L5986 datasheet(23/39 Pages) STMICROELECTRONICS

Teilenummer	L5986

Bauteilbeschribung	2.5 A step-down switching regulator

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L5986 - L5986A

Application information

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6.4.2

Type II compensation network

If the equivalent series resistance (ESR) of the output capacitor introduces a zero with a

frequency lower than the desired bandwidth (that is: 2

π∗ESR∗COUT>1/BW), this zero helps

stabilize the loop. electrolytic capacitors show not negligible ESR (> 30 m

Ω), so with this

kind of output capacitor the type II network combined with the zero of the ESR allows

stabilizing the loop.

In Figure 12 the type II network is shown.

Figure 12.

Type II compensation network

The singularities of the network are:

In Figure 13 the bode diagram of the PWM and LC filter transfer function (GPW0 · GLC(f))

and the open loop gain (GLOOP(f) = GPW0 · GLC(f) · GTYPEII(f)) are drawn.

π R

⋅⋅

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

π R

⋅

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

⋅⋅

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L5986 Datenblatt(PDF) 23 Page - STMicroelectronics