Key Selection Information
| Selection Parameter | Confirmed Information |
|---|---|
| Cell Count | 3, 4 or 5 series cells |
| Control Architecture | MCU-free standalone protector with factory-programmed thresholds and delays |
| Cell Voltage Protection | OV 4.25 V, UV 2.50 V for exact BQ7790509 configuration |
| Current Protection | OCD1 50 mV, OCD2 100 mV, SCD 200 mV exact thresholds |
| Temperature Protection | OTD 70°C, OTC 50°C, UTD −20°C, UTC −5°C target thresholds with specified thermistor network |
| Pack Switching | Independent low-side CHG and DSG NMOS FET drivers |
| Power | 6 µA typical NORMAL mode; 0.5 µA maximum SHUTDOWN stated family features |
| Exact Package / Packing | TSSOP (PW), 20 pins; 2000-piece large tape and reel |
Product Overview
BQ7790509PWR is an ultra-low-power 3S-to-5S battery protector that implements voltage, current, temperature, and open-wire protection without requiring a microcontroller. Its key selection characteristic is that protection thresholds and delays are factory programmed into the exact device option rather than configured by host firmware.
For the BQ7790509 variant, TI’s comparison table specifies a 4.25 V overvoltage threshold and 2.50 V undervoltage threshold, together with defined overcurrent and short-circuit thresholds/delays. That makes the final four-digit option code electrically significant: another BQ77905 suffix can have materially different cell voltage, current, temperature, delay, and recovery behavior even in the same 20-pin package.
The protector is also stackable. Its CHG/DSG control scheme can be cascaded for battery systems above five series cells, but stacking adds inter-device fault propagation and FET-control considerations that need to be validated at the complete pack level.
For related devices, see HKEQGOO’s Battery Management category.
Technical Specifications
| Parameter | Verified Information |
|---|---|
| Manufacturer | Texas Instruments |
| Exact MPN | BQ7790509PWR |
| Supported Cells | 3 to 5 series cells |
| OV Threshold / Delay / Hysteresis | 4250 mV / 1 s / 100 mV |
| UV Threshold / Delay / Hysteresis | 2500 mV / 1 s / 400 mV |
| OCD1 Threshold / Delay | 50 mV / 700 ms |
| OCD2 Threshold / Delay | 100 mV / 90 ms |
| SCD Threshold / Delay | 200 mV / 1 s |
| Current Fault Recovery | Load removal plus delay |
| Temperature Targets | OTD 70°C, OTC 50°C, UTD −20°C, UTC −5°C with TI’s referenced NTC network |
| Open-Wire Detection | Supported |
| FET Drivers | Independent low-side CHG and DSG NMOS drivers |
| Normal Current | 6 µA typical stated family feature |
| Shutdown Current | 0.5 µA maximum stated family feature |
| Package | TSSOP (PW), 20 pins |
| Manufacturer Status | Active / Production |
| Part Marking | B7790509 |
Functional Highlights
Exact threshold option matters more than family name
BQ77905 is offered in multiple factory configurations. The 0509 option uses its own voltage thresholds, current thresholds, delays, temperature targets and recovery behavior. A sourcing substitution to another BQ77905 suffix can therefore change pack safety behavior even when pin count and package remain the same.
Because these values are factory programmed, firmware cannot correct an incorrectly sourced threshold variant. The exact MPN should be part of the battery safety bill of materials and incoming-material verification.
MCU-free protection reduces software dependency
The device multiplexes internal comparators across the configured protection functions and controls CHG/DSG FET drivers without a host MCU. That can simplify packs whose main requirement is fixed hardware protection rather than telemetry or adaptive battery management.
The tradeoff is reduced field configurability. If a future cell revision requires a different OV/UV or current threshold, the protector option itself may need to change.
Temperature thresholds depend on the external NTC network
TI lists target charge/discharge overtemperature and undertemperature values for the option, but notes that actual temperature trip points depend on the external thermistor and resistor network. The temperature table should therefore be treated as a circuit target, not a sensor-independent guaranteed Celsius threshold.
Design Considerations
- Lock the exact 0509 option in procurement. Protection thresholds are device-option data, not software settings.
- Convert current thresholds through the real shunt resistor. The mV thresholds translate into pack current according to RSNS and its tolerance.
- Validate thermistor thresholds with the production NTC network. Component tolerances shift actual temperature trip points.
- Size low-side protection FETs for fault energy and recovery. The IC provides drive/control but not the external MOSFET current capability.
- If stacking, test fault propagation and recovery across all protector levels. A local threshold event can affect the full-series pack switch state.
Product Status and Exact Order Code
Manufacturer status: Active / Production
Texas Instruments lists BQ7790509PWR in the 20-pin TSSOP PW package with a 2000-piece large tape-and-reel carrier, Level-2-260C-1 YEAR MSL classification, an operating-temperature listing of −40°C to +85°C, and part marking B7790509.
Related Engineering Resources
Quality & Verification Support
Third-party inspection or testing can be arranged according to customer requirements. Testing fees are borne by the buyer. Additional verification requirements can be discussed before shipment. After an order is placed, physical product, label, packaging, and Date Code photos may be provided where appropriate.
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