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ADV7403 I2C Series 100 ohm Resistor

Category: Hardware
Product Number: ADV7403BSTZ-110

Hello All,

We are using ADV7403 in our design. I have design query related to I2C interface connections made in ADV7403 Eval Board Schematic.

100 ohms Series Resistor is used SDA and SCL lines of I2C. Please let us know the importance of usage of this resistor. Is 100 ohm Resistor Eval Board Requirement to interface with external board ?

We were planning to have 4K7 Pullup resistor on I2C lines(open drain) to connect with our FPGA. Please let us know.

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  • FormerMember
    FormerMember
Feb 21, 2023 +2 verified

A 100 Ohm series resistor is not needed.  Normally I'll drop a 10-22 Ohm resistor in that position although you can easily get rid of it.  The series resistor has 3 benefits in my opinion.

1) Provides…

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  • FormerMember
    +1 FormerMember
on Feb 21, 2023 12:32 PM

A 100 Ohm series resistor is not needed.  Normally I'll drop a 10-22 Ohm resistor in that position although you can easily get rid of it.  The series resistor has 3 benefits in my opinion.

1) Provides an easy way to disconnect the chip from the I2C bus by removing it in case there's address collisions or other problems.

2) Provides ESD protection to the I2C pins on the part.  If the bus never goes off board then there is no ESD issues to worrry about.

3) Provides an easy probe point to monitor the I2C bus activity.

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  • FormerMember
    +1 FormerMember
on Feb 21, 2023 12:32 PM

A 100 Ohm series resistor is not needed.  Normally I'll drop a 10-22 Ohm resistor in that position although you can easily get rid of it.  The series resistor has 3 benefits in my opinion.

1) Provides an easy way to disconnect the chip from the I2C bus by removing it in case there's address collisions or other problems.

2) Provides ESD protection to the I2C pins on the part.  If the bus never goes off board then there is no ESD issues to worrry about.

3) Provides an easy probe point to monitor the I2C bus activity.

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