Summit Microelectronics - Applications Note 25

Tech Support: Applications Note 25
SMH4804, SMP9210 and SMT4004 Telecom Reference Design

This application note was jointly authored by Summit Microelectronics and Power-One.

Power One is one of the ten largest power conversion equipment manufacturers in the world and is ranked in the S&P 500. Power-One's strengths include financial stability, a reputation for quality and reliability, extensive research and development resources, global customer service capabilities, and one of the industry's broadest power conversion product lines.

Communications Industry Focus
Power conversion solutions are sold to telecom and Internet service providers, and communications equipment manufacturers. Power-One's high-reliability products are also used in critical applications such as test equipment and high-end industrial applications.

A partial customer list includes: Alcatel, Avaya, Cisco Systems, Ericsson, Extreme Networks, Huawei, Lucent, Motorola, Nokia, Nortel Networks, Samsung, and Siemens.

The main web site is: http://www.power-one.com/
This Application Note is also available on the Power One site [click here].

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SMH4804, SMP9210 and SMT4004 Telecom Reference Design

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Introduction
This Application Note presents the design of a power system required to convert the -48V bus to multiple voltages typically required by communication equipment such as network processors, DSPs, and miscellaneous ASICs. Included is a review of the entire design including both power management and power conversion blocks, focusing on areas where difficulties often arise. The power management is implemented using a hot swap controller SMH4804, a quad power supply manager SMT4004 and two dual 10-bit nonvolatile DACPOT™s SMP9210 for trimming. The power conversion block is built using Power-One's QHS series of 50A quarter-bricks. Guidelines and optional solutions are provided to increase the likelihood of a trouble-free system power design.

BLOCK DIAGRAM

Figure 1 below displays the block diagram of a &endash;48V primary-side to secondary-side conversion circuit. The individual blocks are highlighted in broken-line boxes. All featured products contain non-volatile, I²C accessible configuration registers which allow design 'tweaks' and board level changes using a software-level interface instead of redesigns, recalls or component changes. A brief description of each block and its primary functions follows.

Hot-Swap Controller (SMH4804)

Any board or circuit connected to the &endash;48V supply must not cause any disturbance to the bus. A 'Hot-Swap' controller (SMH4804) is used to:

1. Permit live card insertion by soft-starting the in-rush current.
2. Shutdown &endash;48V power to the native board when an overcurrent or other fault jeopardizes the bus.
3. Permit orderly power-on/off sequencing of the DC-DC converters. This includes primary to secondary isolation using opto-isolators with the necessary primary to secondary breakdown voltage rating.

Quad Power Supply Manager (SMT4004)

Once power is available on the secondary-side (the DC-DC converter outputs are active), the SMT4004 provides multiple-voltage tracking and monitors for voltage and current faults. Power supply voltage tracking has become an industry requirement due to nature of network processors, ASIC's and other such devices using multiple voltages for I/O and core circuitry. The SMT4004 is highly programmable, allowing the management of a wide range of power supply voltages.

Figure 1: -48V Primary to Secondary-Side Conversion Circuit Block Diagram

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NOTICE

SUMMIT Microelectronics, Inc. reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. SUMMIT Microelectronics, Inc. assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained herein reflect representative operating parameters, and may vary depending upon a user's specific application. While the information in this publication has been carefully checked, SUMMIT Microelectronics, Inc. shall not be liable for any damages arising as a result of any error or omission.

SUMMIT Microelectronics, Inc. does not recommend the use of any of its products in life support or aviation applications where the failure or malfunction of the product can reasonably be expected to cause any failure of either system or to significantly affect their safety or effectiveness. Products are not authorized for use in such applications unless SUMMIT Microelectronics, Inc. receives written assurances, to its satisfaction, that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; and (c) potential liability of SUMMIT Microelectronics, Inc. is adequately protected under the circumstances.

Version 2.0 - This document supersedes all previous versions.

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