Datasheet

LM3411
www.ti.com SNVS113E –DECEMBER 1999–REVISED APRIL 2013
Figure 27. 3.3V 0.5A Low Dropout Regulator
The circuit in Figure 27 shows a 3.3V low dropout regulator using the LM3411-3.3 and several discrete
components. This circuit is capable of excellent performance with both the dropout voltage and the ground pin
current specifications improved over the LM2941/LM3411 circuit.
The standard LM317 three terminal adjustable regulator circuit can greatly benefit by adding a LM3411.
Performance is increased and features are added. The circuit shown in Figure 28 provides much improved line
and load regulation, lower temperature drift, and full remote output voltage sensing on both the high and low
side. In addition, a precise current limit or constant current feature is simple to add.
Current limit protection in most IC regulators is mainly to protect the IC from gross over-current conditions which
could otherwise fuse bonding wires or blow IC metalization, therefore not much precision is needed for the actual
current limit values. Current limit tolerances can sometimes vary from ±10% to as high as +300% over
manufacturing and temperature variations. Often critical circuitry requires a much tighter control over the amount
of current the power supply can deliver. For example, a power supply may be needed that can deliver 100% of
its design current, but can still limit the maximum current to 110% to protect critical circuitry from high current
fault conditions.
The circuit in Figure 28 can provide a current limit accuracy that is better than ±4%, over all possible variations,
in addition to having excellent line, load and temperature specifications.
Figure 28. Precision Positive Voltage Regulator with Accurate Current Limit
Like the positive regulators, the performance of negative adjustable regulators can also be improved by adding
the LM3411. Output voltages of either 3.3V or 5V at currents up to 1.5A (3A when using a LM333) are possible.
Adding two resistors to the circuit in Figure 29 adds the precision current limit feature as shown in Figure 30.
Current limit tolerances of ±4% over manufacturing and temperature variations are possible with this circuit.
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