DS64MB201 - Output problem

Hi team,

 I support customer with Kawai-san.

 I know RATE setting is affect to DE pulse width.
 I confirmed that auto frequency detect function seems incorrect operation on the board.

  S_INA0 ... 2.4Gbps PRBS-7
  S_INB0 ... 2.4Gbps PRBS-7

  (1) set RATE ="Low" and power up     ... D_OUT0 = wide DE pulse width
  (2) set RATE = "High" and power up   ... D_OUT0 = narrow DE pulse width
  (3) set RATE = floating and power up ... D_OUT0 = narrow DE pulse width

 Customer will use DS64MB201 as CPRI (2.4Gbps and 4.9Gbps) selecter. They must use Auto frequency detect mode. Customer care about the difference between datasheet and bench test results.

 Would you let us know what parameter should we check?

Regards,
 Hiroshi Kezuka

Hi Team,

Please give us your comment about the RATE setting and the DE pulse width relation.

Setting RATE pin to "Auto", it seems that the device cannot detect the correct datarate, which will miss lead to the wrong DE setting.

Is this a  bug ? Can the device only be used in manual RATE setting ?

Best Regards,
Kawai

Kawai-San,

We are not aware of rate being mis-detected.

Please note: the device needs to see idle to active transition so it can automatically detect rate. Like SAS or PCIe applications there should be idle to active data transition. The device will not be able to reliably detect the rate if you just power up the device(i.e it needs to see SAS or PCIe protocol).

Can you please indicate if the customer is checking the auto rate functionality in presence of PCIe or SAS protocol?
Regards,,nasser

Nasser-san,

Thank you for your comment.

Our customer is using in CPRI(2.4576Gbps/4.9152Gbps) protocol application.

I think this device can be used in the protocol other than SAS/SATA or PCIe.
But in this case, do you mean that you cannot use the auto rate detection function ?

I think there is no detail description about auto rate detection function.
It should be written in the datasheet or it will lead to a misdesign.

Best Regards,
Kawai 

Hi Nasser-san,

Please let me ask you one more question.

[Question]
Our customer cannot change their board design from "Auto Rate Detect" to "Manual Rate Setting".
In this case, if our customer sets DeEmphasis to 0dB, can you say that Auto Rate Detect function will not affect the output waveform even in Auto Rate Detect mode ?

* I think that Auto Rate Detect function only affect output wave form of DeEmphasis. So, if DeEmphasis is OFF, I believe there will be no effect to the output waveform whether Rate is selected to 3Gbps or 6Gbps mode.
* Our customer will try to solve the problem. Can this be a solution if DEM is not needed ?

Best Regards,
Kawai

Hi Kawai-San,

Please note table 3 of the DS64MB201 data sheet(pin mode operation). When Rate Pin is floating we are in autorate detection mode(the same mode your customer is using). In this case the DE level is set by VOD settings and DEM setting. The lowest DE setting for auto rate is when we have DEMx = 0 and VOD = 1200mV. So the lowest DE settings can be -2dB. If the customer has SMBUS access then he can force DE = 0 however in pin mode the lowest DE is -2dB.

Regards,,nasser