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  ON Semiconductor Electronic Components Datasheet  

NCP1338 Datasheet

PWM Current-Mode Controller

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NCP1338 pdf
NCP1338
PWM Current-Mode
Controller for Free Running
Quasi-Resonant Operation
The NCP1338 combines a true current mode modulator and a
demagnetization detector which ensures full Borderline/Critical
Conduction Mode in any load/line conditions together with
minimum drain voltage switching (Quasi-Resonant operation). The
transformer core reset detection is done internally, without using any
external signal, due to the Soxyless concept. The frequency is
internally limited to 130 kHz, preventing the controller from
operating above the 150 kHz CISPR-22 EMI starting limit.
By monitoring the feedback pin activity, the controller enters
ripple mode as soon as the power demand falls below a
predetermined level. As each restart is softened by an internal
Soft-Skipt, and as the frequency cannot go below 25 kHz, no
audible noise can be heard.
The NCP1338 also features an efficient protective circuitry which,
in presence of an overcurrent condition, disables the output pulses
and enters a safe burst mode, trying to restart. Once the default has
gone, the device auto-recovers. Also included is a bulk voltage
monitoring function (known as brown-out protection), an adjustable
overpower compensation, and a VCC OVP. Finally, an internal 4.0 ms
Soft-Skip eliminates the traditional startup stress. NCP1338 can be
used in applications where the VCC supply voltage is delivered by an
external dc voltage source.
Features
ăFree-Running Borderline/Critical Mode Quasi-Resonant Operation
ăCurrent-Mode
ăSoft-Skip Mode with Minimum Switching Frequency for Standby
ăAuto-Recovery Short-Circuit Protection Independent of Auxiliary
Voltage
ăOvervoltage Protection
ăBrown-Out Protection
ăTwo Externally Triggerable Fault Comparators (one for a disable
function, and the other for a permanent latch)
ăInternal 4.0 ms Soft-Skip
ă500 mA Peak Current Drive Sink Capability
ă130 kHz Max Frequency
ăInternal Leading Edge Blanking
ăInternal Temperature Shutdown
ăDirect Optocoupler Connection
ăDynamic Self-Supply with Levels of 12 V (On) and 10 V (Off)
ăSPICE Models Available for TRANsient and AC Analysis
www.DatăaTSheseet4aUre.coPmb-Free Devices
Typical Applications
ăAc-dc Adapters for Notebooks, etc.
ăOffline Battery Chargers
ăConsumer Electronics (DVD Players, Set-Top Boxes, TVs, etc.)
ăAuxiliary Power Supplies (USB, Appliances, TVs, etc.)
http://onsemi.com
PDIP-7
P SUFFIX
CASE 626B
MARKING
DIAGRAM
7
NCP1338P
AWL
YYWWG
1
SOIC-7
D SUFFIX
CASE 751U
8
P1338
ALYWāG
G
1
A = Assembly Location
WL, L = Wafer Lot
YY, Y = Year
WW, W = Work Week
G, G = Pb-Free Package
(Note: Microdot may be in either location)
PIN CONNECTIONS
1
BO
2
FB
3
CS
4
GND
8
HV
6
VCC
5
DRV
(Top View)
ORDERING INFORMATION
Device
Package
Shipping
NCP1338PG
PDIP-7
(Pb-Free)
50 Units/Rail
NCP1338DR2G
SOIC-7 2500 Tape & Reel
(Pb-Free)
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specification
Brochure, BRD8011/D.
©Ă Semiconductor Components Industries, LLC, 2008
April, 2008 - Rev. 0
1
Publication Order Number:
NCP1338/D


  ON Semiconductor Electronic Components Datasheet  

NCP1338 Datasheet

PWM Current-Mode Controller

No Preview Available !

NCP1338 pdf
NCP1338
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, thanks to a 500 mV
brown-out comparator.
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-Skip 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.
+
Cbulk
BO
NCP1338
18
2
36
45
Rcomp
VCC
+
VOUT
+
VCC
www.DataSheet4U.com
Figure 1. Typical Application Schematic
http://onsemi.com
2


Part Number NCP1338
Description PWM Current-Mode Controller
Maker ON Semiconductor
Total Page 15 Pages
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