The INA700 is a precise, low-drift, digital power monitor that provides accurate measurements over the entire specified ambient temperature range of –40°C to +105°C. The integrated current-sensing resistor is internally compensated to provide measurement stability over temperature, while simplifying printed circuit board (PCB) layout and size constraints. Figure 6-2 shows the device gain error as a function of current.

The IN+ and IN– pins allow access to the on-chip current-sensing resistor. This resistor features internal sense connections that are factory-calibrated and temperature-compensated to achieve a high level of accuracy. The INA700 is system-calibrated so that the current-sensing resistor and current-sensing amplifier are both precisely matched to one another.

The nominal pin-to-pin resistance from IN+ to IN– is approximately 3.6mΩ, while the internal resistance seen by the digital power monitor is nominally 2mΩ. The power dissipation requirements of the system and package are based on the total package resistance between the IN+ and IN– pins. The material composition of the internal shunt has a resistance that increases with temperature as shown in Figure 6-1.

Figure 6-1 IN+ to IN– Package Resistance vs Temperature

The internal compensation of the INA700 corrects for pin-to-pin resistance increases with temperature, achieving less than 50ppm/°C drift over the ambient temperature range.

The INA700 is most accurate when measuring currents around 5A. As currents increase the error in the current measurement also increases. Figure 6-2 below shows how the gain error of the INA700 varies with the shunt current.

Figure 6-2 Gain Error vs Shunt Current

The change in gain error is consistent enough from device to device that returned values can be scaled up or down depending on the shunt current to give a more accurate result. For example, to achieve higher accuracy when measuring currents around 7A, the returned value can be scaled down by approximately 0.4%.