Document Number: 002-08404 Rev *A

Page 21 of 40

MB39C831

9. Application Notes

Inductor

The MB39C831 is optimized to work with an inductor in the range of 4.7 µH. Select a value of 4.7 µH. Also, select an inductor

with a DC current rating which can permit the peak current for the inductor.

The peak current for the inductor in steady state operation (ILMAX) can be calculated by the following equation according to

Harvester (Photovoltaic Power Generator)

In case of photovoltaic (or solar) energy harvesting, use a solar cell with an open-circuit voltage less than 4.75V and the preset

output voltage. Electric power obtained from a solar or light is increased in proportion to the ambient illuminance.

Silicone-based solar cells are single crystal silicon solar cell, polycrystalline silicon solar cell, and amorphous silicon solar cell.

Organic-based solar cells are dye-sensitized solar cell (DSC), and organic thin film solar cell. Crystal silicon and polycrystalline

silicon solar cells have high energy conversion efficiency. Amorphous silicon solar cells are lightweight, flexible, and produced

at low cost. Dye-sensitized solar cells are composed by sensitizing dye and electrolytes, and are low-cost solar cell. Organic

thin film solar cells are lightweight, flexible, and easily manufactured.

Harvester (Temperature Difference Power Generator)

Temperature difference power generators produce electric power keeping temperature difference between the high

temperature side and the low temperature side. The temperature difference power generators include the peltier elements

utilizing the Seebeck effect and thermopiles that made of thermocouples in series or in parallel.

Sizing of Input and Output Capacitors

Common capacitors are layered ceramic capacitor, electrolytic capacitor, electric double layered capacitor (EDLC), and so on.

Electrostatic capacitance of layered ceramic capacitors is relatively small. However, layered ceramic capacitors are small and

have high voltage resistance characteristic. Electrolytic capacitors have high electrostatic capacitance from µF order to mF

order. The size of capacitor becomes large in proportion to the size of capacitance. Electric double layered capacitors have

high electrostatic capacitance around 0.5F to 1F, but have low voltage resistance characteristics around 3V to 5V. Be very

careful with a voltage resistance characteristic. Also, leak current, equivalent series resistance (ESR), and temperature

characteristic are criteria for selecting,

Table 9-1 Manufactures of Capacitors

Part Number/Series Name

Type, Capacitance

Manufacture

EDLC351420-501-2F-50

EDLC, 500 mF

TDK Corporation

EDLC082520-500-1F-81

EDLC, 50 mF

EDLC041720-050-2F-52

EDLC, 5 mF

Gold capacitor

EDLC

Panasonic Corporation

Energy from harvester should be stored on the Cin and Cout to operate the application block. If the size of these capacitors

were too big, it would take too much time to charge energy into these capacitors, and the system cannot be operated

frequently. On the other hand, if these capacitors were too small, enough energy cannot be stored on these capacitors for the

application block. The sizing of the Cin and Cout is important.