LOG200 datasheet(23/42 Pages) TI

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Begin error analysis by solving for the nominal output voltage at the minimum and maximum currents, without

considering error terms. The results are then used to approximate the contribution of the logarithmic conformity

error, in mV.

VLOG_nominal_atImin=K×log10 IminIREF +VREF=250mVdec×log10 10nA1µA +1.65V=1.15V

(11)

VLOG_nominal_atImax=K×log10 ImaxIREF +VREF=250mVdec×log10 200µA1µA +1.65V=2.2253V

(12)

LCEatImin=LCE× VLOG_nominal_atImin–VREF =–0.0005× 1.15V–1.65V =0.25mV

(13)

LCEatImax=LCE× VLOG_nominal_atImax–VREF =0.0005× 2.2253V–1.65V =0.288mV

(14)

Repeat this exercise, taking into account typical error values as previously calculated, and then determine the

difference of the results to calculate the output error at each current level.

VLOG_actual_atImin=Kactual×log10 Imin

IREF_actual +VREF_actual+VOSO+LCEatImin=1.1521V

(15)

VLOG_actual_atImax=Kactual×log10 Imax

IREF_actual +VREF_actual+VOSO+LCEatImax=2.2290V

(16)

VLOG_error_atImin=VLOG_actual_atImin–VLOG_nominal_atImin=2.117mV

(17)

VLOG_error_atImax=VLOG_actual_atImax–VLOG_nominal_atImax=3.767mV

(18)

The output error at a given current level is then expressed as a percentage of the full-scale range as per

Equation 19 and Equation 20:

ERRORfull_scale_atImin=

VLOG_error_atImin

VLOG_nominal_atImax–VLOG_nominal_atImin=0.197%

(19)

ERRORfull_scale_atImax=

VLOG_error_atImax

VLOG_nominal_atImax–VLOG_nominal_atImin=0.350%

(20)

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LOG200

SBOSA28A – AUGUST 2023 – REVISED DECEMBER 2024

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