ZXLD1352

ZXLD1352

Document number: DS33469 Rev. 3 - 2

15 of 21

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December 2010

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Inductor Selection

Recommended inductor values for the ZXLD1352 are in the range 47µH to 220µH.

Higher values of inductance are recommended at higher supply voltages in order to minimize errors due to switching delays,

which result in increased ripple and lower efficiency. Higher values of inductance also result in a smaller change in output current

over the supply voltage range. (See graphs). The inductor should be mounted as close to the device as possible with low

The chosen coil should have a saturation current higher than the peak output current and a continuous current rating above the

required mean output current.

Suitable coils for use with the ZXLD1352 are listed in the table below:

Part No.

L

(

μH)

DCR

(

Ω)

Manufacturer

DO1608C

47

0.64

0.5

CoilCraft

MSS6132ML

47

0.38

0.56

68

0.58

0.47

100

0.82

0.39

CD104-MC

220

0.55

0.53

Sumida

NP04SB470M

47

0.27

0.38

Taiyo Yuden

The inductor value should be chosen to maintain operating duty cycle and switch 'on'/'off' times within the specified limits over

the supply voltage and load current range.

The following equations can be used as a guide, with reference to Figure 1 - Operating waveforms.

LX Switch 'On' time

L

ΔI

–

++

()

–

----------------------------------------------------------------------------------------

=

LX Switch 'Off' time

L

ΔI

+

()

++

-----------------------------------------------------------------------

=

Where:

L is the coil inductance (H)

rL is the coil resistance (

Ω)

VD is the diode forward voltage at the required load current (V)