NCP1050, NCP1051, NCP1052, NCP1053, NCP1054, NCP1055
+
AC Line
Input
+
Snubber
+
Converter
DC Output
−
Power Switch Circuit Output
V
CC
+
1
5
Startup & V
CC
Regulator Circuit
Power
Switch
Circuit
Fault Detector
Control Input 2
Oscillator &
Gating Logic
Ground
3, 7−8
Figure 1. Typical Application
Pin Function Description
Pin
(SOT−223)
1
Pin
(PDIP−8)
1
Function
V
CC
Description
This is the positive supply voltage input. During startup, power is supplied to this input
from Pin 5. When V
CC
reaches V
CC
(on), the Startup Circuit turns off and the output is
allowed to begin switching with 1.0 V hysteresis on the V
CC
pin. The capacitance con-
nected to this pin programs fault timing and frequency modulation rate.
The Power Switch Circuit is turned off when a current greater than approximately 50
mA
is drawn out of or applied to this pin. A 10 V clamp is built onto the chip to protect the
device from ESD damage or overvoltage conditions.
This pin is the control circuit and Power Switch Circuit ground. It is part of the integrated
circuit lead frame.
2
2
Control Input
4
−
3
3, 7, 8
4
5
Ground
No Connection
Power Switch
Drain
This pin is designed to directly drive the converter transformer primary, and internally
connects to Power Switch and Startup Circuit.
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