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 kΩ.
C1, C3 and C4 are defined in the Boost Regulator section.
C2 ≥ 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 = 190Ω
Vo = −15V
R5 = 82Ω
Vripple = 5 mV
Io = 300 mA
Imin = 60 mA
fosc = 50 kHz
R1 = 160 kΩ
R2 = 10 kΩ
R3 = 0.01Ω
R6 = 220 kΩ
C1 = 1820 pF
C2 = 1000 μF
C3 = 20 pF
C4 = 0.0022 μF
L1 = 150 μH
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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