AMG-LL75x
High Efficiency Step Down LED Driver for High Brightness LED and OLED
8.4. Application Notes
a)
Connecting the LEDs
The maximum of LEDs that can be driven by the AMG-LL75x depends on the supply
voltage and the combined forward voltage of the LEDs. Input voltage needs to be
approximately 2.5V higher than the total forward voltage of the LED string for the proper
operation.
b) Reducing Output Ripple
To reduce output ripple and possibly reducing EMC problems a capacitor maybe put
parallel to the LEDs, preferably connected direct between LEDa and LEDk of the AMG-
LL75x. The 200mA low ripple version comes equipped with a capacitor installed on the
module to optimize it for use with OLED.
c) EMC
The AMG-LL75x has been designed to produce a minimal level of EM emissions. As a
component this product cannot be EMC approved.
d) Brightness Control
The MOD input allows PWM dimming of the LEDs. By applying a voltage >1V≤Vin the
current to the LEDs is shut off. Frequencies up to about 1kHz can be applied to the MOD
input, though for good regulator stability it is recommended not to exceed 500Hz.
Dimming ranges of about 1% to 100% are possible.
e) Regulator Efficiency
The regulator efficiency depends on a number of parameters. Since there are a couple
constant losses independent of the total power delivered by the regulator the basic rule is
that the regulator is more efficient when used at high power (e.g. more LEDs connected).
A lower difference between input and output voltage does also increase efficiency.
AMG-LL75x
Revision: A
28. Mar. 2012
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