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FAN7602
Green Current Mode PWM Controller
Features
Description
Green Current Mode PWM Control
The FAN7602 is a green current mode PWM controller. It
is specially designed for off-line adapter application,
DVDP, VCR, LCD monitor application, and auxiliary
power supplies.
Fixed 65kHz Operation with Frequency Modulation
Internal High-Voltage Start-up Switch
Burst Mode Operation
Line Voltage Feed Forward to Limit Maximum Power
Line Under-Voltage Protection
Latch Protection & Internal Soft-Start (10ms) Function
Overload Protection
Over-Voltage Protection
Low Operation Current: Typical 1mA
8-pin DIP/SOP
The internal high-voltage start-up switch and the burstmode operation reduce the power loss in standby mode.
Because of the internal start-up switch and the burst
mode, it is possible to supply 0.5W load, limiting the
input power to under 1W when the input line voltage is
265VAC. On no-load condition, the input power is under
0.3W.
The maximum power can be limited constantly, regardless of the line voltage change, using the power limit
function.
Applications
Adapter
The switching frequency is internally fixed at 65kHz and
the frequency modulation technique reduces EMI.
LCD Monitor Power
Auxiliary Power Supply
The FAN7602 includes various protections for the system reliability and the internal soft-start prevents the output voltage overshoot at start-up.
Related Application Notes
AN6014 - Green Current Mode PWM Controller
FAN7602
Ordering Information
Part Number
Operating Temp.
Range
Pb-Free
FAN7602N
FAN7602M
-25°C to +125°C
FAN7602MX
© 2006 Fairchild Semiconductor Corporation
FAN7602 Rev. 1.0.2
Yes
Package
Packing Method
Marking
Code
8-DIP
Rail
FAN7602
8-SOP
Rail
FAN7602
Tape & Reel
FAN7602
www.fairchildsemi.com
FAN7602 Green Current Mode PWM Controller
November 2006
FAN7602 Green Current Mode PWM Controller
Typical Application Diagram
FAN7602
FAN7602 Rev. 02
Figure 1. Typical Flyback Application
Internal Block Diagram
Vstr
8
6 VCC
LUVP
1
LUVP
OLP
2V/1.5V
OVP
Auto Restart
Protection
OVP
SS End
Latch
Protection
Latch
Reset
Circuit
Driver
Circuit
5 OUT
Plimit
Offset
3 CS/FB
Delay
Circuit
0.95V/0.88V
Latch
2
12V/8V
UVLO
PWM
Block
65kHz Clock
with
Frequency
Modulation
Latch/
Plimit
5V Ref
VCC
SS End
10ms
Soft Start
19V
PWM+
OLP
4V
Plimit
Offset
Plimit
Offset
Generator
SoftStart
Power Limit
Plimit
Offset
OLP
4 GND
Soft-Start
FAN7602 Rev. 03
Figure 2. Functional Block Diagram of FAN7602
© 2006 Fairchild Semiconductor Corporation
FAN7602 Rev. 1.0.2
www.fairchildsemi.com
2
FAN7602 Green Current Mode PWM Controller
Pin Assignments
Vstr
NC
VCC
OUT
8
7
6
5
FAN7602
YWW
1
2
3
4
LUVP
Latch/
Plimit
CS/FB
GND
FAN7602 Rev. 03
Figure 3. Pin Configuration (Top View)
Pin Definitions
Pin Number
Pin Name
Pin Function Description
1
LUVP
Line Under-Voltage Protection Pin. This pin is used to protect the set when the
input voltage is lower than the rated input voltage range.
2
Latch/Plimit
Latch Protection and Power Limit Pin. When the pin voltage exceeds 4V, the latch
protection works. The latch protection is reset when the VCC voltage is lower than 5V.
For the power limit function, the Over-Current Protection (OCP) level decreases as
the pin voltage increases.
3
CS/FB
Current Sense and Feedback Pin. This pin is used to sense the MOSFET current
for the current mode PWM and OCP. The output voltage feedback information and
the current sense information are added using an external RC filter.
4
GND
Ground Pin. This pin is used for the ground potential of all the pins. For proper operation, the signal ground and the power ground should be separated.
5
OUT
Gate Drive Output Pin. This pin is an output pin to drive an external MOSFET. The
peak sourcing current is 450mA and the peak sinking current is 600mA. For proper
operation, the stray inductance in the gate driving path must be minimized.
6
VCC
Supply Voltage Pin. IC operating current and MOSFET driving current are supplied
using this pin.
7
NC
No Connection.
8
Vstr
Start-up Pin. This pin is used to supply IC operating current during IC start-up. After
start-up, the internal JFET is turned off to reduce power loss.
© 2006 Fairchild Semiconductor Corporation
FAN7602 Rev. 1.0.2
www.fairchildsemi.com
3
The “Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed. The
device should not be operated at these limits. The parametric values defined in the Electrical Characteristics tables are
not guaranteed at the absolute maximum ratings.
Symbol
VCC
Parameter
Supply Voltage
Value
Unit
20
V
IOH, IOL
Peak Drive Output Current
+450/-600
mA
VCS/FB
CS/FB Input Voltage
-0.3 to 20
V
VLUVP
LUVP Input Voltage
-0.3 to 10
V
VLatch
Latch/Plimit Input Voltage
-0.3 to 10
V
Vstr
Vstr Input Voltage
600
V
TJ
Operating Junction Temperature
150
°C
TA
Operating Temperature Range
-25 to 125
°C
Tstg
Storage Temperature Range
-55 to 150
°C
PD
Power Dissipation
1.2
W
VESD_HBM
ESD Capability, Human Body Model
2.0
kV
VESD_MM
ESD Capability, Machine Model
300
V
VESD_CDM
ESD Capability, Charged Device Model
500
V
Thermal Impedance
Symbol
θJA(1)
Parameter
Thermal Resistance, Junction-to-Ambient
8-DIP
Value
Unit
100
°C/W
Note:
1. Regarding the test environment and PCB type, please refer to JESD51-2 and JESD51-10.
© 2006 Fairchild Semiconductor Corporation
FAN7602 Rev. 1.0.2
www.fairchildsemi.com
4
FAN7602 Green Current Mode PWM Controller
Absolute Maximum Ratings
VCC = 14V, TA = -25°C~125°C, unless otherwise specified.
Symbol
Parameter
Condition
Min.
Typ.
Max.
Unit
Vstr = 30V, TA = 25°C
0.7
1
1.4
mA
START UP SECTION
Istr
Vstr Start-up Current
UNDER VOLTAGE LOCK OUT SECTION
Vth(start)
Start Threshold Voltage
VCC increasing
11
12
13
V
Vth(stop)
Stop Threshold Voltage
VCC decreasing
7
8
9
V
HY(uvlo)
UVLO Hysteresis
3.6
4
4.4
V
250
320
μA
1
1.5
mA
5
10
15
ms
59
65
73
kHz
SUPPLY CURRENT SECTION
Ist
Start-up Supply Current
TA = 25°C
ICC
Operating Supply Current
Output no switching
SOFT-START SECTION
TSS
Soft-Start Time(2)
PWM SECTION
FOSC
Operating Frequency
ΔF
Frequency Modulation
VCS/FB1
tD
CS/FB Threshold Voltage
VCS/FB = 0.2V, TA = 25°C
±2
TA = 25°C
0.9
Propagation Delay to Output(2)
DMAX
Maximum Duty Cycle
DMIN
Minimum Duty Cycle
70
kHz
1.0
1.1
V
100
150
ns
75
80
%
0
%
BURST MODE SECTION
VCS/FB2
Burst On Threshold Voltage
TA = 25°C
0.84
0.95
1.06
V
VCS/FB3
Burst Off Threshold Voltage
TA = 25°C
0.77
0.88
0.99
V
VLatch/Plimit = 2V, TA = 25°C
0.12
0.16
0.20
11.5
12
14
V
POWER LIMIT SECTION
KPlimit
Offset Gain
OUTPUT SECTION
VOH
Output Voltage High
TA = 25°C, Isource = 100mA
VOL
Output Voltage Low
TA = 25°C, Isink = 100mA
1
2.5
V
tr
Rising
Time(2)
TA = 25°C, Cl = 1nF
45
150
ns
tf
Falling Time(2)
TA = 25°C, Cl = 1nF
35
150
ns
Note:
2. These parameters, although guaranteed by design, are not tested in production.
© 2006 Fairchild Semiconductor Corporation
FAN7602 Rev. 1.0.2
www.fairchildsemi.com
5
FAN7602 Green Current Mode PWM Controller
Electrical Characteristics
VCC = 14V, TA = -25°C~125°C, unless otherwise specified.
Symbol
Parameter
Condition
Min.
Typ.
Max.
Unit
3.6
4
4.4
V
PROTECTION SECTION
VLatch
TOLP
TOLP_ST
VOLP
Latch Voltage
(3)
Overload Protection Time
20
22
24
ms
Overload Protection Time at Start-up
30
37
44
ms
0
0.1
V
Overload Protection Level
VLUVPoff
Line Under-Voltage Protection On to Off
VLUVPon
VOVP
TA = 25°C
1.9
2
2.1
V
Line Under-Voltage Protection Off to On
TA = 25°C
1.4
1.5
1.6
V
Over Voltage Protection
TA = 25°C
18
19
20
V
Note:
3. These parameters, although guaranteed by design, are not tested in production.
© 2006 Fairchild Semiconductor Corporation
FAN7602 Rev. 1.0.2
www.fairchildsemi.com
6
FAN7602 Green Current Mode PWM Controller
Electrical Characteristics (Continued)
8.8
12.4
8.4
VTL[V]
VTH[V]
12.8
12.0
8.0
11.6
7.6
11.2
7.2
-25
0
25
50
75
100
-25
125
0
25
50
75
100
125
Temperature [°C]
Temperature [°C]
Figure 4. Start Threshold Voltage vs. Temp.
Figure 5. Stop Threshold Voltage vs. Temp.
4.4
350
4.2
300
4.1
Ist [μA]
UVLO Hysteresis [V]
4.3
4.0
250
3.9
3.8
200
3.7
3.6
-25
0
25
50
75
100
150
-25
125
0
Temperature [°C]
25
50
75
100
125
Temperature [°C]
Figure 6. UVLO Hysteresis vs. Temp.
Figure 7. Start-up Supply Current vs. Temp.
1.5
1.3
1.4
1.2
Istr [mA]
Iop [mA]
1.3
1.2
1.1
1.1
1.0
1.0
0.9
0.9
0.8
-25
0
25
50
75
100
0.8
-25
125
Temperature [°C]
25
50
75
100
125
Temperature [°C]
Figure 9. Vstr Star-up Current vs. Temp.
Figure 8. Operating Supply Current vs. Temp.
© 2006 Fairchild Semiconductor Corporation
FAN7602 Rev. 1.0.2
0
www.fairchildsemi.com
7
FAN7602 Green Current Mode PWM Controller
Typical Performance Characteristics
70
1.10
CSFB2
CSFB3
68
1.00
FOSC [kHz]
CS/FB Threshold [V]
1.05
0.95
0.90
0.85
0.80
66
64
62
0.75
0.70
-25
0
25
50
75
100
60
-25
125
0
Temperature [°C]
75
100
125
Figure 11. Operating Frequency vs. Temp.
0.20
80
0.18
78
DMAX [%]
Kplimit
50
Temperature [°C]
Figure 10. Burst On/Off Voltage vs. Temp.
0.16
0.14
0.12
76
74
72
0.10
-25
0
25
50
75
100
70
-25
125
0
Temperature [°C]
25
50
75
100
125
Temperature [°C]
Figure 12. Offset Gain vs. Temp.
Figure 13. Maximum Duty Cycle vs. Temp.
4.4
20.0
19.6
4.2
VLATCH [V]
VOVP [V]
25
19.2
18.8
4.0
3.8
18.4
18.0
-25
0
25
50
75
100
3.6
-25
125
Temperature [°C]
25
50
75
100
125
Temperature [°C]
Figure 14. OVP Voltage vs. Temp.
Figure 15. Latch Voltage vs. Temp.
© 2006 Fairchild Semiconductor Corporation
FAN7602 Rev. 1.0.2
0
www.fairchildsemi.com
8
FAN7602 Green Current Mode PWM Controller
Typical Performance Characteristics (Continued)
2.10
1.70
1.65
VLUVPon [V]
VLUVPoff [V]
2.05
2.00
1.60
1.55
1.50
1.95
1.45
1.90
-25
0
25
50
75
100
1.40
-25
125
Temperature [°C]
25
50
75
100
125
Temperature [°C]
Figure 16. LUVP On to Off Voltage vs. Temp.
CSFB1 Threshold voltage [V]
0
Figure 17. LUVP Off to On Voltage vs. Temp.
1.08
1.04
1.00
0.96
0.92
-25
0
25
50
75
100
125
Temperature [°C]
Figure 18. CS/FB Threshold Voltage vs. Temp.
© 2006 Fairchild Semiconductor Corporation
FAN7602 Rev. 1.0.2
www.fairchildsemi.com
9
FAN7602 Green Current Mode PWM Controller
Typical Performance Characteristics (Continued)
1. Start-up Circuit and Soft-Start Block
Figure 21 shows the current sense and feedback circuits.
RS is the current sense resistor to sense the switch current. The current sense information is filtered by an RC
filter composed of RF and CF. According to the output
voltage feedback information, IFB charges or stops charging CF to adjust the offset voltage. If IFB is zero, CF is discharged through RF and RS to lower the offset voltage.
The FAN7602 contains a start-up switch to reduce the
power loss of the external start-up circuit of the conventional PWM converters. The internal start-up circuit
charges the VCC capacitor with 0.9mA current source if
the AC line is connected. The start-up switch is turned off
15ms after IC starts up, as shown in Figure 19. The softstart function starts when the VCC voltage reaches the
start threshold voltage of 12V and ends when the internal
soft-start voltage reaches 1V. The internal start-up circuit
starts charging the VCC capacitor again if the VCC voltage is lowered to the minimum operating voltage, 8V.
The UVLO block shuts down the output drive circuit and
some blocks to reduce the IC operating current and the
internal soft-start voltage drops to zero. If the VCC voltage reaches the start threshold voltage, the IC starts
switching again and the soft-start block works as well.
67kHz
16 steps
1 step=250Hz
63kHz
125Hz
FAN7602 Rev. 02
Figure 20. Frequency Modulation
Figure 22 shows typical voltage waveforms of the CS/FB
pin. The current sense waveform is added to the offset
voltage as shown in the figure. The CS/FB pin voltage is
compared with PWM+ that is 1V - Plimit offset as shown
in Figure 22. If the CS/FB voltage meets PWM+, the output drive is shut off. As shown in Figure 22, if the feedback offset voltage is low, the switch on time is
increased. If the feedback offset voltage is high, the
switch on time is decreased. In this way, the duty cycle is
controlled according to the output load condition. In general, the maximum output power increases as the input
voltage increases because the current slope during
switch on-time increases. To limit the output power of the
converter constantly, the power limit function is included
in the FAN7602. Sensing the converter input voltage
through the Latch/Plimit pin, the Plimit offset voltage is
subtracted from 1V. As shown in Figure 22, the Plimit offset voltage is subtracted from 1V and the switch on-time
decreases as the Plimit offset voltage increases. If the
converter input voltage increases, the switch on-time
decreases, controlling the output power constant. The
offset voltage is proportional to the Latch/Plimit pin voltage and the gain is 0.16. If the Latch/Plimit voltage is 1V,
the offset voltage is 0.16V.
During the soft-start, pulse-width modulated (PWM) comparator compares the CS/FB pin voltage with the softstart voltage. The soft-start voltage starts from 0.5V and
the soft-start ends when it reaches 1V and the soft-start
time is 10ms. The start-up switch is turned off when the
soft-start voltage reaches 1.5V.
VCC
12V
8V
Start-up
Current
1.5V
1V
0.5V
Soft-Start
Voltage
Soft-Start
Time (10ms)
t
5ms
FAN7602 Rev. 02
Figure 19. Start-up Current and VCC Voltage
2. Oscillator Block
The oscillator frequency is set internally and a frequency
modulation (FM) function reduces EMI. The average frequency is 65kHz and the modulation frequency is ±2kHz.
The frequency varies from 63kHz to 67kHz with 16
steps. The frequency step is 250Hz and FM frequency is
125Hz, as shown in Figure 20.
VCC
PWM
Comparator
PWM+
Soft-Start
3. Current Sense and Feedback Block
RFB
Power
Limit
3
The FAN7602 performs the current sensing for the current mode PWM and the output voltage feedback with
only one pin, pin 3. To achieve the two functions with one
pin, an internal LEB (leading edge blanking) circuit to filter the current sense noise is not included because the
external RC filter is necessary to add the output voltage
feedback information and the current sense information.
CS/FB
IFB
RF
Isw
CF
RS
FAN7602 Rev. 02
Figure 21. Current Sense and Feedback Circuits
© 2006 Fairchild Semiconductor Corporation
FAN7602 Rev. 1.0.2
Plimit
Offset
www.fairchildsemi.com
10
FAN7602 Green Current Mode PWM Controller
Applications Information
Power Limit
Offset
CS/FB
FB
Offset
Clock
GND
OLP
3 CS/FB
22ms
Timer
50mV
Soft-Start
On Time
FAN7602 Rev. 02
(a) Low Power Limit Offset Case
Figure 24. Overload Protection Circuit
1V
Power Limit
Offset
PWM+
CS/FB
5.2 Line Under-Voltage Protection
If the input voltage of the converter is lower than the minimum operating voltage, the converter input current
increases too much, causing components failure. Therefore, if the input voltage is low, the converter should be
protected. In the FAN7602, the LUVP circuit senses the
input voltage using the LUVP pin and, if this voltage is
lower than 2V, the LUVP signal is generated. The comparator has 0.5V hysteresis. If the LUVP signal is generated, the output drive block is shut down, the output
voltage feedback loop is saturated, and the OLP works if
the LUVP condition persists more than 22ms.
FB
Offset
GND
On Time
(b) High Power Limit Offset Case
FAN7602 Rev. 02
Figure 22. CS/FB Pin Voltage Waveforms
4. Burst Mode Block
The FAN7602 contains the burst mode block to reduce
the power loss at a light load and no load as the
FAN7601. A hysteresis comparator senses the offset
voltage of the Burst+ for the burst mode as shown in Figure 23. The Burst+ is the sum of the CS/FB voltage and
Plimit offset voltage. The FAN7602 enters the burst
mode when the offset voltage of the Burst+ is higher than
0.95V and exits the burst mode when the offset voltage
is lower than 0.88V. The offset voltage is sensed during
the switch off time.
Vin
1
+
−
B u rs t+
0 .9 5 V /0 .8 8 V
3
LUVP
2V/1.5V
FAN7602 Rev. 02
Figure 25. Line UVP Circuit
O ffs e t
D e la y
C irc u it
−
+
5.3 Latch Protection
The latch protection is provided to protect the system
against abnormal conditions using the Latch/Plimit pin.
The Latch/Plimit pin can be used for the output overvoltage protection and/or other protections. If the Latch/
Plimit pin voltage is made higher than 4V by an external
circuit, the IC is shut down. The latch protection is reset
when the VCC voltage is lower than 5V.
C S /F B
FA N7602 R ev. 02
Figure 23. Burst Mode Block
5. Protection Block
The FAN7602 contains several protection functions to
improve system reliability.
5.4 Over-Voltage Protection (OVP)
If the VCC voltage reaches 19V, the IC shuts down and
the OVP protection is reset when the VCC voltage is
lower than 5V.
5.1 Overload Protection
The FAN7602 contains the overload protection function.
If the output load is higher than the rated output current,
the output voltage drops and the feedback error amplifier
is saturated. The offset of the CS/FB voltage representing the feedback information is almost zero. As shown in
Figure 24, the CS/FB voltage is compared with 50mV
reference when the internal clock signal is high and, if
the voltage is lower than 50mV, the OLP timer starts
6. Output Drive Block
The FAN7602 contains a single totem-pole output stage
to drive a power MOSFET. The drive output is capable of
up to 450mA sourcing current and 600mA sinking current with typical rise and fall time of 45ns, 35ns respectively with a 1nF load.
© 2006 Fairchild Semiconductor Corporation
FAN7602 Rev. 1.0.2
www.fairchildsemi.com
11
FAN7602 Green Current Mode PWM Controller
1V
PWM+
counting. If the OLP condition persists for 22ms, the
timer generates the OLP signal. And this protection is
reset by the UVLO. The OLP block is enabled after the
soft-start finishes.
Application
Output power
Input voltage
Output voltage
Adapter
48W
Universal input
(85~265VAC)
12V
Features
Low stand-by power (
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