Functional description

ST1S40

10/30

Doc ID 17928 Rev 4

Equation 6

and

Equation 7

The resistor to adjust the output voltage gives the term from output voltage to the FB pin.

The transfer function from FB to Vcc (output of E/A) introduces the singularities (poles and

zeroes) to stabilize the loop. Figure 5 shows the small signal model of the error amplifier

with the internal compensation network.

Figure 5.

Small signal model for the error amplifier

system stability and can be neglected.

Equation 8

Q

P

1

π m

C

1D

–

() 0,5

–

⋅

[]

⋅

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

=

ω

n

π f

SW

⋅

=

G

()

R

2

R

1

R

2

+

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

=

G

()

G

EA0

1s

+

R

c

C

c

⋅⋅

()

⋅

s

2

R

0

C

0

C

p

+

() R

c

C

c

sR

0

C

c

⋅

R

0

C

0

C

p

+

() R

c

C

c

⋅

+

⋅

+

() 1

+

⋅

+

⋅⋅

⋅

⋅

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

=