X3100, X3101 pdf datasheet (3

The X3100 is a protection and monitor IC for use in battery
packs consisting of 4 series Lithium-Ion battery cells. The
X3101 is designed to work in 3-cell applications. Both devices
provide internal over-charge, over-discharge, and overcurrent
protection circuitry, internal EEPROM memory, an
internal voltage regulator, and internal drive circuitry for
external FET devices that control cell charge, discharge, and
cell voltage balancing.
Over-charge, over-discharge, and over-current thresholds
reside in an internal EEPROM memory register and are
selected independently via software using a 3MHz SPI serial
interface. Detection and time-out delays can also be individually
varied using external capacitors.
Using an internal analog multiplexer, the X3100 or X3101
allow battery parameters such as cell voltage and current
(using a sense resistor) to be monitored externally by a
separate microcontroller with A/D converter. Software on this
microcontroller implements gas gauge and cell balancing
functionality in software.
The X3100 and X3101 contain a current sense amplifier.
Selectable gains of 10, 25, 80 and 160 allow an external
10-bit A/D converter to achieve better resolution than a more
expensive 14-bit converter.
An internal 4k-bit EEPROM memory featuring IDLock™
allows the designer to partition and “lock in” written battery
cell/pack data.
The X3100 and X3101 are each housed in a 28 Ld TSSOP
package.