R5478 Series

1-Cell Li-ion Battery Protection IC

The R5478 Series are high voltage CMOS-based protection ICs for over-charge/discharge of rechargeable one-cell Lithium-ion (Li+) / Lithium polymer excess load current, further include a short circuit protector for preventing large external short circuit current and Excess discharge-current.

Each of these ICs is composed of three voltage detectors, a reference unit, a delay circuit, a short circuit protector, an oscillator, a counter, and a logic circuit. When the over-charge voltage crosses the detector threshold from a low value to a high value, the output of COUT pin switches to low level after internal fixed delay time. The conditions to release over-charge detector are different by mask options. In terms of so called “Latch function” version, after detecting over-charge, the detector can be reset and the output of COUT becomes "H" when a kind of load is connected to VDD after a charger is disconnected from the battery pack, and the cell voltage becomes lower than over-charge detector threshold. If a charger is continue to be connected to the battery pack, even the cell voltage becomes lower than over-charge detector threshold, over-charge state is not released. On the other hand, in terms of so called, “Released by voltage level” version, after detecting over-charge, when the cell voltage reaches the released voltage from over-charge, the output of COUT becomes “H”.

The output of DOUT pin, the output of Over-discharge detector and Excess discharge-current detector, switches to “L” level after internally fixed delay time, when discharged voltage crosses the detector threshold from a high value to a value lower than VDET2.

The conditions to release over-discharge detector are also different by mask options. In terms of so called “Latch function” version, after detecting over-discharge voltage, connect a charger to the battery pack, and when the battery supply voltage becomes higher than over-discharge detector threshold, VD2 is released and the voltage of DOUT pin becomes "H" level. On the other hand, in terms of so called “Released by voltage level” version, in case that the charger is not connected, when the cell voltage becomes equal released voltage from over-discharge, over-discharge detector is released. In case that a charger is connected, and when the cell voltage becomes the released voltage from over-discharge, the over-discharge detector is released.

An excess discharge-current and short circuit state can be sensed and cut off through the built in excess current detector, VD3, with DOUT being enabled to low level. Once after detecting excess discharge-current or short circuit, the VD3 is released and DOUT level switches to high by detaching a battery pack from a load system.

After detecting over-discharge, supply current will be kept extremely low by halting internal circuits' operation.

When the output of COUT is “H”, if V- pin level is set at Vss-2V, the delay time of detector can be shortened.

Especially, the delay time of over-charge detector can be reduced into approximately 1/57. Therefore, testing time of protector circuit board can be reduced. Output type of COUT and DOUT are CMOS. 6-pin, SOT-23-6 is available.