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TLK6201EA: Fixed High Frequency Boost

David Wang60
Intellectual 980 points

Part Number: TLK6201EA

I am using the TLK6201 in a serdes application. The settings currently are SWG = LOW, DE0=DE1=LOW, thus no de-emphasis added. Based on the simplified block diagram, it shows a fixed equalizer stage. The electrical table has the high-frequency boost as 14dB. On a 50% duty cycle clock, what kind of effect would it have on the waveform?

  • 0
    TI__Mastermind 19235 points

    HI,

    For the case where you have "SWG = LOW DE0=DE1=LOW thus no de-emphasis added", when transmitting a low frequency pattern such as 8 1's and 8 0's you should see a flat zero and one levels for the signal at the TLK output pins. As de-emphasis is applied you will see increasing amount of peaking on the rising edge as conceptually illustrated on datasheet figure 3 (see link below)

    http://www.ti.com/lit/ds/symlink/tlk6201ea.pdf

    Cordially,

    Rodrigo Natal

    HSSC Applications Engineer

  • 0 in reply to Rodrigo Natal
    Intellectual 980 points

    I understand the concept of de-emphasis. My question was towards the fixed equalizer stage at the front. IF de-emphasis is set at 0dB, I would assume the fixed equalizer stage that shows 14dB on the electrical table will have effect a clean signal input with an overcompensated output. So what kind of effect would that have? That front end stage can not be bypassed so I would assume the output would change.

  • 0
    TI__Mastermind 19235 points

    Hi,

    As listed on the datasheet this device provides a high-frequency boost of 13 dB on the received data at 3.125 GHz. I unfortunately do not have the equalizer boost curve for this legacy TI part number. But what you can expect is a bandpass type of lequalizer response where the peak boost in dB occurs at 3.125GHz and the boost curve rolls off above and below that frequency. In terms of the equalizer time domain output signal, to the extent that the input channel insertion loss is lower than the 13dB fixed Rx equalization you will observe some peaking on the waveform not unlike the de-emphasis effect illustrated on figure 3 of the TLK6201 datasheet. As a basic design rule I would recommend that you implement a minimum insertion loss in the order of 10 to 13dB for the input channel to the TLK6201, to prevent signal over-equalization scenario.

    Cordially,

    Rodrigo Natal

    HSSC Applications Engineer