STMicroelectronics STC3115IJT

Overview

STC3115IJT from STMicroelectronics is a dedicated battery gas gauge IC for Li-ion/Li-polymer cells in handheld devices, featuring OptimGauge™ algorithm, ±0.25% battery voltage monitoring accuracy, 45 µA power-saving mode current, and programmable low-SOC/low-voltage alarm output via open-drain ALM pin. It performs Coulomb counting and voltage-mode state-of-charge (SOC) estimation with internal temperature sensing and battery swap detection.

For engineers reviewing the STC3115IJT datasheet, STC3115IJT pinout, STC3115IJT application, or STC3115IJT equivalent, key selection considerations include mixed-mode SOC tracking accuracy, I²C interface register control of alarm thresholds, dual-package availability (CSP and DFN), and integration of OCV-based voltage-gauge compensation to mitigate Coulomb counter drift in portable medical and consumer electronics.

Technical Context

The STC3115IJT implements a dual-algorithm gas gauge architecture combining a 14-bit sigma-delta ADC-based Coulomb counter (500 ms conversion time, 5.88 µV LSB) with a voltage-mode algorithm using a built-in reference OCV curve and programmable VM_CNF parameter for battery-specific calibration. Its 32.768 kHz internal oscillator provides timing for synchronized 4 s (voltage/temp) and 16 s (temperature) measurement cycles.

It supports two operating modes controlled by the VMODE bit: mixed mode (Coulomb + voltage tracking, 100 µA typ.) for high-accuracy active use, and voltage-only mode (45 µA typ.) for standby. The ALM pin operates as an open-drain interrupt output triggered independently by SOC < REG_SOC_ALM (default 1%) or VIN < REG_ALARM_VOLTAGE (default 3.00 V), both software-programmable via I²C registers.

Key Specifications

Pinout & Package

STC3115IJT is available in a 2.0 × 3.0 mm DFN10 package with wettable flanks, optimized for automated optical inspection and high-density PCB layouts in space-constrained handheld applications.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar battery gas gauge applications.

Compared with BQ27426YZFT and MAX17048G+T, the STC3115IJT uniquely integrates battery swap detection, dual-trigger open-drain ALM, and on-die temperature sensing - reducing BOM count and firmware complexity in handheld medical and consumer devices requiring robust, self-contained fuel gauging.

Availability

STC3115IJT is available at Aetrix Electronics and suitable for smartphone battery management, portable medical monitor power systems, digital camera energy tracking, and wireless headphone charging case designs requiring stable component supply and long-term lifecycle support.

Supply support for STC3115IJT includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, analog ICs, MEMS, and power management solutions for automotive, industrial, and consumer markets.

The STC3115IJT belongs to ST's dedicated battery management IC product line, engineered specifically for high-accuracy, low-power fuel gauging in single-cell Li-ion/Li-polymer applications where space, power, and reliability are critical constraints.

FAQ

What is the function of the RSTIO pin on the STC3115IJT?

The RSTIO pin serves dual roles: as an input to detect battery insertion (BATD function) and as an open-drain output to control external reset or charge inhibit circuits. During power-up, it senses battery presence to trigger automatic OCV measurement; when configured as output, it asserts high to disable charging via external FET control, supporting safe battery swap sequences.

How does the STC3115IJT compensate for battery aging over time?

The STC3115IJT continuously compares Coulomb counter and voltage-mode SOC estimates and updates REG_CC_ADJ and REG_VM_ADJ registers (16-bit, LSB = 1/512%) to correct long-term drift. These adjustment values reflect accumulated discrepancies caused by capacity fade and internal resistance increase, enabling autonomous recalibration without host MCU intervention.

Can the STC3115IJT operate without an external current sense resistor?

Yes - the STC3115IJT supports voltage-only gas gauging mode (VMODE = 1), disabling the Coulomb counter and CG input. In this mode, it relies solely on the OptimGauge™ voltage algorithm and internal temperature sensor to estimate SOC, achieving 45 µA typical current draw and eliminating the need for R_cg, making it suitable for ultra-low-power applications where current measurement is not required.

What are the default alarm thresholds for SOC and battery voltage on the STC3115IJT?

At power-on-reset, the STC3115IJT defaults to a 1% SOC alarm threshold (stored as value 2 in REG_SOC_ALM, where each unit = 0.5%) and a 3.00 V battery voltage alarm threshold (stored as value 170 in REG_ALARM_VOLTAGE, where each unit = 17.6 mV). Both thresholds are fully programmable via I²C register writes during system initialization.