C_pkg of i.MX25 ibis model

[torus1000]

Hi all,

I compared with i.MX25 and i.MX6DQ ibis model.
There was big difference about C_pkg.
I think C_pkg of i.MX25 is too small. (0.21pF << 3.89344pF)

Are both of them correct?  Or which C_pkg is correct?

Thank you.

---
(1)  http://www.freescale.com/webapp/sps/download/license.jsp?colCode=IMX25_IBIS_MODEL

(1)' https://www.freescale.com/webapp/Download?colCode=IMX28IBIS

(2)  https://www.freescale.com/webapp/Download?colCode=IMX6_DQ_IBIS

##########################(1)################################################

|************************************************************************
| IBIS file senna.ibs generated by Viper version: 2008.08.r27
|************************************************************************
|
[IBIS Ver]       3.2
[Comment Char]   |_char
[File Name]      senna.ibs
[File Rev]       REV_Apr8th_2009
[Date]           Wed Apr  8 10:11:04 2009
[Source]         Generated using: Viper
[Notes]          MAPBGA 17x17
[Disclaimer]    
[Copyright]      Copyright (C) 2008 Freescale Semiconductor Ltd.
|
|****************************************************************
|                i.MX25-400MAPBGA17x17               
|****************************************************************
|
[Component]        i.MX25-400MAPBGA17x17
[Manufacturer]     FREESCALE
[Package]
| variable      typ                 min                 max                
R_pkg           356.18m             3.07m               518.52m            
L_pkg           5.20nH              0.09nH              7.90nH             
C_pkg           0.21pF              0.16pF              2.5pF              
|
[Pin] signal_name          model_name           R_pin     L_pin     C_pin   
A10   SD7                  ProgBufferDdr        378.2m    6.01nH    0.19pF  
A12   SD0                  ProgBufferDdr        398.78m   6.02nH    0.23pF  
A13   SD5                  ProgBufferDdr        452.92m   6.1nH     0.22pF  
A14   SDCLK_B              ProgBufferDdr        443.12m   5.96nH    0.23pF  
A15   SDWE                 ProgBufferDdr        435.91m   6.14nH    0.21pF  
...

##########################(2)################################################

|************************************************************************
| IBIS file 21x21_imx6q_consmr_003.ibs generated by Viper version: 2011.06.09
|************************************************************************
|
[IBIS Ver]       4.2
[Comment Char]   |_char
[File Name]      21x21_imx6q_consmr_003.ibs
[File Rev]       003
[Date]           Sun Mar 25 13:48:36 2012
[Source]         FSL Viper 2011.06.09
[Notes]         
[Disclaimer]                             IMPORTANT NOTICE
...
[Copyright]      (C) Copyright Freescale 2004 - 2012, All Rights Reserved.
|
|****************************************************************
|                iMX6Q               
|****************************************************************
|
[Component]        iMX6Q
[Manufacturer]     FREESCALE
[Package]
| variable      typ                 min                 max                
R_pkg           0.3508997           0.0028730           0.895806           
L_pkg           2.62395nH           0.07145nH           5.71558nH          
C_pkg           3.89344pF           0.59645pF           29.3042pF          
|
[Pin] signal_name      model_name   R_pin     L_pin     C_pin   
A2    PCIE_REXT        gpio         0.646088  4.19621nH 1.57274pF
A3    PCIE_TXM         gpio         0.615102  4.09171nH 1.58877pF
A4    GND              GND          NA        NA        NA      
A5    FA_ANA           POWER        0.653689  4.21374nH 1.58401pF
...

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[Yuri]

  First, maximal value of i.MX25 C_pkg is 2.5 pF (not too little).

Also, we should take into account, that i.MX25 package is not the same as i.MX6 one.

Usually the default package values (R_pkg, L_pkg, C_pkg, specified under [Package])
are used, if corresponding R_pin, L_pin, and C_pin parameters are not declared.

Standard Input Model,includes the following elements:

• Package elements resistance, inductance, and capacitance

• A clamp (Power_Clamp)

• A clamp (GND_Clamp) that is active when the input voltage is below Ground

• Die capacitance of the input

Have a great day,
Yuri

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[torus1000]

Dear Yuri,

Thank you for reply.

Probably you didn't have time to check each C_pins.
Please comfirm one more time?

Most(243/246) i.MX25 C_pins are less than 0.35pF and only 3 pins(XN,LD1&LDO) exceed 0.4pF such as 0.41,0.75&2.5pF.
Actually average of 243 C_pins calculated as 0.201852pF

(On the other hand, i.MX6Q I/O pins calculated 1.254312568 and VDD pins were 19.94515041pF. Isn't it big difference 0.20 and 1.25?)

Thanks.

[Yuri]

   The capacitance of i.MX25 pins looks as relatively small, but I am afraid, we do not have another
(than published) IBIS models for i.MX25.

Regards,

Yuri.