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NCP1236

Fixed Frequency Current Mode Controller for Flyback Converters

ON Semiconductor 

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 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

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).

http://onsemi.com

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 VCC

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 VCC 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)

 VCC 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, 2013

1

April, 2013 − Rev. 3

Publication Order Number:

NCP1236/D

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