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bq24705 Datasheet Preview

bq24705 Datasheet

Host-Controlled Multi-Cell Battery Charger

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Not Recommended for New Designs
bq24705
www.ti.com............................................................................................................................................... SLUS779B – DECEMBER 2007 – REVISED MARCH 2009
600-kHz, Host-Controlled Multi-Cell Battery Charger With Input Overvoltage Protection
FEATURES
1
2 NMOS-NMOS Synchronous Buck Converter
with 600 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
– Internal Loop Compensation
– Internal Soft-Start
Safety
– Input Overvoltage Protection (OVP)
– Dynamic Power Management (DPM) with
Status Indicator
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
– Charge Voltage (4-4.512 V/cell)
– Charge Current (up to 8 A, with 10-m
Sense Resistor)
– Adapter Current Limit (DPM)
Status and Monitoring Outputs
– AC/DC Adapter Present with Programmable
Voltage Threshold
– DPM Loop Active (DPMDET)
– Current Drawn from Input Source
Supports Any Battery Chemistry: Li+, NiCd,
NiMH, Lead Acid, etc.
Charge Enable
10-µA Off-State Battery Current
24-pin, 4x4-mm QFN Package
APPLICATIONS
Notebook and Ultra-Mobile Computers
Portable Data-Capture Terminals
Portable Printers
Medical Diagnostics Equipment
Battery Bay Chargers
Battery Back-Up Systems
DESCRIPTION
The bq24705 is a high-efficiency, synchronous
battery charger with integrated compensation,
offering low component count for space-limited
multi-chemistry battery charging applications. Charge
current and voltage programming allows high
regulation accuracies, and can be either hardwired
with resistors, or programmed by the system
power-management microcontroller using a DAC or
GPIOs.
The bq24705 charges two, three, or four series Li+
cells, supporting up to 8 A of charge current, and is
available in a 24-pin, 4x4-mm thin QFN package.
PVCC 1
CHGEN 2
ACN 3
ACP 4
ACDET 5
ACSET 6
24 23 22 21 20 19
bq24705
QFN-24
TOP VIEW
18 DPMDET
17 CELLS
16 SRP
15 SRN
14 BAT
13 SRSET
7 8 9 10 11 12
Figure 1. bq24705, 24 LD QFN, Top View
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.
PowerPad is a trademark of Texas Instruments.
2
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 © 2007–2009, Texas Instruments Incorporated




etcTI

bq24705 Datasheet Preview

bq24705 Datasheet

Host-Controlled Multi-Cell Battery Charger

No Preview Available !

Not Recommended for New Designs
bq24705
SLUS779B – DECEMBER 2007 – REVISED MARCH 2009............................................................................................................................................... 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 bq24705 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.
ADAPTER +
ADAPTER–
R10
2Ω
C1
2.2 µF
PP
Q1 (ACFET) Q2 (ACFET)
SI4435
SI4435
Controlled by
HOST
C2
R1 0.1 µF
432 kΩ
1%
RAC
0.01 Ω
C3
0.1 µF
ACGOOD
R2
66.5 kΩ
1%
VREF
R3
10 kΩ
GPIO
HOST
R4
10 kΩ
C4
1 µF
DAC
ADC
C5
100 pF
D2
BAT54
C6 C7
10 µF 10 µF
SYSTEM
ACN
ACP
ACDET
AGND
ACGOOD
SRSET
ACSET
VREF
bq24705
PVCC
HIDRV
PH
BTST
REGN
LODRV
PGND
C8
0.1 µF
C9
Q3(BATFET)
SI4435
Controlled by
HOST
Q4
FDS6680A
L1
4.7 µH
P
RSR
0.01 Ω
D1 BAT54 0.1 µF
C11
10 µF
C10
1 µF
C13
0.1 µF
Q5
FDS6680A
C14
0.1 µF
DPMDET
CELLS
CHGEN
VADJ
SRP
SRN
BAT
ISYNSET
IADAPT PowerPad
R6
30 kΩ
C15
0.1 µF
C12
10 µF
PACK+
PACK–
(1) Pull-up rail could be either VREF or other system rail.
(2) SRSET/ACSET could come from either DAC or resistor dividers.
(3) 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 DAC
2 Submit Documentation Feedback
Product Folder Link(s) :bq24705
Copyright © 2007–2009, Texas Instruments Incorporated


Part Number bq24705
Description Host-Controlled Multi-Cell Battery Charger
Maker etcTI
Total Page 30 Pages
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