7.3.1 Load Regulation

The LM317A is capable of providing extremely good load regulation but a few precautions are needed to obtain maximum performance. The current set resistor, R1, should be connected near the output terminal of the regulator rather than near the load. If R1 is placed too far from the output terminal, then the increased trace resistance, R_S, will cause an error voltage drop in the adjustment loop and degrade load regulation performance. Therefore, R1 should be placed as close as possible to the output terminal to minimize R_S and maximize load regulation performance.

Figure 16 shows the effect of the trace resistance, R_S, when R1 is placed far from the output terminal of the regulator. It is clear that R_S will cause an error voltage drop especially during higher current loads, so it is important to minimize the R_S trace resistance by keeping R1 close to the regulator output terminal.

Figure 16. Regulator with Line Resistance in Output Lead

With the TO package, care should be taken to minimize the wire length of the output lead. The ground of R2 can be returned near the ground of the load to provide remote ground sensing and improve load regulation.