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Texas Instruments
Texas Instruments

BQ24751A Datasheet

Host-controlled Multi-Chemistry Battery Charger


BQ24751A Datasheet Preview


www.ti.com
bq24751A
SLUS756 – SEPTEMBER 2007
Host-controlled Multi-Chemistry Battery Charger With System Power Selector, AC
Over-Power Protection, Programmable OVP and Low Iq
FEATURES
1
NMOS-NMOS Synchronous Buck Converter
with 300 kHz Frequency and >95% Efficiency
30-ns Minimum Driver Dead-time and 99.5%
Maximum Effective Duty Cycle
High-Accuracy Voltage and Current Regulation
– ±0.5% Charge Voltage Accuracy
– ±3% Charge Current Accuracy
– ±3% Adapter Current Accuracy
– ±2% Input Current Sense Amp Accuracy
Integration
– Automatic System Power Selection From
AC/DC Adapter or Battery
– Internal Loop Compensation
– Internal Soft Start
Safety
– Programmable Input Overvoltage
Protection (OVP)
– Dynamic Power Management (DPM) with
Status Indicator
– Programmable Inrush Adapter Power
(ACOP) and Overcurrent (ACOC) Limits
– Reverse-Conduction Protection Input FET
Supports Two, Three, or Four Li+ Cells
5 – 24 V AC/DC-Adapter Operating Range
Analog Inputs with Ratiometric Programming
via Resistors or DAC/GPIO Host Control
28-pin, 5x5-mm QFN package
Energy Star Low Iq
– < 10-μA Off-State Battery Discharge Current
– < 1.5-mA Off-State Input Quiescent Current
APPLICATIONS
Notebook and Ultra-Mobile Computers
Portable Data Capture Terminals
Portable Printers
Medical Diagnostics Equipment
Battery Bay Chargers
Battery Back-up Systems
DESCRIPTION
The bq24751A is a high-efficiency, synchronous
battery charger with integrated compensation and
system power selector logic, offering low component
count for space-constrained multi-chemistry battery
charging applications. Ratiometric charge current and
voltage programming allows very high regulation
accuracies, and can be either hardwired with resistors
or programmed by the system power-management
microcontroller using a DAC or GPIOs.
The bq24751A charges two, three, or four series Li+
cells, supporting up to 10 A of charge current, and is
available in a 28-pin, 5x5-mm thin QFN package.
– Charge Voltage (4-4.512 V/cell)
– Charge Current (up to 10 A, with 10-m
sense resistor)
CHGEN
ACN
28 27 26 25 24 23 22
1 21
2 20
LEARN
CELLS
– Adapter Current Limit (DPM)
Status and Monitoring Outputs
– AC/DC Adapter Present with Programmable
Voltage Threshold
– Current Drawn from Input Source
Battery Learn Cycle Control
Supports Any Battery Chemistry: Li+, NiCd,
NiMH, Lead Acid, etc.
Charge Enable
ACP
ACDRV
ACDET
3
4
5
bq24751A
28 LD QFN
TOP VIEW
19 SRP
18 SRN
17 BAT
ACSET 6
16 SRSET
ACOP 7
15 IADAPT
8 9 10 11 12 13 14
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1
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.
Copyright © 2007, Texas Instruments Incorporated
Page 1

bq24751A
SLUS756 – SEPTEMBER 2007
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.
DESCRIPTION (CONTINUED)
The bq24751A controls external switches to prevent battery discharge back to the input, connect the adapter to
the system, and to connect the battery to the system using 6-V gate drives for better system efficiency. For
maximum system safety, inrush-power limiting provides instantaneous response to high input voltage multiplied
by current. This AC Over-Power protection (ACOP) feature limits the input-switch power to the programmed level
on the ACOP pin, and latches off if the high-power condition persists to prevent overheating.
The bq24751A features Dynamic Power Management (DPM) and input power limiting. These features reduce
battery charge current when the input power limit is reached to avoid overloading the AC adapter when supplying
the load and the battery charger simultaneously. A highly-accurate current-sense amplifier enables precise
measurement of input current from the AC adapter to monitor the overall system power.
TYPICAL APPLICATION
C17 C18
10 mF 10 mF
C19
10 mF
ADAPTER+
ADAPTER-
P
Q1 (ACFET)
SI4435
P
Q2 (ACFET)
SI4435
C2
0.1 mF
RAC
0.010 W
C3
0.1 mF
ACGOOD
R1
432 kW 1%
R2
66.5
kW
VREF
R4 10 kW
R3 422 kW
DAC
R5 71 kW
HOST
C4 1 mF
DAC
ACN
PVCC
ACP
ACDRV
ACDET
AGND
BATDRV
HIDRV
bq24751A PH
ACGOOD
OVPSET
BTST
REGN
SRSET
ACSET
VREF
LEARN
CELLS
CHGEN
VDAC
VADJ
LODRV
PGND
SRP
SRN
BAT
ACOP
C6 C7
10 mF 10 mF
C8 1 mF
R6 100 kW
Q4
FDS6680A
P
RSR
C9 L1 0.010 W
D1 BAT54 0.1 mF
8.2 mH
C11
C10 1 mF
10 mF
C13
0.1 mF
Q5
FDS6680A
C4
0.1 mF
C16
0.47 mF
C15
0.1 mF
SYSTEM
Q3(BATFET)
SI4435
C12
10 mF
PACK+
PACK-
ADC
C5 100 pH
IADAPT
PowerPad
(1) Pull-up rail could be either VREF or other system rail .
(2) SRSET/ACSET could come from either DAC or resistor dividers .
VIN = 20 V, VBAT = 3-cell Li-Ion, Icharge = 3 A, Iadapter_limit = 4 A
Figure 1. Typical System Schematic, Voltage and Current Programmed by DAC
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2 Submit Documentation Feedback
Product Folder Link(s) :bq24751A
Copyright © 2007, Texas Instruments Incorporated
Page 2

www.ti.com
bq24751A
SLUS756 – SEPTEMBER 2007
C17 C18
10 mF 10 mF
C19
10 mF
ADAPTER+
ADAPTER-
P
Q1 (ACFET)
C1 SI4435
10 mF
P
Q2 (ACFET)
SI4435
C2
0.1 mF
RAC
0.010 W
C3
0.1 mF
ACGOOD
HOST
R1 432 kW
R2
66.5
kW
VREF
R4 10 kW
R3 422 kW
R5 71 kW
R7 43 kW
R6
R8 100 kW
100 kW
R9
66.5 kW
C4
1 mF
GPIO
ADC
C5
100 pF
C6 C7
10 mF 10 mF
SYSTEM
ACN
PVCC
ACP
ACDRV
ACDET
BATDRV
AGND
HIDRV
bq24751A PH
ACGOOD
OVPSET
BTST
REGN
SRSET
ACSET
VREF
LODRV
PGND
C8 1 mF
R10 100 kW
Q4
FDS6680A
C9
D1 BAT54 0.1 mF
C10
1 mF
L1
8.2 mH
C11
10 mF
C13
0.1 mF
Q5
FDS6680A
P
RSR
0.010 W
C4
0.1 mF
Q3(BATFET)
SI4435
C12
10 mF
PACK+
PACK-
LEARN
CELLS
CHGEN
VDAC
VADJ
SRP
SRN
BAT
ACOP
C16
0.47 mF
C15
0.1 mF
IADAPT
PowerPad
(1) Pull-up rail could be either VREF or other system rail .
(2) SRSET/ACSET could come from either DAC or resistor dividers .
VIN = 20 V, VBAT = 3-cell Li-Ion, Icharge = 3 A, Iadapter_limit = 4 A
Figure 2. Typical System Schematic, Voltage and Current Programmed by Resistor
PART NUMBER
bq24751A
ORDERING INFORMATION
PACKAGE
28-PIN 5 x 5 mm QFN
ORDERING NUMBER
(Tape and Reel)
bq24751ARHDR
bq24751ARHDT
QUANTITY
3000
250
PACKAGE THERMAL DATA
PACKAGE
QFN – RHD(1)(2)
θJA
39°C/W
TA = 70°C POWER RATING
2.36 W
DERATING FACTOR ABOVE TA = 25°C
0.028 W/°C
(1) For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
Web site at www.ti.com.
(2) This data is based on using the JEDEC High-K board and the exposed die pad is connected to a Cu pad on the board. This is
connected to the ground plane by a 2x3 via matrix.
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Copyright © 2007, Texas Instruments Incorporated
Product Folder Link(s) :bq24751A
Submit Documentation Feedback
3
Page 3
Part Number BQ24751A
Manufactur Texas Instruments
Description Host-controlled Multi-Chemistry Battery Charger
Total Page 30 Pages
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