BQ25171-Q1 Quick Start Guide

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1 Introduction

The following sections first provide an overview of the external parts required to configure the device, then three reference circuit designs are introduced: 700-mA/70-mA Variable Charge Li-Ion Fast Charge, 200-mA NiMH Time Charge, and 45-mA LiFePO4 Fast Charge. These designed can be implemented as is or modified to meet your design specifications. Note this is a simple explanation of the device and descriptions are brief. For a full explanation of the device and its features refer to the BQ25171-Q1 data sheet.

2 BQ25171-Q1 Design Decisions

The device requires a minimum number of external parts to implement a charging solution. The standard solution only requires the selection of three external resistors to configure the device to given charge specifications.

CHM_TMR – Resistor value to select battery chemistry and charge timer, see table 7-1 in Data sheet.
VSET – Resistor value to program charge voltage and enable optional intermittent charge (for NiMH only), see table 7-2 in Data sheet.
ISET – Resistor value to set fast charge current, see Table 7-1 in this application note.
Other connections:
1. TS – NTC to monitor battery temperature, typically 10 kΩ.
2. Cin and Cout – 1 µF effective capacitance connection to ground at both IN and OUT
3. STAT1 and STAT2 – Open collector status outputs (optional connections)
4. /CE – Charge enable input (optional connection)