MAX40658 connection with SN65LVDT101

Hi ELTAA 

Thank you for reaching out and sharing your inquiries with the team.

For us to be able to give our proper recommendation, we would like to know your design requirements:

• What is the VCC supply used for MAX40658? I assume you are using a typical value =3.3V.
• For the IN pin, what do you intend to use? i.e., connecting it to a photodiode, laser, etc.  How large is the current you intend to use for the IN pin?
• In your applications circuit, do you want to utilize an MAX40658 to amplify the current and then an SN65LVDT101 as a repeater and level translator?  

Regarding your questions,

1. SN65LVDT101: Upon checking, it can recognize only two input levels: an HI or an LO.
   1. HI level is any differential input  (output from MAX40658) greater than 100mV.
   2. LO level is any differential input  (output from MAX40658) less than -100mV.
   3. Between these two levels, the SN65 does not recognize it as an Open or Hi-Z

         2. To differentiate the Open or HiZ states, it would require a pull-up and pulldown.

         3. A 100-ohm termination must be placed at the end of the transmission line.

         4. AC coupling cap ( series cap ) should be placed on the OUT pins of MAX40658.

regards,

Hi,

thank you for your answer.

1. I am using 3.3V supply voltage.

2. the mAX40658 input connected to photodiode, the current is about 10uA.

3. yes,  MAX40658 amplify the current and then an SN65LVDT101 as a repeater and level translator

OK, i will try it and update you.

many thanks

Hi,

Why I need to connect 100ohm resistor between the differential port? SN65 driver already have 110ohm internal impedance?

I tried your suggestion, its still not working yet.

Hi ELTAA 

You need to connect the 100 ohms as stated on the recommended circuit by the SN65. For us to check thoroughly is there a chance you can share your application schematics please?

Here are my additional questions from my side:

• I would like to know what are your voltage measurements for both outputs (OUT+ and OUT-)? 
• it would be better if you can provide scope shots of the OUT pins (thru an oscilloscope).

Regards,

Hi ELTAA,

Please let us know how we can assist you further with this query.

L