UNITRODE Manuals

The document contains information about the SA40-18EWA supplier. The product has features and characteristics, please refer to the document for more details.

The UCC2585/UCC3585 synchronous Buck controller provides flexible high efficiency power conversion for output voltages as low as 1.25V with guaranteed ±1% DC accuracy. Output currents are only limited by the choice of external logic level MOSFETs. With an input voltage range of 2.5V to 6.0V it is the ideal choice for 3.3V only, battery input, or other low voltage systems. Applications include local microprocessor core voltage power supplies for desktop and Notebook computers, and high speed GTL bus regulation. Its fixed frequency oscillator is capable of providing practical PWM operation to 700kHz. With its low voltage capability and inherent “always on” operation, the UCC2585/UCC3585 causes VOUT to track VIN once VIN has exceeded the threshold voltage of the external P channel MOSFET. Tracking can be tailored for any application with a single resistor or disabled by connecting TRACK to VIN. For dual supply rail microprocessors this feature negates the need for external diodes to insure supply voltage tracking between the +3.3V and lower voltage microprocessor core supplies.

The UCC3946 is a microprocessor supervisor with reset and watchdog functions.

UCC2305 UCC3305 integrates all of the functions required to control and drive one HID lamp, and is tailored to the demanding, fast turn-on requirements of automobile headlamps, but is also applicable to all other lighting applications where HID lamps are selected.

UCC18500/1/2/3 UCC28500/1/2/3 UCC38500/1/2/3 is a series of BiCMOS PFC/PWM combination controller, which integrates PFC and second stage DC-DC converter function, controls boost PWM to near unity power factor, and has accurate power limiting, average current mode control in PFC stage, peak current mode control in second stage, programmable oscillator, Leading Edge/Trailing Edge modulation to reduce switching loss.

UCC3857 is a controller for isolated boost PFC converter.

The file is the preliminary description of UCC1858 UCC2858 UCC3858, which provides all the necessary control functions for active power factor corrected preregulators that require high efficiency at low power operation. The controller achieves near unity power factor by shaping the AC input line current waveform to correspond to the AC input line voltage using average current mode control. The operation of the UCC3858 closely resembles that of previously designed Unitrode PFC parts with additional features to allow higher efficiency boost converter operation at light loads. This is accomplished by linearly scaling back the PWM frequency when the output of the voltage error amplifier drops below a predetermined user programmable level indicating a light load condition. The frequency is scaled back by reducing the charging current for the CT ramp (in proportion to the output power), and increasing the dead time. There is also an instantaneous reset input to pull the IC out of foldback mode quickly when the load comes back up. The PWM technique used in the UCC3858 is leading edge modulation. When combined with the more conventional trailing edge modulation on the downstream converter, this scheme offers the benefit of reduced rip- ple current on the bulk storage capacitor. The oscillator is designed for easy synchronization to the downstream converter. A simple synchroni- zation scheme can be implemented by connecting the PWM output of the downstream converter to the SYNC pin.

This document introduces UCC3884, a high-performance current mode PWM controller designed for single-ended switch mode power supplies. The chip implements a frequency foldback scheme that decreases the oscillator frequency as the output voltage falls below a programmed value. This technique decreases the average output current sourced into a low impedance load, which can occur during an output short circuit or overload condition. Excessive short circuit current is more prevalent in high frequency converters where the propagation delay and switch turn-off time forces a minimum attainable duty cycle. An accurate volt-second clamp limits the duty cycle during line or load transient conditions which could otherwise saturate the transformer. The volt-second clamp may also be used with an external overvoltage protection circuit to handle fault conditions such as current sense disconnect or current transformer saturation. The frequency foldback, volt-second clamp, cycle-by-cycle current limit, and overcurrent shutdown functions ensure that the power supply is always in a safe state under various fault conditions.

The UCC3888 is a non-isolated controller for switch mode power supplies and battery chargers. It achieves high efficiency and low cost conversion by using two cascaded flyback converters. The UCC3888 switch frequency can be externally programmed from 200kHz to 500kHz and has an integrated synchronous rectifier.

UCC1889 is a switch-mode power supply controller that can be used in transformerless off-line applications and provides ideal primary-side bias supply. It features an efficient BiCMOS design, wide input range and adjustable low voltage output. This device can use low cost SMD inductors and has short circuit protection and optional isolation capability.

Introducing the characteristics of UCC3890, including low power, low voltage, and can be used for battery trickle charging.