Datasheet FAN8902 Datasheet (Fairchild Semiconductor)

FAN8902(KA3902)

DC FAN Motor Controller

www.fairchildsemi.com

Features

• Built-in PWM Current Control Circuit

• Built-in 5V Regulator

• Low Supply Current

• Stalled Motor Current Limitation

• Built-in Over Voltage Protection (OVP)

• Built-in Over Current Protection (OCP)

• Built-in Load Dump Protection

• Built-in Thermal Shutdown (TSD) Circuit

• Built-in Under Voltage Lockout (UVLO) Circuit

Description

The FAN8902 is a monolithic integrated circuit, designed
for the PWM control of a DC fan motor current in an
automotive systems. It allows the fan motor speed to be
controlled linearly and efficiently.

14-DIP-300

Typical Application

• DC for Motor Control for Automotive

©2002 Fairchild Semiconductor Corporation

Ordering Information

Device Package Operating Temperature

FAN8902 14-DIP-300 -40°C ~ +90°C

Rev. 1.0.3

Pin Assignments

FAN8902(KA3902)

CMD

CMDa

CMDb

R

T

VREF

1

2

3

4

F A N 8 9 0 2

5

6

78

/ C

SG

T

CH

14

La

13

VCC

12

OUT

PG

11

CS

10

9

CL

NC

Pin Definitions

Pin Number Pin Name Pin Function Description

1 CMD Motor Current Command Input
2 CMDa Optional OP Amplifier Output
3 CMDb Optional OP Amplifier (-) Input
4 SGND Signal GND
5R
6 VREF Voltage Reference (5V)
7 CH Maximum Current Reference Input
8 NC No Connection

9 CL Minimum Current Reference Input
10 CS Motor Current Sense Voltage Input
11 PGND Power GND
12 OUT Drive Output
13 V
14 La Motor Current Maximum Reference Input

/ C

T

T

CC

Oscillator Time Constant

V

CC

2

FAN8902(KA3902)

Internal Block Diagram

Vref

CH

CMD

CL

CMDa

CMDb

6

7

1.3V

1

La

14

9

2

3

+
+

−

+

−

−

+
+

−

4R

+

−

R

Vref

+

−

PWM

Comparator

PWM

LOGIC

Oscillator

UVLO

× 5

OVP
TSD

36V

13

V

CC

12

OUT

11

PGND

10

CS

5

R

T/CT

4

SGND

3

FAN8902(KA3902)

Absolute Maximum Ratings

Parameter Symbol Value Unit

Supply Voltage V
CMD Input Voltage V
Peak Output Current I
Power Dissipation P

CC

CMD

OPK

D

32 V

6V

±0.8 A

1W

Operating Voltage

Parameter Symbol Min. Typ. Max Unit

Power Supply Voltage V

CC

9.0 12.0 32.0 V

Temperature Characteristics

Parameter Symbol Temp Value Unit

Vref Temperature Stability V
Frequency Stability F
Operating Temperature T
Storage Temperature T

ST

ST
OPR
STG

-40 ~ +90°C 200 °C

-40 ~ +90°C 20 ~ 30 °C

- -40 ~ +90 °C

- -60 ~ +150 °C

4

FAN8902(KA3902)

Electrical Characteristics

(Unless otherwise, Ta=25°C, VCC=5V, VM=12V)

Parameter Symbol Conditions Min. Typ. Max. Unit
REFERENCE

Reference Voltage Vref Iref=1mA 4.75 5.0 5.25 V
Line Regulation ∆Vref1 V
Load Regulation ∆Vref2 Iref=1mA ~ 10mA - 10 50 mV

UNDER VOLTAGE LOCKOUT (UVLO)

Start Threshold Voltage V
Threshold Hysteresis V

TH(ST)

HYS

PROTECTION

Over Voltage O

OSCILLATOR (R

=75kΩΩΩΩ, CT=1nF)

T

VP

Frequency fosc - 20 25 30 kHz
Duty Cycle Duty - 90 95 - %

CURRENT SENSING INPUT

Threshold Voltage V

TH(ST)VCMD

OUTPUT DRIVER

Output Voltage Switching Limit V
Low Output Voltage

High Output Voltage

OLIM

V

OL1

V

OL2

V

OH1

V

OH2

Rising Time Tr Cld = 1nF - 100 200 ns
Falling Time Tf Cld = 1nF - 100 200 ns

TOTAL STANDBY CURRENT

Start-up Current I
Operating Supply Current I

ST
CC

=9V ~ 32V - 50 150 mV

CC

- 7.5 8.0 8.5 V

- 1.0 1.2 1.4 V

-3336-V

= 5V 0.19 0.20 0.21 V

V

= 18V, Cld =1nF - 15 - V

CC

Iout = 20mA - - 0.4 V
Iout = 200mA - - 2.2 V
Iout = -20mA 10.0 - - V
Iout = -200mA 9.0 - - V

V

= 7V - 1.0 1.5 mA

CC

V

= 9V - 6.0 8.0 mA

CC

5

Application Information

1. Under Voltage Lockout (UVLO)

FAN8902(KA3902)

I

CC

13

T

H(ST)

T

HYS

FAN8902

2. Current Sensing Circuit

Imax=1V

Current amplifier

FAN8902

The peak current, I
For example, if a required maximum current, I

R

S

M(MAX)=VS/RS

1V 5⁄

-------------- - 10 mΩ[]==
20A

Vref &
output driver

8.0V

1.2V

PWM comparator

+

−

× 5

M(MAX)

=20[A]

PWM
Logic

6mA

1mA

8V V

6.8V

M

12

10

R5

I

M

V

S

R

S

TH(ST)

V

BAT

3. Thermal Shutdown (Tsd)

When the chip, temperature rises up to 150°C, the thermal shutdown (TSD) circuit is activated and the output driver turn off,
and then turn on again at 125°C.

6

FAN8902(KA3902)

4. Oscillator Component Selection

Vref

R

T

V/C

T

C

T

I

D

+

−

VHV

L

Logic

The oscillator timing components can be calculated as follows:

TCRTC
T

DCT

fosc 1 T

1.875 R

Duty T

C

× In Vref V

T

VHVL–()I

+()⁄=

CTD

TCT

fosc× 100×=

–()Vref VH–()⁄[]×=

L

⁄[]×=

D

×()⁄=

For example, if fosc = 25kHz and duty = 95%

TDI

C

T

1000 pF[]=

R

1.875 fosc C

T

1.875 25kHz 1000pF×()⁄=
75 kΩ[]=

×()V

D

–()⁄=

HVL

×()⁄=

T

VCT [V]
V

H

=1.75

V

L

=3.0

T=40.0

Td=1.0

T

C

=39.0

t [µs]

5. Current Command Input Section

The current command I* selects the lower value between V

V

CMD

1

CMD

+

V

La

La

14

+

−

FAN8902

CMD

I*

and VLa.

4R

R

+

Logic

−

7

FAN8902(KA3902)

6. Slope Compensation

An unconditional instability of the inner current loop exists for any fixed frequency current-mode converter operating above
50% duty cycle. Therefore, to guarantee current loop stability, the slope of the compensation ramp must be greater than
one-half of the down slope of the current waveform. The ramp voltage for slope compensation is as follow,

V

RAMP

V

CMD

R14

---------- -= ∆V

×

R11

OSC

R12

C2

TR2

R11

Slop Compensation

R14

Vref

1

+

_

To PWM

Comparator

FAN8902

6

5

OSC

7. Motor Stall Current Limitation

FAN8902

V

CMD

1

CMD

I*

4R

Buffer-OP-amp

R

+

−

V

+
+

−

CS

PWM
COMP

VBAT

Logic

× 5

+

C1

C2

V

LA

14

12

10

R10

C4

Q1

R2

R3

D1

R5

M

IM

V

GS

Q2

V

RS

R

S

8

FAN8902(KA3902)

In the steady state, the terminal voltage on a motor is consisted of a back EMF and the voltage drop on the armarture resistors.
When the motor happens to be stalled, the back EMF becomes zero, and the motor current (I

) is quickl y increase d until a

M

maximum values.

Therefore the duty of the pin #12 output becomes lower because of the increase of the sense voltage (V
voltage (V

) be lowered, then it makes the duty become lower again.

La

This mechanism makes the motor current hold very low value in the stalled motor state.

The voltage on pin #14 (V

V

LaVBAT

×= Assumed the saturation voltage of Q1 is zero.

D×

) ia calculated as follows:

La

R3

--------------------- ­R2 R3+

We can choose the ratio of the resistors, R2 and R3, as follows:

- Applied the rated voltage on motor, and then measured the current IRAT

- Matched the maximum command current, V
V

CMD,MAX

for example, if R
V

-V

La,MAX

Ratio = R3 / (R2 + R3) = V

= V

La,MAX
S

CMD,MAX

= 5V = V

= RS × I

= 10mΩ and I

= V

La,MAX

× 1 × R3 / (R2 + R3)

BAT

CMD,MAX

× 5 × 5

RAT

= 20[A] at V

RAT

= 10mΩ × 20 × 25 = 5V

/ V

BAT

CMD,MAX

BAT

= 5 / 13

to I

= 13[V],

RAT

.

Therefore, R2 : R3 = 8 : 5

V

BAT

V

MOTOR

Operating curve

A

B

VLa curve × (1 / R)

). Also it makes the

RS

The voltage drop
on the amarture resistance

B”

V

LA

La

B’

V

LA

than V

V

V

CMD I

LA

RAT

and VLa so as to limit the stalled motor current to very low in

CMD

, the motor operating point stays at A. But th e point gradually moves

CMD

V

MOTOR,STALL

The buffer OP-amp selects the lower command between V
the above figure. Because of much larger V
toward B’ and then B” through the curve from the instance of stall as the below figure.

9

V

CMD

V

La

Reduced switch-on time

FAN8902(KA3902)

V

CS

Motor current

Normal operation

8. Operational Mode Selection

The FAN8902 has three operation modes as follows:

- STOP: Turned-off the power MOSFET

- LINEAR: Linearly controlled the power MOSFET

- FULL-ON: Fully turned-on the power MOSFET

The voltage, V

-V

SRT (PIN #9)

-V

MAX (PIN #7)

SRT (PIN #9)

and V

MAX (PIN #7)

= Vref × R7 / (R5 + R6 + R7)

= Vref × (R6 + R7) / (R5 + R6 + R7)

Motor
current
[A]

, in the application circuit are as follows:

I

MAX

I

SRT

STOP

Uncontrolled without the FAN8902
Controlled with the FAN8902

Stalled state

LINEAR

V

SRT

FULL-ON

V

MAX

V

BAT

V

[V]

CMD

9. Over Voltage Protector (Ovp)

If the voltage, V
the motor is stopped. Then if the voltage, V

≥ 36[V], the output (pin #12) is grounded, and the switching device (power MOSFET) is turned-off, and

BAT

→ 36[V], the switching device is turned-on again, and the motor is operated.

BAT

10. T otem-pole Output

The FAN8902 has a single totem-pole output driver which can be drive current to peak ±0.8[A].

10

FAN8902(KA3902)

Test Circuit

C

O

47µF

IN 6

V

CC

SW 2

A

+

La VCC OUT PG CS CL NC

Cid
1µF

Iout

TP 4

IN 4IN 5

891011121314

F A N 8 9 0 2

CMD CMDa CMDb SG RT / C

123 4567

R2
10k

R1
10k

C
1nF

T

R

T

75k

T

SW 1

VREF CH

C2

+

22µF

11

IN 1 TP 1 IN 2 TP 2

TP 3 IN 3

Iout

Typical Application

FAN8902(KA3902)

Current
command

R12

R11

R14

V

BAT

1

CMD

NC

2

CMDa

NC

C

T

R

T

R5

CMDb

3

4

SG

5

R

T

6

VREF

F A N 8 9 0 2

/ C

T

C1

+

VCC

OUT

PG

CS

CL

C2

M

D1

C4

R10

Q1

R2

R3

R4

R

S

R1

La

14

13

12

11

10

9

C3

+

R7

R6

78

CH

NC

NC

12

FAN8902(KA3902)

13

FAN8902(KA3902)

DISCLAIMER

FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURT HER NOTICE TO ANY
PRODUCTS HEREI N TO IMPROVE RELIABILITY, FUNCTIO N OR DESIGN. FAIRCH IL D DOES NOT ASSUME ANY
LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER
DOES IT CONVEY ANY LICENSE UNDER IT S PATENT RIGHTS, NOR THE RIGHTS OF OTHE RS.

LIFE SUPPORT POL I CY

FAIRCHILD’S PR ODUCTS ARE NOT AUTH ORIZED FOR USE AS C RITICAL COMPONENT S IN LIFE SUPPORT DE VICES
OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR
CORPORATION. As used herein :

1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body,
or (b) support or sustain life, and (c) whose failure to
perform when properly used in accordance with

2. A critical component in any component of a life support
device or sy stem whose fai lure to perform can be
reasonably expec ted to cause the failur e of the life support
device or system, or to affect its safety or effec t iv ene ss .

instructions for use provided in the labeling, can be
reasonably expected to result in a significant injury of the
user.

www.fairchildsemi.com

9/17/02 0.0m 001

 2002 Fairchild Semiconductor Corporation

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