ZXLD1350

30V 350mA LED DRIVER with AEC-Q100

ZXLD1350

Document number: DS33468 Rev. 8 - 2

17 of 22

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March 2011

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Application Information (Continued)

Inductor Selection

Recommended inductor values for the ZXLD1350 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 resistance connections to the LX and VIN pins.

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 ZXLD1350 are listed in the table below:

Part No.

L

(µH)

DCR

(V)

ISAT

(A)

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

()

LX

L

S

avg

LED

IN

ON

R

r

R

I

V

V

I

L

t

+

+

×

−

−

Δ

=

Note: tONnmin > 200ns

LX Switch 'Off' time

()

L

S

avg

D

LED

OFF

r

R

I

V

V

I

L

t

+

×

+

+

Δ

=

Note: tOFFmin > 200ns

Where:

L is the coil inductance (H)

rL is the coil resistance (Ω)

Iavg is the required LED current (A)

ΔI is the coil peak-peak ripple current (A) {Internally set to 0.3 x Iavg}

VIN is the supply voltage (V)

VLED is the total LED forward voltage (V)

RLX is the switch resistance (Ω)

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