How to get the LSM9DS1 recommended power-up sequence?

[jg_spitfire]

Hi, I am reading the datasheet of LSM9DS1 and it says that there are two times (rise and wait) you should respect

I was thinking in a sequencer IC but if we see the schematic of the LSM9DS1 evaluation board (STEVAL-MKI159V1) it does not use any kind of external IC to control the power up time, they just connects the Vdd and Vdd_IO directly to the power supply, why?, is there no consequence in supply the IMU without meet the requirements of the datasheet?, thanks

[Eleon BORLINI]

Hi @jg_spitfire​ , considering the schematic of the STEVAL-MKI159V1 you posted above, there is no short path between Vdd and Vdd_IO: the two lines are separated and are supposed to be tied to a couple of application processor (uC) pins: this is coherent with the sequential power-on scheme of the datasheet. What I however can tell you is that 99.9% of the times you will not encounter issues in connecting together the Vdd and the Vdd_IO lines (but in this way you will maybe have a little extra current consumption in power down), provided that your Vdd / Vdd_IO ramp is not too fast (<< Trise). Regards

[jg_spitfire]

Hi, so I understand that I should implement the delay between the two pins, I am thinking in use a soft start LDO for each pin because with the uC I can not control the Vdd_IO rise time, what do you think?, is there any datasheet with that circuit reference? , thanks

[jg_spitfire]

datasheet, page 14:

For the power-up sequence please refer to the following figure, where:

• Trise is the time for the power supply to rise from 10% to 90% of its final value

• Twait is the delay between the end of the Vdd_IO ramp (90% of its final value) and the

start of the Vdd ramp

why does the start up requirements are so restrictive?, I need to provide a controlled Trise and in the precise time when Vdd_IO achieves the 90% of its final value then start counting the Twait, right?

[Occio]

Hi,

I followed the discussion and I'm wondering if at the end you figured out how to power up correctly the MKI159V1 module.

Thanks in any case.