Shunt Current Sense
Size a current shunt and check amplifier and ADC headroom.
Formulas
Vshunt = I × Rshunt; Vamp = Vshunt × G
D = 2ᴺ (ideal LSB) or 2ᴺ − 1 (endpoint)
ADC code = clamp(floor(Vamp / Vref × D), 0, 2ᴺ − 1)
Current per count = Vref / (D × G × Rshunt)
Pshunt = I² × Rshunt; minimum rating = Pshunt × (1 + margin / 100)
Model & assumptions
Unipolar ideal ADC with floor quantization; no noise, offset, or gain error. Check amplifier common-mode and output swing separately.
The recommended rating is a numerical minimum before temperature derating; choose an appropriate available rating.
Example with default inputs
- Amplifier output
- 2.35 V
- Shunt voltage
- 470 mV
- ADC count
- 2,916 counts
- Current per ADC count
- 3.42836 mA
- Shunt dissipation
- 4.7 W
- Minimum power rating
- 7.05 W
- ADC voltage headroom
- 950 mV