Datasheet

15Atmel LED Driver-MSL2100
Figure 5. Cascade Multiple Atmel LED Driver-MSL2100s to Control a Common Power Supply
Using Multiple Atmel LED Driver-MSL2100s
to Control a Single Power Supply
Cascade multiple MSL2100 devices into a chain
configuration (Figure 5) with the FBIn of one device
connected to the FBOn of the next. Connect the first
FBOn to the power supply feedback resistor node
through a CMPSH-3 or similar Schottky diode, and the
unused FBIn input to ground as close to the MSL2100
as possible. The chained devices work together to
ensure that the system operates at optimum efficiency.
Note that the accuracy of the feedback chain has the
potential to degrade through each link of the FBIn/FBOn
chain by as much as 2%. Determine the worst case
maximum FBOn current, I
FBOn(MAX/MIN)
, using:
I
FBOn(MAX / MIN)
= 45µA* (0.98)
N-1
,
where N is the number of MSL2100s connected
in series. Use this result in the above R
TOP
resistor
equation for the term I
FBOn(MAX)
instead of using the
45µA figure shown here.
Take care in laying out the traces for the Efficiency
Optimizer connections. Minimize the FBIn/FBOn trace
lengths as much as possible. Do not route the signals
close to traces with large variations in voltage or current
because noise may couple into FBIn. If these traces must
be routed near noisy signals, shield them from noise by
using ground planes and/or guard traces.
Atmel LED Driver-MSL2100
8-string, High-power, White or RGB LED Drivers for TVs,
Monitors, or Intelligent Solid-state Lighting