LED7707 datasheet(20/48 Pages) STMICROELECTRONICS

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Operation description

LED7707

20/48

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 (RRILIM) 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 KR = 1850 V.

The graph in Figure 13 better shows the relationship between IROW and RRILIM and helps to

choose the correct value of the resistor to set the desired row current.

Figure 13.

Row current vs RRILIM

The maximum current mismatch between the rows is ± 2 % @ Irowx = 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

ROWx

AM00590v1

LED7707 数据表(PDF) 20 Page - STMicroelectronics