AN2797

DDR memory interface

Doc ID 14841 Rev 1

9/23

other trace lengths must be adjusted to meet within Ltol. The worksheet computes

Lmax for you.

4.

With the longest total trace known (Lmax), the shortest total trace length permitted

(Lmin) can be calculated by Lmin = Lmax-Ltol. Record the value of Lmin.

Note:

Lmin is the total of PCB + substrate trace lengths. The worksheet computes Lmin for you.

5.

Identify all signals within each data lane whose total length is less than Lmin. Tabulate

this difference. The worksheet does this for you.

6.

Add the length computed in step 5 to the traces. The worksheet does this for you.

Table 1.

Package substrate trace length

Signal name

Ball

Package substrate trace length

(mm)

(mils)

DDR_ADD_0

AB3

9.0

354

DDR_ADD_1

AB4

8.2

323

DDR_ADD_2

AA4

7.5

295

DDR_ADD_3

Y4

7.3

287

DDR_ADD_4

W4

5.7

224

DDR_ADD_5

W5

5.7

224

DDR_ADD_6

Y5

6.4

252

DDR_ADD_7

AA5

5.9

232

DDR_ADD_8

AB5

7.6

299

DDR_ADD_9

AB6

8.3

327

DDR_ADD_10

AA6

5.6

220

DDR_ADD_11

Y6

5.9

232

DDR_ADD_12

W6

5.4

213

DDR_ADD_13

W7

4.6

181

DDR_ADD_14

Y7

5.4

213

DDR_BA_0

Y9

3.9

154

DDR_BA_1

W9

4.4

173

DDR_BA_2

W10

6.6

260

DDR_RAS

AB7

7.0

276

DDR_CAS

AA7

6.6

260

DDR_WE

AA8

5.7

224

DDR_CLKEN

AB8

7.0

276

DDR_CLK_P

AA9

5.4

213

DDR_CLK_N

AB9

5.8

228

DDR_CS_0

Y8

5.3

209

DDR_CS_1

W8

4.8

189