NCP1338: PWM Controller, Free Running Quasi-Resonant Current Mode
Description: The NCP1338 combines a true current mode modulator...
The NCP1338 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). The transformer core reset detection is done internally, without using any external signal, due to the Soxyless concept. The frequency is internally limited to 130 kHz, preventing the controller from operating above the 150 kHz CISPR-22 EMI starting limit.
By monitoring the feedback pin activity, the controller enters skip mode as soon as the power demand falls below a predetermined level. As each restart is softened by an internal Soft-Skip™, and as the frequency cannot go below 25 kHz, no audible noise can be heard.
The NCP1338 also features an efficient protective circuitry 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. Also included is a bulk voltage monitoring function (known as brown-out protection), an adjustable overpower compensation, and a VCC OVP. The Fault Timer is reset by any of these conditions, to ensure that the controller immediately restarts when the condition disappear. Finally, an internal 4.0 ms Soft-Start eliminates the traditional startup stress. NCP1338 can be used in applications where the VCC supply voltage is delivered by an external dc voltage source.
NCP1338 vs NCP1337: When a BO condition is applied, both controllers stop. When the BO condition is removed, NCP1337 doesn't restart if the fault timer has timed out; whereas NCP1338 always restarts (if Vcc is higher than 12 V).
Overvoltage Protection - rugged design
Internal Leading Edge Blanking - Noise immunity
Free-Running Borderline/Critical Mode Quasi-Resonant Operation - Reduces EMI and capacitive losses
Soft-Skip Mode with Minimum Switching Frequency for Standby - reduces noise and increases efficiency in stand-by mode
Auto-Recovery Short-Circuit Protection Independent of Auxiliary Voltage
Two Externally Triggerable Fault Comparators (one for a disable function, and the other for a permanent latch)
Internal 4.0 ms Soft-Start
500 mA Peak Current Drive Sink Capability
130 kHz Max Frequency
Internal Temperature Shutdown
Direct Optocoupler Connection
Dynamic Self-Supply with Levels of 12 V (On) and 10 V (Off)
SPICE Models Available for TRANsient and AC Analysis
Ac-dc Adapters for Notebooks, etc.
Offline Battery Chargers
Auxiliary Power Supplies (USB, Appliances, TVs, etc.)
Consumer Electronics (DVD Players, Set-Top Boxes, TVs, etc.)
Technical Documentation & Design Resources
Product Change Notification
Availability and Samples
Compliance: Pb-free Halide free
Description: PWM Controller, Free Running Quasi-Resonant Current Mode
Package Type: SOIC-7
Package Case Outline: 751U
Container Type: REEL
Container Qty: 2500
Market Leadtime (weeks):4 to 8
fsw Typ (kHz):
Short Circuit Protection:
VCC Max (V):
Drive Cap. (mA):
500 / 500