Diodes AH5798 User Manual

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.

Features

• 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

Pin Assignments

( Top View )

Vdd

1

2

Vss

3 7

O1

SOT89-5L

( Top View)

FG

Vss

1

2

O2

TSOT25

Applications

• 3.3V / 5V Min. BLDC Cooling Fans

• Netbook/ Notebook BLDC fans

• Low Voltage/ Low Power BLDC Motors

FG

5

NC

4

O2

5

Vdd

43

O1

AH5798

Document number: DS32001 Rev. 2 - 2

1 of 11

www.diodes.com

June 2010

Typical Application Circuit

SYSTEM

POWER

D1

C1

Dz

AH5798

SINGLE PHASE HALL EFFECT LATCH SMART

FAN MOTOR CONTROLLER

SYSTEM POWER

10Kohm

V

dd

FG

AH5798

V

SS

O1

O2

* 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 Description

Vdd Power Supply Pin Vss Ground Pin

O1 Output Driving & Sinking Pin 1 O2 Output Driving & Sinking Pin 2

NC No Connection

FG Frequency Generator (Note 1)

Notes: 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

Functional Block Diagram

AH5798

SINGLE PHASE HALL EFFECT LATCH SMART

FAN MOTOR CONTROLLER

Operating

Magentic

S

N

Vdd

Vss

Hall

Sensor

Power

AMP

Frequency Generator

Control

Logic

Lock detect,

Shoutdown and

Automatic re-start

Soft Switching

Control

FG

O1

Full Bridge

Driver

O2

O1

FG

Ton

Normal spinning

motor locked detected

Toff

Mechanical lock

“Re-start spinning”

motor locked cleared

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

AH5798

θJAθ

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

= 25°C, unless otherwise noted)

A

Symbol Parameter Rating Unit

Vdd Supply voltage 6 V

I

Maximum Output Current (Peak) 800 mA

O(PEAK)

PD Power Dissipation

TST Storage Temperature Range -65 ~ 150

θ

JA

Notes: 5. θJA should be confirmed with heat sink thermal resistance. If there is no heat sink contact, θJA will almost be the same as θJC.

Thermal Resistance Junction-to-Ambient (Note 5)

TJ

TA

SOT89-5L 800 mW TSOT25 520 mW

o

C

o

SOT89-5L 156

C/W

TSOT25 240 oC/W

Tc

JC

Recommended Operating Conditions (T

Symbol

Parameter Conditions Min Max Unit

= 25°C)

A

Vdd Supply Voltage Operating 1.8 5.5 °C

TA Operating Ambient Temperature Range Operating -40 105 V

AH5798

Document number: DS32001 Rev. 2 - 2

4 of 11

www.diodes.com

June 2010