Quad Power Supply Sequencer & Supervisor from Linear

18th January 2007
ES Admin
The LTC2928 quad supply sequencer and supervisor from Linear Technology offers the flexibility to configure the power supply turn-on and turn-off sequence, monitor the supplies and diagnose supply failures. The device's simple pin-configuration approach to sequencing requires no firmware and allows the four supplies to be placed in any combination of eight time positions with configurable delay between each.
The comparator thresholds during the sequence-up, monitoring and sequence-down phases can be specific to each phase. The comparator outputs are encoded into four digital outputs that provide diagnostics for the type of fault (sequence, under-voltage, external controller or external fault) and the channel that failed. Over-voltage faults are signaled separately and may be optionally tied to the bidirectional FAULT pin to cause a shutdown. These timing, threshold and diagnostic options are configured with only a few external components.

Multiple supply systems often require turn-on and turn-off sequencing of supplies to protect vital circuits from damage and to allow for programmable logic boot-up and configuration. Setting the sequence, timing and thresholds often requires software-programming resources that are not always readily available for this task. The LTC2928 allows the power supply designer the freedom and flexibility to iterate without changing the layout or requesting software code changes. The device sequences and monitors supplies starting as low as 0.5V including negative voltages and can be powered from a supply of 2.9V up to 16.5V. The sequenced supplies can be regulators or power modules with enable inputs or RUN/SS pins. Alternatively, N-channel MOSFETs can be used to pass power from supplies since the enable outputs of the LTC2928 are capable of driving gates to Vcc + 6V. The LTC2928 is easily cascadable to control an unlimited number of power supplies.

Specified over the commercial and industrial temperature ranges, the LTC2928 is offered in 5mm x 7mm 38-lead QFN and 36-lead SSOP packages. Available from stock, pricing begins at $3.95 each in 1,000 piece quantities.

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