LM2598 datasheet(13/47 Pages) TI1

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LM2598

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SNVS125D – MARCH 1998 – REVISED MAY 2016

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Feature Description (continued)

Figure 21. Inverting –5-V Regulator With Shutdown and Soft-start

8.3.2 Inverting Regulator

The circuit in Figure 21 converts a positive input voltage to a negative output voltage with a common ground. The

circuit operates by bootstrapping the regulators ground pin to the negative output voltage, then grounding the

feedback pin, the regulator senses the inverted output voltage and regulates it.

This example uses the LM2598-5 to generate a –5-V output, but other output voltages are possible by selecting

other output voltage versions, including the adjustable version. Because this regulator topology can produce an

output voltage that is either greater than or less than the input voltage, the maximum output current greatly

depends on both the input and output voltage. The curve shown in Figure 22 provides a guide as to the amount

of output load current possible for the different input and output voltage conditions.

The maximum voltage appearing across the regulator is the absolute sum of the input and output voltage, and

this must be limited to a maximum of 40 V. In this example, when converting 20 V to –5 V, the regulator would

see 25 V between the input pin and ground pin. The LM2598 has a maximum input voltage rating of 40 V.

Figure 22. Maximum Load Current for Inverting

Regulator Circuit

LM2598 Datasheet(PDF) 13 Page - Texas Instruments