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1.10 VDD/VSS Rules And Guidelines
Introduction
STD130
1-42
Samsung ASIC
In the above formula,
NVDDOsso = Number of VDD1O (VDD2O, 3O) pad per total SSO buffers
NVSSOsso = Number of VSS1O (VSS2O, 3O) pad per total SSO buffers
- Number of power pads for SSO block limit of electromigration rules:
Calculating the following expression:
2) Number of power pads for non-SSO block
Calculating the following expression:
3) Total number of power pads for VDD1O/VSS1O (VDD2O, 3O/VSS2O, 3O)
Calculating the following expressions:
When open drain type buffers are used, you can consider using VSS1O (VSS2O, 3O) pads since they have
current sink only.
NVDDO2
SSO
NVSSO2
SSO
I
em
----------
=
where,
N_SSO_output is the number of simultaneous switching output buffers used,
N_SSO_bi is the number of simultaneous switching bi-directional buffers used,
C
outload
= Output load capacitance [pF],
V = Operating voltage [V],
F = Maximum I/O operating frequency [MHz],
S = Switching ratio (typically 0.5),
S
out
= Output mode ratio of bi-directional buffers, (typically 0.5).
I
em
= Current limit per V
DD
/V
SS
pad pairs based on electromigration rule. (40mA)
I
eq_o
0.001 C
i_outload
V
i
×
F
i
×
S
i
×
(
)
i
N_SSO_output
∑
0.001 C
j_outload
V
j
×
F
j
×
S
j
×
S
j_out
×
(
)
j
N_SSO_bi
∑
+
=
NVDDO
non_SSO
NVSSO
non_SSO
I
em
----------
=
where,
N_non_SSO_output is the number of non-simultaneous switching output buffers used,
N_non_SSO_bi is the number of non-simultaneous switching bi-directional buffers used,
C
outload
= Output load capacitance [pF],
V = Operating voltage [V],
F = Maximum I/O operating frequency [MHz],
S = Switching ratio (typically 0.5),
S
out
= Output mode ratio of bi-directional buffers, (typically 0.5).
I
em
= Current limit per V
DD
/V
SS
pad pairs based on electromigration rule. (40mA)
I
eq_o
0.001 C
i_outload
V
i
×
F
i
×
S
i
×
(
)
i
N_non_SSO_output
∑
0.001 C
j_outload
V
j
×
F
j
×
S
j
×
S
j_out
×
(
)
j
N_non_SSO_bi
∑
+
=
Number of VDD1O (VDD2O, 3O)
max NVDDO1
SSO
NVDDO2
SSO
,
)
NVDDO
non_SSO
+
round-up
=
Number of VSS1O (VSS2O, 3O)
max NVSSO1
SSO
NVSSO2
SSO
,
)
NVSSO
non_SSO
+
round-up
=