FAN400A — Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback
October 2008
FAN400A —
Low-Power Green-Mode PWM Flyback Power
Controller without Secondary Feedback
Features
Linearly Decreasing PWM Frequency
Green Mode Under Light-Load and Zero-Load
Conditions
Constant Voltage (CV) and Constant Current (CC)
No Secondary Feedback
Low Startup Current: 8μA
Low Operating Current: 3.6mA
Leading-Edge Blanking
Constant Power Limit
Universal AC Input Range
Synchronized Slope Compensation
140°C OTP Sensor with Hysteresis
V
DD
Over-Voltage Clamping
Cycle-by-Cycle Current Limiting
Under-Voltage Lockout (UVLO)
Fixed PWM Frequency with Hopping
Gate Output Maximum Voltage Clamped at 17V
Small SSOT-6 Package
Description
This highly integrated PWM controller provides several
features to enhance the performance of low-power
flyback converters. To minimize standby power
consumption, a proprietary green-mode function
provides off-time modulation to linearly decrease the
switching frequency under light-load and zero-load
conditions. This green mode enables the power supply
to meet international power conservation requirements.
The supply voltage V
DD
is also used for feedback
compensation, to regulate the output voltage without
requiring a conventional TL431 and a photo-coupler.
Another advantage of the FAN400A is that the typical
startup current is only 8μA, while the typical operating
current can be as low as 3.6mA. A large startup
resistance can be used to achieve even higher power
conversion efficiency.
FAN400A integrates a frequency hopping function
internally to reduce EMI emissions with minimum line
filters. Built-in synchronized slope compensation
maintains the stability of peak current-mode control.
Proprietary internal compensation ensures constant
output power limiting over a universal range of AC input
voltages, from 90V
AC
to 264V
AC
.
The FAN400A provides many protection functions.
Pulse-by-pulse current limiting ensures constant output
current, even if a short circuit occurs. The internal
protection circuit disables PWM output if V
DD
exceeds
22.7V. The gate output is clamped at 17V to protect the
power MOS from over-voltage damage. The built-in
over-temperature protection (OTP) function shuts down
the controller at 140°C with a 30°C hysteresis.
The FAN400A is designed to provide a low-cost total
solution for flyback converters. It is available in a small-
footprint, 6-pin, SSOT-6 package.
Applications
General-purpose, switching mode, power supplies and
flyback power converters, such as:
Battery Chargers for Cellular Phones, Cordless
Phones, PDAs, Digital Cameras, Power Tools
Power Adapters for Ink Jet Printers, Video Game
Consoles, Portable Audio Players
Open-Frame SMPS for TV/DVD Standby and
Auxiliary Supplies, Home Appliances, Consumer
Electronics
Replacement for Linear Transformers and RCC SMPS
PC 5V Standby Power
Related Resources
AN-400A Low-Power Green-Mode PWM Flyback
Power Controller without Secondary Feedback
Ordering Information
Part Number
FAN400ATY
FAN400ANY
Operating Temperature Range
-40°C to +105°C
-40°C to +105°C
Package
SSOT-6
DIP-8
Eco Status
Green
Green
Packing Method
Tape & Reel
Tube
For Fairchild’s definition of “green” please visit:
http://www.fairchildsemi.com/company/green/rohs_green.html.
© 2008 Fairchild Semiconductor Corporation
FAN400A Rev. 1.0.2
www.fairchildsemi.com
FAN400A — Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback
Absolute Maximum Ratings
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be
operable above the recommended operating conditions and stressing the parts to these levels is not recommended.
In addition, extended exposure to stresses above the recommended operating conditions may affect device
reliability. The absolute maximum ratings are stress ratings only.
Symbol
V
VDD
V
FB
V
SENSE
T
J
Θ
JA
T
STG
T
L
ESD
DC Supply Voltage
(1, 2)
Parameter
Input Voltage to FB Pin
Input Voltage to Sense Pin
Operating Junction Temperature
Thermal Resistance (Junction-to-Air)
Storage Temperature Range
Lead Temperature (Wave Soldering or IR, 10 Seconds)
Electrostatic Discharge Capability
Human Body Model
JESD22-A114
Machine Model
JESD22-A115
SSOT
DIP
Min.
-0.3
-0.3
Max.
30
7.0
7.0
+150
263.3
135.7
Unit
V
V
V
°C
°C/W
°C/W
°C
°C
kV
V
-55
+150
+260
4
200
Notes:
1. All voltage values, except differential voltages, are given with respect to GND pin.
2. Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device.
© 2008 Fairchild Semiconductor Corporation
FAN400A Rev. 1.0.2
www.fairchildsemi.com
4
FAN400A — Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback
Electrical Characteristics
Unless otherwise noted, V
DD
=15V and T
A
=25°C.
Symbol
V
DD
Section
V
DD-OP
V
DD-ON
V
DD-OFF
I
DD-ST
I
DD-OP
V
DD-G OFF
Parameter
Conditions
With Secondary
Feedback
Without Secondary
Feedback
Min.
Typ.
Max.
Units
20
22.7
16
7.5
17
8.0
8
3.6
V
DD-OFF
+1.2
18
8.5
20
4.6
V
V
V
V
μA
mA
V
Continuously Operation Voltage
Turn-on Threshold Voltage
Turn-off Threshold Voltage
Startup Current
Operating Supply Current
V
DD
Low-threshold Voltage to Exit
Green-off Mode
Input-Voltage to Current-Sense Attenuation
Input Impedance
Open-Loop Voltage
V
DD
Feedback Threshold Voltage
FB is Open
I
FB
=0.4mA
I
FB
=0.1mA to 0.2mA
V
DD
=V
DD-ON
– 0.1V
C
L
=1nF
Feedback Input Section
A
V
Z
FB
V
FB-OPEN
V
DD-FB
0.3
4.6
4.5
20.7
18.4
22.7
20.4
100
V
DD
=18V
V
STHVA
Current Limit Valley Threshold Voltage
V
DD
=15V
V
DD
=10V
V
DD
=18V
V
STHFL
t
LEB
Current Limit Flat Threshold Voltage
Leading-Edge Blanking Time
V
DD
=15V
V
DD
=10V
250
0.81
0.73
0.58
1.10
1.01
0.81
310
370
24.7
22.4
150
V/V
kΩ
V
V
V
ns
V
V
V
V
V
V
ns
Current-Sense Section
t
PD
Propagation Delay
Figure 5.
Saw Limit
© 2008 Fairchild Semiconductor Corporation
FAN400A Rev. 1.0.2
www.fairchildsemi.com
5
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