NCP1380 ON Semiconductor, NCP1380 Datasheet - Page 24

• Manufacturer Part Number: NCP1380
• Description: Quasi-Resonant Current Mode Controller
• Manufacturer: ON Semiconductor

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and overvoltage detection on pin 7.
voltage condition, the pin 7 permanently monitors a fraction
of the bulk voltage through a voltage divider. When this
image of bulk voltage is below the V
controller stops switching. When the bulk voltage comes
back within safe limits, the circuit will restart pulsing only
bulk voltage is high, an internal clamp limits the voltage.
conduct and inject current inside the internal clamp resistor
The C and D versions of NCP1380 combine brown−out
In order to protect the power supply against low input
In order to avoid having a too high voltage on pin 7 if the
In case of overvoltage, the zener diode will start to
HV−Bulk
Rbou
Rbol
VCC
Dz
OVP/BO
7
OVERVOLTAGE PROTECTION / BROWN−OUT (C AND D VERSIONS)
Vclamp
Rc l a mp
VOVP
VDD
Figure 43. Brown−out and Overvoltage Protection
IBO
Figure 44. Brown−out Operating Chronograms
VBO
+
−
−
BO
+
threshold, the
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24
when V
startup sequence with soft−start. The hysteresis for the
brown−out function is implemented with a high side current
source sinking 10 mA when the brown−out comparator is
high (V
R
voltage reaches V
latched until the user cycles down the power supply
(Figure 45).
clamp
gr a nd
BO reset
reset
thus causing pin 7 voltage to increase. When this
CC
bulk
reaches V
> V
bulk(on)
R
S
OVP
Q
Q
CC(on)
, the controller latches−off and stays
)
(Figure 44): this ensures a clean
La tc h
CS c omp
S
R
Q
Q
DRV