NCP1337
PIN FUNCTION DESCRIPTION
Pin No.
Symbol
Function
1
BO
Brown−out and external
triggering
2
FB
Sets the peak current
setpoint
3
CS
Current sense input and
overpower compensation
adjustment
4
GND
IC ground
5
DRV
Output driver
6
VCC
IC supply
8
HV
High−voltage pin
Description
• By connecting this pin to the input voltage through a resistor divider, the
controller ensures operation at a safe mains level.
• If an external event brings this pin above 3.0 V, the controller’s output is
disabled.
• If an external event brings this pin above 5.0 V, the controller is
permanently latched−off.
• By connecting an optocoupler or an auxiliary winding to this pin, the peak
current setpoint is adjusted accordingly to the output power demand.
• When the requested peak current setpoint is below the internal standby
level, the device enters soft ripple mode.
• This pin senses the primary current and routes it to the internal comparator
via an L.E.B.
• Inserting a resistor in series with the pin allows to control the overpower
compensation level.
• To be connected to an external MOSFET.
• Connected to a tank capacitor (and possibly an auxiliary winding).
• When VCC reaches 18.6 V, an internal OVP stops the output pulses.
• Connected to the high−voltage rail, this pin injects a constant current into
the VCC bulk capacitor and ensures a clean lossless startup sequence.
BO
+
Cbulk
NCP1337
1
8
2
3
6
4
5
Rcomp
VCC
+
VOUT
+
VCC
Figure 1. Typical Application Schematic
http://onsemi.com
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