IN+ and IN– pins. Use Equation 1 for ADCRANGE = 0. For ADCRANGE = 1, the value of SHUNT_CAL must be

divided by 4.

SHUNT_CAL =

0.00512

(1)

where

• 0.00512 is an internal fixed value used to ensure scaling is maintained properly.

• CURRENT_LSB is a selected value for the current step size in amperes. Must be greater than or equal to

CURRENT_LSB (minimum), but less than 8 x CURRENT_LSB(minimum) to reduce resolution loss.

• The value of SHUNT_CAL must be divided by 4 for ADCRANGE = 1.

(2)

Note that the current is calculated following a shunt voltage measurement based on the value set in the

SHUNT_CAL register. If the value loaded into the SHUNT_CAL register is zero, the current value reported

through the CURRENT register is also zero.

After programming the SHUNT_CAL register with the calculated value, the measured current in Amperes can be

read from the CURRENT register. The final value is scaled by CURRENT_LSB and calculated in Equation 3:

Current [A] = CURRENT_LSB x CURRENT

(3)

where

• CURRENT is the value read from the CURRENT register

The power value can be read from the POWER register as a 16-bit value and converted to Watts by using

Equation 4:

Power [W] = 32 x CURRENT_LSB x POWER

(4)

where

• POWER is the value read from the POWER register.

• CURRENT_LSB is selected value for the lsb size of the current calculation used in Equation 1.

For a design example using these equations refer to Detailed Design Procedure.

8.1.3 ADC Output Data Rate and Noise Performance

The INA236 noise performance and effective resolution depend on the ADC conversion time. The device

also supports digital averaging which can further help decrease digital noise. The flexibility of the device to

select ADC conversion time and data averaging offers increased signal-to-noise ratio and achieves the highest

dynamic range with lowest offset. The profile of the noise at lower signals levels is dominated by the system

noise that is comprised mainly of 1/f noise or white noise. The effective resolution of the ADC can be increased

by increasing the conversion time and increasing the number of averages.

8.1.4 Filtering and Input Considerations

Measuring current is often noisy and such noise can be difficult to define. The INA236 offers several options

for filtering by allowing the conversion times and number of averages to be selected independently in the

INA236

SBOSA81 – MAY 2021

www.ti.com

20

Submit Document Feedback

Copyright © 2021 Texas Instruments Incorporated

Product Folder Links: INA236