EVALA5970D STMicroelectronics, EVALA5970D Datasheet - Page 14

• Manufacturer Part Number: EVALA5970D
• Description: Power Management Modules & Development Tools EVAL BOARD A5970D Auto Grade
• Manufacturer: STMicroelectronics
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of EVALA5970D

• Input Voltage: 4.4 V to 36 V
• Output Voltage: 1.235 V to 35 V
• Board Size: 23 mm x 20 mm
• Product: Power Management Modules
• Supply Current: 1 A
• Dimensions: 23 mm x 20 mm
• For Use With/related Products: AN1330
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Closing the loop
4.3
14/31
Equation 7
The zero of this transfer function is given by:
Equation 8
F
increase the phase margin of the loop.
The poles of the transfer function can be calculated through the following expression:
Equation 9
In the denominator of A
Equation 10
If the damping coefficient δ is very close to zero, the roots of the equation become a double
root whose value is ω
Similarly, for A
Equation 11
PWM comparator
The PWM gain is given by the following formula:
Equation 12
where V
minimum value. A voltage feed forward is implemented to ensure a constant GPWM. This is
obtained by generating a sawtooth waveform directly proportional to the input voltage V
Equation 13
Where K is equal to 0.076. Therefore the PWM gain is also equal to:
Equation 14
0
is the zero introduced by the ESR of the output capacitor and it is very important to
OSCMAX
LC
is the maximum value of a sawtooth waveform and V
the poles can usually be defined as a double pole whose value is:
F PLC1 2
n
.
LC
A
,
LC
the typical second order system equation can be recognized:
s ( )
=
G
–
------------------------------------------------------------------------------------------------------------------------------------------
PWM
V
ESR C OUT
=
OSCMAX
F
F
--------------------------------------------------------------------------------------------- -
L C
G
PLC
O
s
s ( )
•
•
2
PWM
=
+
=
OUT
2 δ
=
--------------------------------------------------- -
2 π
–
s ( )
•
-------------------------------------------------------------
(
•
1
--------------------------------------------- -
2 π
V
V
±
+
•
OSCMIN
•
OSCMAX
•
•
=
s
ESR C
ω
(
2
2 L
ESR
ESR C OUT
•
--- -
K
1
n
+
•
1
•
ESR C
1
=
L C
s
•
•
V
•
•
C OUT
•
+
=
const
–
cc
C
OUT
ω
V
K V
•
OUT
OUT
OSCMIN
2
•
n
OUT
•
)
2
CC
s
–
•
4 L
)
s
•
+
•
1
C OUT
OSCMIN
is the
AN1330
CC
.