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Mixed signal power control is programmable and non volatile

Posted: 30 Mar 2005 ?? ?Print Version ?Bookmark and Share

Keywords:power supply? logic family? nrz? power over Ethernet? lattice semiconductor?

While the voltages and current ratings of our power supplies may change as new logic families become predominant, the need still exists to use more than one power supply in most designs. They may be needed just for reference level in communication links like NRZ, or for mixed signal supplies for dual rail instrumentation or audio for example.

The need also arises for the same power supply voltages to be sequenced and fault monitored. Plug in interfaces, for example, need to be able to detect, sequence and monitor for faults or out of tolerance conditions. Look at USB, power over Ethernet, flash card interfaces or hot swap boards and you will see that power sequencing, control and monitoring is more than just a luxury.

I've long thought that programmable logic could be a good marriage to both digital and analog functions if done cleverly. I'm happy to see Lattice Semiconductor pushing this approach forward with the additions to its Power Manager programmable mixed-signal product family.

The newest member is the power1208p1 device, which is pin compatible with its predecessor (Power1208) but with extended versatility. The analog inputs are capable of monitoring power supplies with voltages down to 0.67V, and are able to detect faults with greater than 0.5 percent precision. Power off conditions where the supply is 80mv or less can also be detected and used.

I like how each of the 12 high precision analog power monitor inputs has a 384 step programmable threshold. This can detect minor fluctuation in power supplies possibly indicating a fault which has not happened yet (failure is imminent).

Twelve may seem like a lot of monitor inputs, but each level can have alert high and low condition threshold levels as well as emergency shutdown levels if needed. This is doable since the comparators have precisions of 0.5 percent. I like the addition of on-chip programmable voltage references. These can be used for error or compensation feedback. The 4 noise-immune digital inputs and 4 open-drain digital outputs help interface directly to the real world in a noisy environment.

On chip, the digital functionality is pretty neat too. There is an on chip 1MHz timer which can feed the 4 programmable timers. This is perfect for delays or asynchronous timing sequence steps. A 16 macrocell Complex PLD (CPLD) is also on chip to handle Mealy or Moore type state machine sequencers.

I also like how strategic use of non volatile EEPROM memory keeps threshold settings and timing settings stored for next power up cycle. Once programmed via J-Tag (IEEE1149.1) boundary scan protocol, these parts power up ready to go.

The company's PAC-Designer software supports intuitive schematic design entry and simulation. There is also a PACsysPOWR1208P1 evaluation kit available through authorized Lattice distributors or on the Lattice website at a price of $149.

Housed in a 44-pin TQFP package, the Power1208P1 runs on 2.7V to 5.5V. Industrial temperature grade parts (-40C to 85C) are already available. They are priced at $9.95 in 10,000-piece quantities.


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