
Semiconductor Components Industries, LLC, 2006
November, 2006 Rev. P2
1
Publication Order Number:
NCP1351/D
NCP1351
Product Preview
Variable Off Time PWM
Controller
The NCP1351 is a currentmode controller targeting low power
offline flyback Switched Mode Power Supplies (SMPS) where cost
is of utmost importance. Based on a fixed peak current technique
(quasifixed 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 noload 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 shortcircuit or an
overload. Once the timer elapses, NCP1351 stops switching and stays
latched for version A, and tries to restart for Version B.
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.
Features
Quasifixed 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 Offtime Expansion
Internal Temperature Shutdown
SOIC8 Package
Typical Applications
Auxiliary Power Supply
Printer, Game Stations, LowCost Adapters
Offline Battery Charger
This document contains information on a product under development. ON Semiconductor
reserves the right to change or discontinue this product without notice.
SOIC8
D SUFFIX
CASE 751
1
8
MARKING DIAGRAM
8
PIN CONNECTIONS
x
A
Y
WW
= A, B, C, or D Options
= Assembly Location
= Year
= Work Week
= PbFree Device
1
FB
8 TIMER
2
Ct
3
CS
4
GND
7 LATCH
6 V
CC
5 DRV
(Top View)
1351x
AYWW
Device
Package
Shipping
ORDERING INFORMATION
NCP1351ADR2G
SOIC8
(PbFree)
2500 / Tape & Reel
For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specifications
Brochure, BRD8011/D.
1
http://onsemi.com
NCP1351BDR2G
SOIC8
(PbFree)
2500 / Tape & Reel