Unexpected voltage is seen on F5255 DVIO pin

Koichiro Tashiro

Other Parts Discussed in Thread: MSP430F5255

Hi,

My customer is developing their system with MSP430F5255.
In their system, 1.8V is supplied to DVIO pin, but customer observed ~2.1V on the pin.
Customer cut the line between an external LDO and DVIO, but still the 2.1V is seen, i.e. the voltage comes from MSP430.

Is this expected behavior ?

Thanks and regards,
KoT

over 7 years ago

0 KC Xu over 7 years ago

TI__Intellectual 1995 points

Hi KoT,

You mean customer observed 2.1V on DVIO pin even with 1.8V supplied to DVIO pin? What's the power supply on DVCC/AVCC?

regards
KC

0 Clemens Ladisch over 7 years ago

Guru 244610 points

In theory, this could happen if current is injected into the DVIO supply by applying a too-high voltage to some I/O pin(s).

0 Koichiro Tashiro over 7 years ago in reply to Clemens Ladisch

TI__Mastermind 21150 points

KC, Clemens,

Thanks for your reply.

Here are additional info.

1) DVCC/AVDD power voltage is 2.5V.

2) Customer took power-up sequence waveforms.
Please see attached pptx.
VIO, DVCC and AVCC are ramped up simultaneously.

power_waveform.pptx

Thanks and regards,
KoT

0 Clemens Ladisch over 7 years ago in reply to Koichiro Tashiro

Guru 244610 points

Apparently, DVIO is a (Schottky) diode drop below DVCC. This is exactly what would be expected if a DVCC signal is applied to some DVIO pin, and floats up DVIO through the ESD diode.

0 KC Xu over 7 years ago in reply to Koichiro Tashiro

TI__Intellectual 1995 points

KoT,

As you has found the root cause is customer provide 2.5V to IOs which supplided with DVIO 1.8V, I will close this thread, thanks.

regards

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Unexpected voltage is seen on F5255 DVIO pin