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# Regarding Output Voltage Value

For the Above circuit the Output of AD8232 is 0.9V offset +( Diff o/p * system gain ). This output is fed to the ADPD107 PD input configured in TIA ADC mode.

for the out put of TIA ADC should we Consider  eq 11 of Page40?

By using ADCout we should calculate i in the Equation 11 and then substitute in  Iin= (According to data sheet page 47) to get Vin the input Voltage value?.

or should i consider below equation?.

Vout of TIA = Tia_Bias - Iin * Rf  and get Iin

with the Help of Iin and other values calculate the Vin with the help of this equation?

which is the right way ?.

what is the exact output voltage from the ADC for "Measuring Voltages Using the Current Inputs(page 47 of ADPD105/7 data sheet)"?.

Kindly guide me in this regard FormerMember Optical Sensing@kevin

Regards

Lokesh

• Hello Lokesh,

The amount of input current in TIA_ADC mode can be calculated knowing the ADC resolution in TIA_ADC mode from the table in the datasheet:

Knowing the input current, the value of the series resistor to the input of the ADPD10x, and the TIA_VREF voltage, which is 0.9V, then the output voltage from the AD8233 is easily calculated using Ohm's Law.

Regards,

Kevin

• Thanks Kevin,

Then whats the Significance of Equation 11 ?

Why is 146uV/LSB used?.

Regards

Lokesh Kumar K

• Hello Lokesh,

146uV/LSB is the resolution of the ADC. Knowing the input current, you can estimate the output of the ADC using the equation. Or, you can use the equation to calculate the input current based on the ADC output.

Regards,

Kevin

• Hi Kevin,

actually i didnt get your point. Can you clearly explain how 146uV/LSB is derived?.

regards

Lokesh

• Lokesh,

Full scale of the ADC is +/-1.2V. 2.4V/16384codes = 146uV/LSB

Regards,

Kevin