The FS312F-G protection IC for Li-ion/polymer rechargeable one-cell batteries maintains high accurate detections of the abnormal cell activities and the corresponding delay time in order to have protections against the events of over charge, over discharge, and over current.
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12. Design Guide. Selection of External Control MOSFET Suppressing the Ripple and Disturbance. from Charger
12. Design Guide Selection of External Control MOSFET Suppressing the Ripple and Disturbance from Charger To suppress the ripple and disturbance from charger, connecting R1 and C1 to VCC is recommended. FO Fo P R r R ro TU ef pe NE er rti ' en es ce O nl y Because the overcurrent protection voltage is preset, the threshold current for overcurrent detection is determined by the turn-on resistance of the charge and discharge control MOSFETs. The turn-on resistance of the external control MOSFETs can be determined by the equation: RON=VOIP/ (2 x IT) (IT is the overcurrent threshold current). For example, if the overcurrent threshold current IT is designed to be 3A, the turn-on resistance of the external control MOSFET must be 25mΩ. Be aware that turn-on resistance of the MOSFET changes with temperature variation due to heat dissipation. It changes with the voltage between gate and source as well. (Turn-on resistance of MOSFET increases as the voltage between gate and source decreases). As the turn-on resistance of the external MOSFET changes, the design of the overcurrent threshold current changes accordingly. Protection the CS pin R2 is used for latch-up protection when charger is connected under overdischarge condition and overstress protection at reverse connecting of a charger.
