INA700 datasheet(28/43 Pages) TI

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8.1.2 Current and Power, Energy and Charge Calculations

The measured current can be read from the CURRENT register, where the final value is scaled by

CURRENT_LSB. Use Equation 2 to calculate the current in Amperes:

Current A =CURRENT_LSB×CURRENT

(2)

where

• CURRENT is the value read from the CURRENT register

The power value can be read from the POWER register as a 24-bit value. Use Equation 3 to convert the power

value into Watts:

Power W =0.2×CURRENT_LSB×POWER

(3)

where

• POWER is the value read from the POWER register.

• CURRENT_LSB is the lsb size of the current measurement.

The energy value can be read from the ENERGY register as a 40-bit unsigned value in Joules units. Use

Equation 4 to convert the energy value into Joules:

Energy J =16×0.2×CURRENT_LSB×ENERGY

(4)

Upon overflow, the ENERGY register will roll over and start from zero. This register value can also be reset at

any time by setting the RSTACC bit in the CONFIG register.

The charge value can be read from the CHARGE register as a 40-bit, two's complement value in Coulombs. Use

Equation 5 to convert the charge value into Coulomb:

Charge C =CURRENT_LSB×CHARGE

(5)

where

• CHARGE is the value read from the CHARGE register.

• CURRENT_LSB is the lsb size for current..

An overflow event in the CHARGE register is indicated by the CHARGEOF bit. If an overflow condition occurs,

the CHARGE register needs to be manually reset by setting the RSTACC bit in the CONFIG register.

See Detailed Design Procedure for a design example using these equations.

8.1.3 ADC Output Data Rate and Noise Performance

The INA700 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 INA700 effective resolution of the ADC can be

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

Table 8-2 shows the output data rate conversion settings supported by the device. The fastest conversion setting

is 50 µs. Typical noise-free resolution is represented as Effective Number of Bits (ENOB) based on device

measured data. The ENOB is calculated based on noise peak-to-peak values, which assures that full noise

distribution is taken into consideration. The conversion time for the temperature measurement is set to the

power-on default value.

INA700

SBOSAB4 – MAY 2023

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