FS7M0680TU Fairchild Semiconductor, FS7M0680TU Datasheet - Page 5

• Manufacturer Part Number: FS7M0680TU
• Description: IC SWIT PWM CM OVP UVLO HV TO3P
• Manufacturer: Fairchild Semiconductor

Specifications of FS7M0680TU

• Output Isolation: Isolated
• Frequency Range: 60 ~ 72kHz
• Voltage - Input: 9 ~ 30 V
• Voltage - Output: 800V
• Power (watts): 150W
• Operating Temperature: 25°C ~ 150°C
• Package / Case: TO-3P-5
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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
80µA. 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
R start
Ploss
Va
=
=
(
------------------------------------- -
85 2 15
-------------------------- -
Va rms
265 2 15
R Start
80µA
1.3MΩ
(
P loss
–
265V
85V
–
)
=
=
=
=
=
=
=
380kΩ
2 85
--------------------------------------- -
)
82 mW
177V Vp
2
Va rms
-------------------------- -
1.3MΩ
•
------
2π
Rstart
1
=
(
(
∫
0.1 W
2π
π
o
(
2 15π
(
)
(
Vp
) 2
–
=
)
sin
=
265 2
(
----------------- -
t
÷
177
380k
–
(
80µA
15
) 2
)
)
2
dt
)
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
tor, generally about 33µF, because the starting time can be
delayed if it is too large. This operation is described in figure
2. Although V
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
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 1. Undervoltage lockout (UVLO) circuit
CC
Icc
[mA]
0.1
20
7
Power on
Reset
Latch
Comparator
and for no load, about 13~14V is suitable.
LINK
DC
Power On Reset
Range
FPS
6V
Fig 2 < Start-up Waveform >
Figure 2. Variation of Icc according to Vcc
CC
Rstart
needs to be set only above 9V during the
9V
6V
15V
Vz
3
Vcc
15V/9V
UVLO
Good Logic
Good Logic
Vref
5V
CC
FS7M0680
Vz
capaci-
[V]
Vcc
5