically re-starts when the rotor
lock is removed.
A Tachometer output is provided by open-drain Frequency
Generator (FG) Pin which allows external interface to monitor
motor rotation or speed. The FG output is the magnetic
change frequency.
The AH285 is available in SOT89-5L package.
Pin Assignments
(Top View)
Vdd
1
2
285
5
FG
GND
DO
3
7
DOB
4
SOT89-5L
Features
•
•
•
•
•
•
•
•
•
Single-chip solution
Operating Voltage: 3.8V to 20V
Built-in Hall sensor and input amplifier
Tachometer (FG) output
Rotor Lock Protection (Lock detection, output shutdown
and automatic re-start)
Built-in Zener protection for output driver
Average output current up to 500mA
Packaged in SOT89-5L
Green Molding Compound
Applications
•
•
Two-coil BLDC cooling fans
Low to medium voltage, low power BLDC motors
Typical Application Circuit
Vdd (12V)
D2
D1 R
pu
FG
5
4
285
1
2
3
Coil2
Coil1
D3
C3
R1
R2
C2
GND
C1
12V DC Brush-less Fan with FG output function
Notes:
1. Typically it is recommended to us a 56 Ohm resistor for R1 and R2 and a 2.2μF E-Cap capacitor for C1, C2 and C3. These values
may need to be optimized depending on the coils used.
To help with IC protection it’s advised to add a Zener diode between Vdd and ground. The Zener diode should be chosen to help
prevent the supply voltage exceeding the maximum rating of the device.
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AH285
Document number: DS31029 Rev. 8 - 2
AH285
HALL-EFFECT SMART FAN MOTOR CONTROLLER
Pin Descriptions
Pin Name
FG
Vdd
DO
DOB
GND
Description
Frequency Generation
Input Power
Output Pin
Output Pin
Ground
Functional Block Diagram
Vdd
Lock detect,
shutdown and
automatic re-start
Regulator
DO
Hall
Plate
Amp.
Control Logic
DOB
GND
FG
AH285
Document number: DS31029 Rev. 8 - 2
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AH285
HALL-EFFECT SMART FAN MOTOR CONTROLLER
Absolute Maximum Ratings
(T
A
= 25°C)
Symbol
Vdd
I
O
P
D
T
ST
T
J
θ
JA
Supply Voltage
Output Current
Power Dissipation
Storage Temperature
Maximum Junction Temperature
Thermal Resistance Junction to Case (Note 2)
T
A
T
J
Tc
Characteristics
I
O (AVE)
I
O (PEAK)
Rating
24
500
700
800
-55 ~ 150
150
156
Unit
V
mA
mA
mW
°C
°C
°C/W
θ
JA
θ
JC
Notes:
2.
θ
JA
should be confirmed with heat sink thermal resistance. If there is no heat sink contact,
θ
JA
will almost be the same as
θ
JC
..
Recommended Operating Conditions
Symbol
Vdd
T
A
Characteristic
Supply Voltage
Operating Ambient Temperature
Conditions
Operating
Operating
Min
3.8
-40
Max
20
100
Unit
V
°C
AH285
Document number: DS31029 Rev. 8 - 2
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© Diodes Incorporated
AH285
HALL-EFFECT SMART FAN MOTOR CONTROLLER
Electrical Characteristics
(T
A
= 25
°C,
Vdd = 12V, unless otherwise specified)
Symbol
Idd
I
OFF
T
RLP-ON
T
RLP-OFF
V
OUT(SAT)
R
DS(ON)
V
OL
Vz
Truth Table
IN-
H
L
-
Characteristics
Supply Current
Output Leakage Current
Rotor Lock Protection On Time
Rotor Lock Protection Off Time
Output Saturation Voltage
Output On Resistance
FG Output Vds
Output Zener-Breakdown Voltage
Conditions
Operating
V
OUT
=24V
Min
-
-
0.4
2.4
-
-
-
-
35
Typ.
2
< 0.1
0.5
3
375
625
1.25
0.5
42
Max
4
10
0.6
3.6
500
900
1.67
-
60
Unit
mA
μA
Sec
Sec
mV
ohm
V
V
I
O
= 300mA
I
O
= 500mA
I
O
= 300mA
I
O
= 10mA
IN+
L
H
-
CT
L
L
H
OUT1
H
L
off
OUT2
L
H
off
FG
H
L
-
Mode
Rotating
Rotating
Lockup protection activated
Magnetic Characteristics
(T
A
= 25
°C,
Vdd = 12V, unless otherwise specified, Note 3)
(1mT = 10 Gauss)
Symbol
Bop
Brp
Bhy
Notes:
Characteristics
Operation Point
Release Point
Hysteresis
Min
10
-60
-
Typ.
30
-30
60
Max
60
-10
-
Unit
Gauss
Gauss
Gauss
3. The magnetic characteristics may vary with supply voltage, operating temperature and after soldering.
AH285
Document number: DS31029 Rev. 8 - 2
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© Diodes Incorporated
AH285
HALL-EFFECT SMART FAN MOTOR CONTROLLER
Operating Characteristics
DOB
DO
Output Voltage in Volts
RP
12
10
8
6
4
Output Voltage in Volts
OFF
OFF
12
10
8
6
4
OP
ON
2
OP
Vsat
RP
2
ON
Vsat
Brp
0
Bop
Brp
0
Bop
Magnetic Flux Density in Gauss
Magnetic Flux Density in Gauss
S
Marking
side
N
( SOT89-5L )
AH285
Document number: DS31029 Rev. 8 - 2
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