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ISL6291-2CRZTR5155-T Datasheet(PDF) 8 Page - Intersil Corporation |
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ISL6291-2CRZTR5155-T Datasheet(HTML) 8 Page - Intersil Corporation |
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8 / 11 page  8 FN9102.2 May 2, 2005 charge time exceeds the TIMEOUT interval, a fault is issued and the charger is latched. The charger then enters the Fault state. The TIMEOUT limit is disabled when the TOEN pin is pulled to LOW (see TOEN pin description for more information). During the constant current charge mode, the STATUS pin remains LOW and the FAULT pin remains HIGH. Constant Voltage Charge Mode The ISL6291 regulates the battery terminal voltage at VCH in the constant voltage mode. As the battery continues being charged, the charge current starts to decrease, as shown in Figure 1. When the charge current drops to the minimum value IMIN, programmed by the IMIN pin, the charge cycle completes. The total charge time for the constant current mode and the constant voltage mode must not exceed the TIMEOUT interval, unless the TOEN pin is pulled LOW; otherwise, the charger also stops charging and indicates a FAULT status. During the constant voltage mode, the STATUS remains LOW and the FAULT remains HIGH. Two versions of ISL6291 (see Ordering Information) are available: a 4.1V termination voltage version, and a 4.2V termination voltage version. Inhibit State The charger enters the Inhibit State once a normal charge cycle completes. The ISL6291 then monitors the battery voltage. Once the battery voltage falls below the VRECHRG threshold, a new charge cycle starts, as shown in Figure 1. Both STATUS and FAULT are HIGH in this state. Fault State Two types of fault may occur during a charge cycle: the TIMEOUT fault (refer to the TIME pin and the TOEN pin description), and the temperature fault (see TEMP pin description and the Battery Pack Temperature Monitoring section). When a TIMEOUT fault occurs, the charger is latched. The latch is released only by recycling the input power or toggling the EN signal. When a temperature fault occurs, the charger is reset and a new charge cycle starts when the temperature fault ends. In case of a fault, the FAULT pin indicates a logic LOW and the STATUS pin outputs a logic HIGH. Standby State The charger is in the Standby State when the EN pin is held LOW or the wall adapter is removed. The charger draws less than 1µA of standby current when the adapter is removed. Timing Diagram Figure 2 summarizes the operation of the charger and the key signals after an adapter is attached to the charger input. No fault occurs in this diagram and the EN pin is assumed not connected to logic LOW. Internal Current Sensing A 100,000:1 current mirror is employed to sense the current in the pass element, as shown in the Block Diagram. The current mirror is trimmed to 10% accuracy. The second mirrored output, represented by ISEN2 in the block diagram, is used to compare with the IMIN pin current to determine the end-of-charge condition. Charge Current Control The charging current in the pass element is controlled by the current amplifier CA, as shown in the Block Diagram. The CA, the pass element, and the 100,000:1 current mirror form a control loop. During a trickle charge mode or a constant current charge mode, the control reference to the loop is the reference current IR. The voltage amplifier VA does not affect the loop operation because the battery voltage is lower than the charge termination voltage VCH, so that the voltage amplifier output is blocked by the diode connecting to the current reference. If the charge current in the PMOS pass element is too high, its mirrored output is higher than the reference IR. The non-inverting input of the current amplifier has a higher voltage than the inverting input so that the current amplifier output increases, reducing the gate-to- source voltage of the PMOS pass element. The current in the pass element thereby reduces. If the charge current is too low, the current amplifier output reduces to force the current to increase. During the Trickle mode charge, the current reference typically equals 1/10 of the current in the IREF pin. During the constant current mode, the reference current equals the current in the IREF pin. If the temperature inside the IC rises above a typical value of 100°C, the current source block starts to reduce the reference current IR at a rate of 0.4µA/°C for every degree of temperature rise. FIGURE 2. TIMING DIAGRAM AFTER AN ADAPTER IS ATTACHED TO THE CHARGER INPUT VIN V2P8 STATUS FAULT VBAT I CHARGE 15 Cycles to 1/8 TIMEOUT 15 Cycles POR Threshold 200us POR 3.0V V MIN V RECHRG t 0 t 1 t2 t3 t 4 t 5 t 6 t7 t 8 Charge Cycle Charge Cycle |
Similar Part No. - ISL6291-2CRZTR5155-T |
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Similar Description - ISL6291-2CRZTR5155-T |
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