The circuit of

Figure 19 converts a 5V supply into a 15V sup-

ply with 150 mA of output current, a load regulation of 14 mV

(30 mA to 140 mA), and a line regulation of 35 mV (4.5V

≤

V

R1 = (V

R3 = V/(I

where:

∆I

∆I

R4, C3 and C4 are necessary for continuous operation and

are typically 220 k

Ω, 20 pF, and 0.0022 µF respectively.

C1 is the timing capacitor found in

Figure 1.

C2

≥ I

D1 is a Schottky type diode such as a IN5818 or IN5819.

L1 is found as described in the buck converter section, using

the inductance chart for

Figure 16 for the boost configuration

and 20% discontinuity.

INVERTING REGULATOR

Figure 20 shows the basic configuration for an inverting

regulator. The input voltage is of a positive polarity, but the

output is negative. The output may be less than, equal to, or

greater in magnitude than the input. The relationship be-

tween the magnitude of the input voltage and the output volt-

age is V

Figure 21 shows an LM1578A configured as a 5V to −15V

polarity inverter with an output current of 300 mA, a load

regulation of 44 mV (60 mA to 300 mA) and a line regulation

of 50 mV (4.5V

≤ V

R1 = (|V

R3 = V/(I

R4 = 10V

where:

V, V

Boosted Output Current” section.

∆I

R5 is defined in the “Buck with Boosted Output Current” sec-

tion.

R6 serves the same purpose as R4 in the Boost Regulator

circuit and is typically 220 k

Ω.

C1, C3 and C4 are defined in the “Boost Regulator” section.

C2

≥ I

L1 is found as outlined in the section on buck converters, us-

ing the inductance chart of

Figure 16 for the invert configura-

tion and 20% discontinuity.

DS008711-9

FIGURE 18. Basic Boost Regulator

DS008711-11

R4 = 200 k

Ω

C1 = 1820 pF

C2 = 470 µF

C3 = 20 pF

C4 = 0.0022 µF

R1 = 140 k

Ω

L1 = 330 µH

R2 = 10 k

Ω

D1 = 1N5818

R3 = 0.15

Ω

FIGURE 19. Boost or Step-Up Regulator

DS008711-10

FIGURE 20. Basic Inverting Regulator

13

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