EVAL5985 STMicroelectronics, EVAL5985 Datasheet - Page 20

• Manufacturer Part Number: EVAL5985
• Description: BOARD EVAL FOR L5985
• Manufacturer: STMicroelectronics
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of EVAL5985

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 3.3V
• Current - Output: 2A
• Voltage - Input: 3.3 ~ 18V
• Regulator Topology: Buck
• Frequency - Switching: 500kHz
• Board Type: Fully Populated
• Utilized Ic / Part: L5985
• Input Voltage: 2.9 V to 18 V
• Output Voltage: 0.6 V to 16 V
• Product: Power Management Modules
• Silicon Manufacturer: ST Micro
• Silicon Core Number: L5985
• Kit Application Type: Power Management - Voltage Regulator
• Application Sub Type: Step Down Switching Regulator
• Kit Contents: Board
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: L5985
• Other names: 497-6387; EVAL5985

Application information
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Figure 11. Open loop gain: module Bode diagram
The guidelines for positioning the poles and the zeroes and for calculating the component
values can be summarized as follow:
1.
2.
Equation 18
where K is the feed forward constant and 1/K is equals to 9.
3.
Equation 19
4.
Equation 20
5.
Equation 21
Choose a value for R
Choose a gain (R
Calculate C
Calculate C
Set also the first pole at four times the system bandwidth and also the second zero at
the output filter double pole:
4
5
by placing the zero at 50% of the output filter double pole frequency (f
by placing the second pole at four times the system bandwidth (BW):
4
/R
R
1
1
) in order to have the required bandwidth (BW), that means:
, usually between 1 k and 5 k.
3
=
-------------------------- -
4 BW
----------------- 1
Doc ID 13006 Rev 5
⋅
f
C
LC
5
R
1
=
–
R
------------------------------------------------------------- -
2π R
C
4
4
,
⋅
=
=
BW K
----------------- - R
4
-------------------------- -
π R
⋅
f
⋅
LC
C
⋅
C
C
4
1
4
4
⋅
3
⋅
4 BW
⋅
=
f
LC
⋅
---------------------------------------- -
2π R
1
⋅
–
3
1
1
⋅
4 BW
⋅
L5985
LC
):