L7987 datasheet(26/37 Pages) STMICROELECTRONICS

Nome de Peças	L7987

Descrição Electrónicos	Adjustable current limitation

PDF	37 Pages

Scroll/Zoom	100%

Fabricante Electrônico	STMICROELECTRONICS [STMicroelectronics]

Página de início	http://www.st.com

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26 / 37 page

Application information

L7987

26/37

DocID025589 Rev 3

After choosing the regulator bandwidth (typically FBW < 0.2 • FSW) and a value for RU,

usually between 1 k

 and 50 k, in order to achieve CF and CP not comparable with

parasitic capacitance of the board, the RF required value is computed by Equation 22.



Select CF in order to place FZ1 below FLC (typically 0.1 • FLC)



Select CP in order to place FP1 at 0.5 • FSW

Equation 23

The resultant control loop and other transfer functions gain are shown in Figure 12.

Figure 12. Type II compensation - bode plot

5.4.2

Type III compensation network

If FzESR is higher than the target loop bandwidth, as usually happens if the output filter is

based on MLCC ceramic capacitors, a type III compensation network must be designed.

 R

0.1 fLC



------------------------------------------------ CP

;

 R

0.5 fSW



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

L7987 Folha de dados(PDF) 26 Page - STMicroelectronics