Six-supply sequencer with NV configuration & fault logging

September 29, 2015 // By Graham Prophet
LTC2937 is a programmable power supply sequencer and voltage supervisor, with built-in EEPROM, for six voltage rails. It is designed to carefully supervise and control FPGA/ASIC/microprocessor point-of-load supplies, which require tight accuracy and complex sequencing to avoid damage to the processor.

The device turns supplies on and off in a programmable order, separated either with adjustable time delays or by qualifying events (i.e. crossing voltage thresholds). Once sequenced up, a supply is monitored with ±0.75% accurate undervoltage and overvoltage thresholds. LTC2937 provides a flexible and precise supply sequencing and monitoring solution, meeting the demanding sequencing and tolerance requirements of supplies in high availability computers and servers, network routers and switches, enterprise data storage systems and telecommunications equipment.

The IC employs a flexible sequencing technique, turning a supply on or off in any one of 1023 possible sequence positions. A sequence position may be occupied by zero, one or multiple supplies. Empty (or reserved) sequence positions allow for addition of power supplies late in a board design. A simple single wire connection synchronises up to 50 LTC2937s for sequencing expansion to 300 supplies, simplifying board routing. Sequencing can be interleaved between multiple LTC2937s.

An I²C/SMBus digital interface affords register configuration and read back of the sequence positions and delays, supervisor thresholds, fault response and system status. Thresholds are 8-bit programmable from 0.2V to 6V in three range settings, including an adjustable range for greater than 6V and negative voltage supplies. Faults trigger logging to internal EEPROM, speeding debug and failure analysis. LTC2937 register configuration may be accomplished through the LTpowerPlay development environment, eliminating the need to write software code for autonomous operation. The device is capable of directly powering off a 12V intermediate bus, saving the space and cost of an external step-down DC/DC converter. The reset output’s release delay is programmable and the reset can be disabled during board margin testing. A regulated 3.3V output enables level shifting for monitoring negative supplies.

Specified over the 0°C to 70°C commercial and -40°C to 85°C industrial temperature ranges, the LTC2937 comes in a 28-lead 5m x 6mm QFN package for $5.95 (1000).

Linear Technology; www.linear.com/product/LTC2937

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