DS2731 Cache-Memory Battery-Backup Management IC

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The DS2731 is a complete power-management solution for modular backup applications. It is well-suited for 2.5V and below memory bus voltages, with an input voltage of 12V. The DS2731 includes an internal MOSFET switching power stage for charging a one-cell lithium chemistry battery. It has a fully integrated synchronous buck regulator capable of supplying up to 450mA of cache backup supply current, and the necessary logic and power devices for handling the switchover from system power to battery power. The battery charging method of the DS2731 is constant current/constant voltage (CCCV). Output voltage can be margined from 3.8V to 4.6V using a resistor-divider. Charge is terminated when the charging current falls below 5% of full charge current. Switchover to battery backup is initiated by an internal comparator and occurs automatically when a sensed-input voltage drops below 2.93V. At light loads, the 2MHz internal synchronous buck regulator operates in burst mode for maximum efficiency. All nonessential functions of the DS2731 are disabled while supplying holdup current to the cache memory, and the IC goes into very low-current dormant mode when the battery voltage drops below a user-settable threshold. The DS2731 keeps track of charge status and signals the user through open-drain I/O pins that can be used to drive LEDs.

Key Features

Applications/Uses

Lithium Chemistry CCCV Charger
Adjustable Regulated Charging Up to 1.5A DC
Adjustable Charge Voltage from 3.8V to 4.6V
External and Internal Thermal Protection
Safety Timer Secondary Termination
LED Indicator Outputs
Detects Power Outage and Switches Between Normal Power and Backup Battery
Adjustable High-Efficiency Synchronous Buck Regulator with Skip Mode at Light Loads
Low-Power Consumption in Discharge Mode

RAID Server Memory Card

Key Specifications: Battery Backup Circuits

Part Number

Reset Threshold Range (V)

Max. I_CC (µA)

Features

RoHS Available

Package

Operating Temp. Range (°C)

Price^**

DS2731

2.5 to 3.3

150

•	Adjustable Reset Input

•	Stand Alone

•	Thermal Die Regulation

•	Thermistor Input

•

Timer

Yes

TSSOP/28

-20 to +70

$4.81 @ 1k

See All Battery Backup Circuits (89)

Key Specifications: Battery Chargers

Part Number

Cell Chemistry

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

Secondary Charge Termination

Charge Regulation

Features

Package

RoHS Available

Operating Temp. Range (°C)

Price^**

DS2731

Li-Ion
Li-Polymer

13.2

Yes

3.8 to 4.6

Resistor

1.5

Min. Charge Current

Timer

Switchmode

•	Adjustable Reset Input

•	Stand Alone

•	Thermal Die Regulation

•	Thermistor Input

•

Timer

TSSOP/28

Yes

-20 to +70

$4.81 @ 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.