DS2770

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DESCRIPTION

The DS2770 battery monitor and charge controller performs several functions needed for thorough

battery maintenance. When used in conjunction with the host system’s processor, a battery-pack resident

DS2770 may be utilized for applications that include charging, remaining capacity estimation, safety

monitoring, and nonvolatile (NV) parametric storage.

The DS2770 provides a unique ID, a digital temperature sensor, an analog-to-digital converter (ADC) that

measures battery voltage and current, an integrated current accumulator that keeps a running total of all

current entering and leaving the battery, an elapsed time meter, NV memory for storage of important

parameters, and an integrated charge controller supporting rechargeable lithium (including lithium-ion

and lithium-ion polymer) and nickel metal hydride (NiMH) batteries. Current measurement can be

accomplished through the use of an integrated 25m

W sense resistor or through an external sense resistor.

The resolution of the current, voltage, and temperature measurements is sufficient for process monitoring

applications such as battery-charge control and safety. The charge-control technique is user-selectable to

support either pulse charge for rechargeable lithium or dT/dt termination for NiMH. Additionally,

programmable charge timers and low-battery recovery are provided for safety and convenience.

Information is sent to/from the DS2770 over a 1-Wire interface so that only one wire (and ground) needs

to be connected from a processor to a DS2770. This means that DS2770-equipped battery packs need

only four output connectors: battery power, charge source, ground, and the 1-Wire interface. Each device

has a factory-programmed 64-bit net address that allows it to be individually addressed by the host

system.

Two types of memory are provided on the DS2770 for battery information storage: lockable EEPROM

and SRAM. EEPROM memory saves important battery data in true NV memory that is unaffected by

severe battery depletion, accidental shorts, or ESD events and becomes ROM when locked to provide

additional security for unchanging battery data. SRAM provides inexpensive storage for temporary data.