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Power-supply supervisor does reverse sequencing

Posted: 06 Feb 2008 ?? ?Print Version ?Bookmark and Share

Keywords:drop-in power-supply supervisors? reverse sequencing?

Maxim Integrated Products has introduces the MAX16050/MAX16051, drop-in power-supply supervisors. The MAX16050/MAX16051 let customers safely power up and power down their system(s) without the need for programming and/or elaborate board modifications. The devices sequence up and sequence down up to five power supplies, while also monitoring undervoltage and overvoltage conditions. With the additional capability of reverse sequencing, customers can now power down their system safely with no extra effort, cost, or loss of board space. The main applications for MAX16050/MAX16051 are servers/storage, networking and telecom systems, where high reliability is paramount.

Historically, design solutions for sequencing and reverse sequencing were difficult and expensive to implement. Board layouts are typically static and space-limited. Reverse sequencing has been difficult (if not impossible) to implement using discrete components only. Often the architecture used to sequence up required additional components and layout to reverse sequence. Maxim says its the MAX16050/MAX16051 can accomplish both sequencing and reverse sequencing with no programming and no external circuitry.

Pin-configurable sequencing
The MAX16050 offers an additional benefit. MAX16050's novel sequencing engine allows the sequence order to be changed without altering the signal routing to the power supplies. This configurable sequencing order is accomplished without adding bulky discrete components and/or making elaborate layout changes to the board.

The MAX16050 exchanges the 5th sequencing/monitoring channel, found in the MAX16051, for three 3-state pins used to configure the sequencing order of the four remaining channels in any one of 24 possible combinations. Users thus have full control of the sequence up/down order and can change the order on-the-fly. The ability to use a pin-selectable sequencing order is unique to the MAX16050. In striking contrast to the industry's previous work-around, customers now keep the same board layout when startup requirements change. The savings in development time and production costs are significant.

Enhanced reliability
The MAX16050/MAX16051's 85mA pulldown circuitry enables a fast discharge of output capacitance. Integrated comparators ensure that the supply voltages are below 250mV before powering down the next channel in the reverse sequence, regardless of how fast the system power is cycled. This pulldown circuitry increases reliability in complex systems.

External resistor-divider networks set the 1.5 percent accurate undervoltage and overvoltage thresholds. In the event of an overvoltage condition, an independent output signals the system controller. This additional control protects the system, reduces damage to expensive system components, and reduces repair costs.

Users can configure the devices' outputs either to enable point-of-load DC/DC converters or fully enhance the gate of series-pass FETs. An integrated charge pump enables this flexibility. The charge pump functions as a pull-up voltage for FETs, otherwise the open-drain outputs are pulled up to the supply voltage for enabling DC/DC converters. Consequently, users have the versatility of operating with mixed mode by driving both DC/DC converters and series-pass FET simultaneously in their system.

Multiple MAX16050/MAX16051's can be daisy-chained to sequence and reverse sequence across multiple devices. This scalability requires no programming.

The MAX16050/MAX16051 have a wide 2.7V to 13.2V operating voltage range, which allows operation directly from an intermediate bus voltage. The devices are fully specified over the -40C to 85C extended temperature range. The MAX16050/MAX16051 are offered in a small 28-pin, 4mm x 4mm QFN package. Samples are now available.




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