DC-DC converters get right to the point-of-load Richard WilsonPower module suppliers are responding to the need for more power rails driving widely ranging current levels on PCB designs with a new type of low current power regulator which can supply voltages ranging from 5V down to 1V scattered about the PCB at positions close to the point-of-load.
These so-called point-of-load (POL), non-isolated step-down voltage regulators are small single-in-line packaged devices designed to sit close to the load circuits on boards supplying currents in the 10 to 20A range.
According to one supplier, Datel, today’s system boards often require as many as six to seven different voltages (0.8V, 1V, 1.2V, 1.5V, 1.8V, 2.5V, 3.3V, 5V, and so on.) at individual currents ranging from 2 to 60A.
“The days of a power supply per voltage are numbered as such straightforward power delivery simply costs too much. Parallel, isolated power paths from backplanes onto system boards are redundant and no longer affordable,” said Peter Cowan, general manager at Datel (UK).
The most commonly used approach, says Cowan, is a 12V bus supplying power to numerous non-isolated, step-down, buck regulators.
To this end the firm’s latest range of single-in-line non-isolated DC-DC converters accept 12V inputs (10.8V to 13.2V input range) and deliver 1V, 1.2V, 1.5V, 1.8V, 2V, 2.5V, 3.3V or 5V outputs rated at 10A.
The benefit of using a non-isolated approach for the POL of converters, says Cowan, that not needing transformers, optocouplers and complicated FET drive circuits in their secondary, “they are considerably cheaper than their isolated brethan.”
One supplier, Vicor is planning on taking a completely different approach to the POL market.
Vicor’s intention is to introduce a family of isolated point of load devices. It believes there is a problem with ground currents, generating unwanted noise with the more traditional non-isolated device. C&D Technologies is offering isolated 3W dual-output DC-DC converters in a low-profile 24-pin DIL package intended for POL of applications with 12V or 15V intermediate bus.
The NDT converters offer a 2:1 input capability that allows them to handle voltage ranges of 18-36V or 48-75V respectively. Output voltage options are 12 or 15V for each nominal input voltage. In all cases isolation between the input and outputs is rated at 1kV DC.
Offering a power density of 0.90W/cm3, the converters are capable of delivering their full 3W output power at temperatures up to 85ºC without the need for a heatsink or other additional cooling.
The driver for this type of device, says Steve Allen, general manager at Power One, is the increasing number of different voltages required by some PCB designs. “It is not uncommon to see cards with six to eight output voltages,” he points out.
Power One’s SIS12 family of non-isolated POL DC-DC converters offers 22 models with six output voltages and input voltage ranges of 4.5 to 5.5V DC or 10.8 to 13.2V DC to support intermediate bus architectures.
These 12A converters offer output options: 1.2, 1.5, 1.8, 2.1, 2.5 and 3.3V DC. The single-in-line package measures 2.5x0.75in.
Not all designers are opting for a 12V intermediate bus on the board. Some on-board bus voltages can be as low as 3.3V. Module supplier, Lambda is addressing the requirements of on-board distributed power designs with its 70A standard half-brick footprint modules. “Not only are processors and Asics taking more current at lower voltages, many designers are using the 2.5V or 3.3V bus to supply their point-of-load converters,” says Lambda’s marketing director, David Norton.
The company’s PAH200H module, operates from a nominal 48V input, provides a fully regulated output at power levels up to 198W, at nominal single output voltages of 1.8V, 2.5V and 3.3V.
Broadband TelCom Power is tracking the increasing current needs of designs with a 60A quarter-brick DC-DC converter. The US company claims that power efficiencies are not compromised at these higher currents because of its patented transformer technology known as Flat Matrix cores. The SHQ series, which has a 7.2mm transformer core, offers up to 60A output at 1.8V DC and 1.5V DC and 50A at 3.3V DC and 2.5V DC. Efficiencies are up to 92 per cent.
SynQor’s latest family of non-isolated, point-of-load DC-DC converters can deliver up to 20A output in a single-in-line package.
The first modules in the NiQor family non-isolated line have a 3.0 to 5.5V input range and deliver up to 20A at 3.3V, 2.5V, 1.8V, 1.5V, 1.2V and 0.9V.#
The company also plans to extend the range to include a 12V input series (9.6V to 13.2V range) that can deliver up to 15A at 5.0V, 3.3V, 2.5V, 1.8V, 1.5V, 1.2V and 0.9V.
The modules employ synchronous rectification to achieve efficiencies of 92 per cent at full load (3.3Vout).
The company claims that point-of-load power from the isolated high current bus can be designed for as little as a dollar an Amp. It also offers a DC transformer which can be used to implement a 12V intermediate bus architecture. Tyco Electronics Power Systems is offering a non-isolated 12V input point-of-load module delivering 25A of output current. Available in surface mount and single-in-line versions, the NXA025 provides regulated output voltage from 0.9V to 5.0V DC, programmable via an external resistor.
Artesyn has recently introduced dual-output (3.3/1.8V or 3.3/1.2V) 20A quarter-brick and single 1.8V 40A eight-brick DC-DC converters for the POL market. Ericsson is another power module company with a POL step-down regulator on the market. The MacroDens 2 will drive 12A on outputs from 1.2V to 2.5V, from a 3.3V input supply.
Last year di/dt claimed to have the first 25A one-eighth brick DC-DC converters. The SQM48 converters come in an open-frame package that does not require a heat sink. They operate from an input voltage of 36V to 75V and is available in standard output voltages of 2.5V, 2.0V, 1.8V, 1.5V, and 1.2V.