The layout of the HTML version of the application note follows the page breaks in the PDF version. To navigate, you may click on a page number (below) to jump to another other page. You may also download/view the entire application note in PDF format [PDF format].

EDN ACCESS ARTICLE: DESIGNING A NEBS-COMPLIANT POWER SYSTEM
A complete power system guarantees the problem-free operation of telecommunications equipment and that equipment's compliance with applicable standards. Designing the complete power system requires expertise in areas beyond power conversion. [HTML]

1  2 3 4 5 6 7 8 9 10 11 12 Next -->

Designing a NEBS-compliant Power System - SMH4804

PAGE 1

Table Of Contents:
	Page 1	Component Selection for NEBS
	Page 2-8	Pre-testing for NEBS Compliance
	Page 9	The Complete Circuit Schematic
	Page 10	Bill of Materials
	Page 10	Vendor Contact Listing
	Page 11	NEBS: Historical Overview
	Page 12	Bibliography

 
Introduction

A reference circuit design employing a Summit Microelectronics SMH4804 Quad Hot-Swap Controller and SMT4004 Quad Tracking Power Supply Manager is tested and hardened for NEBS EMI/EMC compliance. This reference design is intended to assist the design engineer with component selection and general PCB layout practices required to meet the NEBS Standards. Test results published herein were obtained in Summit Microelectronics' lab and are for reference only as NEBS compliance requires submission to an approved testing facility.

Component Selection for NEBS

The NEBS compliance reference circuit is based on the SMH4804 evaluation board. Testing and hardening of the evaluation board resulted in the circuit displayed in Figure 1. The added components are highlighted in red. NEBS compliance testing begins with an overview of the standards (see "NEBS: An Historical Overview") after which a suitable waveform generator is chosen. The UCS500-M from EM Test generates the necessary waveforms and includes Windows software with preprogrammed test routines to simplify testing and allow for easy documentation of each test step.

Before testing, identify all power and signal lines that interface directly with the host (-48V) supply. In this example, a dual-feed supply is employed. A short pin is used for each feed to hold off the in-rush current until the DUT is inserted. There are 6 external connections to the backplane; 4 must be fused to meet safety standards and otherwise prevent this system card from disrupting the host supply.

Though the NEBS EMI/EMC standards are quite exhaustive, much of the testing and hardening efforts are focused on immunizing the system from external noise sources such as ESD and lightning strikes. Additional noise sources, such as EMI originating from other cards operating on the &endash;48V bus are rendered harmless using the same circuitry (EMI filters) that prevents the DUT itself from becoming a noise source.