Current-Mode Controller. NCP1207 Datasheet
Controller for Free Running
The NCP1207 combines a true current mode modulator and a
demagnetization detector to ensure full borderline/critical
Conduction Mode in any load/line conditions and 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. 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.
The Dynamic Self−Supply (DSS) drastically simplifies the
transformer design in avoiding the use of an auxiliary winding to supply
the NCP1207. This feature is particularly useful in applications where
the output voltage varies during operation (e.g. battery chargers). Due to
its high−voltage technology, the IC is directly connected to the
high−voltage DC rail. As a result, the short−circuit trip point is not
dependent upon any VCC auxiliary level.
The transformer core reset detection is done through an auxiliary
winding which, brought via a dedicated pin, also enables fast
Overvoltage Protection (OVP). Once an OVP has been detected, the IC
permanently latches off.
Finally, the continuous feedback signal monitoring implemented with
an Overcurrent Fault Protection (OCP) circuitry makes the final design
rugged and reliable.
• Pb−Free Packages are Available*
• Free−Running Borderline/Critical Mode Quasi−Resonant Operation
• Current−Mode with Adjustable Skip−Cycle Capability
• No Auxiliary Winding VCC Operation
• Auto−Recovery Overcurrent Protection
• Latching Overvoltage Protection
• External Latch Triggering, e.g. Via Overtemperature Signal
• 500 mA Peak Current Source/Sink Capability
• Internal 1.0 ms Soft−Start
• Internal 8.0 ms Minimum TOFF
• Adjustable Skip Level
• Internal Temperature Shutdown
• Direct Optocoupler Connection
• SPICE Models Available for TRANsient Analysis
• 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.)
*For additional information on our Pb−Free strategy and soldering details, please
download the ON Semiconductor Soldering and Mounting Techniques
Reference Manual, SOLDERRM/D.
© Semiconductor Components Industries, LLC, 2004
October, 2004 − Rev. 8
D1, D2 SUFFIX
1207/P = Device Code
A = Assembly Location
WL, L = Wafer Lot
YY, Y = Year
WW, W = Work Week
SOIC−8 2500/Tape & Reel
NCP1207DR2G SOIC−8 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
Publication Order Number:
+ OVP and
*Please refer to the application information section
Figure 1. Typical Application
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁPIN FUNCTION DESCRIPTION
Core reset detection and OVP
The auxiliary FLYBACK signal ensures discontinuous operation and
offers a fixed overvoltage detection level of 7.2 V.
2 FB Sets the peak current setpoint 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, device shuts off.
3 CS Current sense input and
skip cycle level selection
The IC ground
5 Drv Driving pulses
6 VCC Supplies the IC
8 HV High−voltage pin
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.
12 V, 10 V,
5.3 V (fault)
R* R Q
Driver: src = 20
sink = 10
*S and R are level triggered whereas S is edge
triggered. R has priority over the other inputs.
Soft−Start = 1 ms
1.0 V 200 mA
Figure 2. Internal Circuit Architecture
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Maximum Voltage on all other pins except Pin 8 (HV), Pin 6 (VCC) Pin 5 (Drv) and
Pin 1 (Demag)
−0.3 to 10
Maximum Current into all pins except VCC (6), HV (8) and Demag (1) when 10 V
ESD diodes are activated
Maximum Current in Pin 1
Thermal Resistance, Junction−to−Case
Thermal Resistance, Junction−to−Air, SOIC version
Thermal Resistance, Junction−to−Air, PDIP version
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁOperating Junction Temperature
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁMaximum Junction Temperature
−40 to +125
− 155 °C
Hysteresis in Shutdown
− 30 °C
Storage Temperature Range
−60 to +150
ESD Capability, HBM Model (All pins except HV)
− 2.0 kV
ESD Capability, Machine Model
− 200 V
Maximum Voltage on Pin 8 (HV), Pin 6 (VCC) decoupled to ground with 10 mF
Minimum Voltage on Pin 8 (HV), Pin 6 (VCC) decoupled to ground with 10 mF
Maximum ratings are those values beyond which device damage can occur. Maximum ratings applied to the device are individual stress limit
values (not normal operating conditions) and are not valid simultaneously. If these limits are exceeded, device functional operation is not implied,
damage may occur and reliability may be affected.