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Ricoh R5640 / R5641 secondary protection ICs

17 April 2018

In recent years, the number of applications using high energy density Li-Ion batteries has increased significantly. There is a growing need to comply with functional safety standards, secondary protection ICs are developed to provide an additional safety level for Li-Ion batteries in case the primary protection circuit fails.

Li-Ion batteries are safe in general when used according to the specifications but can become a potential hazard in case of an internal or mechanical failure. Overheating, emitting fumes or even worse can be the result, also the manufacturers reputation can become seriously harmed when a disaster strikes.

The operation of the IC is fully independent from the primary protection and protects for over-charge voltage only. Once triggered and after a delay time, an external N-channel MOSFET is turned on and cuts an internal fuse which prevents the battery pack from charging again and will become beyond repair.

Targeted devices are power tools, laptop computers, medical devices and other portable applications with a multi-cell Li-Ion / Li-Polymer battery pack which require additional safety measures for enhanced reliability.

Significant detail for the R5640 / R5641 is that the current consumption of the IC is equal or lower than most other available solutions on the market and contributes reducing the self-discharge rate of the battery pack. Once the battery pack is discharged and the cell voltages drop below the shutdown detector threshold, the shutdown mode will be enabled causing all internal circuits to halt in order to decrease the self-discharge rate of the battery pack to a minimum.

The R5640 in a MSOP-8 package is a suitable solution for battery packs with two to five cells. As for larger multi-cell battery packs with six cells or more the R5640 has control inputs and outputs available for cascading multiple ICs. In this way it is possible to monitor battery packs with up to 10 or 15 cells for example.

The R5641 in a small DFN2020-8C package is designed for battery packs with two to four cells and has an option to add a thermal sensor to the circuit to monitor the temperature of the battery pack by using an external PTC resistor.

Ricoh Electronic Devices Co., Ltd has over 20 years of experience in developing and manufacturing protection ICs for Li-Ion batteries. We started with 1-Cell protection ICs mainly for mobile phone applications but our portfolio expanded significantly due to the vast popularity of Li-Ion Batteries. Our portfolio now consists of 1-Cell, 2-Cell, Multi-Cell, Secondary Protection and Analog Front End ICs. As for all our protection ICs we especially focus on specifications like low current consumption, high accuracy monitoring threshold settings, small package technology and enhanced safety circuits.

Features R5640 / R5641

Overcharge Detection Voltage:

Overcharge Detection Voltage Accuracy:


Overcharge Release Voltage:

Overcharge Detection Delay Time:

Overcharge Detection Delay Time Reset:

Release Condition:

Supply Voltage Vdd:

Supply Current:

Shutdown Current:

Shutdown Detection Voltage:

2 to 5 / 2 to 4 Cell Protection:

Cascade Function:

Temperature Protection:

CTLC Pin Detection Delay Time:

Output Type:

Package R5640 / R5641:

3.60 V / 4.10 V to 4.60 V (5 mV step)

± 0.015 V (Ta = 25°C)

± 0.020 V (0°C < Ta < 60°C)

Vdet1n 0 V to -0.4 V (50 mV step)

2 - 4 - 6 - 10 - 16 / 2 - 4 - 6 sec


Voltage Release Type

4.0 V to 25 V (30 V)

Typ.2.8 µA / 2.5 µA

Max. 0.2 µA

Typ. 2.5V ± 0.3V / 3.7V ± 0.3V

R5640 / R5641



2 msec

Pch. Open-drain / CMOS

MSOP-8 / DFN2020-8C

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-September 2019+