Datasheet

LM3411

SNVS113E –DECEMBER 1999–REVISED APRIL 2013

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Figure 25. Negative Input, Negative or Positive Output Flyback Regulator

Improved output voltage tolerance and regulation specifications are possible by combining the LM3411A with one

of the SIMPLE SWITCHER buck regulator IC's, such as the LM2574, LM2575, or LM2576. The circuit shown in

Figure 24 can provide a 5V, ±0.5% Output (1% over the operating temperature range) without using any trim-

pots or precision resistors. Typical line regulation numbers are a 1 mV change on the output for a 8V–18V

change on the input, and load regulation of 1 mV with a load change from 100 mA–1A.

A DC-DC flyback converter that accepts a negative input voltage, and delivers either a positive or negative output

is shown in Figure 25. The circuit utilizes a buck regulator (such as the LM2574, LM2575, or LM2576, depending

on how much output current is needed) operating in a flyback configuration. The LM3411 provides the reference

and the required level shifting circuitry needed to make the circuit work correctly.

A unique feature of this circuit is the ability to ground either the high or low side of the output, thus generating

either a negative or a positive output voltage. Although no isolation is provided, with the addition of an opto-

isolator and related components, this circuit could provide input/output isolation.

Combining a LM3411A-5.0 with a 1A low dropout linear regulator results in a 5V ±0.5% (1% over the operating

temperature range) regulator with excellent regulation specifications, with no trimming or 1% resistors needed.

An added benefit of this circuit (and also true of many of the other circuits shown here) is the high-side and low-

side remote output voltage sensing feature. Sensing the output voltage at the load eliminates the voltage drops

associated with wire resistance, thus providing near perfect load regulation.

A 5V, 1A regulator circuit featuring low dropout, very good regulation specifications, self protection features and

allows output voltage sensing is shown in Figure 26. The regulator used is a LM2941 adjustable low dropout

positive regulator, which also features an ON/OFF pin to provide a shutdown feature.

Figure 26. Precision 5V 1A Low Dropout Regulator

Product Folder Links: LM3411