LM3411M5-3.3 National Semiconductor, LM3411M5-3.3 Datasheet - Page 10

• Manufacturer Part Number: LM3411M5-3.3
• Description: Precision Secondary Regulator/Driver
• Manufacturer: National Semiconductor

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Applications Information
The circuit in Figure 8 shows a 3.3V low dropout regulator
using the LM3411-3.3 and several discrete components.
Like the positive regulators, the performance of negative ad-
justable 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
FIGURE 8. 3.3V 0.5A Low Dropout Regulator
FIGURE 9. Precision Positive Voltage Regulator with Accurate Current Limit
FIGURE 7. Precision 5V 1A Low Dropout Regulator
(Continued)
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This circuit is capable of excellent performance with both the
dropout voltage and the ground pin current specifications im-
proved over the LM2941/LM3411 circuit.
The standard LM317 three terminal adjustable regulator cir-
cuit can greatly benefit by adding a LM3411. Performance is
increased and features are added. The circuit shown in Fig-
ure 9 provides much improved line and load regulation,
lower temperature drift, and full remote output voltage sens-
ing on both the high and low side. In addition, a precise cur-
rent limit or constant current feature is simple to add.
Current limit protection in most IC regulators is mainly to pro-
tect the IC from gross over-current conditions which could
otherwise fuse bonding wires or blow IC metalization, there-
fore not much precision is needed for the actual current limit
values. Current limit tolerances can sometimes vary from
perature 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 9 can provide a current limit accuracy
that is better than
tion to having excellent line, load and temperature
specifications.
resistors to the circuit in Figure 10 adds the precision current
limit feature as shown in Figure 11 . Current limit tolerances
of
possible with this circuit.
±
10% to as high as +300% over manufacturing and tem-
±
4% over manufacturing and temperature variations are
±
4%, over all possible variations, in addi-
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