Datasheet LTC4071 (Analog Devices) - 9

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OPERATION Low Battery Disconnect/Connect: LBD/LBC Low Battery Select: LBSEL
The low battery disconnect (VLBD) and connect (VLBC) The low battery discharge cutoff voltage level is pro- voltage levels are programmed by the LBSEL pin. As grammed by the LBSEL pin. shown in the Block Diagram the battery disconnects from The LBSEL pin allows the user to trade-off battery run- VCC by shutting off MP1 when the BAT voltage falls below time and maximum shelf life. A lower battery disconnect VLBD. This disconnect function protects Li-Ion batteries threshold maximizes run time by allowing the battery to from permanent damage due to deep discharge. If the fully discharge before the disconnect event. Conversely, voltage of a Li-Ion cell drops below a certain level, the cell by increasing the low battery disconnect threshold more may be permanently damaged. Disconnecting the battery capacity remains following the disconnect event which from VCC prevents the load at VCC as well as the LTC4071 extends the shelf life of the battery. For maximum run quiescent current from further discharging the battery. time, tie LBSEL to VCC so that the battery disconnects at Once disconnected the VCC voltage collapses towards VCC = 2.7V. For extended shelf life, tie LBSEL to GND so ground. When an input supply is reconnected the bat- that the battery disconnects at VCC = 3.2V. If a high peak tery charges through the internal body diode of MP1. The current event is expected, users may temporarily select input supply voltage should be larger than VLBC_VCC to the lower disconnect threshold. This avoids disconnect- ensure that MP1 is turned on. When the VCC voltage ing the battery too early when the load works against the reaches VLBC_VCC, MP1 turns on and connects VCC and battery series resistance and temporarily reduces VCC. BAT. While disconnected, the BAT pin voltage is indirectly sensed through MP1’s body diode. Therefore VLBC var- ies with charge current and junction temperature. Please see the Typical Performance Characteristics section for more information. Rev. D For more information www.analog.com 9 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Typical Application Related Parts