TCAN1044V-Q1: I/O Supply current in standby mode

Hi Eric-san,
Thank you for helping me always.
I understood.

I have 2 more questions.

Could you also tell me the resistance value or current source value of the internal pull up resistor at TXD pin?
I understand that the Vcc and Vio are connected with the current source by ORING with diode.  Is my understanding correct?

Best Regards, Taki

Hi Taki-san,

The strength of the current source can be estimated using the output current specifications for the device pin. The TXD terminal for TCAN1044 has the following current specifications: 

When 0V is applied to the TXD pin and 5.5V is used for Vio, the maximum leakage through the pin is 200uA. This would imply a maximum pull-up strength (minimum equivalent resistance) of 5.5V / 200uA = 27.5kΩ. 

I'm not sure I understand your second question about Vcc and Vio being connected. These are independant supplies for TCAN1044V. The non-V TCAN1044 internally combines these supplies by shorting them together (Vio shorted to Vcc, which comes out to a pin). 

Regards,
Eric Schott

Hi Eric-san,

About my second question, 

I recognized Fig.8-1 in the datasheet shown in above as the following schematic.

Is mu understanding correct?

When TXD is low, 0V, and Vcc > Vio, the current for pull-up does not flow from Vio, so that Vio is not changed in both case of TXD = 0V and TXD=Vio, isn't it?

Best Regards, Taki

Hi Taki-san,

This current source is always referenced to Vio. For TCAN1044V, when Vio is not supplied, there is no pull-up on this pin regardless of Vcc. 

For TCAN1044, Vio is not externally available, so it is tied internally to Vcc. For this device, the TXD line is still pulled-up to Vio, but internally Vio=Vcc. 

The "or" here refers to whether TCAN1044 or TCAN1044V is used. There is no secondary pull-up path to Vcc. Only through Vio which can be equal to Vcc in TCAN1044's case. 

Regards,
Eric Schott

Hi Eric-san,
I understood.  Thanks.

Let me confirm.
When TXD=0V, I think that IIO should be increased by pull-up current than case of TXD=Vio.
As the result, IIO in each case should be  

  IIO at TXD=0V : 8.5uA + 100uA
  IIO at TXD=Vio : 8.5uA

Am I right?

Best Regards, Taki

Hi Taki-san,

Yes, your understanding is correct. 

Regards,
Eric Schott

Hi Eric-san,
I got it!

After the discussion in above, I think that the Iio spec should be described as shown in below.

Would you change the description of the test condition in this test item from "TXD=0V" to "TXD=Vio" in next chance to revise the datasheet?

The following image is Iio spec of TCAN1046V-Q1 in standby mode.  I will show this here as a reference for similar case.

Best Regards, Taki

Hi Eric-san,
Thanks for communication by mail.
I understand the Iio value of TCAN1044V-Q1 is specified across all operating conditions, from 1.7V to 5.5V of Vio, for this device.

Could you let me know whether the datasheet update with changing the test condition from "TXD=0V" to "TXD=Vio" will be done or not?

Best Regards, Taki