LED2000PUR datasheet(17/40 Pages) STMICROELECTRONICS

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LED2000

Application notes

As a consequence, the LED equivalent circuit gives the

LED(s) term correlating the output

voltage with the high impedance FB input:

Equation 14

6.5

Total loop gain

In summary, the open loop gain can be expressed as:

Equation 15

Example 1

Design specification:

VIN = 12 V, VFW_LED = 3.5 V, nLED = 2, rLED = 1.1 , ILED = 700 mA, ILED RIPPLE = 2%

The inductor and capacitor value are dimensioned in order to meet the ILED RIPPLE

specification (see Section 7.1.2 for output capacitor and inductor selection guidelines):

L = 10

H, COUT = 2.2 F MLCC (negligible ESR)

Accordingly, with Section 7.1.1 the sensing resistor value is:

Equation 16

Equation 17

The gain and phase margin Bode diagrams are plotted respectively in Figure 9 and

Figure 10.



LED nLED



RSENSE

nLED rLED RSENSE



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



GCO s

 A

0 s

 

LED nLED





100 mV

700 mA

--------------------- 140 m







LED nLED



RSENSE

nLED rLED RSENSE



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

140 m



21,1





140 m



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

0,06

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