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Engineering Calculators

Voltage Sensing and ADC Scaling Calculator

Select a practical resistor divider for high-voltage sensing and calculate the corresponding ADC scaling, resolution, current, power, and component stress.

Target ADC utilization: 90%

Inputs

V
V
pcs
Divider Topology

The upper side is one high-voltage resistor string. In the parallel mode, the two lower resistors have the same value and create half the equivalent resistance.

The resistor search favors a practical lower resistance to balance ADC source impedance and divider power.

Calculated Design

Standard resistor combination

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Recommended Upper Resistor String 6 × 1.3 MΩ Series total: 7.8 MΩ
Recommended Lower Resistor Branch 1 × 22 kΩ Equivalent resistance: 22 kΩ
800.0 V 2.250 V ADC 921 / 1023
ADC Range Used 90.0%
Scaling Ratio 355.5 : 1
Standard-Value Fit 99.997% Deviation from target: +0.003%
Input Resolution 868.88 mV/LSB
Divider Current 102.3 µA
Divider Power 81.8 mW

Standard-value fit only indicates how closely the selected E24 or E96 resistor combination matches the 90% ADC utilization target. It does not include resistor tolerance, temperature coefficient, ADC error, or reference-voltage error.

Engineering Check

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ADC headroom

2.250 V at maximum input, using 90.0% of the ADC range.

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Upper resistor voltage stress

133.0 V per upper resistor; typical 0805 screening value is 150 V.

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Upper resistor power

13.6 mW per upper resistor; typical 0805 screening value is 125.0 mW.

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Lower resistor power

230.1 µW per lower resistor. Divider current is 102.3 µA.

Package ratings shown here are typical values for preliminary screening only. Always verify the selected resistor part number, working voltage, pulse rating, power derating, temperature rise, and creepage requirements from the manufacturer datasheet. Current typical 0805 values: 125.0 mW and 150 V.

Firmware Scaling

Input voltage conversion: Vin = ADC code × 0.86887941 V.

const float VIN_PER_COUNT = 0.86887941f; float vin = (float)adc_code * VIN_PER_COUNT;