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100 Ohms Resistor for LVDS receiver

BAS
Expert 2370 points
Other Parts Discussed in Thread: ADS5282

Hi,

I am intending to interface ADS5282 EVM with Altyera DE2-115 development board.

Referring to the DE2_115_User_manual_2013, page # 41;

Additionally, when LVDS is used as the I/O standard of the HSMC connector, the LVDS receivers need to assemble a 100 Ohm resistor between two input signals for each pairs.

I wonder if I have to assemble 100 Ohm resistor myself ? If yes, how ? Wouldn't it be difficult to add extra resistor to HSMC ? 

Thanks.

  • 0
    TI__Mastermind 29220 points

    Hi,

    Any LVDS output will want to see a 100 ohm termination at the end of the signal trace.  Since the LVDS signals in the case of this EVM are sample data from the ADC EVM to the FPGA *inputs*, we usually use the internal 100 ohm termination resistor *in* the FPGA itself.  There is usually an entry in the FPGA constraint file to turn on the use of the internal 100 ohm termination resistor.  There is not a need for a physical resistor soldered to the development board if there is an internal termination resistor in the FPGA.   If there are LVDS *outputs* from an FPGA to external circuitry such as a DAC then there would need to be termination resistors at that external device if that device doesn't have the resistors built in.  But that is not pertinenent to this EVM since the LVDS signals are from the ADC into the FPGA.

    Regards,

    Richard P.

  • 0 in reply to Richard Prentice
    Expert 2370 points

    Thanks Richard.