Question about a weak internal pull-up in ADuC848

Se-woong Question

Jun 15, 2015 00:00

Hello,

My customer uses ADuC848 for making CO2 sensor module and they are willing to export Japan company.

Below qustions are from Japan buyer of my customer.

Please refer below questions and let me know your answers ASAP.

1) What are the value of a weak internal pull-up on SCLK pin and SDATA pin?

2) Does ADuC848 have the function to disable these weak internal pull-up resistansce of I2C bus?

If it has,how to disable these weak internal pull-up resistansce of I2C bus?

Please advise me.

If you have any questions, please let me know.

Regards,

Se-woong

pull-up

microcontrollers

i2c

weak internal pull up

sclk

sdata

8052 Core Products

aduc848

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Se-woong Reply

Jul 6, 2015 00:00

Hello,

I received answers about questions from ADI Korea.

Please refer below answer.

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The pull-up resistor value is not specified.

The pull-up is just there to ensure it will have a defined level if no external drive is applied.

It can not be disabled while it is in I2C mode.

For terminating the I2C lines for I2C operation the customer must use an external resistor and can ignore the pull-up.

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If we need to supply an answer this has to be characterised over all possible conditions and we can not do this large amount of work on this part now.

Please also note that the pullup is an active device that acts as a constant current source when the voltage across the resistance is high and as a resistance when the voltage across it is low.

I suggest the customer should measure it himself in the conditions that exist in his circuit.

As a very rough answer it is somewhere between 10kOhm and 1MOhm.

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