AM3352: DDR mode selection in IBIS

Tony Tang

Part Number: AM3352

In IBIS, there are many mode choice, especially for DDR, some item is not clear to user, for example between Model_479 and Model_480，RExt and Tolerance have different value, how to determine which to use?

I understand the Tolerance is system DDR power supply voltage drift rate, we can measure on the board, am I right?

But what is input load/RExt? how to determine and how to configure it in software(EMIF configuration tool excel) or hardware?

Model_479

Direction = Input

Voltage = 1.5V

Input load = FULLTERM, 0.88 * RExt = 1.125 * Iout (I[2:0] = "100"), 9mA nominal with Rext = 50R

Temperature range = Industrial temperature range (-40C to 125C, 25C nominal)

Tolerance = 10% power supply tolerance

Model_480

Direction = Input

Voltage = 1.5V

Input load = FULLTERM, 1.14 * RExt = 0.875 * Iout (I[2:0] = "010"), 7mA nominal with Rext = 50R

Temperature range = Industrial temperature range (-40C to 125C, 25C nominal)

Tolerance = 5% power supply tolerance

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1022605/am3352-am3352-ibis---ddr-simulation

over 3 years ago

0 melissaw over 3 years ago

TI__Genius 15920 points

Hi Tony,

Our IBIS expert is out of office until next week. He will respond to your question shortly after his return.

Regards,

Melissa

0 Liang Paker over 3 years ago in reply to melissaw

Intellectual 280 points

Hi Melissaw

Maybe I should ask it more detailed. For example Model_340 and Model_976.

1. ODT=”11” is associated with phy_rd_local_odt [9:8], I had knew how to set.

2. Iout=”010” is associated with IO_CONFIG_I [2:0] or IO_CONFIG_I_CLK [7:5],, which one should be set in follow 4 Output Driver Impedance:

Output Driver Impedance Addr/Ctrl,

Output Driver Impedance Data

Output Driver Impedance Clk,

Output Driver Impedance DQS

3. SR[1:0] = "01" is associated with IO_CONFIG_SR[4:3] or IO_CONFIG_SR_CLK [9:8], which one should be set in follow 3 Slew Rate:

Slew Rate: Addr/Ctrl,

Slew Rate: Data/Strobe

Slew Rate: Clk

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Model_340

    Direction         = Output

    Voltage           = 1.5V

    Output drive      = Slow slew rate (SR[1:0] = "01"), 1.60 * RExt = 0.625 * Iout (I[2:0] = "000"), 5mA nominal with Rext = 50R

    Input load        = ODT off (ODT[1:0] = "00") CMOS mode

    Temperature range = Industrial temperature range (-40C to 125C, 25C nominal)

    Tolerance         = 5% power supply tolerance

Model_976

    Direction         = Input

    Voltage           = 1.5V

    Input load        = Half Thevenin termination (Rth = 100R whith RExt = 50R) (ODT[1:0] = "11") VRef mode, 1.14 * RExt = 0.875 * Iout (I[2:0] = "010"), 7mA nominal with Rext = 50R

    Temperature range = Industrial temperature range (-40C to 125C, 25C nominal)

    Tolerance         = 10% power supply tolerance

0 Shriram Moharil over 3 years ago in reply to Liang Paker

TI__Expert 4490 points

Hi Tony,

I believe Rext should be 50ohms but let me confirm that for you and respond.

regards,

-Shriram

0 Shriram Moharil over 3 years ago in reply to Shriram Moharil

TI__Expert 4490 points

Also, I believe this is a duplicate ticket. I had already provided info for the excel sheet in the other ticket. Pasting my response below.

regards,

-Shriram

Hi,

Pl refer the below link for a couple of things which should answer your question:

1. https://www.ti.com/lit/zip/sprcah7 (This is a spreadsheet for calculating overall DDR budget)

2. https://www.ti.com/lit/pdf/SPRACK4 (This is a PDF app note specific to AM335x family of devices which can be used in conjunction with the above sheet and contains specific instructions on completing the same for AM3352)

regards,

-Shriram

0 Liang Paker over 3 years ago in reply to Shriram Moharil

Intellectual 280 points

Hi Shriram,

I would like to learn what's the correlation between EMIF_Tool sheet and IBIS model.

Could you advise more detail ?

0 Shriram Moharil over 3 years ago in reply to Liang Paker

TI__Expert 4490 points

The EMIF tool sheet uses the settings as described in Section 2.2.1 of the PDF app note. Pl follow the procedure as described in the app note. These can be manually entered into the sheet.

The IBIS model can also be used to set the correct I/O settings (e.g. ODT, driver impedance, slew rate etc.) that you are using in your system and is used mainly for more detailed system-level simulations. I am awaiting a response from the team to confirm that Rext is indeed 50ohms but the rest of terms in the IBIS model should be self-explanatory.

0 Shriram Moharil over 3 years ago in reply to Shriram Moharil

TI__Expert 4490 points

Hi,

Pl refer the IBIS settings as below:

1. Rext is set to 50-ohms nominal value via efuse and the value of driver impedance can be calculated directly from the multiplying factor used for Rext in the IBIS model. This can be entered in the xls file as "Output driver impedance".

2. Iout is set to 8mA nominally. Iout and Rext are set simultaneously as Rext=50ohms/Iout=8mA. This setting corresponds to Iout[2:0] = "011". Iout is a 3-bit code that can be programmed for different Rext/Iout settings as required.

3. Slew rate control in the IBIS corresponds to the below setting with "00" as the Fastest and "11" as the slowest.

regards,

-Shriram

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AM3352: DDR mode selection in IBIS