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LMH1208: Input voltage question

K.Shidara
Expert 3225 points
Part Number: LMH1208

Hi Team,

Would you advise Vin0_cm voltage question from my customer below?

■ Check item
I am trying to input LVDS to IN0 +/- of this device.
Looking at the data sheet below, the common mode voltage is high, which is typ 2.06V.

1. When DC coupled, does the input differential signal (LVDS) VCM (crosspoint) need to be around 2.06 V?

Or

2. In case of DC coupling, VCM (cross point) of input differential signal (LVDS) is in the range of 0 to 2.06 V.

Which is the recognition?

□ Composition
LVDS => LMH1208RTVT

□ LVDS specifications
VCM-OUT: typ 1.2 V
| VOD-Diff | = typ 300 mV

□ LMH1208RTVT specifications
VIN0_CM: typ 2.06 V
CD ON_IN0: typ 20 mV p-p

Thanks

Best regards,

Shidara

  • 0
    TI__Guru* 93670 points

    Hi Shidara-San,

    1). Please note - as mentioned in the data sheet - we are recommending AC coupling on IN0+/-. So please recommend AC coupling on input.

    2). At 2.06V common mode voltage, this is mid point for IN0+ or IN0-. For example, with 1000mV input differential voltage, IN0+ is 500mV peak to peak voltage. Meaning IN0+ is centered at 2.06V with 2.06V + 250mV for high level and 2.06V-250mV for low level.  Also, please note maximum input differential voltage is 1000mV. 

    Regards,, Nasser

  • 0 in reply to Nasser Mohammadi
    TI__Expert 3225 points

    Hi Nasser-san

    Thank you very much.

    I'll close this thread.

    Best regards,

    Shidara