Design Talk - Chips and DIPs
High Speed Digital Isolation In PoE+
Amit Gattani, Akros Silicon, www.akrossilicon.com 
The new IEEE 802.3at standard is best known for its expansion of the powered device (PD) maximum power to 25.5 W from the 13 W “.af” level. Perhaps more significant, however, is the added control functions included in the standard that allows for dynamic allocation of power from the power sourcing equipment (PSE) to the network of powered devices. Dynamic and intelligent power allocation makes it possible to manage power over the network much in the same way as bandwidth is now managed. But to take full advantage of this new standard, it is necessary to acquire realtime power usage data from the primary side of each PD and transmit this information back to the PSE over the Ethernet data-link layer packets.
A high-speed digital isolation barrier integrated into the new Akros Silicon AS18x4 system-on-a-chip (SoC) offers designers an alternative to multichip solutions and eliminates the need for discrete optocouplers. By providing a multichannel, multi-megabit, high-isolation (>2KV) GreenEdge interface between the high and low sides, the AS18x4’s HV isolated ADC can provide live monitoring and input power profiling data feedback to the PSE. This feedback delivers valuable information to the PSE, including actual PD power requirements and actual cable loss. Static systems must use maximum possible numbers regardless of the actual power required or the actual cable distance.
As a consequence, a typical PSE switch will be limited either in the number of ports it can support or use a larger and less-efficient power supply. In contrast, by fully utilizing the AS18x4 real time monitoring capabilities in conjunction with the new standard, a typical 48-port PSE switch will be able to support PoE power on all ports with over 20 percent reduction in the PSE power supply. Now PSEs can do dynamic power allocation between various ports to provide better quality of service while reducing power supply cost and associated heat generation.
The typical PoE PD requires several regulated voltages The DigitalEdge isolation barrier of the AS18x4 also provides cross-isolation DC/DC timing management and control, thus improving efficiency and EMC performance over light load to full load conditions.
In customer transformer specifications, it is frequently assumed that the transformer will operate at 60Hz, and Ensign often must ask if the customer also requires 50Hz operation. This is more than simply our version of, "Do you want fries with that?" Whether to include or exclude 50Hz impacts the transformer's performance as well as its cost. Sometimes it also determines the degree of safety the transformer can provide.
REACH and the Electronics Industry
Certain chemical substances contained in electronic products and their components will need to be registered under the new EU Chemicals legislation (‘REACH’).
An essential first step for companies was pre-registration of substances in their electronic products by 1 December 2008 in order to benefit from extended registration deadlines (the first being 30 November 2010) during which they may continue to market their products in the EU.
Companies which missed the December deadline must suspend sales of their products to the EU until submission of a Registration dossier.
Companies can pre-register after the 1 December 2008 deadline in limited circumstances only.
Failure by EU based manufacturers or importers, or EU based agents of non-EU suppliers, to register certain substances contained in electronic products in volumes of one metric tonne or higher with the European Chemicals Agency (ECHA) closes EU markets for those components. For electronic products regarded as ‘articles’ (finished products) under REACH, this obligation applies only to substances intended to be released under normal or reasonably foreseeable conditions of use.
Most EU Member States have already adopted national rules on sanctions (from fines and market withdrawal to criminal penalties) for non-compliance with REACH. Equally, business customers and consumers are demanding proof of REACH compliance.
The next steps to ensure compliance under REACH post pre-registration are significantly more complex and require not only technical skills but also substantial legal advice, supply chain management and adjustments in logistics. Compliance has financial consequences that need to be carefully managed.
(1) Being properly represented
(2) Notification of SVHCs
(3) Supply chain communications
(4) Cooperation with competitors and anti-trust compliance
(5) Establishing ground rules
(6) Managing data
(7) Product defence:
The importance of successful company compliance
There is a very short window of opportunity for electronics companies to take stock and organize themselves to deal with the challenges which REACH raises. Continued EU market access is at stake – not only from a regulatory perspective but also in terms of the broader commercial environment.