FAN5361 Fairchild Semiconductor, FAN5361 Datasheet - Page 13

• Manufacturer Part Number: FAN5361
• Description: The FAN5361 is a 600mA or 750mA, step-down, switching voltage regulator that delivers a fixed output from an input voltage supply of 2
• Manufacturer: Fairchild Semiconductor

Under-Voltage Lockout (UVLO)
When EN is HIGH, the under-voltage lockout keeps the part
from operating until the input supply voltage rises high
enough to properly operate. This ensures no misbehavior of
the regulator during startup or shutdown.
Thermal Shutdown (TSD)
When the die temperature increases, due to a high load
condition and/or a high ambient temperature, the output
switching is disabled until the temperature on the die has
fallen sufficiently. The junction temperature at which the
thermal shutdown activates is nominally 150°C with a 15°C
hysteresis.
Minimum Off-Time Effect on Switching
Frequency
t
output voltage it can provide at low V
fixed switching frequency in PWM mode.
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.1.2
V
OFF(MIN)
V
OUT
IN
that the FAN5361 can provide, or the maximum
is 50ns. This imposes constraints on the maximum
IN
while maintaining a
13
When V
The switching frequency drops when the regulator cannot
provide sufficient duty cycle at 6MHz to maintain regulation.
This occurs when V
V
The calculation for switching frequency is given by:
where:
where:
V
f
t
R
R
SW
SW
V
IN
OUT
OFF
ON
IN
is below 2.9V at high load currents (see Figure 15).
(
MAX

=
=

min
R
IN
R
1
)
DSON


DSON
is LOW, fixed switching is maintained as long as




t
50
OFF
t
SW
ns
_
_
(
P
(
MIN
1
MAX

N






1
DCR
)
OUT

DCR

)
V
f
6 ,
SW
IN
is greater than or equal to 1.82V and
V
L
MHz
L
OUT


I
OUT
0




7 .

I
.
OUT

R
ON

R

OFF
V
OUT
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


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