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NCP1238 Datasheet, PDF (1/30 Pages) ON Semiconductor – Fixed Frequency Current Mode Controller for Flyback Converters | |||
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NCP1238
Fixed Frequency Current
Mode Controller for Flyback
Converters
The NCP1238 is a new generation of the NCP12xx fixedâfrequency
currentâmode controllers featuring Dynamic SelfâSupply (DSS),
pinâtoâpin compatible with the previous generation.
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 its proprietary SoftâSkip⢠mode combined with frequency
foldback, the controller exhibits excellent efficiency in light load
condition while still achieving very low standby power consumption.
This SoftâSkip feature also dramatically reduces the risk of acoustic
noise, which enables the use of inexpensive transformers and
capacitors in the clamping network.
Internal frequency jittering, ramp compensation, and a versatile
latch input make this controller an excellent candidate for converters
where ruggedness and components cost are the key constraints.
In addition, the controller includes a new high voltage circuitry that
combines a startup current source and a brownâout / line OVP detector
able to sense the input voltage either from the rectified ac line or the dc
filtered bulk voltage.
Finally, due to a careful design, the precision of critical parameters
is well controlled over the entire temperature range (â40°C to
+125°C), enabling easier design and increased safety (e.g. ±5% for the
peak current limit, ±7% for the oscillator).
http://onsemi.com
MARKING
DIAGRAM
SOICâ7
CASE 751U
8
38Xff
ALYWX
G
1
38Xff = Specific Device Code
X = A or B
ff = 65, 00, or 33
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
G = PbâFree Package
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 29 of this data sheet.
Features
⢠TimerâBased Overload Protections with Autoâ
Recovery (Option B) or Latched (Option A) Operation
⢠HighâVoltage Current Source with DSS with Builtâin
Brownâout and Line Overvoltage Protections
⢠FixedâFrequency CurrentâMode Operation with
Builtâin Ramp Compensation
⢠Frequency Jittering for a Reduced EMI Signature
⢠Adjustable Overpower Compensation
⢠Latchâoff Input for Severe Fault Conditions, with
Direct Connection of an NTC for Overtemperature
Protection (OTP)
⢠Protection Against Winding ShortâCircuit
⢠Frequency Foldback transitioning into SoftâSkip for
Improved Performance in Standby
⢠65 kHz Oscillator (100 kHz and 133 kHz Versions
Available Upon Request)
⢠VCC Operation up to 28 V
⢠Increased Precision on Critical Parameters
⢠±1.0 A Peak Drive Capability
⢠4.0 ms SoftâStart
⢠Internal Thermal Shutdown with Hysteresis
⢠These Devices are PbâFree, Halogen Free/BFR Free
and are RoHS Compliant*
Typical Applications
⢠acâdc Adapters for Notebooks, LCD, and Printers
⢠Offline Battery Chargers
⢠Consumer Electronic Power Supplies
⢠Auxiliary/Housekeeping Power Supplies
*For additional information on our PbâFree strategy and soldering details, please
download the ON Semiconductor Soldering and Mounting Techniques
Reference Manual, SOLDERRM/D.
© Semiconductor Components Industries, LLC, 2010
1
February, 2010 â Rev. 1
Publication Order Number:
NCP1238/D
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