NCP1255_12 Datasheet, PDF (1/22 Pages) ON Semiconductor – Current-Mode PWM Controller for Off-line Power Supplies featuring Peak Power Excursion

NCP1255
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Current-Mode PWM
Controller for Off-line
Power Supplies featuring
Peak Power Excursion
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.
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
through a dedicated pin or via the V_cc input − and finally, the
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).
Features
• 65−kHz Fixed−frequency Current−mode Control Operation with
130−kHz Excursion
• 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
• Adjustable Slope Compensation
• Internally Fixed 4−ms Soft−start
• Adjustable Timer−based Auto−recovery Overload/Short−circuit
Protection
• 100% to 25% Timer Reduction from Overload to Short−circuit Fault
• Double V_cc Hiccup for a Reduced Average Power in Fault Mode
• 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_cc Maximum Rating
• 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.
http://onsemi.com
8
1
SOIC−8
D1, D2 SUFFIX
CASE 751
MARKING DIAGRAM
8
XXXXX
ALYWX
G
1
XXXXX = Specific Device Code
A
= Assembly Location
L
= Wafer Lot
Y
= Year
W
= Work Week
G
= Pb−Free Package
(Note: Microdot may be in either location)
PIN CONNECTIONS
1
OPP/Latch
2
FB
3
CS
4
GND
8
Timer
7
BO
6
Vcc
5
DRV
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 2 of this data sheet.
© Semiconductor Components Industries, LLC, 2012
1
December, 2012 − Rev. P0
Publication Order Number:
NCP1255/D