Battery pack fuel-gauge IC includes SHA-256 security to prevent cloning

March 29, 2016 // By Graham Prophet
Maxim Integrated presents its MAX1720x/MAX1721x as the first stand-alone ModelGauge m5 Fuel Gauge ICs that include SHA-256 authentication.

The devices are ultra-low power stand-alone fuel gauge ICs that implement the Maxim ModelGauge m5 algorithm without requiring host interaction for configuration. This feature suits the MAX1720x/MAX1721x as “pack-side” fuel gauges. The MAX17201/MAX17211 monitor a single cell pack. The MAX17205/MAX17215 monitor and balance 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. Use the parts, Maxim suggests, in digital still and video cameras; e-readers; handheld computers and terminals; handheld radios; portable game players; portable medical equipment; and smartphones and tablets.


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 ageing, temperature, and discharge rate, and provides 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 special 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 measured using an internal temperature measurement and up to two external thermistors supported by ratiometric measurements on auxiliary inputs. A Maxim 1-Wire (MAX17211/MAX17215) or 2-wire I²C (MAX17201/MAX17205) interface provides access to data and control registers. The ICs are available in lead-free, 3 x 3 mm, 14-pin TDFN packages.


Maxim Integrated;


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