DS280DF810: Support need

Hi,

See below responses to your questions. 

1. The datasheet mentioned that each channel can lock serial data rates from 20.2 Gbps to 28.4 Gbps, can DS280DF810 support PAM4 56G?

The DS280DF810 is NRZ only. However, we have DS560DF810 and DS560DF410 part numbers which support PAM4. I will send you direct email with details

2. How "The two inputs to one output" works? Does it mean merge the two inputs to one output with the data rates doubled or choose one input to one output directly? If it means that choose one input to output, then can it support switching input channel A to input channel B and then to output channel only by operating registers without shutting down the power?

The DS280DF810 only implements cross-point switching function, meaning that you do not aggregate data but rather switch or fan out individual data channels. The crosspoint configuration is indeed implemented via I2C write operations. Refer to the retimer programming guide for details. You may request download access to the retimer programming guide via TI.com link below.

https://www.ti.com/licreg/docs/swlicexportcontrol.tsp?form_id=202045&prod_no=DS280DF810-DESIGN&ref_url=sva_sds

The TI 56G PAM4 retimer part numbers (DS560DF810 and DS560DF410) support both cross-point switching and Gearbox (i.e. aggregation) 

3. Does the "Mux/Fanout" function let the two output channels output the same signal with the one input channel?

Yes, the DS280DF810 crosspoint supports fanout mode.

Regards,

Rodrigo Natal

Hi Xenon,

Xenon Li said:

1. "Do note that these devices would not offer much equalization at the nyquist frequency of SGMII."

Xenon: What does this mean? 

Our redrivers equalize signals using CTLE.  CTLE essentially applies a filter that is designed to compensate for the insertion loss in a channel.  This filter has higher gain at high frequencies than low frequencies in order to compensate for insertion loss.  In our devices, there is typically around 20-30 dB of gain around the nyquist frequency of the intended data rate.  However, there is less gain at lower frequencies.  For our 28G redrivers (DS280MB810, DS280BR810), they can apply up to around 25 dB at 14 GHz.  However, at 5 GHz, they are only applying 15 dB for the same CTLE setting.  The nyquist of SGMII is 1.25 / 2 = 625 MHz.  The CTLE gain would be much lower than 25 dB at 625 MHz.

Xenon Li said:

2. Can our DS280MB810 and DS280BR810 only support SGMII and not support QSGMII? I'm not pretty sure.

I think the DS280MB810 and DS280BR810 could support both SGMII and QSGMII.  It would not have an issue with a 1.25 Gbps and 5 Gbps NRZ signal, although it would not be able to apply significant equalization.

Xenon Li said:

By the way, does DS110DF410 can not support QSGMII since it is also a retimer not a redriver or buffer?

The DS110DF410 would support QSGMII.  It can lock to the signal by setting the VCO to 10 GHz and using the divide by 2 option.  The DS110DF410 can also lock to SGMII by setting the VCO to 10 GHz and using the divide by 8 option.

Thanks,

Drew

Hi Xenon,

Xenon Li said:

According to your reply, the DS110DF410 could support SGMII and QSGMII but the DS280DF810 could not support QSGMII and SGMII since it cannot lock to 1.25 Gbps SGMII right?

This is mostly correct.  The DS280DF810 could technically support SGMII operating in CDR bypass mode, but this makes it impractical to use the retimer.

Xenon Li said:

1. Does CTLE will renegotiate with DFE after the serdes up down (the signal loss due to the temperature lock lost remain)?

Whenever CDR lock is (re)acquired, the retimer goes through the adaptation process.  If in adapt mode 1, it just adapts CTLE.  If in adapt modes 2/3, it adapts CTLE and DFE. 

Xenon Li said:

2. Does DS110DF410 or DS250/280x series support looping the RX of channel 1 to TX of channel 2 internally by setting some parameters? (shown as the figure below)? 

The DS110DF410 does not support this.  The DS2x0DFx10 do support this through the crosspoint.  However, since these are unidirectional devices, the block diagram would look a bit different than what you have pictured (see below).

The DS125DF111 and DS110DF111 are bi-directional two channel devices.  These would support loopback similar to what you have in your block diagram.

Thanks,
Drew

Hi Xenon,

Thanks for reaching out.  I'm a bit confused about your use case.  The DS110DF410 is a part of our 10 Gbps retimer family.  The maximum data rate it can lock to is 11.3 Gbps.  When we look at CTLE gain for a data rate, we observe the Nyquist rate of the data rate (data rate / 2).  For example, the nyquist rate for 10.3125 Gbps is 5.15625 GHz.  This is why we have CTLE measurements at 5 GHz in the datasheet.  For your use case, do you need gain performance at 10 GHz?

Regarding gain performance at different frequencies, I will share this with you via email.

Thanks,

Drew