LM3578AM datasheet(19/30 Pages) TI

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LM2578A, LM3578A

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SNVS767E – AUGUST 2000 – REVISED APRIL 2013

R1 = (|Vo| +1) R2 where R2 = 10 kΩ.

R3 = V/(IL(max, DC) + 0.5 ΔIL).

R4 = 10VBE1Bf/(IL (max, DC) + 0.5 ΔIL)

where:

V, VBE1, Vsat, and Bf are defined in the Buck Converter with Boosted Output Current section.

ΔIL = 2(ILOAD(min))(Vin +|Vo|)/VIN

R5 is defined in the Buck Converter with Boosted Output Current section.

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.

≥ Io |Vo|/[fosc(|Vo| + Vin) Vripple]

L1 is found as outlined in the section on buck converters, using the inductance chart of Figure 29 for the invert

configuration and 20% discontinuity.

Vin = 5V

R4 = 190

Vo = −15V

R5 = 82

Vripple = 5 mV

R6 = 220 k

Io = 300 mA

C1 = 1820 pF

Imin = 60 mA

C2 = 1000

μF

fosc = 50 kHz

C3 = 20 pF

R1 = 160 k

C4 = 0.0022

μF

R2 = 10 k

L1 = 150

μH

R3 = 0.01

D1 = 1N5818

Figure 34. Inverting Regulator

BUCK-BOOST REGULATOR

The Buck-Boost Regulator, shown in Figure 35, may step a voltage up or down, depending upon whether or not

the desired output voltage is greater or less than the input voltage. In this case, the output voltage is 12V with an

input voltage from 9V to 15V. The circuit exhibits an efficiency of 75%, with a load regulation of 60 mV (10 mA to

100 mA) and a line regulation of 52 mV.

R1 = (Vo − 1) R2 where R2 = 10 kΩ

R3 = V/0. 75A

R4, C1, C3 and C4 are defined in the Boost Regulator section.

D1 and D2 are Schottky type diodes such as the 1N5818 or 1N5819.

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