AN2823 datasheet(24/33 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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24 / 33 page

The L5973AD in LED driving applications

AN2823

24/33

Doc ID 15015 Rev 1

and it is plotted in Figure 24.

Figure 23.

αLED(s) plot

K(s) represents the transfer function of the block implemented through the external amplifier

(see Figure 24). The external error amplifier bandwidth is 0.8 MHz, so the correction term of

the ideal gain is introduced into the calculations to obtain a better analytical description of

the real transfer function of the block.

Equation 34

Figure 24.

Equivalent circuit of block K(s)

()

2 s

()

1 s

()

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

loop_EA s

()

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

–

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

2 s

()

1 s

()

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

1 s

() Z

2 s

()

EA s

()

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

1 s

()

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

⋅

⎝⎠

⎛⎞

–

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

AM01374v1

LED1

LED2

LEDn

Rsense

To L5973AD pin 5

AN2823 Datasheet(PDF) 24 Page - STMicroelectronics

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