
1.10 Power Dissipation
Introduction
STDM110
1-38
Samsung ASIC
where
N_2.5V_input is the number of 2.5V interface input buffers used
N_3.3V input is the number of 3.3V interface input buffers used,
N_total_input = N_2.5V_input + N_3.3V input
N_2.5V_output is the number of 2.5V interface output buffers used,
N_3.3V_output is the number of 3.3V interface output buffers used,
N_2.5V_bi is the number of 2.5V interface bidirectional buffers used,
N_3.3V_bi is the number of 3.3V interface bidirectional buffer used,
N_macro is the number of macro cells used,
G is the size of the design in gate count,
F is the operating frequency in MHz,
S is the estimated degree of switching activity (typically 0.1 for internal and 0.5 for I/O),
Sout is the output mode ratio of bidirectional buffers (typically 0.5),
C is the load capacitance in pF.
P is the characterized power for the i-th hard macro block (
μ
W/MHz)
1.10.5 TEMPERATURE AND POWER DISSIPATION
The total power dissipation, P
TOTAL
can be used to find out the device temperature by the following equation:
θ
JA
= (T
J
– T
A
) / P
TOTAL
where
θ
JA
is the thermal impedance,
T
J
is the junction temperature of the device,
T
A
is the ambient temperature.
Thermal impedances of the Samsung packages are given in the following table. The junction temperature,
obtained by multiplying P
TOTAL
by the appropriate
θ
JA
and adding T
A
, determines the derating factor for the
propagation delays and also indicates the reliability measures. Hence, designers can achieve the desired derating
factor and reliability targets by choosing appropriate packages and system cooling methods.
Table 1-10.
Thermal Impedances of Samsung Plastic Packages
SOP/TSOP
44
44-71
Pin Number
θ
JA
[
°
C/W]
20
63
24
58
28
32
50
54
62
66
41-44
46-56
39-59
34-56
27-33
34-46
QFP
Pin Number
θ
JA
[
°
C/W]
44
48
80
100
27-61
120
33-47
128
43-51
160
29-51
208
22-43
240
28-47
256
29-42
51-62
43-56
43-74
TQFP/LQFP
144
38
Pin Number
θ
JA
[
°
C/W]
32
64
47
100
37-70
160
35-62
176
31-34
208
37-56
256
30-42
68-70
PBGA
Pin Number
θ
JA
[
°
C/W]
272
19-22
388
16-19
356 (TEPBGA)
16
452 (TEPBGA)
14
SBGA
352
11.7
Pin Number
θ
JA
[
°
C/W]
256
14.1
304
13.1
432
10.2
600
8.3