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Driving logic level from 0.8 V to less than 0.6 V

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PeterEE

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Hello,

I am asking advice on the following issue:
I need some sort of level translation for the following situation:

Please see attached drawing:



IC_A is providing a low level of 0.8 V but IC_B needs a low level of < 0.6 V.
The high level is not an issue. The signal clocks at 100 kHz but can be lowered if required.

What would be a simple/smart way to achieve this?

Thank you very much for any advice!

Peter
 

Hi Klaus,

thanks for the prompt reply.

> What logic device generates 0.8V low level?
The device is a P82B96 I2C bus buffer.

The NXP datasheet states on page 4:
"The minimum LOW level this chip can achieve on the I2C-bus by a LOW at Rx is typically
0.8 V."

The P82B96 output is switched by a PCA9548 I2C switch and the fed to another P82B96 which needs at least
0.6 V in order to transmit a low level:

P82B96 datasheet page 4:
"A logic LOW is only transmitted to Tx when the voltage at the I2C-bus pin (Sx) is below
0.6 V. "

Thanks again for you help!
Peter
 

Hi,

use a comparator like the MAX9140. And two resistors to set your desired threshold voltage.

Klaus

btw:
What logic device generates 0.8V low level?
Maybe a simple pull down resistor could ensure proper low level.

- - - Updated - - -

Hi,

I2C signals are bidirectional! Therefore you can´t use a typical logic gate, nor can you use the comparator.

I assume (I didn´t check) the P82B96 I2C bus buffer works within specifications. Here you need to read I2C specifications instead of logic families specifications.

Klaus
 

Hi Klaus,

I should have mentioned the I2C bus earlier! Of course you are right regarding the bidirectionality of the bus.
A device like the PCA9306 might do the job.

Thanks again! Always good to learn from the pros !

Peter
 

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