SLYS026A June 2020 – June 2021 INA238-Q1
Parametric values are calculated by multiplying the returned value by the LSB value. Table 8-4 below shows the returned values for this application example assuming the design requirements shown in Table 8-3.
|PARAMETER||Returned Value||LSB Value||Calculated Value|
|Shunt voltage (V)||19440d||5 µV/LSB||0.0972 V|
|Current (A)||19660d||10 A/215 = 305.176 µA/LSB||5.9997 A|
|Bus voltage (V)||15360d||3.125 mV/LSB||48 V|
|Power (W)||4718604d||Current LSB x 0.2 = 61.035156 µW/LSB||288 W|
|Temperature (°C)||200d||125 m°C/LSB||25°C|
Shunt Voltage, Current, Bus Voltage (positive only), and Temperature return values in two's complement format. In two's complement format a negative value in binary is represented by having a 1 in the most significant bit of the returned value. These values can be converted to decimal by first inverting all the bits and adding 1 to obtain the unsigned binary value. This value should then be converted to decimal with the negative sign applied. For example, assume a shunt voltage reading returns 1011 0100 0001 0000. This is a negative value due to the MSB having a value of one. Inverting the bits and adding one results in 0100 1011 1111 0000 (19440d) which from the shunt voltage example in Table 8-4 correlates to a voltage of 97.2 mV. Since the returned value was negative the measured shunt voltage value is -97.2 mV.