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ISL9205BIRZ Datasheet(PDF) 10 Page - Intersil Corporation |
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ISL9205BIRZ Datasheet(HTML) 10 Page - Intersil Corporation |
10 / 14 page 10 FN9252.1 May 16, 2007 During the constant voltage phase, the charge current reduces gradually as the cell voltage rises. Charge Termination and Recharge As the charge current reaches the EOC (end-of-charge) current threshold during the constant voltage phase, the STATUS pin open-drain FET is turned off to indicate an EOC condition. The EOC current is programmable for the ISL9205 by connecting a resistor from the IMIN pin to GND. For others, the EOC current is fixed at 10% of the programmed constant charge current. If the timeout function is available and enabled, the charger will be terminated when the user programmed charge time limit has been reached. If the timeout function is disabled by the TOEN pin (ISL9205), or not available (ISL9205A), the charger will continue to charge until the EN pin is pulled to logic LOW or the input power has been removed. Should the charge be terminated by the timeout function, recharge will occur when the battery voltage falls to 150mV below the constant voltage value. The STATUS open-drain FET is turned on when a recharge condition is met, whether the charger is previously terminated or not. An internal delay is implemented at the STATUS pin for both EOC and recharge conditions to prevent nuisance trips due to noise and fast load current transitions. The delay time is approximately one clock cycle (varies between 0.5 and 1.5 clock) of the internal oscillator, which is programmed by the timer capacitor. The typical charge waveforms in Figure 13 show the complete cycle operation. Temperature Monitoring and Thermal Foldback In the event where the die temperature reaches the thermal foldback threshold (+110°C typical), the charge current is reduced accordingly to prevent further temperature rise. In the ISL9205 and ISL9205D versions, there is an external temperature monitoring function. A negative temperature coefficient (NTC) thermistor can be connected between the TEMP pin and GND to monitor the battery temperature or ambient temperature. The hysteresis comparators internal to the ISL9205 provide a valid temperature window centered at the voltage of the TEMP pin, which is programmed by the NTC and the pull-up resistor connected to the pin. When the measured temperature is outside this window, the charger is paused (both the charger and the timer are stopped) and a fault indication is issued. If the thermistor is attached to the battery, the TEMP function can be used to discover a battery removal condition when the TEMP pin voltage is much higher than the reference threshold. POR The power-on reset (POR) function monitors the supply voltage. The POR has a rising edge threshold of 3.6V typical and 2.5V typical for falling edge. The charger is expected to operate when the input voltage is above the POR threshold. After POR the charger will continue to operate for supply voltage down to 2.5V typical. It is also required that the supply voltage be higher than the VBAT pin voltage by a typical 80mV for the charger to function. Oscillator, TIMEOUT, and Charge Cycle The ISL9205 incorporates with an oscillation circuit using an external timing capacitor connected to the TIME pin. The oscillator sets the limit for the maximum charge time during the trickle mode and the fast mode (CC and CV). The maximum charge time (TIMEOUT) for the fast mode is set by: TIMEOUT = 222tOSC where the tOSC is the oscillator period. The minimum programmable tOSC is 20μS (CTIME = 100pF). The time limit for the trickle charge is 1/8 of the fast mode time limit. In the ISL9205, the time-out function can be disabled by pulling the TOEN pin to logic LOW. When TIMEOUT is disabled, the charger will never be turned off after the EOC but will indicate the EOC condition through the STATUS pin. For the ISL9205B and the ISL9105D, the timeout function is always enforced. For the ISL9105A, there is not timeout function. A charge cycle is the time interval between the time when the charger is enabled to the moment it is disabled. If the battery voltage is lower than the trickle charge threshold at the time the charger is enabled, the charger enters the trickle mode and the timer is reset and its limit is set to 1/8 of TIMEOUT. If the timeout function is enabled, the charger will stop and indicate a TIMEOUT fault if the charge time is longer than the limit. If the trickle mode completes successfully before the time limit, the charger moves to CC mode and the timer is reset and the time limit is set to TIMEOUT. The charger needs to reach the EOC conditions before the TIMEOUT interval elapsed, otherwise, a TIMEOUT fault will be issued. The charger indicates the EOC with the STATUS pin but does not terminate until the TIMEOUT interval elapsed. Disabling TIMEOUT with TOEN In the ISL9205, the time-out function in fast charge state (CC/CV) can be disabled by pulling the TOEN pin to logic IREF TRICKLE CC CV IMIN 4.2V TIME 2.8V CHG CHARGE CURRENT CHARGE VOLTAGE STATUS INDICATION VREC 10% TIMEOUT 1/8 OF TIMEOUT IREF FIGURE 13. TYPICAL CHARGE CYCLE WITH TIMEOUT ISL9205 |
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