Datasheet

Functional description ST1S41
10/27 DocID023654 Rev 2
Equation 3
where:
Equation 4
S
n
represents the ON time slope of the sensed inductor current, S
e
the slope of the external
ramp (V
PP
peak-to-peak amplitude) that implements the slope compensation to avoid sub-
harmonic oscillations at duty cycle over 50%.
The sampling effect contribution F
H
(s) is:
Equation 5
where:
Equation 6
and
Equation 7
The resistor to adjust the output voltage gives the term from output voltage to the FB pin.
G
DIV
(s) is:
Equation 8
ω
p
1
R
LOAD
C
OUT
⋅
----------------------------------------
m
C
1D–()0.5–⋅
LC
OUT
f
SW
⋅⋅
------------------------------------------------+=
m
C
1
S
e
S
n
------
+=
S
e
V
pp
f
SW
⋅=
S
n
V
IN
V
OUT
–
L
----------------------------- -
R
i
⋅=
⎝
⎜
⎜
⎜
⎜
⎜
⎜
⎛
F
H
s()
1
1
s
ω
n
Q
P
⋅
----------------------
s
2
ω
n
2
-------++
----------------------------------------------=
Q
P
1
π m
C
1D–()0.5–⋅[]⋅
--------------------------------------------------------------- -=
ω
n
π f
SW
⋅=
G
DIV
s()
R
2
R
1
R
2
+
--------------------=