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ISL6297 Datasheet(PDF) 9 Page - Intersil Corporation |
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ISL6297 Datasheet(HTML) 9 Page - Intersil Corporation |
9 / 16 page 9 FN9215.1 March 20, 2007 threshold is reached, all counters are reset to zero, the charge state machine is reset, the V2P9 pin outputs 2.9V, the open-drain MOSFET on the DT pin is turned on, and the ambient temperature monitoring circuit starts to function. EN Pin If all other charge conditions are met, pulling the EN pin low starts the ISL6297 charge operation. In a typical application, EN connects to the ID pin of a battery pack. Inside the battery pack the ID pin connects to ground through a resistance of less than 27k Ω. When the battery is not attached to the charger, the ISL6297 internally pulls the EN pin high to disable the charger. An RC filter on the ISL6297 EN input improves the charger ESD protection. Table 1 summarizes the status of each pin when the EN pin disables the IC. Plug-in Indication After power is applied to the ISL6297 and VIN exceeds the POR threshold, the LEDs provide a Plug-in Indication sequence. First the RED LED turns on for 500ms, then the GREEN LED turns on for 500ms, then both turn on for 500ms (giving a YELLOW indication), and finally all the LEDs turn off. The ISL6297 turns on an LED by pulling the output line LOW with a constant current of 10mA (typical). A typical bi-color LED needs no series resistor for the LED connection, however, current can be minimized by adding a serial resistor in each LED path. Idle Condition and Battery Connection Once VIN is greater than (VBAT + 50mV) and the temperature is within the allowed range the ISL6297 is ready to start the charge operation. Charging is initiated by plugging in the battery, which pulls the EN pin low. Connection Verification The EN pin going low starts a 500ms delay. After the delay, the ISL6297 turns on the charger for 70ms with a trickle charge current and an output voltage of VIN. If no battery is connected, the VSEN voltage will go up to approximately VIN. If no battery is detected after the 70ms period, the ISL6297 terminates the charge operation, turns off the output voltage, and sets the LEDs off. The device remains in this state until the EN pin is toggled or the device goes through a power cycle. (See Figure 5.) If the battery is connected within the 70ms open battery detect period, the voltage on VSEN pin needs to drop below the (falling) threshold of about 4.3V before the end of the 70ms period. If not, then the battery has not been properly connected and an open battery connection fault condition exists, requiring a power cycle or a toggle of EN. After the 500ms delay, if a battery is connected, the VSEN voltage will remain below the 4.4V threshold and the ISL6297 assumes that the battery is connected. The device turns on the Red LED to indicate a charge operation and starts a short circuit detection. (See Figure 4.) If the battery positive terminal comes loose and reconnects after this time, the charge operation sequence continues, but the LED indicates an end of charge condition, regardless of the state of charge. Short Circuit Detection To detect a short circuit condition the ISL6297 forces the trickle charge current to the battery. If, after 384 cycles, the battery voltage is below 1V, the ISL6297 considers the battery or connection to be short-circuited. In this condition, the charger turns off and a flashing yellow indicator displays the occurance of this “non-temperture” fault. To clear a short circuit fault condition requires that the enable pin be toggled, by removing the battery pack, or by cycling the power on the charger. Trickle Charge If there is no short circuit the voltage is higher than 1V and the charge operation continues with a trickle charge. In the trickle charge, the ISL6297 applies 10% of the programmed current to the battery. If the voltage on the cell is greater than 2.8V after 15 clock cycles, then the ISL6297 applies the full constant current charge to the cell. However, if the voltage on the cell does not rise above 2.8V in one eighth (1/8) of the TIMEOUT period, then a non-temperature fault occurs and the charger is turned off. A flashing yellow indicator announces this condition. TABLE 1. SUMMARY OF PIN BEHAVIOR WHEN THE IC IS DISABLED BY THE EN PIN PIN BEHAVIOR V2P9 Outputs 2.9V. RED High impedance. GRN High impedance. DT Low impedance. IREF Outputs 0.8V. IMIN Outputs 0.8V. TEMP The temperature monitoring circuit remains functioning. ISL6297 |
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