Dear TI：
Use LSF0108 to IIS level conversion , The output signal distortion. Vin = 1.8V（yellow） , Vout = 3.3V（green）.
Now pull up resistors with 2.2 K. Increases to 4.7 K distortion is more serious . Reduce to 300Ω when the output without distortion , but output cannot be pull down 0 level. Please see the following screenshots.
Many Thanks.
Hi,
The issues you are running into come from a typical trade off between speed and current capability of external devices when using the LSF family for voltage translation. A lower resistance will give you the faster rise time as you see with the second scope capture you submitted, but as the image below shows, you are sinking current into the low side device when the lines are low. Sinking too much current into the low side device could exceed the current capabilities, or the Vol spec, of that device, could you explain what you are using there?
Based on the information provided in your scope capture, could you try using a 700Ω resistor on the high side (3.3v) and a 4.7kΩ resistor on the low side (1.8V)? This should cut your charge time to about 1/3 on the high side while still limiting the current your external device is sinking.
For additional information in designing with this device, please refer to this app note Voltage-Level Translation With the LSF Family
Regards,
Aaron Goodson
Hi Aaron：
I use the input chip internal configuration of pull-up resistor(dozens of KΩ) in the input side(1.8V) and a 1KΩ resistor in the ouput side(3.3V). Please look at the following pictures. I try using 1KΩ and 2.2KΩ and 4.7KΩ pull-up resistor in the input , but almost make no difference ouput.
In view of this kind of situation, Do you have any good suggestions? Thanks you very much.
Dear Aaron:
I tried to use a 680Ω resistor on the high side (3.3v) and a 4.7kΩ resistor on the low side (1.8V). Please look at the following pictures. There is a good change along the rising edge, but output cannot be pull down 0 level.
