AN2823 datasheet(14/33 Pages) STMICROELECTRONICS

Part #	AN2823

Description	Current source for LED driving based on the L5973AD

PDF	33 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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14 / 33 page

The L5973AD in LED driving applications

AN2823

14/33

Doc ID 15015 Rev 1

As a consequence, the term

αLED(s) can be calculated as:

Equation 12

and considering RSENSE << (R1+R6) the equation can be simplified as follows:

Equation 13

The term is plotted as a function of the LED composing the row and the biasing current, as

shown in Figure 13.

Figure 13.

αLED(s) plot

The power components, their stray contributions and the load constitute the equivalent

circuit of the power stage shown in Figure 14.

LED nLED

()

SENSE

LED

SENSE// R1

()

⋅

---------------------------------------------------------------------------------------

SENSE

------------------------------------------------

⋅

LED nLED

()

SENSE

LED

SENSE

⋅

----------------------------------------------------------

--------------------

⋅

≈

AN2823 Datasheet(PDF) 14 Page - STMicroelectronics