3 Rail Simple Power Sequencer with Fixed Time Delay

The LM3880 simple power supply

sequencer offers the easiest method to control powerup sequencing and powerdown

sequencing of multiple Independent voltage rails. By staggering the startup

sequence, it is possible to avoid latch conditions or large in-rush currents that

can affect the reliability of the system.

Available in a 6-pin SOT-23 package, the simple

sequencer contains a precision enable pin and three open-drain output flags. The

open-drain output flags permit that they can be pulled up to distinct voltage

supplies separate from the sequencer VDD (only if they do not exceed the

recommended maximum voltage of 0.3 V greater than VDD), so as to

interface with ICs requiring a range of different enable signals. When the LM3880 is enabled, the three output flags sequentially release,

after individual time delays, thus permitting the connected power supplies to start

up. The output flags follow a reverse sequence during power down to avoid latch

conditions.

EPROM capability allows every delay and sequence

to be fully adjustable. Contact Texas Instruments to request a non-standard

configuration.