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TIOS101: power up sequence / VCC_IN issue

Genius 16335 points
Part Number: TIOS101
Other Parts Discussed in Thread: TPS62088,

Hi all

My customer is working on a design with the TIOS101.

They are using an upfront DC-DC 24V => 5V and then the TPS62088 as 5V => 3.3V step-down to be provided to  PIN 1(VCC_IN).

They apply 24V to Pin 9 (VCC). During startup they experience a behavior as outlined in: 

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/878391/tios101-tios101-power-up-sequence/3250569#3250569

This can lead to the destruction of the TPS62088.

Do you have recommendations how to solve the issue other than what is outlined in the former forum post ?

Best regards

Ueli

  • Hi Ueli,

    We have a new version of this device in development that should correct this issue and samples should be available in the next couple of months.  It is pin-to-pin equivalent with the TIOS101 and should be able to be a drop in replacement once available.  A long term solution would be to use this device.

    Until then, the only solution I can think of is to place a schottky diode with the lowest drop possible (0.3V, etc) between the output of the TPS62088 and the VCC_IN pin of the TIOS101 to block the voltage from the TIOS101.  The TIOS101 will see a small voltage drop but if kept small, should still allow the device to operate and protect the TPS62088.  If possible, the output voltage of the TPS62088 could be biased slightly higher to offset this drop and allow the voltage on the device pins to still be 3.3V after the diode drop.

    If it is possible to isolate the output of the TPS62088 from the TIOS101, then the TIOS1013 device could be used which would be completely powered from the 24V supply and not need an input from the TPS62088.  The 3.3V LDO output voltage does not need to be used anywhere else on the board and therefore this effectively isolates this pin from the rest of the board.

    Regards,

    Jonathan

  • Jonathan

    Thank you for the quick and detailed reply, your comments are very helpful.

    Much appreciated !

    Best regards

    Ueli