Fairchild Semiconductor FAN7556 Datasheet
FAN7556
Voltage Mode PWM Controller
www.fairchildsemi.com
Features
• Voltage Mode Control
• Pulse by Pulse Current Limiting
• Low External Components
• Under Voltage Lockout ( UVLO): 9V/15V
• Stand-by Curr ent : Typ. 100uA
• Power Saving Mode Current: Typ. 200uA
• Operating Current: Typ. 7mA
• Soft Start
• On/off Control
• Over Load Protection (OLP)
• Over Current Protection (OCP)
• Over Voltage Protection (OVP)
• Wide Operating Frequency Range (20kHz ~ 500kHz )
• Auto-Restart Funct io n
Applications
• Off-Line & DC-DC Converter
Internal Block Diagram
Description
The FAN7556 is a fixed frequency voltage mode PWM
controller. It is specially designed for off-line and DC-DC
converter applications with minimal external components.
These integrated circuits feature a trimmed oscillator for
precise duty cycle control, a temperature compensated
reference, an on/off control, a high gain error amplifier, a
current sensing comparator, and a high current totem-pole
output. The FAN7556 has various protection functions such
as an over load protection (OLP), an over current
protection(O CP), and an over voltage protection(OVP) . The
FAN7556 is available in the 8DIP package as well as the
8SOP package.
8-DIP
1
8-SOP
1
LA
LA
S/S
S/S
FB
FB
1
1
8
8
2
2
0.3V
0.3V
2V
2V
Vref
Vref
100uA
100uA
+
+
_
_
COM
COM
+
+
_
_
5uA
5uA
6V
6V
1k
1k
Vcc
Vcc
3.5V
3.5V
Vref
Vref
+
+
_
_
1.5V
1.5V
1mA
1mA
OLP
OLP
COM-out
COM-out
_
_
+
+
_
_
+
+
OVP-out
OVP-out
S R
S R
Q
Q
3k
3k
CT Vcc
CT Vcc
7
4
4
off
off
on
on
+
+
_
_
_
_
2.7V
2.7V
UVLO-out
UVLO-out
PWR
PWR
/
/
SAVE
SAVE
PWM
PWM
OSC
OSC
OVP
OVP
+
+
_
_
UVLO
UVLO
+
+
Vref
Vref
CLK
CLK
R
R
Q
Q
S
S
S
S
Q
Q
R
R
_
_
OCP
OCP
34V
34V
15/9V
15/9V
14V
14V
+
+
_
_
6
6
0.25V
0.25V
5
55
OUT
OUT
I S
I S
3
33
4
4
GND
GND
Rev. 1.0.1
©2002 Fairchild Semiconductor Corporation
FAN7556
Absolute Maximum Ratings
( Ta = 25°C, unless otherwise specified )
Parameter Symbol Value Unit
Supply Voltage Vcc 30 V
Output Current I
Input Voltage to FB Pin V
Input Voltage to IS Pin V
Power Dissipation (Ta ≤ 25°C)
8-DIP
8-SOP
Operating Temperature T
Storage Temperature T
Thermal Resistance, Junction-to-Air(Note1)
8-DIP
8-SOP
Note:
1. Junction -to -air thermal resistance test environments.
-. Pneumatic heat sink fixture.
-. Clamping pressure 60psi through 12mm diameter cylinder.
-. Thermal gr ease applied be tween PKG and h eat sink fixtur e
O
FB
IS
P
D
OPR
STG
Rθja 147.1
±1 A
V
SD
-0.3 to V
OC
0.85
0.62
-25 to +125 °C
-55 to +150 °C
°C/W
201.6
V
V
W
Temperature Characteristics
( -25°C ≤ Ta ≤ 125°C )
Parameter Symbol Value Unit
Fosc Temperature Stability ∆F
2
2±5 %
OSC
PIN Array
S/S
S/S
8
8
1
1
LA
LA
CT
CT
7
7
FFFFAAAANNNN7777555555556666
FFFFAAAANNNN7777555555556666
2
2
FB
FB
Vcc
Vcc
6
6
YYYYWWWWWWWW
YYYYWWWWWWWW
3
3
IS
IS
OUT
OUT
5
5
4
4
GND
GND
FAN7556
YWW : Work Week Code
PIN Definitions
Pin Number Pin Name Pin Function Description
1 LA Optional Protection
2 FB Inverting (-) Input of PWM Comparator, ON/OFF Control & Over Load Sensing
3 IS Over Current Sensing
4 GND Ground
5 OUT Output of Gate Driver
6 Vcc Power Supply
7 CT Oscillator Timing Capacitor Ct
8 S/S Soft Start
3
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