Texas Instruments' bq77905 device is a low-power battery pack protector that implements a suite of voltage, current, and temperature protections without microcontroller (MCU) control. Protection thresholds and delays are factory-programmed and available in a variety of configurations. Separate over-temperature and under-temperature thresholds for discharge (OTD and UTD) and charge (OTC and UTC) are provided for added flexibility.
The device achieves pack protection via the integrated, independent CHG and DSG, low-side NMOS FET drivers, which may be disabled via two control pins. These control pins may also be used to achieve cell-protection solutions for higher series (6S and beyond) in a simple and economical manner. To do this, simply cascade a higher device's CHG and DSG outputs to the immediate lower device's control pins. For reduced component count, all protection faults use internal delay timers.
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- Voltage protection (accuracy ±10 mV)
- Over-voltage: 3 V to 4.575 V
- Under-voltage: 1.2 V to 3 V
- Open-cell and open-wire detection (OW)
- Current protection
- Over-current discharge 1: -10 mV to -85 mV
- Over-current 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
- Normal mode: 6 µA
- Shutdown mode: 0.5 µA (max.)
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- Temperature protection
- Over-temperature charge: 45°C or 50°C
- Over-temperature discharge: 65°C or 70°C
- Under-temperature charge: -5°C or 0°C
- Under-temperature discharge: -20°C or -10°C
- Additional features
- Independent charge (CHG) and discharge (DSG) FET drivers
- SimpleStack interface for easy stacking
- 36 V absolute maximum rating per cell input
- Built-in, self-test functions for high reliability
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