Datasheet

16 Atmel LED Driver-MSL3162
Using Multiple Atmel LED Driver-MSL3162s to Control a Single Power Supply
To use multiple MSL3162s to control a single power supply, connect the FBOx output of one MSL3162 to the FBIx input
of another MSL3162 to form a chain(Figure 6). The Efficiency Optimizer decides whether the current at the FBIx input
is less than what the FBOx output is programmed to. If the FBIx current is less than the programmed current, the FBIx
current is transferred to the FBOx output. Otherwise, the programmed current is used at FBOx. The power supply output
is, therefore, programmed to the minimum voltage required by all MSL3162s controlling it, and so all LED strings have
sufficient voltage to maintain current regulation and power supply noise rejection.
Figure 6. Cascade Multiple Atmel LED Driver-MSL3162s
to Control a Common Power Supply
The accuracy of the FBOx output current can degrade through each link of the FBIx/FBOx chain by as much as 2%.
Therefore, the maximum output voltage correction current can drop by 2% per link. Calculate the worst-case FBOx
current by the equation:
( )
1
)/(
98.0*45
−
=
N
MINMAXFBOx
µAI
where I
FBOx(MAX/MIN)
is the worst-case (minimum) maximum FBOx output current, and N is the number of MSL3162 FBIx/
FBOx I/Os connected in series.
Take care in laying out the traces for the Efficiency Optimizer FBIx/FBOx I/Os. If the FBIx input is not used, connect it
to GND as close to the MSL3162 as possible. When routing the FBIx/FBOx signals across circuit boards, minimize the
trace length as much as possible. Do not route the traces close to other traces with large variations in voltage or current
because such traces may couple noise into the FBIx/FBOx I/Os. If these traces must be routed near noisy signals, shield
them from noise by use of ground planes or guard traces.