Ricoh launches two secondary protection ICs for multi-cell Li-Ion / Li-Polymer battery packs

Amstelveen, the Netherlands, 30 March 2018 - Ricoh Electronic Devices Co., Ltd. in Japan has launched the R5640 and R5641 secondary protection ICs. Designed to use in Li-Ion / Li-Polymer rechargeable battery packs with two to four / five cells, the ICs feature high accuracy overvoltage detection, low current consumption, cascade function and over-temperature detection.

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

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.

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 R5641 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.

As for large multi-cell battery packs with 6 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 R5640 is available in a MSOP-8 package whilst the R5641 has a small DFN2020-8C package.

Features R5640 / R5641
Overcharge Detection Voltage:	3.60 V / 4.10 V to 4.60 V (5 mV step)
Overcharge Detection Voltage Accuracy:	± 0.015 V (Ta = 25°C)
± 0.020 V (0°C < Ta < 60°C)
Overcharge Release Voltage:	Vdet1n 0 V to -0.4 V (50 mV step)
Overcharge Detection Delay Time:	2 - 4 - 6 - 10 - 16 / 2 - 4 - 6 sec
Overcharge Detection Delay Time Reset:	Optional
Release Condition:	Voltage Release Type
Supply Voltage Vdd:	4.0 V to 25 V (30 V)
Supply Current:	Typ.2.8 µA / 2.5 μA
Shutdown Current:	Max. 0.2 μA
Shutdown Detection Voltage	Typ. 2.5V ± 0.3V / 3.7V ± 0.3V
2 to 5 / 2 to 4 Cell Protection:	R5640 / R5641
Cascade Function:	R5640
Temperature Protection:	R5641
CTLC Pin Detection Delay Time:	2 msec
Output Type:	Pch. Open-drain / CMOS
Package R5640 / R5641:	MSOP-8 / DFN2020-8C