SLYA042 July 2024 FDC1004 , FDC1004-Q1
Data is checked against a potential theoretical model of the device using equations from Section 6. Although, nearly impossible to back calculate internal device parameters from measured data given many possible combination of error sources, data checks were performed here to verify equations.
First, circuit conditions and all resistors tolerances and drifts were set as shown in Table 9-2.
Value | Tolerance | ppm/°C | |
---|---|---|---|
IB, CM ON (A) | 5.80E-05 | 3.00% | 300 |
IOS (A) | -5.00E-08 | -3.00% | 10 |
PV (%) | 0% | -0.45% | -25 |
REXT1 (Ω) | 110 | 0.23% | 33 |
REXT2 (Ω) | 110 | 0.12% | 30.3 |
Ra (Ω) | 4.99E+04 | -0.200% | 30 |
Rb (Ω) | 1500 | 0.300% | 25 |
Next, theoretical values of resistors and constants were calculated for each temperature. All values were calculated using equations from Section 6. The total predicted gain (GTotal, predicted) was calculated by multiplying the GEF of modeled internal resistors and the measured device gain. Note that the GEF found in Equation 22 was used.
TA (°C) | -40 | 25 | 125 |
---|---|---|---|
REXT1 (Ω) | 110.0165073 | 110.253 | 110.6168349 |
REXT2 (Ω) | 109.915095 | 110.132 | 110.4657 |
RBIAS (Ω) | 2492.794219 | 2488.75 | 2482.528125 |
RINT (Ω) | 2493.504306 | 2490.022268 | 2483.970779 |
RFB (Ω) | 498558.8438 | 497750 | 496505.625 |
IOS (A) | -4.8468E-08 | -4.8500E-08 | -4.8549E-08 |
IB, CM ON (A) | 5.8575E-05 | 5.9740E-05 | 6.1532E-05 |
GDevice, Measured(V/V) | 199.9430451 | 199.8978107 | 199.883843 |
CEG | 0.000219523 | 0.000220352 | 0.000221633 |
GTotal, predicted(V/V) | 176.5801647 | 176.4662982 | 176.3379943 |
CEV | 0.999999798 | 0.999999758 | 0.999999697 |
VOS, EXT predicted | -2.64999E-06 | -4.18505E-06 | -6.62529E-06 |
Lastly, the prediction model was finished by calculating variable external resistances at the REF pin. Error constants c and m are dependent upon REXT and thus two values are calculated for each REXT. The parameters here have the same terminology and follow the same equations as this Driving Voltage Reference Pins of Current-Sensing Amplifiers, application note.
TA (°C) | -40 | 25 | 125 |
---|---|---|---|
Ra (Ω) | 49703.08961 | 49800.2 | 49949.6006 |
Rb (Ω) | 1502.055188 | 1504.5 | 1508.26125 |
Rx (Ω) | 1457.993799 | 1460.38084 | 1464.053195 |
Vref_x (V) | 0.146670339 | 0.146623994 | 0.146553043 |
c | 0.002909863 | 0.00291936 | 0.002934036 |
m | 0.00290142 | 0.002910862 | 0.002925452 |
c (REXT = 110Ω) | 0.002909224 | 0.002918717 | 0.002933385 |
m (REXT = 110Ω) | 0.002900785 | 0.002910223 | 0.002924806 |
Note that this theoretical models only assume linear resistor temperature coefficients; when realistically the temperature coefficient can be highly non-linear. Thus the model was tuned to get best matching to the data for change in ambient temperature from 25°C to 125°C.