LMZ14203HTZXSLASHNOPB datasheet(20/31 Pages) TI

20 / 31 page

0.0

0.5

1.0

1.5

2.0

2.5

3.0

100

OUTPUT CURRENT (A)

VIN = 28V

VIN = 30V

VIN = 36V

VIN = 42V

LMZ14203H

SNVS692G – JANUARY 2011 – REVISED OCTOBER 2015

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Typical Application (continued)

In CCM, current flows through the inductor through the entire switching cycle and never falls to zero during the

OFF-time. The switching frequency remains relatively constant with load current and line voltage variations. The

CCM operating frequency can be calculated using Equation 16.

The approximate formula for determining the DCM/CCM boundary is as follows:

IDCB ≊ VO × (VIN–VO) / ( 2 × 10 μH × fSW(CCM) × VIN)

(22)

The inductor internal to the module is 10

μH. This value was chosen as a good balance between low and high

input voltage applications. The main parameter affected by the inductor is the amplitude of the inductor ripple

current (ILR). ILR can be calculated with:

ILR P-P = VO × (VIN- VO) / (10 µH × fSW × VIN)

where

•

VIN is the maximum input voltage and fSW is determined from Equation 16.

(23)

If the output current IO is determined by assuming that IO = IL, the higher and lower peak of ILR can be

determined. Be aware that the lower peak of ILR must be positive if CCM operation is required.

8.2.3 Application Curve

Figure 47. Efficiency VOUT = 24 V, TA = 25°C

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