STMicroelectronics

The L4971 is a step down monolithic power switching regulator delivering 1.5A at a voltage between 3.3V and 50V (selected by a simple external divider). Realized in BCD mixed technology, the device uses an internal power D-MOS transistor (with a typical Rdson of 0.25Ω) to obtain very high efficency and high switching speed. A switching frequency up to 300KHz is achievable (the maximum power dissipation of the packages must be observed). A wide input voltage range between 8V to 55V and output voltages regulated from 3.3V to 50V cover the majority of today’s applications. Features of this new generations of DC-DC converter include pulse-by-pulse current limit, hiccup mode for short circuit protection, voltage feedforward regulation, soft-start, protection against feedback loop disconnection, inhibit for zero current consumption and thermal shutdown. The device is available in plastic dual in line, DIP8 for standard assembly, and SO16W for SMD assembly.

The L4978 is a step down monolithic power switching regulator delivering 2A at a voltage between 3.3V and 50V (selected by a simple external divider). Realized in BCD mixed technology, the device uses an internal power D-MOS transistor (with a typical Rdsonof 0.25Ω) to obtain very high efficency and high switching speed. A switching frequency up to 300KHz is achievable (the maximum power dissipation of the packages must be observed). A wide input voltage range between 8V to 55V and output voltages regulated from 3.3V to 50V cover the majority of today’s applications. Features of this new generations of DC-DC converter include pulse-by-pulse current limit, hiccup mode for short circuit protection, voltage feedforward regulation, soft-start, protection against feedback loop disconnection, inhibit for zero current consumption and thermal shutdown. The device is available in plastic dual in line, DIP-8 for standard assembly, and SO16W for SMD assembly.

L4979D and L4979MD are low dropout linear regulators with microprocessor control functions such as low voltage reset, watchdog, on/off control. Typical quiescent current is 100 μA in very low output current mode and enabled regulator. The devices drop to 6 μA with not enabled regulators. On chip trimming results in high output voltage accuracy (+/-2%). Accuracy is kept over wide temperature range, line and load variation. The maximum input voltage is 40 V. The max output current is internally limited. Internal temperature protection disables the voltage regulator output.

The L4981 I.C. provides the necessary features to achieve a very high power factor up to 0.99. Realized in BCD 60II technology this power factor corrector (PFC) pre-regulator contains all the control functions for designing a high efficiency-mode power supply with sinusoidal line current consumption. The L4981 can be easily used in systems with mains voltages between 85V to 265V without anyline switch. This new PFC offers the possibility to work at fixed frequency (L4981A) or modulated frequency (L4981B) optimizing the size of the input filter; both the operating frequency modes working with an average current mode PWM controller, maintaining sinusoidal line current without slope compensation. Besides power MOSFET gate driver, precise voltage reference (externally available), error amplifier, under voltage lockout, current sense and the soft start are included. To limit the number of the external components, the device integrates protections as overvoltage and overcurrent. The overcurrent level can be programmed using simple resistor for L4981A. For a better precision and for L4981B an external divider must be used.

The EVL4984-350W demonstration board, based on the new L4984D continuous conduction mode PFC controller, implements a 350 W wide-range input PFC pre-conditioner. It is suitable for all SMPS from 150 W to several kWs, and is compliant with IEC61000-3-2 and JEITA-MITI standards.

The L4984D is a current-mode PFC controller operating with line-modulated fixed-off-time (LM-FOT) control. A proprietary LM-FOT modulator allows fixed-frequency operation for boost PFC converters as long as they are operated in CCM (continuous conduction mode). The chip comes in a 10-pin SO package and offers a low-cost solution for CCM-operated boost PFC pre-regulators in EN61000-3-2 and JEIDA-MITI compliant applications, in a power range that spans from few hundred W to 1 KW and above. The highly linear multiplier includes a special circuit, able to reduce the crossover distortion of the AC input current, that allows wide-range-mains operation with a reasonably low THD, even over a large load range. The output voltage is controlled by means of a voltage-mode error amplifier and an accurate (1% at Tj = 25 °C) internal voltage reference. Loop stability is optimized by the voltage feedforward function (1/V2correction), which in this IC uses a proprietary technique that also significantly improves line transient response in the case of mains drops and surges ("bi-directional"). The device features low consumption and includes a disable function suitable for IC remote on/off. These features allow use in applications which also comply with the latest energy saving requirements (Blue Angel, ENERGY STAR, Energy 2000, etc.). In addition to overvoltage protection able to keep the output voltage under control during transient conditions, the IC is also provided with protection against feedback loop failures or erroneous settings. Other onboard protection functions allow that brownout conditions and boost inductor saturation can be safely handled. Soft-start limits peak current and extends off-time to prevent flux runaway in the initial cycles. The totem pole output stage, capable of 600 mA source and 800 mA sink current, is suitable for big MOSFETs or IGBT drive.