CS30 Datasheet, PDF (15/18 Pages) List of Unclassifed Manufacturers – METAL STRIP SHUNT RESISTROS FOR DETECTING ELETRICAL CURRENT

CS30
5
Application information
Application information
The CS30 can be used to measure current and to feed back the information to a
microcontroller, as shown in Figure 23.
2.8 V to 30 V
Figure 23. Typical application schematic
Vsense
Iload
Rsense
Load
Vp
Rg1
Vm
CS30
Rg2
VCC
5V
Vreg
Rg3
Gnd
VCC
ADC
Out
Vout
Microcontroller
Gnd
AM06163v1
The current from the supply flows to the load through the R_sense resistor causing a voltage
drop equal to V_sense across R_sense. The amplifier input currents are negligible, therefore its
inverting input voltage is equal to V_m. The amplifier's open-loop gain forces its non-inverting
input to the same voltage as the inverting input. As a consequence, the amplifier adjusts
current flowing through Rg1 so that the voltage drop across Rg1 exactly matches V_sense.
Therefore, the drop across Rg1 is: V_Rg1=V_sense=R_sense.I_load
If I_Rg1 is the current flowing through Rg1, then I_Rg1 is given by the formula: I_Rg1=V_sense/Rg1
The I_Rg1 current flows entirely into resistor R_g3 (the input bias current of the buffer is
negligible). Therefore, the voltage drop on the R_g3 resistor can be calculated as follows:
V_Rg3=R_g3.I_Rg1=(R_g3/R_g1).V_sense
Because the voltage across the R_g3 resistor is buffered to the Out pin, V_out can be
expressed as:
V_out=(R_g3/R_g1).V_sense or V_out=(R_g3/R_g1).R_sense.I_load
The resistor ratio R_g3/R_g1 is internally set to 20V/V for CS30A, to 50V/V for CS30B and to
100V/V for CS30C.
The R_sense resistor and the R_g3/R_g1 resistor ratio (equal to A_v) are important parameters
because they define the full scale output range of your application. Therefore, they must be
selected carefully.
DocID026040 Rev 1
15/18
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