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BQ77905

ACTIVE

3- to 5-series li-ion and li-phosphate ultra-low-power stackable battery protector

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Data sheet
3- to 5-series li-ion and li-phosphate ultra-low-power stackable battery protector

BQ77905

ACTIVE
Data sheet Order now

Product details

Function Protection Number of series cells (Min) 3, 4, 5 Number of series cells (Max) 4, 5 Features Overvoltage, Undervoltage, Overcurrent during discharge (OCD), Short-circuit Discharge (SCD), Open wire (OW), Over-temperature (OT), Under-temperature (UT), Stackable, FET drive Typical operating current (Typ) (uA) 6 Rating Catalog Vin (Max) (V) 25 TI functional safety category Functional Safety-Capable
Function Protection Number of series cells (Min) 3, 4, 5 Number of series cells (Max) 4, 5 Features Overvoltage, Undervoltage, Overcurrent during discharge (OCD), Short-circuit Discharge (SCD), Open wire (OW), Over-temperature (OT), Under-temperature (UT), Stackable, FET drive Typical operating current (Typ) (uA) 6 Rating Catalog Vin (Max) (V) 25 TI functional safety category Functional Safety-Capable
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TSSOP (PW) 20 29 mm² 6.5 x 4.4
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  • 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
  • Functional Safety-Capable
  • 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
  • Functional Safety-Capable
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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.

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
* Data sheet BQ77904, BQ77905 3-Series to 20-Series Ultra Low-Power Voltage, Current, Temperature, and Open-Wire Stackable Lithium-Ion Battery Protector datasheet (Rev. K) 31 Jul 2020
Application note bq77905 20S Cell Stacking Configuration (Rev. B) 23 Jun 2021
Functional safety information BQ77905 Function Safety Capable 13 Jul 2020
E-book Ein Techniker-Leitfaden für Industrieroboter-Designs 25 Mar 2020
E-book E-book: An engineer’s guide to industrial robot designs 12 Feb 2020
Application note High Side Charge FET Implementation 23 Jul 2018
Application note bq77905 Pin Equivalent Diagrams 28 Nov 2017
Application note bq77905 Shutdown for Current Reduction 21 Jul 2017
Application note BQ77905 Design Considerations in High-Current Applications 05 Dec 2016
Technical article Protecting your battery isn’t as hard as you think 17 Oct 2016
Application note Bq77905 Using Multiple FETs 15 Jul 2016
Application note bq77905 Separate Current Paths (Rev. A) 07 Jul 2016
User guide bq77905 3-5S Low-Power Protector Evaluation Module (Rev. A) 07 Jul 2016

Design & development

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Evaluation board

BQ77905EVM-707 — bq77905 3- to 5-Series Advanced Stackable Low-Power Battery Protector Evaluation Module

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 (...)

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