The RT9426A Li-Ion / Li-Polymer battery fuel gauge is a microcontroller peripheral that provides fuel gauging for single-cell battery packs. The RT9426A resides within the battery pack or on the system's main board and manages a non-removable battery or removable battery pack.

The RT9426A reports StateOfCharge, StateOfHealth, FullChargeCapacity, TimeToEmpty and CycleCount based on the Voltaic Gauge with Current Sensing (VGCS) algorithm by using the voltage difference between battery voltage and OCV to calculate the increasing or decreasing SOC, with current sensing compensation to report battery SOC.

Voltaic Gauge with Current Sensing algorithm can support smoothly SOC and does not accumulate error with time and current. That is an advantage compared to coulomb counter which suffer from SOC drift caused by current sense error and battery self-discharge.

The RT9426A provides complete battery status monitor with interrupt alarm function. It could alert to host processor actively when condition of battery over/under-voltage and over-temperature in charge/discharge. Especially for high C-rate battery charging application, it can measure battery voltage by kelvin sense connection to eliminate the IR drop effect for optimal charging profile and safety. More useful alarm functions are Under SOC alert, SOC Change and battery presence status change.


  • Smartphones
  • Tablet PC
  • Wearable Device
  • Digital Still Cameras
  • Digital Video Cameras
  • Handheld and Portable Applications
Key Spec.
Status Active
Number of Series Cells 1
Supply Voltage (min) (V) 2.5
Supply Voltage (max) (V) 5.5
Communication Interface I2C
Package Type WL-CSP2.29x1.74-9(BSC);WDFN2.5x4-12;WL-CSP2.29x1.74-9(BSC)
  • Support System Side Fuel Gauging
  • Battery Fuel Gauge for 1-Series (1sXp) Li-Ion/Li-Polymer Applications
  • State of Charge (SOC) Calculated by VoltaicGaugeTM with Current Sensing (VGCS)
  • No Accumulation Error on Capacity Calculation
  • Battery SOC, SOH, FCC, TTE and Cycle Count Report
  • Voltage Measurement : ±7.5mV
  • Current Measurement : ±1%
  • Battery Temperature Measurement : ±3°C
  • Battery Monitor with Alert Indicator for Voltage, Current, Temperature, SOC and Presence
  • High C-Rate Battery Charging Compliance
  • Low Power Consumption
  • Low-Value Sense Resistor (1mΩ to 40mΩ, Typical 10mΩ)
  • 12 Pin WDFN Package with 0.4mm Pitch
  • 9 Bump WL-CSP Package with 0.5mm Pitch
  • I2C Controlled Interface
TitleLast UpdateDownload
System Side Single Cell Fuel Gauge2020/11/26
Technical Documents
TitleItem TypeLast UpdateDownload
Richtek Product Selection Guide [Jan., 2024] Selection Guide2024/01/18
Richtek Featured Product Tree [Aug., 2023] Selection Guide2023/08/07
Power Management for Video Doorbell App. Note2021/10/08
Li-ion Battery and Gauge Introduction App. Note2014/09/01
Part NumberPackage TypePackage Qty.Free SampleBuy From Authorized Distributor
RT9426AWSCWL-CSP2.29x1.74-9(BSC)3000 Request Buy from Distributor