SBOSA86 March 2023 INA310A , INA310B
PRODUCTION DATA
To maximize the accuracy of a current sense amplifier, TI recommends to choose the largest current sense resistor value possible in an application. A larger value sense resistor maximizes the differential input signal for a given amount of current flow and reduces the error contribution of the offset voltage. However, there are practical limits as to how large the current-sense resistor value can be in a given application because of the physical dimensions of the resistor, package construction and maximum power dissipation. Equation 2 gives the maximum value for the current-sense resistor for a given power dissipation budget:
where:
An additional limitation on the size of the current sense resistor and device gain is due to the power-supply voltage, VS, and device swing-to-rail limitations. To make sure that the current-sense signal is properly passed to the output, both positive and negative output swing limitations must be examined. Equation 3 provides the maximum values of RSENSE and GAIN to keep the device from exceeding the positive swing limitation.
where:
To avoid positive output swing limitations when selecting the value of RSENSE, there is always a trade-off between the value of the sense resistor and the gain of the device under consideration. If the sense resistor selected for the maximum power dissipation is too large, then it is possible to select a lower-gain device to avoid positive swing limitations.
The negative swing limitation places a limit on how small the sense resistor value can be for a given application. Equation 4 provides the limit on the minimum value of the sense resistor.
where:
Table 8-1 shows an example of the different results obtained from using five different gain versions of the INA310x. From the table data, the highest gain device allows a smaller current-shunt resistor and decreased power dissipation in the element.
PARAMETER | EQUATION | RESULTS AT VS = 5 V | |||||
---|---|---|---|---|---|---|---|
A1, B1 DEVICES | A2, B2 DEVICES | A3, B3 DEVICES | A4, B4 DEVICES | A5, B5 DEVICES | |||
G | Gain | 20 V/V | 50 V/V | 100 V/V | 200 V/V | 500 V/V | |
VDIFF | Ideal differential input voltage | VDIFF = VOUT / G | 250 mV | 100 mV | 50 mV | 25 mV | 10mV |
RSENSE | Current sense resistor value | RSENSE = VDIFF / IMAX | 25 mΩ | 10 mΩ | 5 mΩ | 2.5 mΩ | 1 mΩ |
PSENSE | Current-sense resistor power dissipation | RSENSE × IMAX2 | 2.5 W | 1 W | 0.5 W | 0.25 W | 0.1 W |