3 Mission Profile Examples

The values shown in the section SAM9X7 Series Lifetime Estimates are based on estimates for an always-on device (100% up time). However, all applications are not up 100% of the time and may switch from one operating point (T_J, VDD) to another. Such considerations must be taken into account when estimating lifetime.

To estimate a specific mission profile, use the following tables and examples.

The following table provides relevant definitions of terms.

Table 3-1. Definitions⁽¹⁾
Symbol	Definitions
Generic
T_J	Device junction temperature
VDD	VDDCORE voltage
User Mission Profile Data
MP	User Mission Profile: a set of operating points (T_J,VDD)
PoH_{MP_TARGET}	User Power-on Hours target with MP mission profile. This is the total time when the device is powered.
U%	Percentage of time spent in each MP operating point
PoH(T_J)	Power-on Hours spent at T_J. PoH (T_J) = PoH_{MP_TARGET} x U%
Technological Data (see Figure 2-1 and Table 3-2)
PoH_Q(T_J,VDD)	Qualified equivalent hours at T_J, VDD. In particular, PoH_Q(125°C,1.15V) = 2347 Hrs
DR(T_J)	Temperature-derating ratio at T_{J :}PoH_[Q](T_J,VDD) = DR(T_J) x PoH_[Q](125°C, VDD). See Table 3-2.
VAF	Voltage Acceleration Factor PoH_[Q](T_J, VDD) = VAF x PoH_[Q](T_J, 1.15V) VAF = 2.72 for VDD = 1.05V operation VAF = 1.00 for VDD = 1.15V operation
Calculated Quantities
PoH_MP(125°C, 1.15V)	Mission profile equivalent Power-on Hours at one point (125°C, 1.15V): PoH(125°C, 1.15V) = PoH(T_J) / (VAF.DR(T_J)) If this number exceeds PoH_Q(125°C, 1.15V) then the mission profile MP is more demanding than the HTOL test.
PoH_{MP_EST}	Estimated Power-on Hours with given MP: PoH_{MP_EST} = PoH_{MP_TARGET} x PoH_Q(125°C, 1.15V) / PoH_MP(125°C, 1.15V)

Note:

In the above table, PoH_[Q](T_J, VDD) means either PoH(T_J, VDD) or PoH_Q(T_J, VDD).

Table 3-2, built from applicable product qualification, temperature and voltage aging acceleration values, lists the A, B, C and D operating points referred to in the example below.

Table 3-2. SAM9X75 Power-on Hours Derating Values
T_J	DR(T_J)	Mission Profile Example
T_J°C < 25°C	938
30	598	A
35	387
40	254
45	169
50	114	B
55	77.7
60	53.6
65	37.3
70	26.3	C
75	18.7
80	13.5
85	9.8
90	7.1
95	5.3
100	3.9	D
105	2.9
110	2.2
115	1.7
120	1.3
125	1

Table 3 summarizes a mission profile example having:

A target lifetime: PoH_{MP_TARGET},
4 operating points (VDD, T_J)
A usage percentage in each operating point.

PoH_{MP_TARGET} = 60000 Hrs

Table 3-3. Mission Profile Example
MP	U%	PoH(T_J, VDD)	T_J °C	V_DD (V)	DR(T_J)	VAF	PoH(125°C, 1.15V)	Comment
A	25	15000	30	1.05	598	2.72	9	15000 / 598 / 2.72 = 9
B	25	15000	50	1.15	114	1.00	132	15000 / 114 / 1 = 132
C	25	15000	70	1.05	26.3	2.72	210	15000 / 26.3 / 2.72 = 210
D	25	15000	100	1.15	3.9	1.00	3823	15000 / 3.9 / 1 = 3823
PoH_MP(125°C, 1.15V) =							4174

The PoH(125°C, 1.15V) column is computed for each line of the mission profile by derating PoH(T_J, VDD) with DR(T_J) and VAF (temperature and voltage derating). Computation results are then summed up into a single value.

If the computed PoH_MP(125°C, 1.15V) is greater than PoH_Q(125°C, 1.15V), then the required PoH_{MP_TARGET} exceeds the device lifetime emulated during the HTOL tests, as in this example. In such case, the mission profile must be reviewed.
Conversely, if PoH_MP(125°C, 1.15V) is less than PoH_Q(125°C, 1.15V), then the mission profile MP is covered by the HTOL tests.

As explained above, PoH_{MP_TARGET} = 60 kHrs cannot be reached with the example mission profile MP. However, it is interesting to estimate the Power-on Hours with such mission profile, PoH_{MP_EST}. See applicable formula in Table 3-1 and its application in the following table.

Table 3-4. Estimated PoH for Example Mission Profile
Result	Value in Hours	Comment
PoH_{MP_EST}	33700	60000 * 2347 / 4174