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MAX1926 Datasheet(PDF) 10 Page - Maxim Integrated Products |
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MAX1926 Datasheet(HTML) 10 Page - Maxim Integrated Products |
10 / 16 page Detailed Description The MAX1925/MAX1926 switch-mode battery chargers form a complete solution for a single-cell Li+ battery. The devices include battery undervoltage/overvoltage fault protection. The MAX1925/MAX1926 use EN and THRM for shutdown, battery detection, and temperature monitor- ing. The devices provide outputs to indicate charge sta- tus (CHG) and presence of input power (ACON). The MAX1925/MAX1926 include two prequalification modes that must be passed before the charger enters the fast-charge state. During fast charge, the charger operates initially in constant-current mode until the bat- tery voltage reaches 4.2V. When the battery voltage has reached 4.2V, the charger operates in constant- voltage mode. In constant-current mode, the charger acts as a hysteretic current source, controlling the inductor’s peak and valley currents. In constant-voltage mode, the charger regulates the peak and valley of the output ripple. Charge Cycle The MAX1925/MAX1926 initiate PREQUAL when one of the following occurs: • When an external power source is connected • The cell voltage falls to 4V after charging is finished • EB is toggled • Input power is cycled Some Li+ cells can be damaged when fast-charged from a completely dead state. Moreover, an over-dis- charged cell may indicate a dangerous abnormal cell condition. As a built-in safety feature, the MAX1925/ MAX1926 use a two-level prequalification charge to determine if it is safe to charge. When the cell voltage is less than 2V, the cell is charged from an internal Switch-Mode 1-Cell Li+ Chargers 10 ______________________________________________________________________________________ RESET (ACON IS LOW) OFF (ACON HIGH Z) SHDN (ACON HIGH Z) ANY STATE (INCLUDING FAULT) EN HIGH AND IN WITHIN ACON WINDOW* EN LOW OR IN OUTSIDE ACON WINDOW* VBATT > 2V (DEBOUNCED) VBATT > 3V (DEBOUNCED) FULL TOPOFF (CHG LED OFF) DONE (CHG LED OFF) KELVIN (CHG LED OFF) F_PQ1 F_VB tPREQUAL1 TIMES OUT BEFORE VBATT > 2V F_PQ2 F_FULL tPREQUAL2 TIMES OUT BEFORE VBATT > 3V tFULLCHG TIMES OUT BEFORE ENTERING FULL TOP-OFF STATE 10-SECOND TIMER FULL-CHARGE TIMER TIMES OUT VBATT < 4.2V *SEE TABLE 2 FOR ACON WINDOW FOR MAX1925/MAX1926 VBATT > 4.35V AND IN WITHIN ACON WINDOW* AND EN HIGH VIN WITHIN ACON WINDOW* VIN < VBATT VIN > VBATT VIN < VBATT VIN > VBATT AND VIN OUTSIDE ACON WINDOW* AUTOMATIC RESTART BATT DROPS TO 4V VBATT > 4.2V F-TEMP TEMP IN RANGE TEMP OUT OF RANGE VIN OUTSIDE ACON WINDOW* PREQUAL1 (ICHG = 4mA) (CHG LED ON) PREQUAL2 (ICHG = C/10) (CHG LED ON) FASTCHG (ICHG = C) (CHG LED ON) ICHG < C/8 (DEBOUNCED) FAULT (CHG LED BLINK AT 0.5Hz) (EXT HIGH FET OFF) Figure 2. MAX1925/MAX1926 State Diagram |
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Similar Description - MAX1926 |
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