The MAX1720x/MAX1721x are ultra-low power stand-alone fuel gauge ICs that implement the Maxim ModelGauge™ m5 algorithm without requiring host interaction for configura- tion. This feature makes the MAX1720x/MAX1721x excellent pack-side fuel gauges. The MAX17201/MAX17211 monitor a single cell pack. The MAX17205/MAX17215 monitor and bal- ance a 2S or 3S pack or monitor a multiple-series cell pack. To prevent battery pack cloning, the ICs integrate SHA- 256 authentication with a 160-bit secret key. Each IC incorporates a unique 64-bit ID. The ModelGauge™ m5 algorithm combines the short-term accuracy and linearity of a coulomb counter with the long- term stability of a voltage-based fuel gauge, along with temperature compensation to provide industry-leading fuel gauge accuracy. The IC automatically compensates for cell aging, temperature, and discharge rate, and pro- vides accurate state of charge (SOC) in milliampere-hours (mAh) or percentage (%) over a wide range of operating conditions. As the battery approaches the critical region near empty, the ModelGauge m5 algorithm invokes a spe- cial error correction mechanism that eliminates any error. The ICs provide accurate estimation of time-to-empty and time-to-full, Cycle+™ age forecast, and three methods for reporting the age of the battery: reduction in capacity, increase in battery resistance, and cycle odometer. The ICs provide precision measurements of current, voltage, and temperature. Temperature of the battery pack is mea- sured using an internal temperature measurement and up to two external thermistors supported by ratiometric measure- ments on auxiliary inputs. A Maxim 1-Wire® (MAX17211/ MAX17215) or 2-wire I2C (MAX17201/MAX17205) inter- face provides access to data and control registers. The ICs are available in lead-free, 3mm x 3mm, 14-pin TDFN and 1.6mm x 2.4mm 15-bump WLP packages.