Not able to use I2C interface as Noise margin is negative. Why VoH is so high for I2C signal?
On carrier board I2C interface with U54 (FUSB301TMX) has issue with noise margin (Vih - Vol).
Kindly clarify.
Are you testing on devkit or custom board? There is no issue on devkit.
We are designing the custom circuit and we are facing noise margin issue. Wanted to know, why I2C interface has non-standard Voh?
We are not able to interface i2C with available standards slaves devices.
This may works on dev kit, but as standard design practice interface has design issue
Voh of host is to meet Vih of device, and so the Vol of host and Vil of device. Can you share the waveform of the noise you mean?
We are in design phase, 0.3xVdd is non standard Voh Vol. We are not getting devices which has ViH more than Voh(0.3xVdd) of the Orin nano.
What do you mean? 0.3xVdd is Vol.
Yes… Vol
Then what is the Vil of your device? As said, Vol of host is to match Vil of device.
0.25 x Vdd is standard across multiple devices
As per manual shared by you, it is VIL (0.3xVDD).
Issue is with Vol. Please check Vol specification in the same manual. It is not matching with Orin Nano
You can refer to this topic for Vol: Orin Nano : 3V3 I2C to 1V8 I2C
I have gone through suggested link. I did not found how to handle non-standard I2C Vol parameter.
Could you please explain how to interface standard I2C device?
What do you mean? What’s the wanted Vil of your device? As said in that topic as below, Vol is tunable.
The Vol needs to be tuned accordingly if necessary. The VDD is the internal pin supply which is 1.2V or 1.8V. The real Vol value= internal pull down res * Iol. The internal pull down can be tuned so as to fulfill the Vol of I2C spec. In fact, the current default value can fulfill the I2C spec.
Could you please what setting to be done to make Vol specification as per I2C standard (i.e. NXP UM10204 I2C-bus specification and user manual)
Please for all I2C interfaces supported by Orin Nano. It has both 3.3V I2C and 1.8V I2C
I don’t think you have gone through that topic…
The VDD is the internal pin supply which is 1.2V or 1.8V…
Our internal pull down res is around 50 ohm. So no matter 0.2VDD or 0.4 V, it will meet spec…
Do you mean that VDD referring internal supply in below equation?
“Vol = 0.3xVDD” Kindly confirm.
If it is internal Voltage, then Vil = 0.25 x VDD specifications becomes non-standard, if we use 3.3V I2C line of Orin Nano and 3.3V device.
Vol = 0.3xVDD is the capability of OD pin. For I2C pin, Iol is about 1 or 2 mA, Vol value= internal pull down res * Iol. Default internal pull down is 50 ohm. So it can meet the spec.
Is the VDD referring in VIL and Vol specifications is internal voltage or I2C bus voltage?
e.g. Vil = 0.25 x VDD or Vol = 0.3xVDD