Datasheet LTC4010 (Analog Devices) - 10

LTC4010 operaTion
(Refer to Figure 1) Shutdown State
returns to the charge qualification state. If VCELL exceeds The LTC4010 remains in micropower shutdown until V 1.95V, charging stops and the IC enters the fault state. If an CC (Pin 15) is driven above BAT (Pin 10). In shutdown all external thermistor indicates sensed temperature is beyond status and PWM outputs and internally generated supply a range of 5°C to 60°C, or the internal die temperature voltages are inactive. Current consumption from V exceeds a resonable value, charging is suspended, the CC and BAT is reduced to a very low level. charge timer is paused and the LTC4010 indicates a fault condition. Normal charging resumes from the previous
Charge Qualification State
state when the sensed temperature returns to a satisfactory range. In addition, other battery faults are detected during Once VCC is greater than BAT, the LTC4010 exits micropower specific charging states as described below. shutdown, enables its own internal supplies and switches VCDIV to GND to allow measurement of the average single-
Precharge State
cell voltage. The IC also verifies that VCC is at or above 4.2V, V If the initial voltage on VCELL is below 900mV, the LTC4010 CC is 510mV above BAT and VCELL is between 350mV and 1.95V. If V enters the precharge state and enables the PWM current CELL is below 350mV, no charging will occur, and if V source to trickle charge using one-fifth the programmed CELL is above 1.95V, the fault state is entered, which is described in more detail below. Once adequate voltage charge current. The CHRG status output is active during conditions exist for charging, READY is asserted. precharge. The precharge state duration is limited to tMAX/12 minutes, where tMAX is the maximum fast charge If the voltage between VTEMP and GND is below 200mV, the period programmed with the TIMER pin. If sufficient VCELL LTC4010 is paused. If VTEMP is above 200mV but below voltage cannot be developed in this length of time, the fault 2.85V, the LTC4010 verifies that the sensed temperature state is entered, otherwise fast charge begins. is between 5°C and 45°C. If these temperature limits are not met or if its own die temperature is too high, the
Fast Charge State
LTC4010 will indicate a fault and not allow charging to If adequate average single-cell voltage exists, the LTC4010 begin. If VTEMP is greater than 2.85V, battery temperature enters the fast charge state and begins charging at the related charge qualification, monitoring and termination programmed current set by the external current sense are disabled. resistor connected between the SENSE and BAT pins. Once charging is fully qualified, precharge begins (unless The CHRG status output is active during fast charge. If the LTC4010 is paused). In that case, the VTEMP pin is VCELL is initially above 1.325V, voltage-based termination monitored for further control. The charge status indicators processing begins immediately. Otherwise –∆V termination and PWM outputs remain inactive until charging begins. is disabled for a stabilization period of tMAX/12. In that case, the LTC4010 makes another fault check at tMAX/12,
Charge Monitoring
requiring the average cell voltage to be above 1.22V. This The LTC4010 continues to monitor important voltage and ensures the battery pack is accepting a fast charge. If temperature parameters during all charging states. If V V CC CELL is not above this voltage threshold, the fault state is drops to the BAT voltage or lower, charging stops and the entered. Fast charge state duration is limited to tMAX and shutdown state is entered. If V the fault state is entered if this limit is exceeded. CC drops below 4.25V or VCELL drops below 350mV, charging stops and the LTC4010 4010fb 0 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Related Parts