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Texas Instruments BQ77908DBTR
- Part No.:
- BQ77908DBTR
- Manufacturer:
- Texas Instruments
- Category:
- Battery Management
- Package:
- 38-TFSOP (0.173", 4.40mm Width)
- Datasheet:
-
BQ77908DBTR.pdf
- Description:
- IC BAT MFUNC LI-ION 4-8C 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,399
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Product details
Overview
BQ77908DBTR from Texas Instruments is a stand-alone, self-contained lithium-ion/polymer battery protector IC for 4–8 series cell packs. It provides individual cell-voltage monitoring (±50 mV OV/UV accuracy), low-side NMOS FET drive for charge/discharge control, integrated 3.3-V micro-power LDO, and internal 50-mA automatic cell balancing. It is deployed in cordless power tools and electric bikes to prevent overvoltage, undervoltage, discharge overcurrent, and short-circuit faults.
For engineers reviewing the BQ77908DBTR datasheet, BQ77908DBTR pinout, BQ77908DBTR application, or BQ77908DBTR equivalent, key selection considerations include programmable protection thresholds (OV: 2.8–4.375 V, UV: 1.4–2.9 V), 50-µA typical supply current in normal mode, TSSOP-38 package compatibility, and EEPROM-configurable delay times for safety responses.
Technical Context
The BQ77908DBTR implements a hardware-based, non-volatile (EEPROM) programmable protection architecture with independent comparators per cell and dual-path current sensing (×1/×5 gain). Its gate drivers support low-side NMOS FETs with 9–14 V turn-on voltage and <140 µs rise/fall times under 50 nF load.
It integrates a 3.3-V/10-mA LDO regulator, open-cell and thermistor fault detection circuitry, and split power-path control via CHG/DSG outputs. Balancing operates continuously, only during charge, or disabled - all configurable via EEPROM bits CBEN, CBTM, and CBMODE.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Cell count support | 4 to 8 series Li-ion/polymer cells - enables scalable pack design without firmware changes |
| Supply voltage range | 5.6 V to 35 V - matches nominal pack voltages from 4S (16.8 V) to 8S (29.6 V) |
| Normal-mode supply current | 50 µA typical - minimizes quiescent drain on idle battery packs |
| Cell-voltage monitoring accuracy | ±50 mV at 4.2 V OV threshold - ensures precise overcharge prevention across temperature |
| Discharge short-circuit response | 60 µs to 960 µs programmable delay - balances speed vs. noise immunity in motor-driven loads |
| Integrated LDO output | 3.3 V ±5%, 10 mA max - powers external thermistors or logic without auxiliary supply |
| Cell balancing current | 50 mA max - supports passive balancing with external 10 Ω series resistor for ≤0.5 W dissipation |
Pinout & Package
Package: 38-pin TSSOP (DBT), 0.65 mm pitch, exposed pad not present. Thermal resistance θJA = 71.7°C/W (non-LDO), suitable for compact battery pack PCB layouts with moderate airflow.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BAT | High-side pack voltage reference | Connects to most-positive cell terminal; supplies internal regulators and comparators |
| VC1–VC8 | Cell voltage sense inputs | Differential inputs for 4–8 series cells; VC1 = highest potential, VC8 = lowest (BAT–) |
| VC9 | Most-negative cell reference | Direct connection to pack negative; used as analog ground reference for cell sensing |
| CHG / DSG | Low-side NMOS gate drivers | Open-drain outputs driving external N-channel FETs; 9–14 V swing, <140 µs switching |
| SENSE(+) / SENSE(–) | Current-sense differential inputs | Accepts 1–5 mΩ shunt; ×1/×5 gain selectable for 25–500 mV full-scale range |
| TS / VTSB | Thermistor interface | VTSB supplies bias to NTC; TS reads ratiometric voltage for open/short/overtemp detection |
| VREG | LDO output | 3.3-V regulated supply; powers external sensors or logic; 1 µF decoupling required |
| GND / VSS1 / VSS2 | Analog/digital ground references | VSS1/VSS2 are substrate grounds; GND is logic ground - must be tied together at single point |
Key Features
| Feature | Design Value |
|---|---|
| Programmable protection thresholds | OV (2.8–4.375 V), UV (1.4–2.9 V), OCD/SCD (25–950 mV), with 15% delay tolerance - enables fine-tuned safety margins per chemistry |
| Internal 50-mA cell balancing | Configurable activation (always/charge-only/off); eliminates need for external balancing ICs in mid-tier packs |
| Split power-path MOSFET control | Independent CHG and DSG outputs - allows asymmetric charge/discharge FET sizing and thermal management |
| Open-cell and thermistor fault detection | Detects >100 kΩ open-cell impedance and NTC open/short within 4×N seconds - prevents false trips from wiring faults |
| EEPROM configuration storage | Non-volatile settings survive power loss; 3 write cycles recommended per byte for 10-year data retention |
Applications
| Cordless Power Tools | Electric Bikes |
|---|---|
|
Use Scenario: High-pulse discharge (≥30 A) during trigger pull in drills, saws, and impact drivers. IC Role / Device Role / Timing Role: Real-time cell-voltage and current monitoring with 60 µs short-circuit shutdown to protect 18650 cells from thermal runaway. Use Value: Prevents FET destruction during motor stall while maintaining 50 µA quiescent current during tool standby. |
Use Scenario: Regenerative braking and hill-climb overload in 36 V/48 V e-bike battery packs. IC Role / Device Role / Timing Role: Dual-path current sensing (×5 gain) detects 100 mV SCD events; UV recovery with load-removal detection avoids cycling under sustained low-voltage load. Use Value: Enables safe operation at 20–30 A continuous discharge without false undervoltage lockout. |
| Medical Portable Devices | Light Electric Vehicles (LEV) |
|
Use Scenario: Battery-powered infusion pumps requiring >8-hour runtime and fail-safe shutdown on cell imbalance. IC Role / Device Role / Timing Role: Automatic 50-mA balancing maintains ≤10 mV inter-cell delta during multi-day float charging. Use Value: Extends usable capacity by 8–12% and reduces risk of premature pack failure due to drift. |
Use Scenario: Scooters and mobility scooters with 60 V nominal packs subject to vibration-induced connector faults. IC Role / Device Role / Timing Role: Open-cell detection identifies >100 kΩ disconnect at VCx pins; brownout protection disables FETs below 5.6 V to avoid gate driver instability. Use Value: Eliminates need for redundant cell monitors in cost-sensitive LEV BMS designs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar multi-cell lithium protection applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| BQ77905DBTR | Supports only 4–5 series cells; lacks internal balancing; lower OV/UV threshold resolution (100 mV steps) | Suitable for smaller packs where balancing is handled externally or unnecessary | Select when pack size is fixed ≤5S and system-level balancing is already implemented |
| MP2672AGU-Z | Integrated charge controller + protector; requires external MCU for configuration; no EEPROM storage | Targets designs needing combined charging and protection in single IC, with firmware flexibility | Choose when USB-PD or proprietary charging protocol integration is required alongside protection |
Compared with BQ77908DBTR, BQ77905DBTR reduces feature set for cost-sensitive 4S–5S tools, while MP2672AGU-Z trades autonomous EEPROM-based operation for MCU-dependent configurability - making BQ77908DBTR optimal for standalone, field-programmable, high-reliability battery packs.
Availability
BQ77908DBTR is available at Aetrix Electronics and suitable for cordless power tools, electric bikes, and medical portable devices requiring stable component supply, long-term lifecycle support, and automotive-grade reliability without software dependencies.
Supply support for BQ77908DBTR includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management technologies, with decades of battery management system expertise.
The BQ77908DBTR belongs to TI's precision protector product line, designed specifically for robust, firmware-free, high-accuracy protection of multi-cell lithium-ion and lithium-polymer battery packs in demanding portable and industrial applications.
FAQ
What is the maximum number of series cells supported by the BQ77908DBTR?
The BQ77908DBTR supports up to 8 series-connected lithium-ion or lithium-polymer cells. Its VC1–VC8 inputs accommodate differential sensing across 4–8 cells, with VC9 serving as the pack-negative reference. This enables direct use in common 24 V (6S), 36 V (10S), and 48 V (13S) configurations when paired with appropriate external FETs and layout.
Does the BQ77908DBTR require an external microcontroller to operate?
No, the BQ77908DBTR is a fully stand-alone protector IC. All protection functions - including overvoltage, undervoltage, overcurrent, short-circuit, and temperature monitoring - are implemented in hardware with EEPROM-stored thresholds and delays. The BQ77908DBTR operates autonomously after initial programming and needs no host MCU for real-time supervision.
How is cell balancing configured on the BQ77908DBTR?
Cell balancing on the BQ77908DBTR is enabled via EEPROM bits CBEN, CBTM, and CBMODE. It can be set to run continuously, only during charging, or disabled entirely. Balancing uses internal 50-mA switches with external series resistors; the BQ77908DBTR does not regulate balancing current - external RBAL sets final current (e.g., 10 Ω yields ~50 mA at 3.9 V).
What is the purpose of the ZEDE pin on the BQ77908DBTR?
The ZEDE pin on the BQ77908DBTR enables zero-delay test mode when pulled high. In this mode, serial communication (SCLK/SDATA) becomes active and all protection delay timers are minimized for bench validation. For normal operation, ZEDE must be tied to VSS with a strong connection - floating or weak pull-down may cause erratic behavior or unintended test-mode entry.
Can the BQ77908DBTR detect open thermistor connections?
Yes, the BQ77908DBTR detects open thermistor connections using its TS and VTSB pins. With VTSB supplying bias to the NTC, the IC measures ratiometric voltage at TS. An open circuit causes TS voltage to exceed 90–98% of VTSB, triggering an open-fault flag within 4 seconds per cell. This is confirmed in the Electrical Characteristics table under "Thermistor open detection" (VTH_OPEN).
BQ77908DBTR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 38-TFSOP (0.173", 4.40mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Function:
- Multi-Function Controller
- Battery Chemistry:
- Lithium Ion/Polymer
- Number of Cells:
- 4 ~ 8
- Fault Protection:
- Over Current, Over Temperature, Over/Under Voltage, Short Circuit
- Interface:
- I2C
- Operating Temperature:
- -25°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP
BQ77908DBTR FAQ
1.How can I place an order for BQ77908DBTR through Aetrix?
Please submit a Request for Quotation (RFQ) for BQ77908DBTR on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for BQ77908DBTR reliable?
The price and inventory of BQ77908DBTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BQ77908DBTR is usually 5 days.
3.What payment methods are accepted for BQ77908DBTR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BQ77908DBTR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BQ77908DBTR?
BQ77908DBTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BQ77908DBTR order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for BQ77908DBTR?
For technical support, including BQ77908DBTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BQ77908DBTR requirements.
6.How does Aetrix verify that BQ77908DBTR is sourced from the original manufacturer or authorized distributors?
All BQ77908DBTR products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that BQ77908DBTR meets industry standards.
7.What is the process for return or replacement of BQ77908DBTR?
All BQ77908DBTR units undergo pre-shipment inspection (PSI). If there is an issue with BQ77908DBTR, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The BQ77908DBTR part is unused and in its original packaging.
Return procedure for BQ77908DBTR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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