EX128-TQG100A Datasheet, PDF (19/44 Pages) Actel Corporation – eX Automotive Family FPGAs

eX Automotive Family FPGAs
Table 1-11 shows the capacitance of the clock
components of eX devices.
Table 1-11 • Capacitance of Clock Components of eX
Devices
eX64 eX128 eX256
Dedicated array clock –
variable (Ceqhv)
0.85 pF 0.85 pF 0.85 pF
Dedicated array clock – fixed 18.00 pF 20.00 pF 25.00 pF
(Ceqhf)
Routed array clock A (r1)
23.00 pF 28.00 pF 35.00 pF
Routed array clock B (r2)
23.00 pF 28.00 pF 35.00 pF
The estimation of the dynamic power dissipation is a
piece-wise linear summation of the power dissipation of
each component.
Dynamic power dissipation
= V_CCA2 * [(m_c * C_eqcm * fm_C)_{Comb Modules} + (m_s * C_eqsm *
fm_S)_{Seq Modules} + (n * C_eqi * fn)_{Input Buffers} + (0.5 * (q1 *
C_eqcr * fq1) + (r1 * fq1))_RCLKA + (0.5 * (q2 * C_eqcr * fq2) +
(r2 * fq2))_RCLKB + (0.5 * (s1 * C_eqhv * fs1)+(C_eqhf *
fs1))_HCLK] + V_CCI2 * [(p * (C_eqo + C_L) * fp)_{Output Buffers}]
where:
m_c = Number of combinatorial cells switching at
frequency fm, typically 20% of C-cells
m_s = Number of sequential cells switching at
frequency fm, typically 20% of R-cells
n = Number of input buffers switching at
frequency fn, typically number of inputs / 4
p = Number of output buffers switching at
frequency fp, typically number of outputs / 4
q1 = Number of R-cells driven by routed array
clock A
q2 = Number of R-cells driven by routed array
clock B
r1 = Fixed capacitance due to routed array clock A
r2 = Fixed capacitance due to routed array clock B
s1 = Number of R-cells driven by dedicated array
clock
C_eqcm = Equivalent capacitance of combinatorial
modules
C_eqsm = Equivalent capacitance of sequential modules
C_eqi = Equivalent capacitance of input buffers
C_eqcr = Equivalent capacitance of routed array clocks
C_eqhv = Variable capacitance of dedicated array clock
C_eqhf = Fixed capacitance of dedicated array clock
C_eqo = Equivalent capacitance of output buffers
C_L = Average output loading capacitance, typically
10pF
fm_c = Average C-cell switching frequency, typically
F/10
fm_s = Average R-cell switching frequency, typically
F/10
fn = Average input buffer switching frequency,
typically F/5
fp = Average output buffer switching frequency,
typically F/5
fq1 = Frequency of routed clock A
fq2 = Frequency of routed clock B
fs1 = Frequency of dedicated array clock
The eX, SX-A and RTSX-S Power Calculator can be used to
estimate the total power dissipation (static and dynamic)
of eX devices and can be found at
http://www.actel.com/products/rescenter/power/
calculators.aspx.
Junction Temperature
The temperature variable in the Designer software refers
to the junction temperature, not the ambient
temperature. This is an important distinction because the
heat generated from dynamic power consumption is
usually hotter than the ambient temperature. EQ 1-1,
shown below, can be used to calculate junction
temperature. Please refer to Table 1-9 on page 1-12 for
the recommended operating conditions.
EQ 1-1
Junction Temperature = ∆T + T_a(1)
Where:
T_a = Ambient Temperature
∆T = Temperature gradient between junction (silicon)
and ambient = θ_ja * P
P = Power
θ_ja = Junction to ambient of package. θ_ja numbers are
located in the "Package Thermal Characteristics" section
on page 1-16.
v3.2
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