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# Supply Current of SN65LVDS34

Other Parts Discussed in Thread: SN65LVDS34

Hello,

I am working on a circuit with several SN65LVDS34 and therefore need to know their supply current. In the datasheet I found 12 mA for the steady state. There is also a graph for the non steady case. There is shown as much as 120 mA at a switching frequency of 200 MHz. Is this for one channel? for all channels? for the LVDS33 or the LVDS34? with or without load? However, 120mA is a very high value in my opinion, even if it is for four channels. Is it really that high?

I don't exactly remember the values I have seen with my prototype, but I think it was less than 30 mA increase, when I applied 200MHz.

Also, the scale is quite strange. There are 0, 100, 150, and 200 MHz on the x-axis, i. e. a finer scale above 100 MHz. Because of this I would expect a sharp bend of the measured line at 100 MHz (=where the scale changes), but there isn't.

How much current does it really draw at high frequencies?

Best regards,

Christian

Edit:

Maybe I found the answer by myself: If I assume a capacitive Load of 10pF (as shown in fig. 3), a switching frequency of 100MHz (i.e. 2E8 transitions between 0 and 3,3V per second), and that four channels are driven, I get: 16 mA + 10pF*100MHz*2*4*3,3V = 42 mA. This is rather close to 48 mA, which is the value I would read in the graph at 100MHz switching frequency. If I include the load shown in the figure on page 9, I get 46 mA. But maybe this is just coincidental.

However, it's still strange that the next step on the scale is 150 MHz and not 200 MHz. Maybe this is just a mistake?

• Hi Christian,

I attempting to locate the characterization data for thir s part now but since it is an older part it is proving to be difficult. I agreed that the data sheet is not clear with the information that it is presenting and will try to best answer your questions when I am able to locate the information.

Regards,

Mike