LSF0108: LSF0108 for 1.05V to 1.8V level shift

John Liu59

Intellectual 2735 points

Part Number: LSF0108

Dear,

Could you please help check if LSF0108 can be used as 1.05V to 1.8V SPI level shift application?

In the datasheet, it is recommended to VB is higher than VA+0.8V，do you have any suggestions for this application?

Thanks.

over 5 years ago

0 Karan Kotadia over 5 years ago

TI__Genius 16735 points

Hi,

What supplies do you have? The requirement of VB being VA+.8V is so that the biasing fet turns on completely. Most supplies are also not entirely steady and vary by at least 5%. So, if you have other supplies available that can turn on the fet. The device channel translation can be done at a different voltage than the supplies. Please watch the following series on the LSF to understand what I mean.

https://training.ti.com/introduction-voltage-level-translation-lsf-family?context=1134826-1139264-1134789

Thanks!

-Karan

0 John Liu59 over 5 years ago in reply to Karan Kotadia

TI__Intellectual 2735 points

Hi Karan,

The signal on A side is 1.05V, B side is 1.8V, then we can give supply to A 1.05V,and B to 3.3V to meet 1.05+0.8 requirement, the device can be used at this condition, am I right?

Thanks.

0 Karan Kotadia over 5 years ago in reply to John Liu59

TI__Genius 16735 points

Hi,

Thats correct. However, you will still need pullups on the B channels to 1.8V. During up translation from 1.05V to 1.8V, on a positive edge rising to 1.05V, the internal fets will turn off at around 1.05V at which point your pullup resistor will pull up your B channel to 1.8V.

Thanks!

-Karan

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LSF0108: LSF0108 for 1.05V to 1.8V level shift