Product details


Function Protection Number of series cells (Min) 3 Number of series cells (Max) 5 Communication interface No Communication Features Analog current sense, Low-Side NCH CHG/DSG FET Drive, Programmable EEPROM or EPROM, Stackable (built-in interface), Temperature sense, Open wire detection, Over-current in Discharge (OCD), Over-temperature (OT), Over-voltage (OV), Short-circuit Discharge (SCD), Under-temperature (UT), Under-voltage (UV) Typical operating current (Typ) (uA) 6 Rating Catalog Vin (Max) (V) 25 Approx. price (US$) 0.55 | 1ku TI functional safety category Functional Safety-Capable open-in-new Find other Battery protectors

Package | Pins | Size

TSSOP (PW) 20 42 mm² 6.5 x 6.4 open-in-new Find other Battery protectors


  • NORMAL mode: 6 µA (BQ77904 and BQ77905)
  • Full suite of voltage, current, and temperature protections
  • Scalable cell count from 3 series to 20 series or more
  • Voltage protection (accuracy ±10 mV)
    • Overvoltage: 3 V to 4.575 V
    • Undervoltage: 1.2 V to 3 V
  • Open cell and open-wire detection (OW)
  • Current Protection
    • Overcurrent discharge 1: –10 mV to –85 mV
    • Overcurrent discharge 2: –20 mV to +170 mV
    • Short circuit discharge: –40 mV to +340 mV
    • Accuracy ±20% for ≤ 20 mV, ±30% for > 20 mV across full temperature
  • Temperature protection
    • Overtemperature charge: 45°C or 50°C
    • Overtemperature discharge: 65°C or 70°C
    • Undertemperature charge: –5°C or 0°C
    • Undertemperature discharge: –20°C or –10°C
  • Additional Features
    • Independent charge (CHG) and discharge (DSG) FET drivers
    • 36-V absolute maximum rating per cell input
    • Built-in-self-test functions for high reliability
  • SHUTDOWN mode: 0.5-µA maximum

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The BQ77904 and BQ77905 devices are low-power battery pack protectors that implement a suite of voltage, current, and temperature protections without microcontroller (MCU) control. The device’s stackable interface provides simple scaling to support battery cell applications from 3 series to 20 series or more. Protection thresholds and delays are factory-programmed and available in a variety of configurations. Separate overtemperature and undertemperature thresholds for discharge (OTD and UTD) and charge (OTC and UTC) are provided for added flexibility.

The device achieves pack protection through the integrated independent CHG and DSG low-side NMOS FET drivers, which may be disabled through two control pins. These control pins may also be used to achieve cell protection solutions for higher series (6 series and beyond) in a simple and economical manner. To do this, simply cascade a higher device CHG and DSG outputs to the immediate lower device control pins. For a reduced component count, all protection faults use internal delay timers.

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Technical documentation

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Type Title Date
* Datasheet BQ77904, BQ77905 3-Series to 20-Series Ultra Low-Power Voltage, Current, Temperature, and Open-Wire Stackable Lithium-Ion Battery Protector datasheet (Rev. J) Apr. 17, 2020
More literature Ein Techniker-Leitfaden für Industrieroboter-Designs Mar. 25, 2020
Application notes High Side Charge FET Implementation Jul. 23, 2018
Application notes bq77905 Pin Equivalent Diagrams Nov. 28, 2017
Application notes bq77905 20S Cell Stacking Configuration (Rev. A) Jul. 28, 2017
Application notes bq77905 Shutdown for Current Reduction Jul. 21, 2017
Application notes BQ77905 Design Considerations in High-Current Applications Dec. 05, 2016
Technical articles Protecting your battery isn’t as hard as you think Oct. 17, 2016
Application notes Bq77905 Using Multiple FETs Jul. 15, 2016
Application notes bq77905 Separate Current Paths (Rev. A) Jul. 07, 2016
User guides bq77905 3-5S Low-Power Protector Evaluation Module (Rev. A) Jul. 07, 2016

Design & development

For additional terms or required resources, click any title below to view the detail page where available.

Hardware development

document-generic User guide

The bq77905EVM-707 is an evaluation board for the bq77905, low power battery protector IC.  The bq77905 IC supports 3-5S battery cell configurations and can be stacked to support comfortably a full stack of 20 series cells. In addition, the bq77905 implements a suite of voltage, current and (...)

  • bq7790500PW configuration for protection thresholds and delays
  • Terminal blocks allow easy connection for easy prototyping
  • Allows for stacking EVMs
  • Onboard charge (CHG) and discharge (DSG) FETs
  • Jumpers (Shunts) allowing for easy temperature charge simulation (hot or cold)

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TSSOP (PW) 20 View options

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