Datasheet LT1585A, LT1585A-3.3 (Analog Devices) - 8

LT1585A/LT1585A-3.3
U U W U APPLICATIONS INFORMATION Load Regulation
load regulation is obtained when the top of resistor divider R1 connects directly to the regulator output and not to the It is not possible to provide true remote load sensing load. Figure 5 illustrates this point. If R1 connects to the because the LT1585A/LT1585A-3.3 are 3-terminal de- load, the effective resistance between the regulator and vices. Load regulation is limited by the resistance of the the load is: wire connecting the regulators to the load. Load regula- tion per the data sheet specification is measured at the RP(1 + R2/R1), RP = Parasitic Line Resistance bottom of the package. The connection shown in Figure 5 does not multiply RP by For fixed voltage devices, negative side sensing is a true the divider ratio. As an example, RP is about four milliohms Kelvin connection with the ground pin of the device per foot with 16-gauge wire. This translates to 4mV per returned to the negative side of the load. This is illustrated foot at 1A load current. At higher load currents, this drop in Figure 4. represents a significant percentage of the overall regula- tion. It is important to keep the positive lead between the For adjustable voltage devices, negative side sensing is a regulator and the load as short as possible and to use large true Kelvin connection with the bottom of the output wire or PC board traces. divider returned to the negative side of the load. The best RP PARASITIC LT1585A-3.3 LINE RESISTANCE VIN IN OUT GND RL LT1585A • F04
Figure 4. Connection for Best Load Regulation
RP PARASITIC LT1585A LINE RESISTANCE V IN OUT IN ADJ R1* RL R2* *CONNECT R1 TO CASE CONNECT R2 TO LOAD LT1585A • F05
Figure 5. Connection for Best Load Regulation
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