Power Chips Raise the Bar on Operating Voltage

Jan 1, 2008 12:00 PM
By David Morrison, Editor in Chief

Voltage Regulators

Another high-voltage part unveiled in December was Intersil's ISL6719 100-V linear regulator. This device, which complements Intersil's recently released 100-V triple output linear regulator (the ISL6720A) is said to handle the functions of up to 15 discrete components. Moreover, the ISL6719's 9-lead, 3-mm × 3-mm DFN package occupies less than half the board space of a discrete solution.

Aimed at a variety of telecom and networking applications, the ISL6719 is well suited for use as a single startup linear regulator in isolated power designs, or as an output bias supply for point-of-load regulators in telecom/datacom applications. Unit pricing for the ISL6719 is approximately $1.25.

Switching regulators are also moving to higher operating voltages. Introduced last month, National Semiconductor's LM5015 is a monolithic, two-switch forward dc-dc regulator that features a wide input-voltage range from 4.25 V to 75 V. Targeting telecom, automotive and industrial applications, the regulator can be used to design either isolated or nonisolated dc-dc converters.

The LM5015 features all of the functions necessary to implement efficient two-switch forward and two-switch flyback power converters with a minimum of external components. The regulator integrates high-side and low-side 75-V n-channel MOSFETs with a minimum 1-A peak current limit. The voltage across the MOSFETs employed in the two-switch topology is clamped to the input voltage, allowing the input-voltage range to approach the rating of the MOSFETs.

The regulator control method is based on current-mode control, providing inherent ease-of-loop compensation and line feed-forward for superior rejection of input transients.

The operating frequency of the LM5015 is set with a single resistor and is programmable up to 750 kHz. Protection features include cycle-by-cycle current limiting, thermal shutdown, undervoltage lockout and remote shutdown capability. Available now, the LM5015 is offered in a 14-pin TSSOP package, featuring an exposed die attach pad. Pricing is $2.05 each in 1000-unit quantities.

Some other parts that were announced earlier in the year are also worth noting. Intersil's ISL8560 2-A buck regulator supports an input-voltage range of 9 V to 60 V with programmable output voltages from 1.21 V to 55 V. A related buck regulator, the ISL8540 has an input-voltage range of 9 V to 40 V with a programmable output-voltage range of 1.21 V to 35 V. Both devices have the capability to manage transient spikes of up to 100 V for 400 ms.

Two other devices are 100-V current-mode buck controllers. One is Linear Technology's LTC3810, a synchronous stepdown switching regulator controller that can directly step down voltages from 100 V to output voltages ranging from 0.8 V to 93% of V_IN. This chip device employs a constant on-time valley current-mode-control architecture to deliver very low duty cycles and fast transient response with accurate cycle-by-cycle current limiting without requiring a sense resistor.

Another is National Semiconductor's LM5116, a 6-V to 100-V buck controller that produces a programmable 1.215-V to 80-V output. This device uses the company's emulated current-mode control to overcome the noise susceptibility and duty-cycle limitations of traditional peak current-mode control, by emulating the buck switch current signal.

Going down in the voltage range, Micrel's MIC2130/1 series of high-voltage synchronous buck controller ICs offers a frequency-dithering feature that minimizes EMI and adheres to global EMC standards. Targeted at the industrial, communication, automotive and high-end consumer markets, the controllers operate over an input-voltage range of 8 V to 40 V, generating an adjustable output voltage down to 0.7 V.