FAN7528 Fairchild Semiconductor, FAN7528 Datasheet - Page 14

• Manufacturer Part Number: FAN7528
• Description: Dual Output Critical Conduction Mode PFC Controller
• Manufacturer: Fairchild Semiconductor

AC line voltage and maximum output power. The resistor value
should be designed properly.
O ff S ign al
1 V
M O T
S aw T o oth
3
G en era tor
1 V
E rror A m p
O u tp u t
Figure 37. Zero current detector block
4. Over Current Protection Block
The MOSFET current is sensed using an external sensing
resistor for the over current protection. If the CS pin voltage is
higher than 0.8V, the over current protection comparator gener-
ates a protection signal. An internal RC filter is included to filter
switching noise.
OCP
40k
4
Signal
CS
8pF
Over Current
Protection
0.8V
Comparator
Figure 38. Over current protection block
5. Switch Drive Block
The FAN7528 contains a single totem-pole output stage
designed for a direct drive of power MOSFET. The drive output
is capable of up to 400mA peak current with a typical rise and
fall time of 50ns with 1nF load. The output voltage is clamped to
be 13V to protect MOSFET gate even if the Vcc voltage is
higher than 20V.
6. Under Voltage Lock Out Block
If the Vcc voltage reaches 12V, the IC’s internal blocks are
enabled and start operation. If the Vcc voltage drops below
8.5V, most of the internal blocks are disabled to reduce the
operating current. Vcc voltage should be higher than 8.5V under
normal conditions.
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FAN7528 Rev. 1.0.1