ncp3155a ON Semiconductor, ncp3155a Datasheet - Page 11

• Manufacturer Part Number: ncp3155a
• Description: Ncp3155a, Ncp3155b 3 A Synchronous Buck Regulator
• Manufacturer: ON Semiconductor

OOV and OUV
the feedback pin of the output power stage. Two
comparators are placed on the feedback node of the OTA to
monitor the operating window of the feedback voltage as
shown in Figures 31 and 32. All comparator outputs are
ignored during the soft−start sequence as soft−start is
regulated by the OTA and false trips would be generated.
After the soft−start period has ended, if the feedback is
below the reference voltage of comparator 2 (V
The output voltage of the buck converter is monitored at
FB
Vref = 0.8 V
Hysteresis = 5 mV
Hysteresis = 5 mV
Figure 32. OOV and OUV Window Diagram
Figure 31. OOV and OUV Circuit Diagram
Vref*125%
Vref*75%
FB
< 0.6 V),
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OOVP & Power Good = 0
OUVP & Power Good = 0
Power Good = 1
Power Good = 1
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the output is considered “undervoltage” and the device will
initiate a restart. When the feedback pin voltage rises
between the reference voltages of comparator 1 and
comparator 2 (0.6 < V
considered “Power Good.” Finally, if the feedback voltage
is greater than comparator 1 (V
voltage is considered “overvoltage,” and the device will
latch off. To clear a latch fault, input voltage must be
recycled. Graphical representation of the OOV and OUV is
shown in Figures 33 and 34.
Comparator 1
Comparator 2
Soft Start Complete
LOGIC
Voov = Vref * 125%
Vref = 0.8 V
Power Not Good Low
Vouv = Vref * 75%
Power Not good High
FB
< 1.0), then the output voltage is
FB
Latch off
Restart
> 1.0 V), the output