NCP1351 Datasheet, PDF (1/19 Pages) ON Semiconductor – Variable Off Time PWM Controller

NCP1351
Product Preview
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.
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
• 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
• Internal Temperature Shutdown
• SOIC−8 Package
Typical Applications
• Auxiliary Power Supply
• Printer, Game Stations, Low−Cost Adapters
• Off−line Battery Charger
This document contains information on a product under development. ON Semiconductor
reserves the right to change or discontinue this product without notice.
http://onsemi.com
8
1
MARKING DIAGRAM
SOIC−8
D SUFFIX
CASE 751
8
1351x
AYWW
G
1
x
= A, B, C, or D Options
A
= Assembly Location
Y
= Year
WW = Work Week
G
= Pb−Free Device
PIN CONNECTIONS
FB 1
Ct 2
CS 3
GND 4
8 TIMER
7 LATCH
6 V_CC
5 DRV
(Top View)
ORDERING INFORMATION
Device
Package
Shipping^†
NCP1351ADR2G SOIC−8 2500 / Tape & Reel
(Pb−Free)
NCP1351BDR2G SOIC−8 2500 / Tape & Reel
(Pb−Free)
†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.
© Semiconductor Components Industries, LLC, 2006
1
November, 2006 − Rev. P2
Publication Order Number:
NCP1351/D