A6985F datasheet(41/77 Pages) STMICROELECTRONICS

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A6985F

Closing the loop

Equation 26

whereas the zero is defined as:

Equation 27

6.3

Voltage divider

6.3.1

Internal voltage divider

In the A6985F3V3 and A6985F5V, the voltage divider contribution is equal to:

Equation 28

6.3.2

External voltage divider

In the A6985F the simple voltage divider contribution is:

Equation 29

A small signal capacitor in parallel to the upper resistor (see Figure 29) of the voltage divider

implements a leading network (fzero < fpole), sometimes necessary to improve the system

phase margin.

Figure 29. Leading network example

fPHF

 R

C0 Cp





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

 R



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

GDIV s

 G

DIV INT





VREF

VOUT

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

0.85

3.3

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

0.2576

0.85

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

0.17

A6985F3V3

A6985F5V

GDIV s



R1 R2

-------------------- GDIV INT





R1 R2

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



A6985F

A6985F 数据表(PDF) 41 Page - STMicroelectronics

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