May 2010In conjunction with the electronic publication of the Power 2 You eBook, Lattice has also released four new reference designs that enable designers to accelerate time to market with several power management solutions.
A hot swap controller is used to limit the inrush current when a circuit board is plugged into a powered backplane. In addition, a hot swap controller may offer some or all of the following features: over-current protection (electronic circuit breaker), over-voltage protection, and under-voltage protection. Hot swap controllers are also required to isolate the board from the backplane which is useful in troubleshooting, maintenance, and upgrade activities. The power-down request may come from the backplane (remote) or an on-board switch (manual).
Reference Design RD1068, 12V Hot Swap Controller with ispPAC-POWR1220AT8, describes how a Lattice Power Manager II ispPAC-POWR1220AT8 can be used to implement the functions required for 12V hot swap applications. This reference design is targeted to operate on the Power Manager II Hercules Development Kit (PAC-POWR1220AT8-HS-EVN – Standard or PAC-POWR1220AT8-HA-EVN – Advanced).
Features:
For more information on hot swap controller theory and how the Power Manager II can be applied, see Chapter 5, "Hot Swap Controllers" of the Power 2 You eBook.
Reference Design RD1070, AMC Module Power Management, describes the use of a Lattice Power Manager II ispPAC-POWR1014A device as a Payload Power Management Coprocessor in an Advanced Mezzanine Card (AMC) system. The Advanced Mezzanine Card is intended to be plugged into a carrier system, either a card or a shelf, and supports the hot swapping of the Mezzanine card in the carrier system without affecting the operation of the host carrier system. The electrical and mechanical specifications for the AMC system are specified by the PICMG 3.0 subcommittee, AMC.0 R2.0.
The AMC specifications incorporate a system management section that is an extension of the hierarchical ATCA (Advanced Telecommunication Computing Architecture) shelf management scheme. A processor in the Mezzanine card module management section, called the Module Management Controller (MMC), sends the details of the payload circuitry along with the power requirements to the host system processor and also receives commands from the host system processor. The system uses a payload power rail (+12V) and a management power rail (+3.3V) so that when the AMC module is plugged in, only the module management section is powered on. When the MMC receives the command from the host system processor it will then turn on the payload power rail and the AMC card will become active in the system.
By using a Lattice Power Manager II device as the Payload Power Management Coprocessor, the design of the MMC can be simplified since it is used to supply the Module Management section functions which are defined by the AMC.0 R2.0 specification. The Power Manager II device can provide the monitoring and control functions of the payload power supplies and provide this information to the MMC over an I2C link and several status signals.
Features:
For more information on AMC power management, power and supply feed control theory, and how the Power Manager II can be applied, see Chapter 7, "Power Feed Controllers" of the Power 2 You eBook.
For systems using microprocessors or computers there are usually numerous power supplies. If a power supply fails the power manager circuits may, as a minimum, force a shutdown. For maintenance and troubleshooting it is very desirable to know which power supply failed and the type of failure condition (over-voltage or under-voltage). This reference design presents a solution that records the supply fault condition in non-volatile memory so the fault(s) can read back at a later time. This solution is fast, reliable, and cost effective because it is based on a Power Manager II, MachXO or LatticeXP2 and non-volatile SPI Flash memory.
Reference Design RD1072, Voltage Monitoring for Fault Logging with ispPAC-POWR1220AT8 presents a solution using the Power Manager II ispPAC-POWR1220AT8. This reference design is targeted to operate on the Power Manager II Hercules Development Kit (PAC-POWR1220AT8-HS-EVN – Standard or PAC-POWR1220AT8-HA-EVN – Advanced).
Features:
For more information on voltage monitoring theory and how the Power Manager II can be applied, see Chapter 3, "Reset Generators & Supervisors" of the Power 2 You eBook.
One method used to increase the reliability of high availability systems is though the use of redundant power supplies. These systems are powered by two or more supplies. These supplies are generated either by multiple sources or the system is connected to the main supply by the use multiple paths. Boards connected to these redundant supplies derive a single high availability rail through the use of a diode circuit as shown below. This arrangement is called power rail OR’ing.
This is a simple arrangement. Only the supply that has the highest voltage drives the main board voltage. Also, if the supply voltages are roughly equal, the load power is shared between each of the sources. If a supply fails, the load is transferred to other supplies automatically without any interruption.
Although this is the simplest and most reliable way of OR’ing supplies, this circuit has a disadvantage: it wastes power. Diodes usually drop about 700 mV. If the load current is, say, 2A, the power dissipated by the diode is 1.4W.
Modern power OR’ing circuits use MOSFETs in place of the diodes to reduce the power dissipation significantly. If the turn-on resistance of the N-channel MOSFET is about 25 miliohms, the power dissipated by this MOSFET at 2A is 100 mW (2*2*25 E-3). In other words, the power dissipation is reduced by 93%.
Reference Design RD1064, Redundant Power Supply Management, uses the Power Manager II ispPAC-POWR1220AT8 device to control two power supply rails using MOSFETs with current sensing for each power supply. This allows the design to monitor the current in each power supply and prevent reverse current flowing between each power supply by turning off the MOSFET when the current falls below a minimum threshold value.
Features:
For more information on power supply OR’ing theory and how the Power Manager II can be applied, see Chapter 6, "Power Supply OR’ing Controllers" of the Power 2 You eBook.
For further information about these and other reference designs, visit the Lattice web site.
© Lattice Semiconductor Corporation 2012
