On Semiconductor NCP1351 Evaluation Board NCP1351LEDGEVB NCP1351LEDGEVB Data Sheet

© Semiconductor Components Industries, LLC, 2007

Publication Order Number:

NCP1351

Variable Off Time PWM

Controller

The NCP1351 is a current-mode controller targeting low power

off-line flyback Switched Mode Power Supplies (SMPS) where cost
is of utmost importance. Based on a fixed peak current technique
(quasi-fixed T

ON

), the controller decreases its switching frequency as

the load becomes lighter. As a result, a power supply using the
NCP1351 naturally offers excellent no-load power consumption,
while optimizing the efficiency in other loading conditions. When the
frequency decreases, the peak current is gradually reduced down to
approximately 30% of the maximum peak current to prevent
transformer mechanical resonance. The risk of acoustic noise is thus
greatly diminished while keeping good standby power performance.

An externally adjustable timer permanently monitors the feedback

activity and protects the supply in presence of a short-circuit or an
overload. Once the timer elapses, NCP1351 stops switching and stays
latched for version A, and tries to restart for version B.

Versions C and D include a dual overcurrent protection trip point,

allowing the implementation of the controller in peak-power
requirements applications such as printers and so on. When the fault is
acknowledged, C version latches-off whereas D version
auto-recovers.

The internal structure features an optimized arrangement which

allows one of the lowest available startup current, a fundamental
parameter when designing low standby power supplies.

The negative current sensing technique minimizes the impact of the

switching noise on the controller operation and offers the user to select
the maximum peak voltage across his current sense resistor. Its power
dissipation can thus be application optimized.

Finally, the bulk input ripple ensures a natural frequency smearing

which smooths the EMI signature.

•

Quasi-fixed T

ON

, Variable T

OFF

 Current Mode Control

•

Extremely Low Current Consumption at Startup

•

Peak Current Compression Reduces Transformer Noise

•

Primary or Secondary Side Regulation

•

Dedicated Latch Input for OTP, OVP

•

Programmable Current Sense Resistor Peak Voltage

•

Natural Frequency Dithering for Improved EMI Signature

•

Easy External Over Power Protection (OPP)

•

Undervoltage Lockout

•

Very Low Standby Power via Off-time Expansion

•

SOIC-8 Package

•

Standard Overcurrent Protection, Latched or
Auto-Recovery, A & B Versions

•

Dual Trip Point Overcurrent Protection, Latched or
Auto-Recovery, C & D Versions

•

These are Pb-Free Devices

•

Auxiliary Power Supply

•

Printer, Game Stations, Low-Cost Adapters

•

Off-line Battery Charger

1

8

1

FB

8 TIMER

2

Ct

3

CS

4

GND

7 LATCH

6 V

CC

5 DRV

(Top View)

1351x
ALYW

G

1

8

1

8

NCP1351x

AWL

YYWWG

1

x

= A, B, C, or D Options

A

= Assembly Location

L, WL

= Wafer Lot

Y, YY

= Year

W, WW = Work Week
G or G = Pb-Free Package

(Note: Microdot may be in either location)

See detailed ordering and shipping information in the package
dimensions section on page 25 of this data sheet.