Datasheet

General Description
The MAX1909/MAX8725 highly integrated control ICs
simplify construction of accurate and efficient multi-
chemistry battery chargers. The MAX1909/MAX8725
use analog inputs to control charge current and volt-
age, and can be programmed by a host microcontroller
(µC) or hardwired. High efficiency is achieved through
use of buck topology with synchronous rectification.
The maximum current drawn from the AC adapter is pro-
grammable to avoid overloading the AC adapter when
supplying the load and the battery charger simultane-
ously. The MAX1909/MAX8725 provide a digital output
that indicates the presence of an AC adapter, and an
analog output that monitors the current drawn from the
AC adapter. Based on the presence or absence of the
AC adapter, the MAX1909/MAX8725 automatically select
the appropriate source for supplying power to the sys-
tem by controlling two external p-channel MOSFETs.
Under system control, the MAX1909/MAX8725 allow the
battery to undergo a relearning or conditioning cycle in
which the battery is completely discharged through the
system load and then recharged.
The MAX1909 includes a conditioning charge feature
while the MAX8725 does not. The MAX1909/MAX8725
are available in space-saving 28-pin, 5mm
5mm thin
QFN packages and operate over the extended -40°C to
+85°C temperature range. The MAX1909/MAX8725 are
now available in lead-free packages.
Applications
Notebook and Subnotebook Computers
Hand-Held Data Terminals
Features
±0.5% Accurate Charge Voltage (0°C to +85°C)
±3% Accurate Input Current Limiting
±5% Accurate Charge Current
Programmable Charge Current >4A
Automatic System Power-Source Selection
Analog Inputs Control Charge Current and
Charge Voltage
Monitor Outputs for
Current Drawn from AC Input Source
AC Adapter Presence
Up to 17.65V (max) Battery Voltage
Maximum 28V Input Voltage
Greater than 95% Efficiency
Charge Any Battery Chemistry: Li+, NiCd, NiMH,
Lead Acid, etc.
MAX1909/MAX8725
Multichemistry Battery Chargers with Automatic
System Power Selector
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
19-2805; Rev 2; 9/04
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
PART TEMP RANGE PIN-PACKAGE
MAX1909ETI -40°C to +85°C 28 Thin QFN
MAX1909ETI+ -40°C to +85°C 28 Thin QFN
MAX8725ETI -40°C to +85°C 28 Thin QFN
MAX8725ETI+ -40°C to +85°C 28 Thin QFN
28 27 26 25 24 23 22
8 9 10 11 12 13 14
15
16
17
18
19
20
21
7
6
5
4
3
2
1
MAX1909
MAX8725
THIN QFN
TOP VIEW
LDO
DCIN
ACIN
REF
GND/PKPRES
ACOK
MODE
PDL
PDS
CSSP
CSSN
SRC
DHI
DHIV
DLOV
DLO
PGND
CSIP
CSIN
BATT
GND
CCS
CCV
CCI
VCTL
ICTL
CLS
IINP
Pin Configuration
CSSP CSSN
LDO
DHI
DLOV
DLO
PGND
CSIP
CSIN
BATT
GND
DCIN
VCTL
ICTL
MODE
ACIN
ACOK
CLS
CCV
CCI
CCS
REF
LDO
AC ADAPTER: INPUT
P3
0.01
10µH
N1
P1
0.015
TO
EXTERNAL LOAD
LDO
PDS
PDL
SRC
LDO
REF
IINP
IINP
DHIV
SRC
P2
MAX1909
MAX8725
PKPRES
MAX8725 ONLY
Minimum Operating Circuit
+
Denotes lead-free package.
EVALUATION KIT AVAILABLE

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