FAN2108 Fairchild Semiconductor, FAN2108 Datasheet - Page 12

• Manufacturer Part Number: FAN2108
• Description: This part is covered in Fairchild's href="http://www
• Manufacturer: Fairchild Semiconductor

© 2008 Fairchild Semiconductor Corporation
FAN2108 • Rev. 1.0.1
Auto-Restart
After a fault, EN pin is discharged by a 1µA current sink
to a 1.1V threshold before the internal 800KΩ pull-up is
restored. A new soft-start cycle begins when EN
charges above 1.35V.
Depending on the external circuit, the FAN2108 can be
configured to remain latched-off or to automatically
restart after a fault.
Table 1. Fault / Restart Configurations
EN Pin
Pull to GND
Pull-up to V
100K
Open
Cap. to GND
With EN is left open, restart is immediate.
If auto-restart is not desired, tie the EN pin to the VCC
pin or pull it HIGH after V
to keep the 1µA current sink from discharging EN to
1.1V. Figure 23 shows one method to pull up EN to V
for a latch configuration.
Figure 23.
CC
with
Enable Control with Latch Option
100K
Controller / Restart State
OFF (Disabled)
No Restart – Latched OFF(After
V
Immediate Restart After Fault
New Soft-Start Cycle After:
t
DELAY
CC
Comes Up)
CC
(ms)=3.9 • C(nf)
comes up with a logic gate
3.3n
15
14
EN
VCC
FAN2108
CC
12
Over-Temperature Protection (OTP)
The chip incorporates an over-temperature protection
circuit that sets the fault latch when a die temperature of
about 150°C is reached. The IC restarts when the die
temperature falls below 125°C.
Power-Good (PGOOD) Signal
PGOOD is an open-drain output that asserts LOW
when V
pin.
Specifications section. PGOOD does not assert HIGH
until the fault latch is enabled (T1.0).
PCB Layout
Thresholds
Figure 24. Recommended PCB Layout
OUT
is out of regulation, as measured at the FB
are
specified
in
the
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Electrical