Multi-Cell Li-ion Battery Protection ICs
Ricoh's multi-cell Li-ion/polymer battery protection ICs have several advanced features such as Cell Balance Function, Cascade Connection and Breaking Wire Detection.
Cell Balance Operation
(1) When a cell voltage is lower than the cell balance threshold, a cell is charged.
(2) When a cell voltage becomes higher than the cell balance threshold, CB1 pin becomes "H" and N-channel transistor turns on, and then the cell balance operation starts. Then a bypass current flows to the direction of a arrow and a charge current becomes suppressed by the bypass current.
(3) When a cell voltage reaches to the over-charge threshold, cell charging stops after the output delay time.
(4) If charging to a cell stops, the cell balance operation continues until a cell voltage becomes lower than the cell balance released threshold. The bypass current continues to flow decreasing the cell voltage.
(5) When a cell voltage reaches to the cell balance released voltage, CB1 pin becomes "L" and N-channel transistor turns off, and then cell balance operation stops.
Breaking Wire Detection
In case of using a battery pack in electric power tools exposed to heavy vibrations, there is a risk that the protection circuit fails due to a breaking wire condition between battery cells and protection circuit board.
The Breaking Wire Detection circuit performs a test at fixed intervals, depending on the capacitance connected to CTLT pin. When a breaking wire event occurs, it results in interrupting the charge or discharge condition.
Multi cell Li-ion/polymer battery protection ICs can protect over 6cells by cascade connection.