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1 Introduction
1.1 EVM 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
1.2 General 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.
1.3 I/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
spacer
Jumper Description See Functions and Features section for more information.
JP1 Connects I
SNSM
for current sense for I
TAPER
. It can connect I
SNSM
to either side of the sense
resistor, R4.
JP2 Connects I
FB
for current sense for I
MAX.
It can connect I
FB
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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