L7986TA datasheet(24/43 Pages) STMICROELECTRONICS

tên linh kiện	L7986TA

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Application information

L7986TA

24/43

Doc ID 022098 Rev 3

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 non-negligible ESR (>30 m

Ω), so with this

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

stabilize the loop.

In Figure 12 the type II network is shown.

Figure 12.

Type II compensation network

The singularities of the network are:

Equation 29

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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