FAN4802LNY Fairchild Semiconductor, FAN4802LNY Datasheet - Page 19

• Manufacturer Part Number: FAN4802LNY
• Description: IC PFC CTRLR AVERAGE CURR 16DIP
• Manufacturer: Fairchild Semiconductor

Specifications of FAN4802LNY

• Mode: Average Current
• Frequency - Switching: 64kHz
• Current - Startup: 30µA
• Voltage - Supply: 11 V ~ 22 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Through Hole
• Package / Case: 16-DIP (0.300", 7.62mm)
• Operating Temperature (max): 105C
• Operating Temperature (min): -40C
• Pin Count: 16
• Mounting: Through Hole
• Screening Level: Industrial
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

© 2008 Fairchild Semiconductor Corporation
FAN4800A/C, FAN4801/02/02L • Rev. 1.0.3
R
TriFault Detect™
To improve power supply reliability, reduce system
component count, and simplify compliance to UL 1950
safety standards, the FAN4800A/C, FAN4801/02/02L
includes TriFault Detect. This feature monitors FBPFC
for certain PFC fault conditions.
In a feedback path failure, the output of the PFC could
exceed safe operating limits. With such a failure,
FBPFC exceeds its normal operating area. Should
FBPFC go too LOW, too HIGH, or OPEN, TriFault
Detect senses the error and terminates the PFC output
drive.
TriFault detect is an entirely internal circuit. It requires
no external components to serve its protective function.
PFC Over-Voltage Protection
In the FAN4800A/C, FAN4801/02/02L, the PFC OVP
comparator serves to protect the power circuit from
being subjected to excessive voltages if the load
changes suddenly. A resistor divider from the high-
voltage DC output of the PFC is fed to FBPFC. When
the voltage on FBPFC exceeds 2.75V, the PFC output
driver is shut down. The PWM section continues to
operate. The OVP comparator has 250mV of hysteresis
and the PFC does not restart until the voltage at FBPFC
drops below 2.50V. V
redundant PFC OVP protection. V
28V with 1V hysteresis.
Selecting PFC R
R
converter. During the steady state, line input current x
R
At full load, the average V
ripple on the VEA needs to be less than 400mV.
Choose the resistance of the sensing resistor:
where 5.6 is V
PFC Soft-Start
PFC startup is controlled by V
voltage reaches 2.4V, the V
90V
PFC Brownout
The AC UVP comparator monitors the AC input voltage.
The FAN4800A/C, FAN4801/02 disables PFC as lower
AC input such that the VRMS is less than 1.05V. The
brownout
FAN4801/1S/2, such that the VRMS is less than 0.9V.
sense
SENSE
SENSE
AC
, the PFC soft-start time is 90ms.

equals I
is the sensing resistor of the PFC boost

4.5 0.7
voltage
2


EA
GAINMOD

5.6 0.7
maximum output.



5.7
SENSE
of
x 5.7KΩ.
K
DD

 

FAN4802L
EA
OVP can also serve as a
Line input Power
EA
IAC Gain V
needs to around 4.5V and
EA
level is around 2.8V. At

level. Before FBPFC
DD
OVP threshold is
is

IN
lower

2
than
(2)
19
Error Amplifier Compensation
The PWM loading of the PFC can be modeled as a
negative resistor because an increase in the input
voltage to the PWM causes a decrease in the input
current.
compensation of the two transconductance error
amplifiers. Figure 46 shows the types of compensation
networks most commonly used for the voltage and
current error amplifiers, along with their respective
return
returned to VREF to produce a soft-start characteristic
on the PFC: As the reference voltage increases from
0V, it creates a differentiated voltage on IEA, which
prevents the PFC from immediately demanding a full
duty cycle on its boost converter. Complete design is
referred in application note AN-6078SC.
There is an RC filter between R
There are two reasons to add a filter at the ISENSE pin:
1. Protection:
2. To reduce L, the boost inductor: The ISENSE filter
The ISENSE filter is an RC filter. The resistor value of
the ISENSE filter is between 100Ω and 50Ω because
I
of IEA. Selecting an R
offset of the IEA less than 3mV. Design the pole of
ISENSE filter at f
frequency, so the boost inductor can be reduced six
times without disturbing the stability. The capacitor of
the ISENSE filter, C
OFFSET
Figure 46. Compensation Network Connection for the
conditions, there is a large voltage across R
which is the sensing resistor of the PFC boost
converter. It requires the ISENSE filter to attenuate
the energy.
also can reduce the boost inductor value since the
ISENSE filter behaves like an integrator before the
ISENSE pin, which is the input of the current error
amplifier, IEA.
x R
points.
FILTER
This
Voltage and Current Error Amplifiers
During
can generate a negative offset voltage
The
PFC
response
FILTER
/6, one sixth of the PFC switching
current-loop
FILTER
, is approximately 100nF.
startup
equal to 50Ω keeps the
dictates
SENSE
or
compensation
and ISENSE pin.
inrush
the
www.fairchildsemi.com
current
proper
SENSE
is
,