3.1 Industrial Device Mission Profile Example

The values shown in the section Industrial Device 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.

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

Table 3-3 summarizes a mission profile example with the following details:

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

PoH_{MP_TARGET} = 60,000 Hrs

Table 3-3. Industrial Device 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	50	1.05	114	2.72	48	15000 / 114 / 2.72 = 48
B	25	15000	70	1.15	26.3	1.00	570	15000 / 26.3 / 1 = 570
C	25	15000	100	1.05	4	2.72	1406	15000 / 4 / 2.72 = 1406
D	25	15000	125	1.25	1	0.368	40774	15000 / 1 / 1 = 40774
PoH_MP(125°C, 1.15V) =							42799

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 a 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 a mission profile, PoH_{MP_EST}. See the applicable formula in Table 2-1 and its application in the following table.

Table 3-4. Estimated PoH for Example Industrial Device Mission Profile
Result	Value in Hours	Comment
PoH_{MP_EST}	41463	60,000 * 29576 / 42799