STEVAL-ISA038V1 STMicroelectronics, STEVAL-ISA038V1 Datasheet - Page 19

• Manufacturer Part Number: STEVAL-ISA038V1
• Description: BOARD EVALUATION W/L6728
• Manufacturer: STMicroelectronics
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of STEVAL-ISA038V1

• Design Resources: STEVAL-ISA038V1 Schematic STEVAL-ISA038V1 Bill of Material
• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 1.25V
• Current - Output: 5A
• Voltage - Input: 5 ~ 12V
• Regulator Topology: Buck
• Frequency - Switching: 300kHz
• Board Type: Fully Populated
• Utilized Ic / Part: L6728
• Input Voltage: 5 V to 12 V
• Output Voltage: 1.25 V
• Product: Power Management Modules
• Silicon Manufacturer: ST Micro
• Silicon Core Number: L6728D
• Kit Application Type: Power Management - Voltage Regulator
• Application Sub Type: Step Down DC/DC Controller
• 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: L6728
• Other names: 497-8228; STEVAL-ISA038V1

L6728
11
11.1
Application information
Inductor design
The inductance value is defined by a compromise between the dynamic response time, the
efficiency, the cost and the size. The inductor has to be calculated to maintain the ripple
current (ΔI
value can be calculated with the following relationship:
Where F
voltage.
inductor, with V
Increasing the value of the inductance reduces the current ripple but, at the same time,
increases the converter response time to a dynamic load change. The response time is the
time required by the inductor to change its current from initial to final value. Until the inductor
has not finished its charging time, the output current is supplied by the output capacitors.
Minimizing the response time can minimize the output capacitance required. If the
compensation network is well designed, during a load variation the device is able to set a
duty cycle value very different (0 % or 80 %) from steady state one. When this condition is
reached, the response time is limited by the time required to change the inductor current.
Figure 9.
L
=
V
----------------------------- -
F
IN
SW
–
Figure 9
SW
V
⋅
L
ΔI
OUT
) between 20 % and 30 % of the maximum output current (typ). The inductance
is the switching frequency, V
Inductor current ripple vs output voltage
L
⋅
IN
V
--------------
V
shows the ripple current vs. the output voltage for different values of the
OUT
= 5 V and V
IN
IN
= 12 V.
IN
is the input voltage and V
Application information
OUT
is the output
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