FAIRCHILD FAN8902

www.fairchildsemi.com
FAN8902(KA3902)
DC FAN Motor Controller
Features
Description
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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.
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
Typical Application
• DC for Motor Control for Automotive
14-DIP-300
Ordering Information
Device
Package
Operating Temperature
FAN8902
14-DIP-300
-40°C ~ +90°C
Rev. 1.0.3
©2002 Fairchild Semiconductor Corporation
FAN8902(KA3902)
Pin Assignments
CMD
1
14
La
CMDa
2
13
VCC
CMDb
3
12
OUT
SG
4
11
PG
RT / CT
5
10
CS
VREF
6
9
CL
CH
7
8
NC
FAN8902
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
5
RT / CT
Oscillator Time Constant
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
VCC
VCC
14
La
Motor Current Maximum Reference Input
2
FAN8902(KA3902)
Internal Block Diagram
Vref
6
UVLO
Vref
OVP
CH
+
−
1.3V
PWM
CMD
OUT
11
PGND
10
CS
LOGIC
4R
+
+
−
+
−
R
3
12
36V
1
La 14
CL
VCC
TSD
−
+
7
13
PWM
Comparator
+
−
9
×5
+
CMDa
2
CMDb
3
−
Oscillator
5
RT/CT
4
SGND
FAN8902(KA3902)
Absolute Maximum Ratings
Parameter
Symbol
Value
Unit
VCC
32
V
CMD Input Voltage
VCMD
6
V
Peak Output Current
IOPK
±0.8
A
PD
1
W
Supply Voltage
Power Dissipation
Operating Voltage
Parameter
Symbol
Min.
Typ.
Max
Unit
VCC
9.0
12.0
32.0
V
Power Supply Voltage
Temperature Characteristics
Parameter
Symbol
Temp
Value
Unit
Vref Temperature Stability
VST
-40 ~ +90°C
200
°C
Frequency Stability
FST
-40 ~ +90°C
20 ~ 30
°C
Operating Temperature
TOPR
-
-40 ~ +90
°C
Storage Temperature
TSTG
-
-60 ~ +150
°C
4
FAN8902(KA3902)
Electrical Characteristics
(Unless otherwise, Ta=25°C, VCC=5V, VM=12V)
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Unit
4.75
5.0
5.25
V
REFERENCE
Reference Voltage
Vref
Iref=1mA
Line Regulation
∆Vref1
VCC=9V ~ 32V
-
50
150
mV
Load Regulation
∆Vref2
Iref=1mA ~ 10mA
-
10
50
mV
UNDER VOLTAGE LOCKOUT (UVLO)
Start Threshold Voltage
VTH(ST)
-
7.5
8.0
8.5
V
VHYS
-
1.0
1.2
1.4
V
OVP
-
33
36
-
V
Frequency
fosc
-
20
25
30
kHz
Duty Cycle
Duty
-
90
95
-
%
0.19
0.20
0.21
V
Threshold Hysteresis
PROTECTION
Over Voltage
Ω, CT=1nF)
OSCILLATOR (RT=75kΩ
CURRENT SENSING INPUT
Threshold Voltage
VTH(ST)
VCMD = 5V
OUTPUT DRIVER
Output Voltage Switching Limit
Low Output Voltage
High Output Voltage
VOLIM
VCC = 18V, Cld =1nF
-
15
-
V
VOL1
Iout = 20mA
-
-
0.4
V
VOL2
Iout = 200mA
-
-
2.2
V
VOH1
Iout = -20mA
10.0
-
-
V
VOH2
Iout = -200mA
9.0
-
-
V
Rising Time
Tr
Cld = 1nF
-
100
200
ns
Falling Time
Tf
Cld = 1nF
-
100
200
ns
Start-up Current
IST
VCC = 7V
-
1.0
1.5
mA
Operating Supply Current
ICC
VCC = 9V
-
6.0
8.0
mA
TOTAL STANDBY CURRENT
5
FAN8902(KA3902)
Application Information
1. Under Voltage Lockout (UVLO)
ICC
6mA
13
Vref &
output driver
TH(ST)
THYS
1mA
8.0V
1.2V
FAN8902
6.8V
8V
VTH(ST)
2. Current Sensing Circuit
M
VBAT
PWM comparator
Imax=1V
+
PWM
Logic
−
×5
Current amplifier
R5
12
IM
VS
10
RS
FAN8902
The peak current, IM(MAX)=VS/RS
For example, if a required maximum current, IM(MAX)=20[A]
1V ⁄ 5
R S = --------------- = 10 [ mΩ ]
20A
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
VCT [V]
RT
T=40.0
VH=3.0
V/CT
Logic
+
CT
−
VL=1.75
ID
VL
VH
Td=1.0
The oscillator timing components can be calculated as follows:
T C = R T × C T × In [ ( Vref – V L ) ⁄ ( Vref – V H ) ]
TD = CT × [ ( VH – VL ) ⁄ ID ]
fosc = 1 ⁄ ( TC + T D )
= 1.875 ⁄ ( R T × C T )
Duty = T C × fosc × 100
For example, if fosc = 25kHz and duty = 95%
C T = ( T D × ID ) ⁄ ( VH – VL )
= 1000 [ pF ]
R T = 1.875 ⁄ ( fosc × C T )
= 1.875 ⁄ ( 25kHz × 1000pF )
= 75 [ kΩ ]
5. Current Command Input Section
The current command I* selects the lower value between VCMD and VLa.
VCMD
CMD 1
La 14
VLa
+
+
−
FAN8902
7
I*
4R
+
R
−
Logic
TC=39.0
t [µs]
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,
R14
V RAMP = ----------- × ∆V OSC
R11
R12
VCMD
1
+
To PWM
Comparator
_
C2
R14
FAN8902
Vref
6
TR2
OSC
5
R11
Slop Compensation
7. Motor Stall Current Limitation
+
D1
VBAT
C1
C2
M
FAN8902
Q1
CMD
VCMD
1
VLA
R2
I*
R10
+
+
−
14
IM
C4
4R
R3
Buffer-OP-amp
Logic
+
R
−
VGS
12
Q2
R5
PWM
COMP
×5
VRS
10
VCS
RS
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 (IM) is quickly increased until a
maximum values.
Therefore the duty of the pin #12 output becomes lower because of the increase of the sense voltage (VRS). Also it makes the
voltage (VLa) be lowered, then it makes the duty become lower again.
This mechanism makes the motor current hold very low value in the stalled motor state.
The voltage on pin #14 (VLa) ia calculated as follows:
R3
V La = V BAT × D × ---------------------R2 + R3
Assumed the saturation voltage of Q1 is zero.
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, VCMD,MAX to IRAT.
VCMD,MAX = VLa,MAX = RS × IRAT × 5 × 5
for example, if RS = 10mΩ and IRAT = 20[A] at VBAT = 13[V],
VCMD,MAX = VLa,MAX = 10mΩ × 20 × 25 = 5V
- VLa,MAX = 5V = VBAT × 1 × R3 / (R2 + R3)
Ratio = R3 / (R2 + R3) = VCMD,MAX / VBAT = 5 / 13
Therefore, R2 : R3 = 8 : 5
VBAT
Operating curve
A
VMOTOR
VLa curve × (1 / R)
B
The voltage drop
on the amarture resistance
B’
VMOTOR,STALL
B”
VLA VLA
VCMD
VLA
IRAT
The buffer OP-amp selects the lower command between VCMD and VLa so as to limit the stalled motor current to very low in
the above figure. Because of much larger VLa than VCMD, the motor operating point stays at A. But the point gradually moves
toward B’ and then B” through the curve from the instance of stall as the below figure.
9
FAN8902(KA3902)
VCMD
VLa
VCS
Reduced switch-on time
Motor current
Uncontrolled without the FAN8902
Controlled with the FAN8902
Stalled state
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, VSRT (PIN #9) and VMAX (PIN #7), in the application circuit are as follows:
- VSRT (PIN #9) = Vref × R7 / (R5 + R6 + R7)
- VMAX (PIN #7) = Vref × (R6 + R7) / (R5 + R6 + R7)
IMAX
Motor
current
[A]
ISRT
STOP
LINEAR
VSRT
FULL-ON
VMAX
VBAT
VCMD [V]
9. Over Voltage Protector (Ovp)
If the voltage, VBAT ≥ 36[V], the output (pin #12) is grounded, and the switching device (power MOSFET) is turned-off, and
the motor is stopped. Then if the voltage, VBAT → 36[V], the switching device is turned-on again, and the motor is operated.
10. Totem-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
IN 6
Iout
TP 4
IN 5
IN 4
9
8
VCC
SW 2
A
CO
47µF
Cid
1µF
+
14
La
13
12
11
10
VCC
OUT
PG
CS
CL
NC
SG
RT / CT
VREF
CH
4
5
6
7
TP 3
IN 3
FAN8902
CMD
CMDa
1
2
CMDb
3
R2
10k
CT
1nF
C2
+
22µF
RT
75k
R1
10k
SW 1
IN 1
TP 1
IN 2
TP 2
Iout
11
FAN8902(KA3902)
Typical Application
VBAT
+
C1
C2
M
D1
Q1
R1
R2
R10
R12
1
CMD
La
14
Current
command
C4
NC
2
CMDa
VCC
13
R3
+
C3
NC
3
CMDb
OUT
12
R4
4
R11
SG
PG
11
FAN8902
CT
5
RT / CT
CS
10
6
VREF
CL
9
RT
RS
R14
R7
R5
7
CH
NC
8
NC
R6
12
FAN8902(KA3902)
13
FAN8902(KA3902)
DISCLAIMER
FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY
PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD 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 ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.
LIFE SUPPORT POLICY
FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES
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
instructions for use provided in the labeling, can be
reasonably expected to result in a significant injury of the
user.
2. A critical component in any component of a life support
device or system whose failure to perform can be
reasonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
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 2002 Fairchild Semiconductor Corporation