CC8531: Poor GIO driving capability when as status indication

Walter Wang80

Part Number: CC8531

Dear TI experts:

We connected an LED and a 1K resistor between VCC 3.3V and GIO3 of CC8531, then config GIO3 to working status indication in PPW Configurator, then use scope to check the output of GIO3 when LED blinking (in idle state). We found the low level output of GIO3 is almost 1V, it is too high to be recognized as a logic '0', then we changed the resistor to 10K to reduce the load current pulled by GIO3 when low level, but still saw a nearly 1V low level.

We did not find the output capability definition in CC8531's datasheet and user manual, so can anyone help to let us know how much current the GIO3 (when use as LED state indication) can sink?

Thanks.

Walter

over 7 years ago

0 Fredrik K over 7 years ago

TI__Guru** 106705 points

Hi Walter,

The drive strength of the IOs is 4 mA. Can your share your schematic?

Regards,
Fredrik

0 Walter Wang80 over 7 years ago in reply to Fredrik K

Prodigy 70 points

Hi Fredrik,

Schematic had been sent to you via private message.

One more finding is:
The GIO driving capability seems related to active IO level configured in PPWC.
The driving strength became very low if active IO level set to "Active high" in PPWC IO Mapping setting, as described in my post.
But if set to "Active low", the driving strength looks no problem, output low level can reach near 0V even with 2mA load.
Not sure if this is a bug, FYI.

Walter
20190310

0 Fredrik K over 7 years ago in reply to Walter Wang80

TI__Guru** 106705 points

Hi Walter,

According to your schematic, you have configured the LED to be active low. You must thus select the appropriate configuration in PPW Configurator.

Regards,
Fredrik

0 Walter Wang80 over 7 years ago in reply to Fredrik K

Prodigy 70 points

Hi Fredrik,

Thanks for reply. The GIO output now OK after configuring to active low in PPW Configurator.

Walter

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CC8531: Poor GIO driving capability when as status indication