Datasheet

LED7707 Operation description
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5.2 Backlight driver section
5.2.1 Current generators
The LED7707 is a LEDs driver with six channels (rows); each row is able to drive multiple
LEDs in series (max. 36 V) and to sink up to 85 mA maximum current, allowing to manage
different kinds of LEDs.
The LEDs current can be set by connecting an external resistor (R
RILIM
) between the RILIM
pin and ground. The voltage across the RILIM pin is internally set to 1.23 V and the rows
current is proportional to the RILIM current according to the following equation:
Equation 9
Where K
R
= 1850 V.
The graph in
Figure 13 better shows the relationship between I
ROW
and R
RILIM
and helps to
choose the correct value of the resistor to set the desired row current.
Figure 13. Row current vs R
RILIM
The maximum current mismatch between the rows is ± 2 % @ I
rowx
= 60 mA.
The LED7707 allows parallelism different rows if required by the application. If the maximum
current provided by a single row (85 mA) is not enough for the load, two or more current
generators can be connected together, as shown in
Figure 14. To keep the parallelism
generators stable, the row current should be higher than 40 mA.The connection between
channels in parallel must be done as close as possible to the device in order to minimize
parasitic inductance.
RILIM
R
ROWx
R
K
I =
AM00590v1