Quad supply supervisor eases on/off sequencing

Linear Technology's LTC2928 quad supply sequencer and supervisor simplifies monitoring, diagnosis, and configuration of turn-on and turn-off sequence.

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 signalled 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.

The device can work with supplies down to 0.5V and supplies with negative voltage outputs. 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 5-by-7mm, 38-lead QFN and 36-lead SSOP packages. Available from stock, pricing begins at $3.95 each in 1,000-piece quantities.

- Vince Biancomano
eeProductCenter