Datasheet

Application notes ST1CC40
12/37 DocID18279 Rev 5
6 Application notes
6.1 Closing the loop
Figure 5. Block diagram of the loop
6.2 G
CO
(s) control to output transfer function
The accurate control to output transfer function for a buck peak current mode converter can
be written as:
Equation 1
where R
0
represents the load resistance, R
i
the equivalent sensing resistor of the current
sense circuitry, 
p
the single pole introduced by the LC filter and 
z
the zero given by the
ESR of the output capacitor.
F
H
(s) accounts for the sampling effect performed by the PWM comparator on the output of
the error amplifier that introduces a double pole at one half of the switching frequency.
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G
CO
s
R
0
R
i
------ -
1
1
R
0
T
SW

L
----------------------- m
C
1D–0,5–+
----------------------------------------------------------------------------------------
1
s

z
------+


1
s

p
------+


---------------------- F
H
s=