TMS320F28377D: Logic Low Threshold

Jacob Olstad

Hi,

Quick question on the logic thresholds for the GPIO. The datasheet spec is a little oddly worded, it states logic low threshold as Vss-.3 to .8V just want to verify that anything in this range is guaranteed to read as a logic low.

Thanks,

Jake

over 8 years ago

0 Devin Cottier over 8 years ago

TI__Guru 60865 points

Hi Jacob,

Yeah, based on this table:
www.ti.com/.../specifications

Anything in the range of (VSSA - 0.3V) to (+0.8V) is guaranteed to read low. Normally VSS = 0, so this is the range -0.3V to 0.8V. If you are above this range, but below Vih, then the read value is unpredictable. If you are below this range, the input will start clamping and you will need to worry about damaging the device. The logic level may also become unpredictable in the case of an under-voltage event.

0 Jacob Olstad over 8 years ago in reply to Devin Cottier

TI__Intellectual 1320 points

Thanks Devin,

Just a quick follow up question. You're answer implies that there is no hysteresis on the GPIO inputs. So these are not schmitt trigger inputs? Is there any chance of excess current flow while in one of the undetermined voltage levels?

Regards,
Jake

0 Devin Cottier over 8 years ago in reply to Jacob Olstad

TI__Guru 60865 points

Hi Jacob,

These inputs will have some hysteresis. This will typically be about 150mV (but this is not currently specified in the datasheet).

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TMS320F28377D: Logic Low Threshold