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LMX2594: LVDS SYNC input spec, termination and register setting

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Replies: 1

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Part Number: LMX2594

Hello,

 

I have some questions about LVDS SYNC input as follows.

 

Q1:

Datasheet 7.3.10.4 says “LVDS works to 250 mVpp, but is not ensured in production.”.

I do not understand this well.

For SYNC input pin, how much LVDS differential amplitude (Vpp) is required at minimum?

 

Q2:

In Datasheet Figure 31, how much ohm is the resistance?

This should be an usual 100ohms LVDS termination?

 

Q3:

For LVDS SYNC input, INPIN_HYST should be enabled or disabled?

How to decide disable or enable?

 

Q4:

LVDS input Vcm could be what voltage range?

Could it be 0.2V to 2.2V like usual LVDS?

 

Q5:

SYNC pulse width could be more than one OSCin cycle?

For example, after SYNC gets high with enough tSETUP/tHOLD to OSCin rising edge, SYNC can stay high for multiple cycle of OSCin period or forever? Or SYNC must be one OSCin cycle pulse?

 

Best regards,

 

K.Hirano

  • Hello Hirano-san,

    Q1) This means that the LVDS format at the SYNC input is not specifically tested for in the device test procedure. Using 250 mVpp is a suggestion and can be considered as a typical suggestion, not guarenteed.

    Q2) 100-ohm is correct

    Q3) I recommend experimenting with this bit in combination with the INPIN_LVL. The default setting 0, is otherwise ok. 

    Q4) This is ok, please see "7.6.6 SYNC and SysRefReq Input Pin Register". You may also consider changing INPIN_LVL.

    Q5) Yes, only the rising edge of the SYNC pulse is critical. Doesn't have to be only  1 OSCin cycle.

    Thanks,

    Vibhu