NASA Office of Logic Design

A scientific study of the problems of digital engineering for space flight systems,
with a view to their practical solution.

RTAX-S Grounds

Introduction

The RTAX-S series of FPGAs, like many sophisticated digital devices, has multiple ground pins and multiple ground signals.  For RTAX-S, these are the quiet ground, the I/O driving grounds, and a ground for the logic array circuits.  The following sections detail which device "pins" are connected to each ground.

RTAX250S-CQ208

• GNDQs are connected to the same ground plane as the GNDA

• Done to keep as many available signal pins as possible

• GNDIs are on a separate ground plane

• GNDA/GNDQ = 15, 39, 65, 94, 119, 143, 169, 196

• GNDI = 9, 21, 32, 46, 51, 59, 69, 90, 99, 113, 125, 136, 150, 155, 164, 173, 194, 201

• Programming ground = 104, 208

RTAX250S-CQ352, RTAX1000S-CQ352 and RTAX2000S-CQ352

• GNDAs and GNDIs are on separate ground planes

• GNDQ are direct connect = 1, 45, 89, 133, 177, 222, 265, 310

• GNDA = 15, 33, 57, 75, 103, 115, 151, 163, 192, 210, 234, 252, 280, 292, 330, 340

• GNDI = 9, 21, 27, 39, 51, 63, 69, 81, 97, 109, 121, 145, 157, 169, 186, 198, 204, 216, 228, 240, 246, 258, 274, 286, 298, 322, 334, 345

• Programming ground = 88, 176, 264, 352

RTAX1000S-CG624 and RTAX2000S-CG624

• Physically smaller package

• GNDAs and GNDIs are on same ground plane

• GNDQ are direct connect = AA10, AA16, E10, E16, K21, K5, T21, T5

• GNDA/GNDI = A18, A2, A24, A25, A8, AA21, AA5, AB22, AB4, AC10, AC16, AC23, AC3, AD1, AD2, AD24, AD25, AE1, AE18, AE2, AE24, AE25, AE8, B1, B2, B24, B25, C10, C16, C23, C3, D22, D4, E21, E5, H1, H25, K23, K3, L11, L12, L13, L14, L15, M11, M12, M13, M14, M15, N11, N12, N13, N14, N15, P11, P12, P13, P14, P15, R11, R12, R13, R14, R15, T23, T3, V1, V25

• Programming ground = AA18, E8, H21, V5

Reference:

• Data courtesy of Bill King of Actel Corporation.

 

RTAX-S and AX Application Notes

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