NCP1212P ON Semiconductor, NCP1212P Datasheet - Page 14

• Manufacturer Part Number: NCP1212P
• Description: IC CTRLR PWM PROG CM OVP 8DIP
• Manufacturer: ON Semiconductor
• Type: PWM Controller for Both Forward and Flyback Convertersr

Specifications of NCP1212P

• Output Isolation: Isolated
• Operating Temperature: -40°C ~ 150°C
• Package / Case: 8-DIP (0.300", 7.62mm)
• Input Voltage Range: - 0.3 V to + 28 V
• Operating Temperature Range: - 40 C to + 150 C
• Mounting Style: Through Hole
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: NCP1212POS

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
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 × V Bulk_H )
Bulk_L
0.5 V
+
--
(V Bulk_H − V Bulk_L )
and R
are the desired upper and
Overload
45 mA
Lower
. Equations to
Shutdown
SS/DMAX