Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsPMICsPMIC - battery management Charge management VRLA SOIC 16 Surface-mount

1516

EXT

External

Supply

ISNS

VRLA

Battery

ISNSP

COMP

ISNSM

IFB

DRVC

DRVE

PRE-CHG

VFB

STAT1

PGOOD

GND

COMP

STAT2

ISNS

BSTOP

bq24450

www.ti.com

SLUS929C –APRIL 2009– REVISED FEBRUARY 2012

INTEGRATED CHARGE CONTROLLER FOR LEAD-ACID BATTERIES

Check for Samples: bq24450

FEATURES

• Supports Different Configurations

• Minimum External Components

• Regulates Both Voltage and Current During

Charging

• Available in 16-Pin SOIC (DW)

• Precision Temperature-Compensated

APPLICATIONS

Reference:

– Maximizes Battery Capacity Over • Emergency Lighting Systems

Temperature

• Security and Alarm Systems

– Ensures Safety While Charging Over

• Telecommunication Backup Power

Temperature

• Uninterruptible Power Supplies

• Optimum Control to Maximize Battery Capacity

and Life

DESCRIPTION

The bq24450 contains all the necessary circuitry to optimally control the charging of valve-regulated 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 ICs low current consumption 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 supports both NPN and PNP types

and 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.

Figure 1. TYPICAL APPLICATION SCHEMATIC

A dual-level Float-cum-Boost Charger with Pre-Charge

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas

Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (22 pages)

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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com ELECTRICAL CHARACTERISTICS Over junction temperature range –40°C ≤ TJ ≤ 70°C, VIN = 10V, TJ = TA. (Positive currents are into, and negative currents out of, the specified terminal) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT INPUT UVLO Input power detected threshold VIN increasing from 0V to 5V 4.5 4.8 V VHYS-UVLO Hysteresis on UVLO VIN decreasing from 5V to 0V 4.2 200 300 mV VIN = 10V 1.6 3.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com IFB ISNSP ISNSM DRVC DRVE 12W Driver + 25 mV Q1 VIN ISNS + 250mV COMP Current Sense Comparator Current Limit VREF Voltage Loop VIN Q5 VREF IN VIN Voltage Reference o 2.3V at 25 C -3.5 mV/C VFB VVFB PRE-CHG Enable Comparator UVLO CE Q2 VIN Q3 VREF Q4 PGOOD Q7 VVFB S1 Voltage Sense Comparator S0 0.95VREF 0.90VREF STAT1 Q8 STAT2 R R Q L1 Q9 L2 S BSTOP Q S GN Figure 2.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com PIN FUNCTIONS PIN NO. NAME I/O DESCRIPTION 1 ISNS O Output of the current-sense comparator. Open-Collector. 2 ISNSM I Negative input of the current-sense comparator. 3 ISNSP I Positive input of the current-sense comparator. 4 IFB I Input for the current-regulating loop. External resistor between IN and IFB sets the charging current value. 5 IN I Supply voltage pin. Connect to external DC source.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com TYPICAL OPERATING PERFORMANCE Compensated Voltage Reference vs Temperature 2.6 2.5 VREF - Voltage Reference − V VIN = 10V Specified Error Band 2.4 2.3 2.2 Specified Error Band 2.1 2 -40 -30 -20 -10 0 10 20 30 40 50 60 70 o T − Temperature − C Figure 3.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com DETAILED FUNCTIONAL DESCRIPTION The bq24450 contains all the necessary circuitry to optimally control the charging of sealed 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.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com DETAILED OPERATION AND APPLICATION INFORMATION A Simple Dual-Level Float-Cum-Boost Charger Figure 4 shows the bq24450 configured as a simple dual-level float-cum-boost charger. Figure 5 shows the sequence of events that occur in a normal charge cycle. At (1) in Figure 5, power is switched ON. As long as the input voltage VIN is below the undervoltage lockout threshold UVLO, Q2 is ON, disabling the driver transistor Q1.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com As charging proceeds, the voltage at the VFB pin increases further to VREF. At this point, the voltage regulating amplifier prevents the voltage at the VFB pin from rising further, maintaining the battery voltage at VBOOST. [(4) in Figure 4]. VBOOST = VREF × (RA + RB//RC ) ÷ RB//RC ICHG keeps flowing into the battery.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com An Improved Dual-Level Float-Cum-Boost Charger with Pre-Charge The problem with the charger circuit shown in Figure 4 is that even with deeply discharged batteries, charging starts at full current level IMAX-CHG. This can sometimes be hazardous, resulting in out-gassing from the battery. The bq24450 can be configured to pre-charge the battery till the voltage levels rise to levels safe enough to permit charging at IMAX-CHG.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com 1 2 VIN IMAX-CHG ICHG ITAPER IPRE VBOOST VBI VFLOAT VRCH VTH VBAT Figure 7. Further Improvements to the Circuit of Figure 6 In applications where the load current is low, the current through the VBAT voltage divider can be a non-negligible proportion of the load current. Current flowing back thorough QEXT when the input power is removed constitutes another drainage path. The modifications in Figure 8 fix both these issues.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com RISNS DEXT QEXT ICHG VBAT External Supply ISNSP ISNSM 3 ISNS IFB 2 DRVC 4 1 RT 15 COMP Q1 250mV 14 + + 25mV Q6 RA DRVE 16 VRLA Battery VREF 13 Q5 RB VFB 11 PRE-CHG RC VREF IN Voltage Reference 5 12 Q2 VIN CE Q3 VREF Q4 7 Q7 10 8 BSTOP STAT1 RD Q8 0.95VREF Charging State Logic 9 Q9 0.90VREF VVFB 6 GND Figure 8.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com Selecting the External Pass Transistor All the examples so far have used a PNP transistor for the external pass element. But the driver transistor in the bq24450 can be configured to drive many different types of pass transistors. This section will look at some of the different configurations that are possible. In all configurations, though, these factors hold: 1.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com External Quasi-Darlington IMAX-CHG range: 0.6A to 15A Minimum ΔV: 1.2V VIN RP = (VIN(MIN) – 0.7 V) ÷ IMAX-CHG × hFE1(MIN)hFE2(MIN) PD = (VIN(MAX) – 0.7 V) ÷ (hFE1 × hFE2) × IMAX-CHG – (IMAX-CHG)2 ÷ (hFE1 × hFE2)2 × RP CCOMP = 0.22μF with 470Ω series resistor to GND VOUT Q2 Q1 DRVC 16 Q1 15 DRVE RP NPN Emitter-Follower IMAX-CHG range: 25mA to 1000mA Minimum ΔV: 2.7V VIN QEXT VOUT RP RP = (VIN(MIN) – VOUT(MAX) – 1.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com RISNS DEXT QEXT SLA Battery External Supply 3 2 5 IN 1 ISNS RT 16 4 ISNSP ISNSM IFB DRVC PRE-CHG 11 RA CE 12 8 9 RB VFB 13 bq24450 RD BSTOP STAT1 10 STAT2 GND COMP DRVE 6 14 15 CCOMP PGOOD 7 RC RP Figure 10. The first step is to decide on the value of the current in the voltage divider resistor string in FLOAT mode.
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bq24450 SLUS929C – APRIL 2009 – REVISED FEBRUARY 2012 www.ti.com REVISION HISTORY NOTE: Page numbers of previous versions may differ from current version. Changes from Original (April 2009) to Revision A Page • Deleted PDIP package option from Features ....................................................................................................................... 1 • Deleted PDIP package from Ordering Information table ...........................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 TAPE AND REEL INFORMATION *All dimensions are nominal Device BQ24450DWTR Package Package Pins Type Drawing SOIC DW 16 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2000 330.0 16.4 Pack Materials-Page 1 10.75 B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 10.7 2.7 12.0 16.
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PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) BQ24450DWTR SOIC DW 16 2000 367.0 367.0 38.
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IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46C and to discontinue any product or service per JESD48B. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.