Datasheet LTC4015 (Analog Devices) - 27

LTC4015
OPERATION Li-Ion/LiFePO4 Battery Charger Operation
CV) charging. If the Li-Ion battery voltage is very low the The LTC4015 provides ful featured, inherently safe, charger will charge at a reduced (precharge) CC rate until constant-current/constant-voltage Li-Ion/LiFePO the battery voltage reaches an acceptable level. Then it will 4 battery charging. Features include battery presence detection, be charged at the full CC rate. CC-CV charging continues automatic recharge, maximum charge time safety timer, until the charge cycle terminates based on time (default) precharge (Li-Ion only), rapid absorb charge (LiFePO or battery current (C/x for Li-Ion programmable option). 4 only), programmable CV timer and C/x termination, therm-
LiFePO4 Charge Algorithm (without Absorption
istor temperature controlled charging, programmable
Phase) Overview
end-of-charge indication, programmable charge voltage, programmable charge current, J.E.I.T.A. support, battery (See Figure 5B for LiFePO4 battery charging state diagram) series resistance measurement, detailed status reporting, The charge algorithm begins with a battery detection test and programmable interrupt generation. and proceeds to constant-current constant-voltage (CC- CV) charging. CC-CV charging continues until the charge
LTC4015 Charge Algorithm Overview
cycle terminates based on time in CV mode (default) or The LTC4015 charge algorithms are based on a constant- battery current (C/x for LiFePO4 programmable option). current constant-voltage charging (CC-CV)technique. The Remaining in constant-voltage mode without termination battery is charged at a constant-current (CC) until the is also a LiFePO4 programmable option. battery reaches its charge voltage (VCHARGE) whereupon the delivered charge current is automatically reduced
LiFePO4 Charge Algorithm (with Absorption Phase)
to maintain the battery at a constant VCHARGE (CV). The
Overview
LTC4015 does not monitor or balance individual cells – (See Figure 5B for Li-FePO the full battery stack voltage is divided by number of cells 4 battery charging state diagram) (V/cell) for simplicity only. The 4015 is not a substitute An absorb phase can allow accelerated charging by raising for pack protection! the charge voltage, which may result in a higher CC rate, for a portion of the charge cycle. The charge algorithm Under voltage current limiting (UVCL) is used to automati- begins with a battery detection test and proceeds to CC-CV cally reduce charge current to help keep VIN from falling charging with a charge voltage of V below a minimum voltage. Input current limiting (ICL) is ABSORB, which is an absorb delta added to V used to automatically limit charge current to help keep CHARGE. CC-CV absorption charging continues until the V Input current below a maximum level. However, UVCL ABSORB is reached and charge current has dropped below the C/x threshold, or the maximum and ICL can only reduce charge current. The total load absorb phase time has passed. Upon exiting the absorb current from VIN cannot be limited by the LTC4015 if the phase the charge voltage is reduced from V load on the system exceeds the ICL setpoint. ABSORB to VCHARGE. CC-CV charging continues until the charge cycle terminates based on time in CV mode (default) or charge
Li-Ion Charge Algorithm Overview
current (C/x) (LiFePO4 programmable option). Remaining (See Figure 5A for Li-Ion battery charging state diagram) in constant-voltage mode without termination is also a The charge algorithm begins with a battery detection test LiFePO4 programmable option. and proceeds to constant-current constant-voltage (CC- 4015fb For more information www.linear.com/LTC4015 27 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Data Sheet Conventions Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram I2C Timing Diagram Operation Applications Information Register Description DETAILED Register Descriptions Typical Applications Package Description Revision History Typical Application Related Parts