ST1S14 STMicroelectronics, ST1S14 Datasheet - Page 15

• Manufacturer Part Number: ST1S14
• Description: Up to 3 A step down switching regulator
• Manufacturer: STMicroelectronics

ST1S14
6.1
G
The accurate control to output transfer function for a buck peak current mode converter can
be written as:
Equation 2
where R
sense circuitry, ω
ESR of the output capacitor.
F
error amplifier that introduces a double pole at one half of the switching frequency.
Equation 3
Equation 4
where:
Equation 5
S
external ramp (V
avoid sub-harmonic oscillations at duty cycle over 50%
The sampling effect contribution F
Equation 6
where:
Equation 7
H
n
CO
(s) accounts the sampling effect performed by the PWM comparator on the output of the
represents the on time slope of the sensed inductor current, S
(s) Control to output transfer function
0
represents the load resistance, R
G
CO
PP
p
s ( )
the single pole introduced by the LC filter and ω
peak to peak amplitude) that implements the slope compensation to
=
R
------ -
R
0
i
⋅
ω
--------------------------------------------------------------------------------------- -
1
n
+
Doc ID 17977 Rev 1
=
R
---------------------- -
Q
------------------------------------- -
R
0
H
P
⋅
LOAD
L
(s) is:
⎛
⎜
⎜
⎜
⎜
⎜
⎜
⎝
T
m
S
S
=
SW
ω
e
n
C
--------------------------------------------------------- -
π
Z
1
⋅
=
=
⋅
=
⋅
C
=
[
[
V
----------------------------- - R
m
V
m
OUT
1
1
-------------------------------
ESR C
i
IN
pp
C
C
+
the equivalent sensing resistor of the current
⋅
⋅
–
S
------
S
⋅
(
+
L
(
f
V
1 D
e
n
1 D
SW
⋅
1
1
m
---------------------------------------------
OUT
–
–
L C
C
OUT
⋅
⋅
) 0.5
) 0.5
(
⋅
–
–
1 D
OUT
–
i
]
]
⋅
) 0.5
⋅
f
–
SW
⎛
⎝
--------------------- - F
⎛
⎝
1
1
+
+
----- -
ω
------
ω
s
s
e
z
p
z
⎞
⎠
⎞
⎠
the on time slope of the
the zero given by the
⋅
H
s ( )
Closing the loop
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