I2C - level translator and multiple slaves.

Thread Starter

robotDR

Joined Mar 17, 2020
21
Hi Thank you for taking a look.

I am using level translator TCA9803.

I have a 1.8v master and (4x) 3.3v slaves.

The datasheet seems to imply that I have to run a TCA9803 translator for each slave. Is that true? So I have a 1.8v bus with 4 translators each with a slave on 4 isolated 3.3v bus?

Or can I do (1x) translator with 4 slaves on the (1) 3.3v bus. It seems to say the leakage current could be too much for the TCA9803 if I have multiple slaves on one translator?

Thank you for your time.
 

Thread Starter

robotDR

Joined Mar 17, 2020
21
it says the leekage current must be below 100 uA
what is the leekage current of your devices ?
Hi Thanks for taking your time to look over this.

I am using (4)
TCA9555DBR
GPIO expanders as the 4 slaves.

It says the SDA and SCL input leakage current is +/- 1uA so that should be fine right?

So does that mean I can use 1 translator, and 4 slaves on the translated bus (3.3v)


MASTER (1.8v) --> Translator --> Slave 1 (3.3v)
|---> Slave 2 (3.3v)
|---> Slave 3 (3.3v)
|---> Slave 4 (3.3v)
 

andrewmm

Joined Feb 25, 2011
1,497
Hi Thanks for taking your time to look over this.

I am using (4)
TCA9555DBR
GPIO expanders as the 4 slaves.

It says the SDA and SCL input leakage current is +/- 1uA so that should be fine right?

So does that mean I can use 1 translator, and 4 slaves on the translated bus (3.3v)


MASTER (1.8v) --> Translator --> Slave 1 (3.3v)
|---> Slave 2 (3.3v)
|---> Slave 3 (3.3v)
|---> Slave 4 (3.3v)

to me 4 * 1 uA is much less than the limit,
so 4 slaves afte rthe dirver is fine,

Remember, no pull up needed after the driver,
pull up is built in the driver,
 
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