Adding a Simple Package Model to the Channel Response

Transcription

1 Adding a Simple Package Model to the Channel Response Richard Mellitz, Intel Corporation Liav Ben Artsi, Marvell Technology Group Adam Healey, LSI Corporation Charles Moore, Avago Technologies 1 IEEE 802.3bj Task Force

2 Supporters Rick Rabinovich, Alcatel-Lucent Adee Ran, Intel Corporation 2 IEEE 802.3bj Task Force

3 In support of comment 36, 129, 132 resolution Eliminate the problem caused by looking at the signal the package/board interface (aka bga ball). It causes a shelf on the SBR edge which is correct at the ball but not at the pad. It causes too much precursor equalization with reduces the available signal. The caveat is that the Rx package loss is added back in because exact s-parameter concatenation replaces the VTF (voltage transfer function) Such impairments cannot be addressed adequately with guard band. To help specify Tx and Rx Return loss using the test fixture Enable changes for and review of COM code as these values may change through the ballot process as RL speciation evolve (comment ) Provide potential applicability to other IEEE standards (like CAUI). Provide direct understandable physical implementation rational This would suggest not how to build a package, but in the line of Tx/Rx architecture, provide a package architecture to be use in COM with a clear relationship to the Tx/Rx RL spec Define a model for COM that is understandable and alterable with a table 3 IEEE 802.3bj Task Force

4 Simplest Useful Package Modeling Load and source impedance Rx Pkg_len Rdiepad Lossy Transmission Line Cdiepad Cpkg_board Die Side Rdiepad Tx Pkg_len Board Side of Package Lossy Transmission Line Cdiepad Cpkg_board 4 IEEE 802.3bj Task Force

5 Estimate differential s-parameters for a small segment of uniform lossy transmission line (replaces 93A.1.2) Segment can be either solved or measured. Recommend: 1mm package transmission line s4p file Fit RL and IL using clause 93A.2 Find a il and a fl from S11 and s21 Determine γ IL and γ RL Were γ x = a0 + a1 f + a2 f + a4 f 2 This form is from clause 93A.2, eq. (93A 31) For the transmission line s11tline = e γ RL segments e γ IL 2 n 2 n=1 s21tline = e γ il segements i.e. [S tline ] The package transmission line is defined by 9 parameters in a table in 93a.1.2 a il (0, 1, 2, 4), a rl (0, 1, 2, 4), number of segments (Pkg_length in mm) 5 IEEE 802.3bj Task Force

6 Comparison for 12 mm line between math estimated and circuit model Math Estimate circuit model 6 IEEE 802.3bj Task Force

7 Example of an estimated package and tline model 0 package return loss db 5 Package Insertion Loss db -5 IL at fb/2= IL at fb/2= RL: looking into BGA ball RL at fb/2= RL at fb/2= x mm Rdiepad =55 Cdiepad = 250ff Cpkg_board = 180e mm IL: looking between die pad and BGA ball x IEEE 802.3bj Task Force

8 Create s parameters for pad and ball (more replacements for 93A.1.2) Zpad = s11 pad = Z ball = s11 ball = 1 2 π i f Cdiepad 2 Z0 Z pad +2 Z0, s21 pad = 1 2 π i f Cpkg_board 2 Z0 Z ball +2 Z0, s21 pad = Γ 1 = Γ 2 = Z0 Rdiepad Z0+Rdiepad 2 Zpad Z pad +2 Z0 [S pad] 2 Zball Z ball +2 Z0 [Sball] 3 parameters: Rdiepad, Cdiepad, Cpkg_board 8 IEEE 802.3bj Task Force

9 Combining 2 port S parameters T 1 = Given [S 1 ] and [S 2 ] First convert to T matrixes 1 s22 1 s21 1 s21 1 s11 1 s11 1 s22 1 s12 1 s21 1 s21 1 s21 1 T 2 = Combine T matrixes 1 s22 2 s21 2 s21 2 s11 2 s11 2 s22 2 s12 2 s21 2 s21 2 s21 2 T 3 = T 1 T 2 Determine [S 3 ] S 3 = t21 3 t11 3 t22 3 t12 3 t21 3 t11 3 t t12 3 t11 3 t IEEE 802.3bj Task Force

10 Combine parameters (replaces eq. 96a-5) [S pkgtx ]=combine([combine([s pad ], ([S tline ]), [S ball ]) Create [T pkgtx ] [S pkgtx ] [S pkgrx ]=combine([s ball, combine([s tline ], [S pad ]) Create [T pkgrx ] Channel response: [T] = [T pkgtx ] * [T channel ] * [T pkgrx ] [S] H 21 =. S 21 1 Γ 1 (1+Γ 2 ) 1 S 11 Γ 1 S 22 Γ 2 S 21 S 12 Γ 1 Γ 2 +S 11 Γ 1 S 22 Γ 2 10 IEEE 802.3bj Task Force

11 Commercial simulation circuit used to examine response with proposed COM package at tp0a Ideal 0 ohm data voltage source: 1p edge 400 mv amplitude No device jitter No transmitter filter 250fF Package Transmission line 0 0 No load eye probe 180fF testfixtiure_1p5db Port1 Port2 Port1 Port2 Port3 Port4 Port3 Port4 55 pkg_tine_12mm fF 180fF 1.5dB fixture TP0a 11 IEEE 802.3bj Task Force 0

12 25Gbps NRZ eye diagram at tp0a suggests removing transmitter filter from COM is OK because the package and die load limits transition time 12 IEEE 802.3bj Task Force

13 Parameters (Table 93A 2) a_il_0 a_il_1 a_il_ e e-05i e e-08i e e-11i a_il_ e e-23i a_rl_ i a_rl_ e e-07i a_rl_ e e-11i a_rl_4 Cdiepad 250 Rdiepad 55 Cpkg_board 180 Pkg_len e e-22i a_il_0, 1, 2 and 4 are insertion loss fit coefficients for a il (0, 1, 2, 4) on slide 5 a_rl_0, 1, 2 and 4 are return loss fit coefficients for a rl (0, 1, 2, 4) on slide 5 Cdiepad, Rdiepad, Cpkg_board, and Pkg_len are the package parameter on slide 4 Remove parameter f v f f amd f n and associated clauses. 13 IEEE 802.3bj Task Force