STEVAL-ISA043V2 STMicroelectronics, STEVAL-ISA043V2 Datasheet - Page 4

• Manufacturer Part Number: STEVAL-ISA043V2
• Description: BOARD EVAL BASED ON ST1S06
• Manufacturer: STMicroelectronics

Specifications of STEVAL-ISA043V2

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 3.3V
• Current - Output: 1.5A
• Voltage - Input: 2.7 ~ 6V
• Regulator Topology: Buck
• Frequency - Switching: 1.5MHz
• Board Type: Fully Populated
• Utilized Ic / Part: ST1S06
• Product: Power Management Modules
• Silicon Manufacturer: ST Micro
• Silicon Core Number: ST1S06PUR
• Kit Application Type: Power Management - Voltage Regulator
• Application Sub Type: Synchronous Buck Converter
• Kit Contents: Board
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 497-6420; STEVAL-ISA043V2

Selecting components for your application
1
1.1
4/12
Selecting components for your application
This section provides information to help you select the best-adapted components for your
application.
Figure 1.
Input capacitor
The input capacitor must be able to support the maximum input operating voltage and the
maximum RMS input current.
Since step-down converters draw current from the input in pulses, the input current is
squared and the height of each pulse is equal to the output current. The input capacitor has
to absorb all this switching current that can be up to the load current divided by two (worst
case, with duty cycle of 50%).
For this reason, the quality of these capacitors must be very high to minimize the power
dissipation generated by the internal ESR, thus improving system reliability and efficiency.
The critical parameter is usually the RMS current rating that has to be higher than the RMS
input current. The maximum RMS input current (flowing through the input capacitor) is:
Equation 2
where η is the expected system efficiency, D is the duty cycle and I
This function reaches its maximum value at D = 0.5 and the equivalent RMS current is equal
to I
O
divided by 2 (considering η = 1).
Simplified schematic
I
RMS
=
I
O
⋅
D 2
–
-----------------
⋅
η
D
2
+
D
------ -
η
2
O
the output DC current.
AN2371