JAJSJK2B August 2020 – October 2021 LM2902LV-Q1 , LM2904LV-Q1
PRODUCTION DATA
The transfer function of the circuit in Figure 8-1 is given in Equation 1:
The load current (ILOAD) produces a voltage drop across the shunt resistor (RSHUNT). The load current is set from 0 A to 1 A. To keep the shunt voltage below 100 mV at maximum load current, the largest allowable shunt resistor is shown using Equation 2:
Using Equation 2, RSHUNT is calculated to be 100 mΩ. The voltage drop produced by ILOAD and RSHUNT is amplified by the LM290xLV-Q1 device to produce an output voltage of approximately 0 V to 3.5 V. The gain needed by the LM290xLV-Q1 to produce the necessary output voltage is calculated using Equation 3:
Using Equation 3, the required gain is calculated to be 35 V/V, which is set with resistors RF and RG. Equation 4 sizes the resistors RF and RG, to set the gain of the LM290xLV-Q1 device to 35 V/V.