NCP1236 Datasheet, PDF (1/34 Pages) ON Semiconductor – Fixed Frequency Current Mode Controller for Flyback Converters

NCP1236
Fixed Frequency Current
Mode Controller for Flyback
Converters
The NCP1236 is a new fixed−frequency current−mode controller
featuring Dynamic Self−Supply (DSS). This device is pin−to−pin
compatible with the previous NCP12xx families.
The DSS function greatly simplifies the design of the auxiliary
supply and the V_CC 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
standby power consumption. Internal frequency jittering, ramp
compensation, and a versatile latch input make this controller an
excellent candidate for converters where components cost is the key
constraints.
In addition, the controller includes a new high voltage circuitry that
combines a start−up current source and a brown−out detector able to
sense the input voltage either from the rectified ac line or the dc
filtered bulk voltage. The high voltage sensing circuitry is used for the
overpower protection purposes as well. Overpower protection,
overload protection, and next protective features increases safety level
of the final application.
Finally, due to a careful design, the precision of critical parameters
is well controlled over the entire temperature range (−40°C to
+125°C).
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MARKING
DIAGRAM
SOIC−7
CASE 751U
8
36Xff
ALYWX
G
1
36Xff = Specific Device Code
X = A, B, C or D
ff = 65 or 100
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
G
= Pb−Free Package
PIN CONNECTIONS
Latch 1
FB 2
8 HV
Features
• Fixed−Frequency Current−Mode Operation with Built−In Ramp
Compensation
• 65 kHz or 100 kHz Oscillator Frequency
CS 3
GND 4
6 V_CC
5 DRV
(Top View)
• Frequency Foldback then Skip Mode for Maximized Performance in
Light Load and Standby Conditions
• Timer−Based Overload Protection with Latched (option A) or
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 33 of this data sheet.
Auto−Recovery (option B) Operation, Shortened Overload Timer for
Increased Safety (options C and D), (see all options on page 2)
• High−voltage Current Source with Brown−Out
• Internal Thermal Shutdown
detection and Dynamic Self−Supply, Simplifying the
• Pin−to−Pin Compatible with the Existing NCP12xx
Design of the V_CC Capacitor
• Frequency Modulation for Softened EMI Signature,
Series
• These Devices are Pb−Free, Halogen Free/BFR Free
including during Frequency Foldback mode
• Adjustable Overpower Compensation
• Latch−off Input for Severe Fault Conditions, Allowing
Direct Connection of an NTC for Overtemperature
Protection (OTP)
• V_CC Operation up to 28 V, with Overvoltage Detection
• $500 mA Peak Source / Sink Current Drive Capability
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
• 4.0 ms Soft−Start
© Semiconductor Components Industries, LLC, 2012
1
January, 2012 − Rev. 2
Publication Order Number:
NCP1236/D