Product details


Function Protection Number of series cells (Min) 4 Number of series cells (Max) 8 Communication interface No Communication Features Low-Side NCH CHG/DSG FET Drive Typical operating current (Typ) (uA) 5 Rating Catalog Vin (Max) (V) 50 Approx. price (US$) 5.06 | 1ku open-in-new Find other Battery protectors

Package | Pins | Size

TSSOP (DBT) 38 62 mm² 9.7 x 6.4 open-in-new Find other Battery protectors


  • 4-, 5-, 6-, 7-, or 8-Series Cell Protection
  • Individual Cell-Voltage Monitoring
  • Low-Side NMOS FET Drive for Charge and Discharge Control
  • Compatible With 1-mΩ Current-Sense Resistor
  • Supply-Voltage Range From 5.6 V to 40 V
  • Integrated 3.3-V Micro-Power LDO Regulator
  • Low Supply Current
    • Normal Mode: 50 µA, Typical
    • Shutdown Mode, LDO OFF: 5 µA, Typical
  • 38-Pin TSSOP Package
  • Internal 50-mA Automatic Cell Balancing

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The bq77908A is a battery protection and cell balancing device intended for Li-Ion and Li-Polymer battery packs.

The bq77908A monitors 4- to 8-series individual cell voltages and provides fast-acting outputs that may be used to drive N-channel MOSFETs to interrupt the power path. Activation delays and recovery methods for safety conditions are fully programmable in non-volatile memory.

Automatic cell balancing is provided using internal 50-mA cell circuits. A robust balancing algorithm ensures optimum performance by maintaining all cell voltages in balance. Balancing may be configured to operate at all times, only during charge, or can be disabled completely.

Additional advanced safety features of the bq77908A include the ability to control split power-path MOSFETs, an open-cell sense-line detection mechanism, and the ability to detect an open or shorted external temperature sensor fault condition.

Programmable Protection Functions

  • Wide range of programmable detection thresholds and delay times
  • Configurable for multiple cell types and application requirements:
    • Cell overvoltage
    • Cell undervoltage
    • Pack discharge overcurrent
    • Pack discharge short circuit
    • Pack charge short-circuit current
  • Variable gain (×1 or ×5) current-sense circuit
    • Compatible with a wide range of current-sense resistors (1-mΩ to 5-mΩ typical) sized for application requirements

Fixed Hardware Protection Functions

  • Preset overtemperature protections
  • Open-cell detection
  • Open and shorted thermistor detection
  • Brownout protection quickly shuts off FETs under low-battery conditions to minimize the risk of FET overheating
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Similar but not functionally equivalent to the compared device:
BQ77915 ACTIVE 3-Series to 5-Series Stackable Ultra-Low-Power Primary Protector With Autonomous Cell Balancing This product is a 3-series to 5-series stackable ultra-low-power primary protector with autonomous cell balancing.

Technical documentation

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Type Title Date
* Datasheet bq77908A Multi-Cell Lithium-Ion/Polymer Precision Protector datasheet (Rev. A) Sep. 22, 2014
Technical articles Cell Balancing: Better safe than sorry (Part 1) Mar. 11, 2014
Application notes Programming Software for bq77910 and bq77908 Jul. 09, 2012
Application notes bq77908/910 series FET Considerations (Rev. A) Apr. 25, 2012
User guides bq77908AEVM Evaluation Module Jan. 26, 2012

Design & development

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

Hardware development

The BQ77908-10-GUI-SW evaluation software is useful for configuring the bq77908EVM and the bq77910EVM for operation with safety and timing parameters.

CAD/CAE symbols

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TSSOP (DBT) 38 View options

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