LED5000 datasheet(17/52 Pages) STMICROELECTRONICS

部件名	LED5000

功能描述	3 A monolithic step-down current source with dimming capability

PDF	52 Pages

Scroll/Zoom	100%

制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

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17 / 52 page

LED5000

Application notes - buck conversion

Doc ID 023951 Rev 1

17/51

Figure 9.

Load equivalent circuit

As a consequence the LED equivalent circuit gives the

αLED(s) term correlating the output

voltage with the high impedance FB input:

Equation 13

5.5

Total loop gain

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

Equation 14

5.6

Compensation network design

The maximum bandwidth of the system can be designed up to fSW/6 to guarantee a valid

small signal model.

Equation 15

where

P (Equation 3) is the pole introduced by the power components. The following

calculations are valid in the hypothesis that BW >

P which is the typical condition.

VIN

Rd1

COUT

Rd2

Dled1

COUT

VIN

Dled2

AM13493v1

LED nLED

()

SENSE

LED

SENSE

⋅

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

()

CO s

() A

0 s

() α

LED nLED

()

⋅⋅

⋅

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

MAX

≤

---------

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