MAX1909, MAX8725 Multichemistry Battery Chargers with Automatic System Power Selector

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The MAX1909/MAX8725 highly integrated control ICs simplify construction of accurate and efficient multichemistry battery chargers. The MAX1909/MAX8725 use analog inputs to control charge current and voltage, 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 programmable to avoid overloading the AC adapter when supplying the load and the battery charger simultaneously. 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 system 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 x 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.

Key Features

Applications/Uses

±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.

	Handheld Data Terminals
	Notebook and Subnotebook Computers

Key Specifications: Battery Chargers

Part Number

Cell Chemistry

Number of NiMH or NiCd cells

Number of Lithium-Ion cells

Protected V_IN (max) (V)

Charging V_IN (max) (V)

Internal FET/Transistor

Charger (V)

Charge Rate Set by

Max. Charge Current (A)

Charge Termination

Charge Regulation

Features

EV-Kit

Package

Smallest Available Package (max w/pins) (mm²)

RoHS Available

Operating Temp. Range (°C)

Price^**

MAX1909

Lead Acid
Li-Ion
Li-Polymer
NiCd
NiMH
Universal

10
4
5
6
7
8
9

3
4

0 to 17.6

Analog Input
Resistor

Current Limit
Max. Voltage

Switchmode

•	Input Current Limit

•	Smart Power Selector

•	Stand Alone

Yes

THIN QFN/28
THIN QFN/32

Yes

-40 to +85

$5.04 @ 1k

MAX8725

$5.04 @ 1k

See All Battery Chargers (60)

Notes:
^**This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific prices and delivery, please see the price and availability page or contact an authorized distributor.