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BQ77908A

ACTIVE

Stand-Alone Multi-Cell Li-Ion/Li-Polymer Precision Protector

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Data sheet

BQ77908A

ACTIVE
Data sheet Order now

Product details

Function Protection Number of series cells (min) 4, 5, 6, 7, 8 Number of series cells (max) 5, 6, 7, 8 Features Cell balancing, FET drive, LDO output, Overvoltage Operating current (typ) (µA) 5 Rating Catalog Vin (max) (V) 50 Overvoltage protection 4.2 Operating temperature range (°C) -40 to 85 Battery overvoltage protection (min) (V) 4.15 Battery overvoltage protection (max) (V) 4.25
Function Protection Number of series cells (min) 4, 5, 6, 7, 8 Number of series cells (max) 5, 6, 7, 8 Features Cell balancing, FET drive, LDO output, Overvoltage Operating current (typ) (µA) 5 Rating Catalog Vin (max) (V) 50 Overvoltage protection 4.2 Operating temperature range (°C) -40 to 85 Battery overvoltage protection (min) (V) 4.15 Battery overvoltage protection (max) (V) 4.25
TSSOP (DBT) 38 62.08 mm² 9.7 x 6.4
  • 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
  • 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

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

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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Technical documentation

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Type Title Date
* Data sheet bq77908A Multi-Cell Lithium-Ion/Polymer Precision Protector datasheet (Rev. A) 22 Sep 2014
Application note Programming Software for bq77910 and bq77908 09 Jul 2012
Application note bq77908/910 series FET Considerations (Rev. A) 25 Apr 2012
EVM User's guide bq77908AEVM Evaluation Module 26 Jan 2012

Design & development

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TSSOP (DBT) 38 Ultra Librarian
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