AH5798
SINGLE PHASE HALL EFFECT LATCH SMART
FAN MOTOR CONTROLLER
Description
The AH5798 is a single chip solution for driving single-coil
brushless direct current (BLDC) fans and motors. The
integrated full-bridge driver output stage uses soft switching
to minimize audible switching noise and electromagnetic
interference (EMI) providing a low noise solution.
To help protect the motor coil, the AH5798 provides Rotor
Lock Protection which shuts down output drive if rotor lock is
detected. The device automatically re-starts when the rotor
lock is removed. Over temperature shutdown provides
thermal protection for the device.
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 AH5798 is available in space saving SOT89-5L and
thinner TSOT25 packages.
Pin Assignments
( Top View )
Vdd 1
Vss
2
5 FG
NC
7 O2
4
O1 3
SOT89-5L
( Top View)
FG
Vss
O2
1
2
3
4
5
Vdd
O1
Features
TSOT25
•
•
•
•
•
•
•
•
•
•
Supports single-coil full-wave DC fan drivers
Built-in Hall sensor and input amplifier
Operating Voltage: 1.8V to 5.5V
Soft switching for low noise DC fan motor applications
Rotor Lock Protection (Lock detection, output shutdown
and automatic re-start)
Thermal protection
Tachometer (FG) output
No external timing capacitor - Reduces the numbers of
external components required
Low profile packages: SOT89-5L and TSOT25
“Green” Molding Compound
Applications
•
•
•
3.3V / 5V Min. BLDC Cooling Fans
Netbook/ Notebook BLDC fans
Low Voltage/ Low Power BLDC Motors
AH5798
Document number: DS32001 Rev. 2 - 2
1 of 11
www.diodes.com
June 2010
© Diodes Incorporated
AH5798
SINGLE PHASE HALL EFFECT LATCH SMART
FAN MOTOR CONTROLLER
Typical Application Circuit
SYSTEM
POWER
10Kohm
SYSTEM
POWER
V
dd
D1
C1
Dz
FG
FG
AH5798
O1
O2
V
SS
* Reverse connection of power supply may damage the device. To prevent reverse power damage, a protection (reverse blocking)
Diode D1 is needed between power supply and Vdd terminal. If a reverse power protection diode D1 is used, there
is no current return path to power supply, so it is necessary to follow measures such as below.
- Connect Dz (Zener diode) between Vdd and Vss terminal, to prevent voltage exceeding the absolute maximum rating of the device.
- Connect a capacitor C1 between Vdd and Vss terminal, to complete the current return path to power supply.
The AH5798 has an open-drain tachometer FG output that follows the magnetic change frequency. Typically, a pull-up resistor of 10kΩ is
recommended from FG pin to the supply voltage.
Pin Descriptions
Pin Name
Vdd
Vss
O1
O2
NC
FG
Notes:
Description
Power Supply Pin
Ground Pin
Output Driving & Sinking Pin 1
Output Driving & Sinking Pin 2
No Connection
Frequency Generator (Note 1)
1. The FG is the same as the magnetic change frequency.
AH5798
Document number: DS32001 Rev. 2 - 2
2 of 11
www.diodes.com
June 2010
© Diodes Incorporated
AH5798
SINGLE PHASE HALL EFFECT LATCH SMART
FAN MOTOR CONTROLLER
Functional Block Diagram
Vdd
Power
Frequency
Generator
FG
O1
Hall
Sensor
AMP
Control
Logic
Soft Switching
Control
Full Bridge
Driver
O2
Vss
Lock detect,
Shoutdown and
Automatic re-start
Operating
Magentic
S
N
O2
O1
FG
Normal spinning
Ton
Toff
Mechanical lock
“Re-start spinning”
motor locked cleared
motor locked detected
Notes:
2. In “Normal spinning”, the FG changes its state at each rising edge of O1.
3. When the motor locks with South pole at the Hall element, O2 is kept on “L” and O1 is a clock with Ton/Toff ratio. When motor
locks with North pole at the Hall element, O1 is kept on “L”, O2 is a clock with Ton/Toff ratio.
4. When “Re-start spinning” occurs, the motor speed ramps up to the “Normal Spinning” speed from zero. Speed ramp-up profile
depends on motor characteristics.
AH5798
Document number: DS32001 Rev. 2 - 2
3 of 11
www.diodes.com
June 2010
© Diodes Incorporated
AH5798
SINGLE PHASE HALL EFFECT LATCH SMART
FAN MOTOR CONTROLLER
Soft Switching
AH5798 employs soft switching of output drive at commutation to reduce audible noise and EMI for low noise
applications.
Vdd
Vout 1
Vout 2
GND
100µs typ.
Absolute Maximum Ratings
(T
A
= 25°C, unless otherwise noted)
Symbol
Vdd
I
O(PEAK)
P
D
T
ST
Parameter
Supply voltage
Maximum Output Current (Peak)
Power Dissipation
Storage Temperature Range
Thermal Resistance Junction-to-Ambient
(Note 5)
T
A
T
J
Tc
SOT89-5L
TSOT25
SOT89-5L
TSOT25
θ
JA
Rating
6
800
800
520
-65 ~ 150
156
240
Unit
V
mA
mW
mW
o
C
o
C/W
o
C/W
θ
JA
θ
JC
Notes:
5.
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
(T
A
= 25°C)
Symbol
Vdd
T
A
AH5798
Document number: DS32001 Rev. 2 - 2
Parameter
Supply Voltage
Operating Ambient Temperature Range
Conditions
Operating
Operating
Min
1.8
-40
Max
5.5
105
Unit
°C
V
June 2010
© Diodes Incorporated
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AH5798
SINGLE PHASE HALL EFFECT LATCH SMART
FAN MOTOR CONTROLLER
Electrical Characteristics
(T
A
= 25°C, Vdd = 5V)
Symbol
Parameter
Test Conditions
Min
Typ.
Max
Unit
Idd
V
OH
V
OL
T
SW
I
LEAK
V
FGOL
T
ON
R
DR
Supply Current
Output Voltage High
Output Voltage Low
Output Switching Slope Duration
FG Output Leakage Current
FG Output Voltage Low
On Time
Duty Ratio
No Load
I
OUT
= 300mA
I
OUT
= 300mA
50Ω load on out1/out2
I
FG
= 5mA
T
OFF
/ T
ON
-
4.4
-
-
-
-
350
-
5
4.65
0.35
100
-
-
500
10
-
-
0.6
-
5
0.4
650
-
mA
V
V
μs
μA
V
ms
Magnetic Characteristics
(T
A
= 25°C, Vdd = 1.8V~5V, Note 6)
(1mT = 10 G)
Max
Unit
50
-10
-
G
G
G
Symbol
B
op
Brp
B
hy
Notes:
Parameter
Min
10
-50
-
Typ.
25
-25
50
Operate Point
Release Point
Hysteresis
6. The magnetic characteristics may vary with supply voltage, operating temperature and after soldering.
AH5798
Document number: DS32001 Rev. 2 - 2
5 of 11
www.diodes.com
June 2010
© Diodes Incorporated
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