SN65LVCP408: Interface forum

Leo Wang

Part Number: SN65LVCP408
Other Parts Discussed in Thread: LMK00304,

As shown in the figure above, the output terminal is LMK00304, its output level is LVPECL, the input terminal is SN65LVCP408, and its receiving terminal is CML level, so DC coupling needs to increase the resistance network to achieve its common mode level requirements, according to the input The parameters of the terminal and output terminal (as shown in Figure 1 and Figure 2 below) and the scaa056.pdf document can be calculated: R1=1k, R2=176, R3=25 ohms, at this time, the VBB of SN65LVCP408 is 1.6V, corresponding to its VBB Is the pin floating? Please confirm if this calculation is correct?

图1：LMK00304

图2：SN65LVCP408

In addition, if we want to change the voltage of VBB Pin of SN65LVCP408, how should we design it?

over 4 years ago

0 Malik Barton57 over 4 years ago

TI__Guru 64326 points

Hi,

When VBB is floating the internal bias voltage is 1.6V. I am double checking on the resistors and will get back to you.

0 Leo Wang over 4 years ago in reply to Malik Barton57

Prodigy 20 points

thanks Malik

0 Malik Barton57 over 4 years ago in reply to Leo Wang

TI__Guru 64326 points

Hi Leo,

Looking at this I will recommend to use this device AC coupled. As you probably ran into the equation do not work out nicely with Vbb at its default state. I am not able to find any evidence that the VBB terminal can/should be used to change the internal bias voltage. It is simply meant as a output to be monitored.