Interpreting Complex Data Sheet Specifications—Part IV

Next up in our ongoing series on interpreting complex data sheets is packaging. In the past, power supply manufacturers typically offered only two mounting options: PC or chassis. But now, products must be available in a variety of other mounting options—all of which require mechanical drawings that must be included on data sheets.

Let’s take a more detailed look at this trend:

More Mounting Options Than Ever. Originally, power supplies were mounted one of two ways: PC mount with pins or chassis mount with screw terminal. But now, customers want smaller power supply packages to fit ever-shrinking end products. Manufacturers have responded by providing more mounting and remote placement options, including DIN rail, open-frame and enclosed types, terminal block, surface mount—and more.

Here’s a rundown of some of these options:

• In a PC mount, the power supply is soldered directly onto the printed circuit board using pins. This was the standard for producing larger circuits contained in even larger multi-board designs.

• Chassis mounts allow you to remotely mount the power supply in a variety of ways: close to the load, on a frame inside the enclosure or outside the enclosure. What you ultimately choose depends on available real estate, the dimensions of your power supply and the operating environment.

• DIN rails let you mount power supplies and other industrial control equipment within enclosures or equipment racks. This mounting option utilizes space efficiently, as devices can be mounted next to each other in a variety of ways to meet system requirements.

• Surface mounts are the future of the PC mount. Nowadays, many products—and power supplies, for that matter—are getting smaller. Surface mount technology favors this trend: it utilizes solder paste rather than larger pins, taking up less space.

More Options Means More Drawings. But your options don’t end there. Depending on the direction of your connection, you may require a right angle, straight on or vertical mount. You may also require mounting types that integrate fans, heat sinks, input and output cables, connectors and safety tabs.

Not only do these various packages have to be listed on data sheets, but they must be accompanied by mechanical drawings that outline their dimensions and in some cases, provide a view from the top, front and bottom. Additional graphs, indicating derating curves versus ambient temperature, for example, are also needed when adding fans and heat sinks.