SBOS944D September 2018 – September 2019 LM321LV , LM324LV , LM358LV

PRODUCTION DATA.

- 1 Features
- 2 Applications
- 3 Description
- 4 Revision History
- 5 Pin Configuration and Functions
- 6 Specifications
- 7 Detailed Description
- 8 Application and Implementation
- 9 Power Supply Recommendations
- 10Layout
- 11Device and Documentation Support
- 12Mechanical, Packaging, and Orderable Information

- DCK|5

The transfer function of the circuit in Figure 31 is given in Equation 1:

Equation 1.

The load current (I_{LOAD}) produces a voltage drop across the shunt resistor (R_{SHUNT}). 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:

Equation 2.

Using Equation 2, R_{SHUNT} is calculated to be 100 mΩ. The voltage drop produced by I_{LOAD} and R_{SHUNT} is amplified by the LM3xxLV device to produce an output voltage of approximately 0 V to 3.5 V. The gain needed by the LM3xxLV to produce the necessary output voltage is calculated using Equation 3:

Equation 3.

Using Equation 3, the required gain is calculated to be 35 V/V, which is set with resistors R_{F} and R_{G}. Equation 4 sizes the resistors R_{F} and R_{G}, to set the gain of the LM3xxLV device to 35 V/V.

Equation 4.