NCP1212_05 ONSEMI [ON Semiconductor], NCP1212_05 Datasheet - Page 14

• Manufacturer Part Number: NCP1212_05
• Description: Current Mode PWM Controller for Both Forward and Flyback Converters
• Manufacturer: ONSEMI [ON Semiconductor]

Brownout Protection
detection as shown in Figure 39. Positive terminal of the
comparator is connected to a +1.21 V bandgap reference.
The IC is prohibited from switching until Brownout Detect
pin exceeds 1.21 V. Once the brownout detect threshold is
exceeded, 45 mA flows out of the pin and the voltage at this
pin is further pushed up to provide hysteresis effect. The
Brownout voltage setting is determined by the potential
CT
NCP1212 has a built−in comparator for brownout
Current
Sense
From
Clock
OSC
+
−
DMAX
1 V
Current Limit
48% or 82%
Max. Duty
Cycle
3.2 V
−
+
+
−
Figure 38. Overload Detection Block Diagram
8 mA
+
−
+5 V
±
+
−
http://onsemi.com
−
+
S
D
CLK
S
NCP1212
Q
14
Q
Q
divider formed with R
calculate the resistors are shown below:
lower bulk capacitor voltage for brownout detection.
Overload Enable
D
Where V
CLK
R Upper ) R Lower +
Q
R Lower +
Bulk_H
28 mA
Reset
and V
±
+
−
[1.21 V(V Bulk_H * V Bulk_L )]
+
−
Upper
(45 mA
Bulk_L
0.5 V
−
+
(V Bulk_H * V Bulk_L )
and R
are the desired upper and
Overload
V Bulk_H )
45 mA
Lower
. Equations to
Shutdown
SS/DMAX