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IC chip set for managing multi-cell series-connected lithium-ion batteries

2009 News Release

December 7, 2009

Oki Semiconductor starts mass production of an IC chip set for managing multi-cell series-connected lithium-ion batteries

Adaptable to lithium-ion battery packs with 5 to 13 cells, with the optimum configuration for electric bicycles and tools

Oki Semiconductor has completed development of the chip set “MK5207”, capable of providing all functions for controlling, monitoring and protecting systems using multiple-cell series-connected lithium-ion battery packs, which production launches in December. This chip set consists of the following two ICs:

ML5207 Analog front end IC for monitoring
ML5227 Controller IC

By using this chip set, it will become possible to construct a battery pack protection system with functions such as cell-balancing during charging ^(Note1), overcharge/over-discharge detection ^(Note2), and short circuit detection ^(Note3). It is possible to store parameters such as those for overcharge/over-discharge detection in the built-in Flash Memory, making it adaptable for various systems according to customer’s needs. Also, since the control program code for this chip set is stored in the built-in Flash Memory, no external memory is required. As effective utilization of energy is required from the viewpoint of global efforts concerning environmental issues, leadstorage batteries are being replaced by energy-efficient lithium-ion batteries at an accelerated rate, in the fields of industrial and commercial equipments. Meanwhile, since lithium-ion batteries are vulnerable to overcharge and over-discharge, careful control is required when charging/discharging them.
”Responding to these market needs, we have developed the chip set “MK5207”, to provide all functions for controlling, monitoring and protecting systems using multiple-cell series-connected lithium-ion battery packs” says HIROSHI ENOMOTO, President of OKI Semiconductor. “Lithium-ion battery is key device for Hybrid Electric Vehicle/Electric Vehicle. We are aiming that market” adds ENOMOTO.

This chip set is co-developed with Chinese design firm “Tianjin Nanda Qiangxin IC Design Co.,Ltd.” and Japanese “Hakutsu Technology Corporation.”

Features

Compatible with multiple-cell series-connected (5 to 13 cells) lithium-ion battery packs, adopting high-voltage process (80V)
Highly accurate overcharge/over-discharge voltage detection for each cell (detection accuracy: ±35mV @Ta=25°C)
Creates a bypass route for each cell, and realizes a highly accurate cell-balancing function during charging
Mounted with system protection function to deal with irregular operation
Low power consumption (under normal operation: 232μA @typ)

Field of application

Electrically assisted bicycles, electric bicycles
Electric tools
UPS (Uninterruptible Power Supply)

Future developments

Oki Semiconductor is planning to expand product lineup of charge/discharge controller ICs for multiple-cell series-connected lithium-ion battery packs, for industrial and commercial equipments and vehicle uses.

Sales plan

Product name: MK5207
Sample shipment: Currently being supplied
Evaluation board (rental): December 2009
Evaluation board (sales): December 2009 (with control software for PC)
Product launch: Starting from December 2009

Overview/features

Compatible with multi-cell series-connected battery packs

This chip set is compatible with battery packs using 5 to 13 cells.
High accuracy voltage detection of each cell

Overcharge detection voltage: 3.6V to 4.4V (arbitrarily settable) Detection accuracy: ±35mV (Ta=25°C)

Overcharge release voltage: 3.4V to 4.4V (arbitrarily settable) Detection accuracy: ±35mV (Ta=25°C)

Over-discharge detection voltage: 2.0V to 3.0V (arbitrarily settable) Detection accuracy: ±35mV (Ta=25°C)

Over-discharge release voltage: 2.0V to 3.0V (arbitrarily settable) Detection accuracy: ±35mV (Ta=25°C)

Bypass circuit will be created for each cell, and a highly accurate cell balancing function will be realized during charge.
Mounted with system protection function to deal with irregular operation

Short circuit detection protection function:

Short circuit detection time can be set using an external capacitor.

Secondary protection function:

ML5207 is independently equipped with the function of overcharge/over-discharge detection for the total voltage of the battery pack, and also equipped with the function of communication clock halt detection for detecting communication abnormalities between ML5227 and ML5207.
Low consumption current

Under normal operation:

232μA (typ, total of the whole chip set)

Under power save mode:

105μA (typ, total of the whole chip set)

Under power-down mode:

58μA (typ, total of the whole chip set)
Range of operation temperature: -25°C to +85°C
Power-supply voltage: +8V to +57.2V (supplied to ML5207)
Package

ML5207:44pin plastic QFP (QFP44-P-910-0.80-2K)

ML5227:48pin plastic TQFP(TQFP48-P-0707-0.50-K)

Glossary

Note1: Cell-balancing: A function to balance cell voltage by creating a bypass route for each cell, so that when charging, charging current to cells with high voltage shall be bypassed, and only cells with low voltage is charged.
Note2: Overcharge/over-discharge detection: Overcharge detection is a function to detect overcharging when the voltage of each cell exceeds a certain level, or when the charging current exceeds a certain level, while charging.
Over-discharge detection is a function to detect over-discharging when the voltage of each cell falls below a certain level, or when the discharging current exceeds a certain level, while discharging.
By detecting overcharge/over-discharge, MK5207 controls the MOSFET (Metal Oxide Semiconductor Field Effect Transistor), makes it block the current path, and automatically protects the battery pack and the connected device (charger or load).
Note3: Short circuit detection: This is a function to detect short circuits when more than a certain amount of current (more than that of over-discharge detection) flows from the battery pack to the load. When short circuit is detected, MK5207 controls the MOSFET (Metal Oxide Semiconductor Field Effect Transistor) for charge/discharge, makes it block the current path, and automatically protects the battery pack and the load.

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