Nisshinbo Micro Devices NB7123

The NB7123 is an exceptional protection IC equipped with all standard safety features, such as overcharge/over-discharge voltage, charge/discharge overcurrent and short circuit detection, making the application highly reliable. The additional safety measures are mainly focussed on the detection range and improved accuracy level of these measurements, which is particularly important for small devices worn on the human body to prevent unintentional injuries when the Li-ion battery may fail, such as:

• High-accuracy overcharge and over-discharge detection (OVP & UVP) Both support extending battery life as the battery voltage can get nearer to the detection threshold level.
• High-accuracy overcurrent detection (OCP) and a low current sense voltage. Resulting in a more accurate overcurrent detection, but also the use of a small (Rsens) current-sense resistor causes lower heat generation at high currents.
• High-accuracy 0 V Battery Charging Inhibition Voltage. Charging a deep discharged battery from 0 V can cause an internal short circuit, the inhibition threshold voltage can be set in a 0.001 V step rate from a safety point of view.
• A TIN pin is available to connect a sensor to monitor the temperature of the battery cell. A unique feature of the NB7123 is the use of high-side MOSFETs which allow the ground of the protection circuit to be connected directly to the battery's negative terminal. This simplifies the design complexity as all measurement and control signals can be referenced to the same ground potential.

While using high-side MOSFETs offers advantages, they typically require a more complex gate control circuitry, as the gate voltage must be higher than the source voltage. Therefore, a dedicated charge pump is integrated, and no additional external components are required. Finally, the additional STB input offers a Forced Standby Function to set the product into a standby mode. Current consumption and further battery discharge can be significantly reduced in this way, the IC returns to the normal mode again when a charger is connected.

Key features

• Supply current: Normal mode: Typ. 7.0 μA / Max. 10.0 μA, Standby mode: Max. 0.04 μA
• Detector selectable range and accuracy:
  • Overcharge Detection Voltage (VDET1): 4.3 V to 4.7 V, ±6.5 mV
  • Over-discharge Detection Voltage (VDET2): 2.0 V to 3.0 V, ±17 mV
  • Discharge Overcurrent Detection Voltage (VDET3): 0.0060 V to 0.0400 V, ±1.00 mV
  • Charge Overcurrent Detection Voltage (VDET4): –0.0060 V to –0.0500 V, ±1.00 mV
  • Short Circuit Detection Voltage (VSHORT1): 0.0200 V to 0.1000 V, ±1.00 mV
• 0 V Battery Charging Inhibition Voltage (VNOCHG): 1.200 V to 2.000 V, ±20.0 mV
• Overtemperature Detection temperature (TDET): 40°C to 85°C, ±2.0°C
• Overcharge & Discharge:
  • Overcharge release: Latch
  • Over-discharge release: Latch
  • Discharge overcurrent release selectable: Auto release / Latch
• NTC Thermistor selectable: 100 kΩ / 470 kΩ
• Package NB7123ZA: WLCSP-8-ZA2

Applications

• Hearing aids
• Wearables
• Smartphones
• Handheld data terminals