TCA9801: # of fan out in B-side

Isao Takigasaki

Part Number: TCA9801

Hi,

How many TCA9801 as slave can be connected with B-side of TCA9801 as master?

Please ignore the capacitance of the BUS between the master and the slaves.
Please also refer BUS-B or BUS-C in Fig.31 of the datasheet.

Best Regards, Taki

over 6 years ago

0 Miguel Robertson over 6 years ago

TI__Guru 62920 points

Hello Taki-san,

The primary limitation to consider for the B side is that the pull-down leakage current (called IEXT-O in the datasheet) should not exceed 100 uA. The A side presents a maximum leakage of 10 uA, so up to 10 TCA9801 "A sides" could be connected to one TCA9801 "B side." Please let me know if this is unclear or if you have any further questions.

Regards,
Max

0 Isao Takigasaki over 6 years ago in reply to Miguel Robertson

TI__Expert 3360 points

Hi, Max-san
Thank you for your quick reply.

I got it.
And do we also have to also consider the rise time and load capacitance based on Formula 2 and Figure 23 to 28?

Best Regards, Taki

0 Miguel Robertson over 6 years ago in reply to Isao Takigasaki

TI__Guru 62920 points

Taki-san,

Yes, you are correct, the load capacitance and associated rise times should be evaluated as well to make sure they are compatible with the desired operating frequency.

Regards,
Max

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TCA9801: # of fan out in B-side