Low-profile converter IC supports power-over-Ethernet applications
By Jeff Berman, News Editor -- EDN, July 20, 2005
Power Integrations this week introduced a low-profile packaging option for its DPA-Switch family of high-voltage, dc-dc converter ICs. Compared with the existing TO-263 package, the S-PAK delivers savings of 40% in board space and 55% in height while offering equivalent thermal impedance, according to the company.
The DPA-Switch family combines detection and control circuitry and a high-voltage MOSFET on a monolithic chip, reducing design time, component count and overall system cost, said Doug Bailey, Power Integrations vice president of marketing, in an e-mail. The ICs, which suit POE (power over Ethernet) implementations in devices such as IP phones, wireless access points, and security cameras, can be combined with a "handful" of discrete components to produce the simplest option available for dc-dc power conversion, he added.
"We think designers will most appreciate the design simplicity that DPA-Switch offers," Bailey said. "The people designing POE client devices like IP phones and wireless access points are typically going to be experts in digital design engineering rather than power-supply design. DPA-Switch enables these designers to design the power supply themselves, rather than outsourcing it, which should save them both time and money."
While engineers can choose from several other discrete and integrated options for POE, including offerings from Linear Technology, Texas Instruments, and Maxim Integrated Products, Bailey said those competing products require an external MOSFET, which creates a more difficult design challenge.
"[Our] ICs include the MOSFET on the silicon, improving performance and requiring external components only for the more straightforward parts of the circuit," Bailey said.
Pricing for the DPA-Switch in the S-PAK package ranges from $1.36 to $2.66 (1000). The package is lead-free, complies with RoHS, and meets the J-STD-020C 260ºC solder-reflow requirements, according to the company.
The DPA-Switch family includes four variants. The DPA423SN supports maximum power output of 18W and suits Class 1 and Class 2 POE applications. The DPA424SN offers 35W maximum power and targets Class 0 and Class 3 POE applications. And the DPA425SN and DPA426SN, with maximum outputs of 70W and 100W, respectively, support future POE-Plus classes that will target higher-power devices such as notebook computers.
