FAN7585 Ver la hoja de datos (PDF) - Fairchild Semiconductor
Número de pieza
componentes Descripción
Fabricante
FAN7585 Datasheet PDF : 16 Pages
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FAN7585
2. UVP Block
3.3V 5V 12V
14 16 18
R1
R3
R5
Vref=5V
A
B
C
R2
R4
R6 1.25V
SET of
R/S Latch
UVP COMP
The block is made up of a comparator with three detecting inputs and without hysteresis voltage. Each UVP level is
determined by resistor ratio and the typical values are 2.3V/4.0V/10V respectively.
• UVP detecting voltage for +3.3V
VU V P 1 ( + 3.3 V )
=
R-----1-----+-----R----2--
R2
×
VA
=
R-----1-----+-----R----2--
R2
×
Vref
=
2.3V
• UVP detecting voltage for +5V
VUVP2(+5V)
=
R-----3-----+-----R----4--
R4
×
VB
=
R-----3-----+-----R----4--
R4
×
Vref
=
4V
• UVP detecting voltage for +12V
VU V P 3 ( + 12 V )
=
R-----5-----+-----R----6--
R6
×
VC
=
R-----5-----+-----R----6--
R6
×
Vref
=
10V
In the case of UVP, a system designer should know a fact that the main power can be dropped after some delay. (38msec@
CTUVP=0.47uF)
So when the UVP level is tested with a set, you should remove protection delay capacitor(Pin20) and check PG(Pin11). You
can know the each UVP level as checking each output voltage in just time that PG(Pin11) is triggered from high to low.
10
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