lowpowerZONE Products for the week of August 13, 2001

Texas Instruments Says . . .
TI Simplifies Power Supply Design With Low-Voltage DC/DC Converters for Optical Communications Systems and Notebook PCs
High-Performance DC/DC Converter Integrates Power FETs, Provides 6-A Continuous Output for DSP, FPGA, MCU Applications

Making power supply design easier and faster, Texas Instruments (TI) announced a series of high-performance synchronous-buck DC/DC converters that enable designers to quickly develop a power supply with as few as six external components. The new synchronous DC/DC converters with internal 12A MOSFET switches are capable of supplying greater than 6-A of continuous output current over the entire operating temperature range and operate over a 3.0 to 6.0V input voltage range. By integrating power MOSFETs in a synchronous-buck configuration, the devices are capable of up to 95 percent efficiency and are well suited for powering point-of-load DSP, FPGA and microcontroller applications, notebook PCs, networking and optical communications systems, and low voltage, high density distributed power systems.

The TPS5461x SWIFT (Switcher With Integrated FET Technology) DC/DC converters save development effort not only with the integration of power FETs and compensation circuitry, but also with an interactive software development tool that speeds novice and veteran power supply designers through the entire external component selection process. The development tool provides a bill of materials, reference schematic, loop response graphs and an efficiency curve based on the designer's inputs. External inductors and capacitors are chosen from the tool's database of components (users can also add their favorite components to the database).

"Strong time-to-market pressures make power supply development a critical path for manufacturers of a variety of advanced end equipments," said Rich Nowakowski, product marketing manager, TI Power Management Products. "When a complex DC/DC controller design using external MOSFETs is too time-consuming or risky, and a DC/DC module is too expensive, TI's high-performance TPS5461x SWIFT DC/DC converter will make designing power supplies from a 3.3/5V bus easier and faster."

Integrated Features Provide High Performance, Flexibility and Ease of Design

The TPS5461x devices offer a high output current in a small space while providing integrated protection features, such as power good, over-current protection, thermal shutdown and under voltage lockout. An integrated synchronous rectifier and a low 30mW rds(on) of the power MOSFETs enable the device to achieve efficiencies greater than 95 percent. To address an application's switching noise sensitivity, the switching frequency can be one of two preset values or adjusted anywhere between the range of 280 to 700 kilohertz (kHz). Additionally, excellent heat transfer resulting from TI's PowerPAD package enables up to three times the thermal performance of other packaging without the need for bulky heat sinks. An externally compensated option is also available, which adds flexibility for adjusting the output voltages or customizing loop response characteristics to the specific needs of the application.

analogZONE Says . . .

The trend to lower operating voltages in the microprocessor and DSP worlds has not come to any end. With cores at 1.8 V now quite common there is still going to be movement further downwards. With every reduction in rail potential Ohm's Law tells us that the current is going to go up linearly; some pundits are even predicting 20-A draws for some processors in just a couple of years. With every reduction in voltage the job of the power supply designer -- and the IC manufacturers -- gets tougher: The chances of problems causing catastrophic failure increase dramatically and the margins being worked with get smaller and smaller in the measurable units of voltage, rather than just percentages. The OEM manufacturers are also demanding better and better power management techniques with the result that current loads being demanded are considerably more variable than they were just a short while ago. All this pressure goes directly back to the method(s) chosen for dc-dc conversion, especially when other circuit areas in a product are still using rail voltages at 3.3 V, or even 5.0 V, so that they can interface with the outside world.

The TPS5461x family is an elegant, complete, solution for 6-A needs and will be extremely easy for the digital engineer to drop into a design with very little concern about successful operation. The input voltage is designed to be 5 V while the output voltage range of the parts is from 3.3 V down to 0.9 V for the internally compensated versions (i.e. the feedback is set up internal to the device) with an adjustable version (from 3.3 V down to 0.9 V) that requires external compensation -- a solution that might be desirable for an even more accurate output, or for a non-standard voltage application. Efficiencies are dependent on operating conditions, of course, but efficiencies approach 90% across the board with highest numbers approaching 95% down around the 1-A load mark.

The most significant savings in using the parts -- as against using a controller IC with external MOSFETs -- is that the parts count is reduced from over 20 down to just 7, including the TPS5461x, and certainly the overall parts cost will be significantly lowered. The potential divider, filter and decoupling for the externally-compensated, adjustable version -- the TPS54610 -- adds a further five components.

The parts have a 1.0% initial accuracy with the PWM switching frequency changeable between 350 kHz and 550 kHz (with a single pin select), or an external -- synchronizable -- source can be used between 280 kHz to 700 kHz to maximize efficiency. The parts will allow for 12-A peak current and 6-A continuous current loads with 9 pins paralleled for the output and 5 pins paralleled for the input on the TI thermally-enhanced TSSOP with a bottom heat pad. Protection circuitry is complete and sophisticated with only a couple of clock cycles required for an event to be noted and acted on . The integrated MOSFETs have an extremely low 30 millohm Rds(on); the quiescent current at the higher internal clock frequency is a typical 16 mA, while shutdown current is a typical 1.0 mA.

TI offers free designer software support as well as evaluation modules and users' guides. These high current parts will be quickly adopted by designers wanting to solve their supply problems quickly and with as little fuss as possible. 3-A parts, the TPS5431x family, will be sampling soon and in the near future there will be 1-A parts in a TPS5411x family.

The versions of the TPS5461x available now are the TPS54610 (adjustable output), the TPS54611 (0.9 V), the TPS54612 (1.2 V), the TPS54613 (1.5 V), the TPS54614 (1.8 V), the TPS54615 (2.5 V), and the TPS54616 (3.3 V). All are in thermally-enhanced TSSOP-28 and are priced at $4.99 in 1000-piece lots.

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