NCP1255
Product Preview
Current-Mode PWM
Controller for Off-line
Power Supplies featuring
Peak Power Excursion
http://onsemi.com
The NCP1255 is a highly integrated PWM controller capable of
delivering a rugged and high performance offline power supply in a
SOIC−8 package. With a supply range up to 35 V, the controller hosts a
jittered 65−kHz switching circuitry operated in peak current mode
control. When the power on the secondary side starts to decrease, the
controller automatically folds back its switching frequency down to a
minimum level of 26 kHz. As the power further goes down, the part
enters skip cycle while freezing the peak current setpoint.
8
1
SOIC−8
D1, D2 SUFFIX
CASE 751
To help build rugged converters, the controller features several key
protective features: a brown−out, a non−dissipative Over Power
Protection for a constant maximum output current regardless of the
input voltage, two latched over voltage protection inputs − either
MARKING DIAGRAM
8
XXXXX
ALYWX
through a dedicated pin or via the V input − and finally, the
cc
G
possibility to externally adjust an auto−recovery timer duration.
The controller architecture is arranged to authorize a transient peak
power excursion when the peak current hits the limit. At this point, the
switching frequency is increased from 65 kHz to 130 kHz until the
peak requirement disappears. The timer duration is then modulated as
the converter crosses a peak power excursion mode (long) or
undergoes a short circuit (short).
1
XXXXX = Specific Device Code
A
L
Y
W
G
= Assembly Location
= Wafer Lot
= Year
= Work Week
= Pb−Free Package
Features
(Note: Microdot may be in either location)
• 65−kHz Fixed−frequency Current−mode Control Operation with
130−kHz Excursion
PIN CONNECTIONS
• Internal and Adjustable Over Power Protection (OPP) Circuit
• Adjustable Brown−Out Protection Circuit
• Frequency Foldback down to 26 kHz and Skip−cycle in Light Load
Conditions
1
2
3
4
8
7
6
5
OPP/Latch
FB
Timer
BO
CS
Vcc
• Adjustable Slope Compensation
GND
DRV
• Internally Fixed 4−ms Soft−start
(Top View)
• Adjustable Timer−based Auto−recovery Overload/Short−circuit
Protection
• 100% to 25% Timer Reduction from Overload to Short−circuit Fault
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 2 of this data sheet.
• Double V Hiccup for a Reduced Average Power in Fault Mode
cc
• Frequency Jittering in Normal and Frequency Foldback Modes
• Latched OVP Input for Improved Robustness and Latched OVP on V
cc
• Up to 35−V V Maximum Rating
cc
• Extremely Low No−load Standby Power
• This is a Pb−Free Device
Typical Applications
• Converters requiring peak−power capability such as printers power
supplies, ac−dc adapters for game stations.
This document contains information on a product under development. ON Semiconductor
reserves the right to change or discontinue this product without notice.
© Semiconductor Components Industries, LLC, 2012
1
Publication Order Number:
December, 2012 − Rev. P0
NCP1255/D