2003 Fairchild Semiconductor Corporation
www.fairchildsemi.com
Rev.1.0.0
Features
Precise Fixed Operating Frequency
FS7M0680(66kHz)
Pulse By Pulse Current Limiting
Over Current Protection
Over Load Protection
Over Voltage Protection (Min. 25V)
Internal Thermal Shutdown Function
Under Voltage Lockout with Hysteresis
Internal High Voltage Sense FET
Latch Up Mode
Soft Start
Description
The Fairchild Power Switch (FPS) product family is specially
designed for an off line SMPS with minimal external compo-
nents. The Fairchild Power Switch (FPS) consists of high volt-
age power SenseFET and current mode PWM controller. The
PWM controller includes integrated fixed oscillator, under volt-
age lock out, leading edge blanking block, optimized gate turn-
on/turn-off driver, thermal shut down protection, over voltage
protection, temperature compensated precise current sources for
loop compensation and fault protection circuit. Compared to
discrete MOSFET and PWM controller or ring choke converter
(RCC) solutions, the Fairchild Power Switch (FPS) can reduce
total cost, component count, size and weight simultaneously
increasing efficiency, productivity, and system reliability. It has
simple applications well suited for cost down design for flyback
converter or forward converter.
TO-3P-5L
1. DRAIN 2. GND 3. V
CC
4. FB 5. S/S
1
Internal Block Diagram
# 4
Feedback
-
+
Therm al
S hutdo w n
-
+
Vref
-
+
R
V cc
R eset
# 1
D R AIN
# 2
S o urce
G N D
# 3
Vcc
# 5
S o ft S ta rt
O SC
UVLO
Internal
Vias
R o ff
Vo cp
R sense
D elay
12 0ns
Q
S
R
S
R
Q
Vfb
offset
PW M
Com parator
Vref
Vref
Idelay
Ifb
Vovp
Vcc
Vsd
3R
R o n
FS7M0680
Fairchild Power Switch(FPS)
FS7M0680
2
Absolute Maximum Ratings
Note:
1. T
j
= 25
C to 150C
2. Repetitive rating: Pulse width limited by maximum junction temperature
3. L = 24mH, V
DD
= 50V, R
G
= 25
, starting Tj =25C
4. L = 13
H, starting T
j
= 25
C
Parameter
Symbol
Value
Unit
Maximum Drain Voltage
(1)
V
D,MAX
800
V
Drain-Gate Voltage (R
GS
=1M
)
V
DGR
800
V
Gate-Source (GND) Voltage
V
GS
30
V
Drain Current Pulsed
(2)
I
DM
24.0
A
DC
Single Pulsed Avalanche Energy
(3)
E
AS
455
mJ
Avalanche Current
(4)
I
AS
20
A
Continuous Drain Current (T
C
=25
C)
I
D
6.0
A
DC
Continuous Drain Current (T
C
=100
C)
I
D
3.8
A
DC
Maximum Supply Voltage
V
CC,MAX
30
V
Input Voltage Range
V
FB
-0.3 to V
SD
V
Total Power Dissipation
P
D
150
W
Derating
1.21
W/
C
Operating Ambient Temperature
T
A
-25 to +85
C
Storage Temperature
T
STG
-55 to +150
C
FS7M0680
3
Electrical Characteristics (SenseFET part)
(Ta=25
C unless otherwise specified)
Note:
1. Pulse test: Pulse width
300S, duty cycle 2%
2.
Parameter
Symbol
Condition
Min.
Typ.
Max.
Unit
Drain-Source Breakdown Voltage
BV
DSS
V
GS
=0V, I
D
=50
A
800
-
-
V
Zero Gate Voltage Drain Current
I
DSS
V
DS
=Max., Rating,
V
GS
=0V
-
-
50
A
V
DS
=0.8Max., Rating,
V
GS
=0V, T
C
=125
C
-
-
200
A
Static Drain-Source On Resistance
(note1)
R
DS(ON)
V
GS
=10V, I
D
=5.0A
-
1.6
2.0
Forward Transconductance
(note1)
gfs
V
DS
=15V, I
D
=5.0A
1.5
2.5
-
S
Input Capacitance
Ciss
V
GS
=0V, V
DS
=25V,
f=1MHz
-
1600
-
pF
Output Capacitance
Coss
-
140
-
Reverse Transfer Capacitance
Crss
-
42
-
Turn On Delay Time
td(on)
V
DD
=0.5BV
DSS
, I
D
=8.0A
(MOSFET switching
time are essentially
independent of
operating temperature)
-
60
-
nS
Rise Time
tr
-
150
-
Turn Off Delay Time
td(off)
-
300
-
Fall Time
tf
-
130
-
Total Gate Charge
(Gate-Source+Gate-Drain)
Qg
V
GS
=10V, I
D
=8.0A,
V
DS
=0.5BV
DSS
(MOSFET
switching time are
essentially independent of
operating temperature)
-
70
-
nC
Gate-Source Charge
Qgs
-
16
-
Gate-Drain (Miller) Charge
Qgd
-
27
-
S
1
R
----
=
FS7M0680
4
Electrical Characteristics (control part)
(Continued)
(Ta=25
C unless otherwise specified)
Note:
1. These parameters, although guaranteed, are not 100% tested in production
2. These parameters, although guaranteed, are tested in EDS (wafer test) process
Parameter
Symbol
Condition
Min.
Typ.
Max.
Unit
UVLO SECTION
Start Threshold Voltage
V
START
-
14
15
16
V
Stop Threshold Voltage
V
STOP
After turn on
8
9
10
V
OSCILLATOR SECTION
Initial Frequency
F
OSC
-
60
66
72
kHz
Frequency Change With Temperature
(2)
F/T
-25
C Ta +85C
-
5
10
%
Maximum Duty Cycle
Dmax
-
45
50
55
%
Voltage Stability
Fstable
12V
Vcc 23V
0
1
3
%
FEEDBACK SECTION
Feedback Source Current
I
FB
Ta=25
C, 0V Vfb 3V
0.7
0.9
1.1
mA
Shutdown Delay Current
Idelay
Ta=25
C, 5V Vfb V
SD
4.0
5.0
6.0
A
Shutdown Feedback Voltage
Vsd
6.9
7.5
8.1
V
SOFT START SECTION
Soft Start Voltage
V
SS
V
FB
=2V
4.7
5.0
5.3
V
Soft Start Resistor
Rsoft
Bias=Vref, SS=0V
16.0
18.5
22.0
k
REFERENCE SECTION
Output Voltage
(1)
Vref
Ta=25
C
4.80
5.00
5.20
V
Temperature Stability
(1)(2)
Vref/
T
-25
C Ta +85C
-
0.3
0.6
mV/
C
CURRENT LIMIT (SELT-PROTECTION)SECTION
Peak Current Limit
I
OVER
Max. inductor current
3.52
4.00
4.48
A
PROTECTION SECTION
Thermal Shutdown Temperature (Tj)
(1)
T
SD
-
140
-
-
C
Over Voltage Protection Voltage
V
OVP
-
25
28
31
V
Over Current Protection Voltage
V
OCP
-
1.05
1.10
1.15
V
TOTAL DEVICE SECTION
Start Up Current
I
START
V
CC
=14V
-
40
80
uA
Operating Supply Current
(Control Part Only)
I
OP
Ta=25
C
-
8
12
mA
Iop(lat)
After latch,
Vcc=Vstop-0.1V
150
250
350
uA
FS7M0680
5
General Application
In general, the FPS consists of several functional sections:
under voltage lockout circuit (UVLO), reference voltage,
oscillator (OSC), pulse width modulation (PWM) block, pro-
tection circuits and gate drive circuit.
Start-Up
The minimum current that FPS requires for the start-up is
80
A. This current can be provided by the DC link bulk
capacitor (DC start-up) or directly by the AC line (AC start-
up).
DC start-up
Assuming wide range input voltage (85-265V), the maxi-
mum value of Rstart is calculated with the minimum input
voltage as follows:
The maximum power dissipation in Rstart is calculated with
the maximum input voltage as follows:
AC start-up
When the start-up current is provided directly by the AC line
through a single rectifier diode, the maximum value of Rstart
is calculated with the minimum input voltage as follows:
The maximum power dissipation in Rstart is calculated with
the maximum input voltage as follows:
The current provided through the starting resistor charges the
Vcc capacitor. When Vcc becomes higher than the threshold
voltage, the FPS starts the switching operation of the built-in
power MOSFET. Then, the current required by the control
IC is suddenly increased to 7mA, which makes it difficult for
FPS to operate with the current provided through Rstart.
Therefore, after FPS starts, the auxiliary winding of the
transformer should supply most of the power required by the
FPS. It is suitable to use an appropriately sized V
CC
capaci-
tor, generally about 33
F, because the starting time can be
delayed if it is too large. This operation is described in figure
2. Although V
CC
needs to be set only above 9V during the
normal operation, it should be set to such an extent that over
voltage protection (OVP) is not activated during an overload
condition. For full load, about 18~20V is appropriate for
V
CC
and for no load, about 13~14V is suitable.
Protection
The FPS has not only pulse by pulse current limit circuit, but
also several self-protection circuits. These protection circuits
are fully integrated and do not require external components.
After the protection circuits are activated, the FPS com-
pletely stops the SMPS (Latch Mode Protection) until the
power on reset circuit is activated by removing and restoring
input power, or restarts the SMPS automatically (Auto
Restart Mode Protection).
These two operations are user-selected operations, so the
user can select proper device according to the shutdown
mode. The operations principle and applications for each
protection are described as follows.
Figure 2. Variation of Icc according to Vcc
Rstart
85 2 15
80
A
---------------------------
1.3M
=
=
Ploss
265 2 15
(
)
2
1.3M
--------------------------------------
0.1 W
( )
=
=
265V
85V
Va
RStart
2 85
2 15
2
----------------------------------------
80
A
(
)
=
380k
=
Va rms
(
)
1
2
------
Vp
t
sin
15
(
)
2
dt
o
=
177V Vp
265 2
=
(
)
=
Ploss
Va rms
(
)2
Rstart
---------------------------
177
(
)2
380k
------------------
=
=
82 mW
(
)
=
Figure 1. Undervoltage lockout (UVLO) circuit
5V
Vref
Good Logic
Good Logic
Power on
Reset
Latch
Comparator
DC
LINK
Rstart
3
FPS
Vz
15V/9V
6V
UVLO
Vcc
Fig 2 < Start-up Waveform >
Vcc
Vz
15V
9V
20
Icc
[mA]
[V]
0.1
6V
Power On Reset
Range
7
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