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  ON Semiconductor Electronic Components Datasheet  

NCP1234 Datasheet

Fixed Frequency Current Mode Controller

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NCP1234 pdf
NCP1234
Fixed Frequency Current
Mode Controller for Flyback
Converters
The NCP1234 is a new fixed−frequency current−mode controller
featuring Dynamic Self−Supply (DSS). This device is pin−to−pin
www.onsemi.com
compatible with the previous NCP12xx families.
The DSS function greatly simplifies the design of the auxiliary
supply and the VCC capacitor by activating the internal startup current
source to supply the controller during transients.
Due to frequency foldback, the controller exhibits excellent
efficiency in light load condition while still achieving very low
SOIC−7
CASE 751U
standby power consumption. Internal frequency jittering, ramp
compensation, and a versatile latch input make this controller an
MARKING DIAGRAM
excellent candidate for converters where components cost is the key
8
constraints.
It features a timer−based fault detection that ensures the detection of
overload independently of an auxiliary winding, and an adjustable
compensation to help keep the maximum power independent of the
input voltage.
Finally, due to a careful design, the precision of critical parameters
is well controlled over the entire temperature range (−40°C to
+125°C).
Features
Fixed−Frequency Current−Mode Operation with Built−In Ramp
34Xff
ALYWX
G
1
34Xff = Specific Device Code
X = A or B
ff = 65 or 100
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
G = Pb−Free Package
Compensation
65 kHz or 100 kHz Oscillator Frequency version
PIN CONNECTIONS
Frequency Foldback then Skip Mode for Maximized Performance in
Latch 1
8 HV
Light Load and Standby Conditions
FB 2
Timer−Based Overload Protection with Latched (option A) or
Auto−Recovery (option B) Operation
High−voltage Current Source with Dynamic Self−Supply,
Simplifying the Design of the VCC Capacitor
Frequency Modulation for Softened EMI Signature, including during
Frequency Foldback mode
Adjustable Overpower Compensation
CS 3
GND 4
6 VCC
5 DRV
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 32 of this data sheet.
Latch−off Input for Severe Fault Conditions, Allowing Direct
Connection of an NTC for Overtemperature Protection (OTP)
VCC Operation up to 28 V, with Overvoltage Detection
±500 mA Peak Source/Sink Current Drive Capability
4.0 ms Soft−Start
Internal Thermal Shutdown
Pin−to−Pin Compatible with the Existing NCP12xx
Series
These Devices are Pb−Free, Halogen Free/BFR Free
and are RoHS Compliant
Typical Applications
AC−DC Adapters for Notebooks, LCD, and Printers
Offline Battery Chargers
Consumer Electronic Power Supplies
Auxiliary/Housekeeping Power Supplies
© Semiconductor Components Industries, LLC, 2016
January, 2016 − Rev. 2
1
Publication Order Number:
NCP1234/D


  ON Semiconductor Electronic Components Datasheet  

NCP1234 Datasheet

Fixed Frequency Current Mode Controller

No Preview Available !

NCP1234 pdf
NCP1234
TYPICAL APPLICATION EXAMPLE
VIN
(dc)
LATCH
FB
CS
GND
NCP1234
HV
VCC
DRV
VOUT
Figure 1. Flyback Converter Application Using the NCP1234
PIN FUNCTION DESCRIPTION
Pin No Pin Name
Function
1 LATCH
Latch−Off Input
2 FB
3 CS
Feedback
Current Sense
4 GND
5 DRV
6 VCC
Drive output
VCC input
8 HV
High−voltage pin
Pin Description
Pull the pin up or down to latch−off the controller. An internal current source
allows the direct connection of an NTC for over temperature detection
An optocoupler collector to ground controls the output regulation.
This Input senses the Primary Current for current−mode operation, and Offers
an overpower compensation adjustment.
IC Ground
Drives external MOSFET
This supply pin accepts up to 28 Vdc, with overvoltage detection
Connects to the bulk capacitor or the rectified AC line to perform the functions
of Start−up Current Source and Dynamic Self−Supply
www.onsemi.com
2


Part Number NCP1234
Description Fixed Frequency Current Mode Controller
Maker ON Semiconductor
Total Page 30 Pages
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