LED2472G datasheet(26/39 Pages) STMICROELECTRONICS

26 / 39 page

Current adjustment

LED2472G

26/39

DocID024620 Rev 3

Current adjustment

The LED2472G is designed to provide a current in the range between 4 mA and 72 mA per

channel. The current is programmed for all color groups by connecting an external resistor

(see Figure 15) to the pin ISET and then adjusted separately for each color by the gain

CFG-1, CFG-2 of the configuration register (respectively, for RED, GREEN and BLUE). The

current for each color can be adjusted in 64 steps using 6 bits (per color) contained in the

gain register.

Figure 15. External resistor to connect to ISET pin

When the device is switched on, the default value of the gain register together with the bits

of the configuration register selecting the current range set a current value that can be

calculated as follows:

Where VREF ≈ 1.23 V is the voltage of the ISET pin and K is the mirroring current ratio,

whose value depends on the selected current range:

K = 55 with low current range selected (CFG-0, CFG-1 or CFG-2 set to “0”)

K = 160 with high current range selected (CFG-0, CFG-1 or CFG-2 set to “1”)

The relationship between the programmed current and the current gain settings is the

following:

where G is the current gain (decimal value) defined by the dedicated bits of the current gain

ΔI

step can be instead defined as follows:

EXT

REF

default

⋅

)

(

step

default

⋅

LED2472G 数据表(PDF) 26 Page - STMicroelectronics