Current Sensor Practical 3- Weikewei - Domestic Replacement, Performance Upgrade
If the INA826 current sensor is used for low-end measurement (Vcm ≈ 0V), the output voltage range of the device only extends from~0.1V to~1.2V when Vs=5V (single power supply), Vref=0V, and G= 100. This range may be too limited to utilize the full input range of a typical ADC.
However, using dual power sources to power the device allows for a larger output voltage range, as shown in Figure 12.
When the gain is 1 or 100 and Vcm=0V, Vs=± 5V can cause the output to swing from -4.9V to+4.85V. However, depending on the system and application, an additional -5V power supply may be required.
Non traditional IA technologies such as INA326 utilize unique topological structures to achieve true rail to rail input and output voltage ranges. When the single power supply voltage is 5V, the input voltage range of INA326 is -20 mV to 5.1V. The output voltage range can swing to within 75 mV of any power supply rail. This makes such devices attractive for low-end current measurement.
outline
In summary, we have introduced four commonly used DC sensing devices for current sensors: operational amplifiers, DA, IA, and CSM. RRIO operational amplifiers have been found to be suitable for low side current detection. However, in the presence of high common mode voltage, differential amplifiers can be used for high-end current detection, but they will consume the current of the system bus power supply. They can also be used for low side sensing and eliminate the impact of parasitic resistance on ground. Instrumentation amplifiers (such as operational amplifiers) are limited to the common mode voltage within their power supply and are typically used for low side sensing.
Finally, CSM adopts a unique input stage topology that can provide multiple common mode voltages while bringing less load to the system than DA. Most CSM can be used for high-end or low-end detection. Table 1 provides general solution recommendations based on the power supply voltage (Vdevice) of the device relative to the system bus voltage (Vcm) and the magnitude of the load current.