March 2013

DocID022816 Rev 2

1/19

AN4050

Application note

STEVAL-ISV012V1: lithium-ion solar battery charger

By Domenico Ragonese, Alessandro Nicosia and Giovanni Conti

Introduction

The STEVAL-ISV012V1 is a demonstration board that mounts the SPV1040 (solar energy

harvester) as the input stage and the L6924D (Li-Ion battery charger) as the output stage. It

targets any portable application powered by lithium-ion batteries and merges the capability

of the SPV1040 to maximize the power extraction from the solar module with the linear

regulation of the L6924D, to optimize the battery charge and to protect the load while

reducing the power dissipation at the bottom. It is shown in

Figure 1.

Figure 1. STEVAL-ISV012V1 demonstration board

The board has been designed to charge lithium-ion and lithium-polymer batteries with

VBATT_max = 4.1 or 4.2 V and it includes a 400 mW

pk

polycrystalline PV panel

(SZGD6060-4P from NBSZGD) with V

oc

= 2.2 V and I

sc

= 220 mA.

According to specific application requirements, some components may be replaced as per

the following guidelines:

•

The PV panel can be replaced by a different one as long as V

oc

< VBATT_max and I

sc

< 1.65 A.

•

The inductor L1 can be replaced by considering that it affects the maximum peak

current and that an input overcurrent limit must not be triggered.

•

The maximum output current can be limited by replacing the current sensing resistor

Rs (0

Ω by default).

•

The resistor R14, which limits the charge current threshold, by default is set to 500 mA.

For further details on component selection, please refer to the section “external component

selection” of the AN3319 application note. For details about SPV1040 and L6924D features

please refer to the related datasheets.

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