Datasheet

Data Sheet
©2014
Würth Elektronik eiSos GmbH & Co. KG - REV 0.1
PRELIMINARY
11/ 21
172946001
MagI³C Power Module Product Family
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
Max. V
IN
(V)
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.
 Place C
IN
as close as possible to the V
IN
pin and GND exposed pad (EP).
 Place C
OUT
(optional for reduction of LED current ripple and EMI compliance) as close as possible to the
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 μF capacitor (C
OUT
) across the LED+ pin and LED- pin. This
will minimize the ripple current so that it can reduce radiated EMI.
LED driver module current loops
29D
C
IN
LED+
GND
LED-
Module
Loop 1
Loop 2
V
IN
High Power LED String
C
OUT
di/dt