Texas Instruments BQ24450EVM manual Introduction, EVM Features, General Description, O Description

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1 Introduction

1.1EVM Features

•Evaluation module for bq24450 (HPA691)

•Charge controller for lead-acid batteries

•Constant current and constant voltage modes

•Accommodates external transistor in DPAK or TO-220 package

•Programmable charge current

•Pre-Charge for deeply discharged batteries

1.2General Description

The bq24450 contains all the necessary circuitry to optimally control the charging of lead-acid batteries. The IC controls the charging current as well as the charging voltage to safely and efficiently charge the battery, maximizing battery capacity and life. Depending on the application, the IC can be configured as a simple constant-voltage float charge controller or a dual-voltage float-cum-boost charge controller.

The built-in precision voltage reference is especially temperature-compensated to track the characteristics of lead-acid cells, and maintains optimum charging voltage over an extended temperature range without using any external components. The low current consumption of the IC allows for accurate temperature monitoring by minimizing self-heating effects.

The IC can support a wide range of battery capacities and charging currents, limited only by the selection of the external pass transistor. The versatile driver for the external pass transistor provides at least 25mA of base drive.

In addition to the voltage- and current-regulating amplifiers, the IC features comparators that monitor the charging voltage and current. These comparators feed into an internal state machine that sequences the charge cycle. Some of these comparator outputs are made available as status signals at external pins of the IC. These status and control pins can be connected to a processor, or they can be connected up in flexible ways for standalone applications.

1.3I/O Description and Jumper Functions

		Table 1. I/O Description
Header			Description
J1	– Vin		Power Supply Positive
J2	– GND		Power Supply Negative
J3	– GND		Ground
J4	– Vout		Connected to Battery/System Load
J5	– GND		Ground

Jumper	Description See Functions and Features section for more information.
JP1	Connects ISNSM for current sense for ITAPER. It can connect ISNSM to either side of the sense
	resistor, R4.
JP2	Connects IFB for current sense for IMAX. It can connect IFB to either side of the sense resistor, R4.
JP3	Selects the topology for the external transistor. The external transistor can be configured for
	either Common-Emitter topology or Quasi-Darlington topology.

2	bq24450EVM	SLUU464 –November 2010
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