VDD and VDIO power on sequence

i have bmp183 chip, in form of breakout board, every powers in appears "stuck" mode. pressure , temperature reported library incorrect , unchanging. when happens other spi devices in system function correctly. else seems fine. reset fixes it, it's minor annoyance only.

looking @ datasheet chip states:

     "the preferred power on sequence vdd first. though vddio can powered on before vdd,
     there chance of excessive power consumption (a few ma) if sequence used, , state
     of output pins undefined bus can locked. therefore, vdd must powered
     before vddio unless limitations above understood , not critical."

the breakout board has 3.3v regulator , feeds both vdd , vdio (tied together) have no easy way test see if problem. i'm not sure how anyway.

how 1 arrange power sequence vdd , vddio?

i never saw happen when testing breakout board itself, or in initial form of project. appeared more addition of sensor. have resulted in power glitch triggers lockup? wish had oscilloscope.

i've had sort of problem before. assuming it's same, it's called latch-up (sometimes scr latch-up or cmos latch-up). in case, needed power analogue 5v before digital 5v. if got timing wrong, latched , shorted 5v ground.
something lm3881 power sequencer quite useful.

ian.

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