Data Sheet

©2014

Würth Elektronik eiSos GmbH & Co. KG - REV 0.1

PRELIMINARY

11/ 21

172946001

LDHM - LED Step Down High Current Module

Minimum Switch On-Time

The on-time of the internal switch should be no shorter than 400 ns. The number of LED (typical forward voltage at

3.2 V) to input voltage is constrained by that as shown in the following table.

No. of LED

1

2

3

4

5

6-16

10

20

30

40

50

60

Step 2. Layout consideration

The overall performance of the LED driver module highly depends on the PCB layout. Poor board layout can disrupt

the performance of the LED driver module and surrounding circuitry by contributing to EMI, ground bounce and

resistive voltage drop in the traces. These can send incorrect signals to the LED driver module resulting in poor

regulation and stability. Good layout can be implemented by following a few simple design rules.





VLED+ pin and VLED- pin.



The exposed pad (EP) must be connected to the GND pin directly.

Step 3. EMI design considerations

From an EMI reduction standpoint, it is imperative to minimize the di/dt current paths (refer to LED driver module

current loops). Therefore, it is essential to connect an 2.2

will minimize the ripple current so that it can reduce radiated EMI.

LED driver module current loops

29D

LED+

GND

LED-

Module

Loop 1

Loop 2

High Power LED String

di/dt