SIM100MLP datasheet(7/19 Pages) SENSATA

7 / 19 page

Preliminary

Rev 1.1a

Sendyne SIM100MLP

During the transition and while SIM100 is estimating

the new isolation state, it will indicate a high level of

uncertainty, so the host ECU can ignore those transi-

tion results. Similar results were obtained when test-

ing the SIM100 on the positive side of the battery.

Thermal stability

Per UL 2231-2, the SIM100 was tested using the test

apparatus of Figure 9 at different environmental tem-

peratures. In the following illustrations the colored

dots indicate the average error at each temperature

obtained through approximately 1100 reports. The

experiments were repeated for different Y-capacitor

values (2 x 100 nF and 2 x 1 uF). The colored dots

show the average values while the greyed areas show

the spread of error in the reports indicating the max

and min error on each experiment. We illustrate the

worst case errors that occur at the smaller insertion

resistance R

F,x . As can be seen all errors are well below

the ±15% of the UL requirements.

-35

-20

-15

-10

-5

Temperature oC

Average, min & max error for R

F,N = 100 Ω/V * 500 V

-20

-15

-10

-5

Temperature OC

Average, min & max error for R

F,P = 100 Ω/V * 500 V

UL2231-2

Figure 9: Inserted resistance estimate error at differ-

ent temperatures

Uncertainty

Along with each report the SIM100 submits an esti-

mate of the uncertainty associated with the estimates.

The uncertainty is reported as a percentage of the

estimated values and takes into consideration both the

measurement and processing uncertainties. Uncer-

tainty is derived in the interval of two standard devia-

tions (95.45% of samples) and rounded to the next

higher absolute value. For example, if the uncertainty

calculated is ±1.4 % it will be rounded to ±2%. The

SIM100 then adds to this value another ±3% to ac-

commodate for factors that cannot be calculated, such

as part values shifting over age, etc. As a result, the

uncertainty value provided is a conservative one.

An illustration of the relationship between measure-

ments distribution and uncertainties reported is

shown in Figure 10. The green vertical line shows

the actual value of the isolation resistance of the test

circuit. Its value is the parallel combination of the 250

Ω inserted resistance with the 2.7 MΩ resistance of

the SIM100. The red vertical line shows the average

value of SIM100 reports; the actual estimate error

is 1.8%. Uncertainty is estimated to ±2% and then

augmented by ±3% to provide the final estimate of

±5%. As can be seen in this experiment, uncertainty

provides a very conservative estimate of the reported

accuracy.

How to use the uncertainty

Uncertainties should be used in the most conservative

way to calculate worst case scenarios. If, for example,

the SIM100 reports a value of 100 k

Ω with uncertainty

of ±5%, the host should assume the worst case pos-

sibility that the actual isolation resistance is (100 – 5)

Ω.

Very high uncertainties

There may be instances that the SIM100 reports very

high uncertainties. This may happen when there is no

voltage present and there is a lot of noise in the IT sys-

tem or during a large and rapid transition of isolation

resistance values. During these instances, the SIM100

will flag the “High Uncertainty” bit to notify the host

that these reports may be discarded.

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