Current-Mode Controller. NCP1377B Datasheet
Controller for Free-Running
The NCP1377 combines a true current mode modulator and a
demagnetization detector which ensures full borderline/critical
Conduction Mode in any load/line conditions together with
minimum drain voltage switching (Quasi−Resonant operation). Due
to its inherent skip cycle capability, the controller enters burst mode
as soon as the power demand falls below a predetermined level. As
this happens at low peak current, no audible noise can be heard. For
NCP1377, an internal 8.0 ms timer prevents the free−run frequency to
exceed 100 kHz (therefore below the 150 kHz CISPR−22 EMI
starting limit), while the skip adjustment capability lets the user
select the frequency at which the burst foldback takes place. For
NC1377B, the internal timer duration is reduced to 3.0 ms to allow
operation at higher frequencies (up to 300 kHz).
The transformer core reset detection is done through an auxiliary
winding which, brought via a dedicated pin, also enables fast
Over Voltage Protection (OVP). Once an OVP has been detected, the
IC permanently latches off. The 1377 features a sampling time of
4.5 ms whereas it is 1.5 ms for the B version.
The NCP1377 also features an efficient protective circuitries
which, in presence of an overcurrent condition, disables the output
pulses and enters a safe burst mode, trying to restart. Once the default
has gone, the device auto−recovers. Finally an internal 1.0 ms
Soft−Start eliminates the traditional startup stress.
• Free−Running Borderline/Critical Mode Quasi−Resonant Operation
• Latched Overvoltage Protection
• Auto−Recovery Short−Circuit Protection Via UVLO Crossover
• External Latch Triggering, e.g. Via Overtemperature Signal
• Current−Mode with Adjustable Skip Cycle Capability
• Internal 1.0 ms Soft−Start
• Internal Temperature Shutdown
• Internal Leading Edge Blanking
• 500 mA Peak Current Source/Sink Capability
• Under Voltage Lockout Level of 12.5 V (On) and 7.5 V (Min)
• Direct Optocoupler Connection
• SPICE Models Available for TRANsient Analysis
• Internal Minimum TOFF
• These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS
• AC−DC Adapters for Notebooks, etc.
• Offline Battery Chargers
• Consumer Electronics (DVD Players, Set−Top Boxes, TVs, etc.)
• Auxiliary Power Supplies (USB, Appliances, TVs, etc.)
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 14 of this data sheet.
© Semiconductor Components Industries, LLC, 2015
October, 2015 − Rev. 13
Publication Order Number:
OVP and NCP1377
12 V @ 1 A
*Please refer to the application information section.
Figure 1. Typical Application Schematic
PIN FUNCTION DESCRIPTION
1 Demag Core reset detection and OVP
2 FB Sets the peak current setpoint
3 CS Current sense input and skip
cycle level selection
The IC ground
Supplies the IC
The auxiliary FLYBACK signal ensures discontinuous operation and offers a fixed
overvoltage detection level of 7.2 V.
By connecting an optocoupler to this pin, the peak current setpoint is adjusted
accordingly to the output power demand. By bringing this pin below the internal
skip level, you shut off the device.
This pin senses the primary current and routes it to the internal comparator via an
L.E.B. By inserting a resistor in series with the pin, you control the level at which
the skip operation takes place.
The driver’s output to an external MOSFET.
This pin is connected to an external bulk capacitor of typically 10 mF.
This unconnected pin ensures adequate creepage distance.
Connected to the high−voltage rail, this pin injects a constant current into the VCC
bulk capacitor and ensures a clean lossless startup sequence.