Q10. On the AD4111/AD4112/AD4114/AD4115 what’s the equivalent TUE (total uncompensated error) spec across different input voltage ranges for example ±10V, ±5V, ±2.5V or 0-10V, 0-5V, 0-2.5V?
AD4111/AD41112/AD4114/AD4115 are specified for a TUE spec at ±10V full scale range. When input span is reduced the error will change as TUE is specified as a percentage of Full-scale range (%FSR).
In order to calculate the equivalent TUE spec for smaller ranges, we would take the assumption that gain-error and offset error both account for 50% of the total TUE. Please take note that this method provides only an estimated value, the actual performance could be better or worse as we only guaranteed the TUE spec at ±10V input range.
We can start by working through the errors in mV or V initially and then translating to a final TUE Specification
If we take an input span of ±10V and take the TUE from the datasheet specification for ±10V input at 25°C.
For AD4111/AD4112, TUE specs at 25°C is 0.06% Thus,
Offset error = 0.03% of 20V span =>6mV
Full-Scale error at +10V (after correcting for offset error) = 0.03% of 20V span =>6mV
TUE = (6mV+6mV)/20 *100 = 0.06%
For AD4114/AD4115, TUE specs at 25°C is specified as 0.07%. Taking the same steps as above will give you
Offset error = 0.035% of 20V span =>7mV
Full-Scale error at +10V (after correcting for offset error) = 0.035% of 20V span =>7mV
TUE = (7mV+7mV)/20 *100 = 0.07%
Table 2 shows the TUE estimation at 25°C across different ranges. The same approach can be applied when calculating TUE across different temperature.
Table 2. AD411x TUE estimation at 25°C
|
Input span |
AD4111/AD4112 |
AD4114/AD4115 |
|
±5V |
Offset error = 6mV; Full-Scale error = 6mV*(5V/10V) = 3mV; TUE = (6mV + 3mV)/10 *100 = 0.09% |
Offset error = 7mV; Full-Scale error = 7mV*(5V/10V) = 3.5mV; TUE = (7mV + 3.5mV)/10 *100 = 0.105% |
|
±2.5V |
Offset error = 6mV; Full-Scale error = 6mV*(2.5V/10V) = 1.5mV; TUE = (6mV + 1.5mV)/5 *100 = 0.15% |
Offset error = 7mV; Full-Scale error = 7mV*(2.5V/10V) = 1.75mV; TUE = (7mV + 1.75mV)/5 *100 = 0.175% |
|
0 – 10 V |
Offset error = 6mV; Full-Scale error = 6mV*(10V/10V) = 6mV; TUE = (6mV + 6mV)/10 *100 = 0.12%
|
Offset error = 7mV; Full-Scale error = 7mV*(10V/10V) = 7mV; TUE = (7mV + 7mV)/10 *100 = 0.14% |
|
0 – 5 V |
Offset error = 6mV; Full-Scale error = 6mV*(5V/10V) = 3mV; TUE = (6mV + 3mV)/5 *100 = 0.18% |
Offset error = 7mV; Full-Scale error = 7mV*(5V/10V) = 3.5mV; TUE = (7mV + 3.5mV)/5 *100 = 0.21% |
|
0 – 2.5 V |
Offset error = 6mV; Full-Scale error = 6mV*(2.5V/10V) = 1.5mV; TUE = (6mV + 1.5mV)/2.5 *100 = 0.3% |
Offset error = 7mV; Full-Scale error = 7mV*(2.5V/10V) = 1.75mV; TUE = (7mV + 1.75mV)/2.5 *100 = 0.35% |
