Signal Integrity Simulation for DAC3xJ84 using IBIS

Stephen Lau96

Other Parts Discussed in Thread: DAC37J82

Hi there,

I'm trying to understand how the termination works in this DAC in order to do signal integrity simulation for the digtial inputs of the DACDAC3xJ84 using the provided IBIS files.

Basically I'm interested in verifying that the transmission line + vias feeding the digital inputs are okay and the line is well terminated. From what I understand I can use IBIS to get the termination characteristics for the driver in the receiver. However, I'm not sure how the common mode termination from the 50 pF capactor is accounted for or whether it needs to be accounted for.

The broader question is I'm new at doing this sort of SI work let me know if I'm completly going down the wrong path on this one.

-Stephen

over 8 years ago

0 Kang Hsia over 8 years ago

TI__Guru 66184 points

Stephen,

The IBIS model on the web can be good estimates for the CMOS IO, LVDS IO, and understanding the output impedance of the DAC analog core. You can use any IBIS simulator such as ADS or Hyperlink to perform signal integrity testing.

For SERDES RX IO, we can provide you offline the IBIS AMI model. You will need ADS to perform the high speed signal integrity modeling.

Please advise the 50pF cap that you referred to. I don't recall any 50pF common mode cap on the schematic.

-Kang

0 Stephen Lau96 over 8 years ago in reply to Kang Hsia

Prodigy 110 points

Hi Kang, the IBIS-AMI model would be great, we have ADS in house for RF work, so I can find someone.

The 50 pF cap was for the common mode termination on the RX SER DES. Section 7.3.1 (page 25, figure 55) on the datasheet: www.ti.com/.../slase17b.pdf

0 Stephen Lau96 over 8 years ago in reply to Kang Hsia

Prodigy 110 points

Hi Kang can you send me the model?

Thanks!

0 Kang Hsia over 8 years ago in reply to Stephen Lau96

TI__Guru 66184 points

Hi Stephen,

I have private messaged you. Please accept the request so I can forward a TI Box account link for the C-based IBIS AMI model.

I believe the 50pF cap is internal to each SERDES RX port and is part of the IBIS AMI model. I am confirming with design team and will get back to you.

-Kang

0 Stephen Lau96 over 8 years ago in reply to Kang Hsia

Prodigy 110 points

Done, thank you.

0 Kang Hsia over 8 years ago in reply to Kang Hsia

TI__Guru 66184 points

Stephen,

50ohm + 50pF caps on the SERDES RX block are all internal to the device. The behavior will be included in the IBIS AMI model. AC coupling is recommended for the JESD204B operation.

-Kang

0 Michael Kolodchak over 7 years ago in reply to Kang Hsia

Prodigy 60 points

Kang,

We too need the IBIS AMI model (for DAC37J82 specifically) to simulate in ADS. Can you please provide?
Thanks,
Mike

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Signal Integrity Simulation for DAC3xJ84 using IBIS