Nisshinbo Two New Series of 1-cell Li-ion Battery Protection Ics:NB7141, The World‘s First Product with A Built-in Watchdog Timer, and NB7140, A Product with Forced Reset Function

PublishTime： 2022-12-09 Article Source：Nisshinbo News

Nisshinbo Micro Devices Inc. has launched two new series of 1-cell Li-ion Battery Protection ICs. These are the NB7141 series, the world's first^(*1) product with a built-in watchdog timer, and the NB7140 series, a product with a forced reset function.

Overview

Devices that use 1-cell Li-ion batteries, such as wearable/hearable devices, hearing aids, and health devices, have a growing market due to the proliferation of VR/AR (Virtual Reality/Augmented Reality) devices and increasing health awareness. Furthermore, demands for safety improvement are increasing as people wear those devices directly, and safety measures are also becoming more important for the protection functions of batteries.

These two new products feature industry-leading high-accuracy overcharge, over-discharge, and discharge overcurrent detection functions for 1-cell batteries, as well as a forced standby function. In addition, the 0V battery charging inhibition voltage of the two new ICs is configurable more flexibly than that of conventional ones. Furthermore, the NB7140 series has a forced reset function, and the NB7141 series is the world's first 1-cell protection IC equipped with a watchdog timer function. They contribute to the competitiveness of customers' Li-ion battery applications with high accuracy, low consumption, improved safety, and small dimensions.

NB7140 Series (WLCSP-8-P10 Package)

*1 Based on Nisshinbo Micro Devices Inc. research, as of December 2022.

*2 The price is based on the consumption tax rate as of December 2022.

Features

1. World's First Product with Built-in Watchdog Timer (NB7141)

Incorporating a watchdog timer makes it possible to externally monitor a microcontroller in case of uncontrolled operation. This eliminates the need for additional specialized ICs and reduces mounting area. Compared to a watchdog timer embedded in a microcontroller, it can ensure more safety because there is no risk of watchdog timer malfunction due to common causes with the microcontroller.

2. Forced Reset Function (NB7140)

Using the RST (reset) terminal enables to turn off of the charge and the discharge FETs, which makes the leak test of the protection circuit easy. Additionally, installing the RST terminal allows the system power supply to be cut off by turning off the FETs when a microcontroller runs out of control, which can reset the power supply to the microcontroller. This improves the stability of the system.

3. Industry-leading High-accuracy Two-step Discharge Overcurrent Detection

Discharge overcurrent detection voltage 1：

0.005 V to 0.030 V, Accuracy: ±1.0mV,

0.0305 V to 0.050 V, Accuracy: ±1.5mV

Discharge overcurrent detection voltage 2：

0.011 V to 0.060 V, Accuracy: ±2.0mV,

0.0605 V to 0.100 V, Accuracy: ±4.0%

The low voltage and higher accuracy of the overcurrent detection allow using a sense resistor with low resistance. This reduces the impedance of a battery pack, thereby reducing the heat generation at high currents and simplifying the thermal design of a board.

4. Industry-leading High-accuracy Overcharge Detection

Detection voltage range: 4.2V to 4.7V, Accuracy: ±15mV
The improved accuracy contributes to strengthening safety in the trend of charging voltage increase.

5. Industry-leading High-accuracy Over-discharge Detection

Detection voltage range: 2.1V to 3.2V, Accuracy: ±35mV
This contributes to longer battery life by enabling the remaining battery charge to be used as close to an allowable value as possible.

6. Industry-leading Low Supply Current

(Normal Mode) NB7140: Typ. 1.5μA / Max. 3.0μA (25% improvement compared to our conventional product),

NB7141: Typ. 2.0μA / Max. 4.0μA

(Standby Mode) Max. 0.04μA (Over-discharge detection latch type),

Max. 0.20μA (Over-discharge detection auto-release type)

A long operating time of applications is achieved thanks to low supply current at normal mode and standby mode.

7. High-accuracy 0 V Battery Charging Inhibition Voltage

Setting range: 1V to 2.5V, Accuracy: ±4.0%
Since charging 0V batteries (low-voltage batteries) may cause an internal short circuit, it can meet the demand for detailed settings of the inhibition voltage from a safety viewpoint.

8. Forced Standby Function

The STB (standby) terminal makes it possible to enter forced standby mode without putting batteries into the over-discharge state, which reduces current consumption significantly until a charger is connected. This makes it possible to minimize battery loss during inventory periods prior to product shipment.

9. Package

An ultra-thin, ultra-small, and leadless package WLCSP-8-P10 (1.6×1.0× 0.3mm) is adopted.

Main Specifications

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