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ISL6291-2CR Datasheet(PDF) 7 Page - Intersil Corporation |
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ISL6291-2CR Datasheet(HTML) 7 Page - Intersil Corporation |
7 / 11 page 7 FN9102.2 May 2, 2005 Description Initialization The ISL6291 initializes as the input voltage rises above the power-on-reset (POR) threshold. Once the input voltage reaches the POR level, the V2P8 pin outputs a 2.8V voltage. This output voltage can be used as an adapter presence indication and to bias the thermistor circuit. The POR takes about 200 µs. During the POR, the STATUS pin outputs a logic HIGH signal, and the FAULT pin outputs a logic LOW signal. Operation States Immediately after the POR, the charger enters a charge state. A charge state always cycles through a trickle mode, a constant-current mode, and a constant voltage mode, as shown in Figure 1. If the battery completes a charge cycle without a fault, the operation moves to the inhibit state, waiting for the battery to be discharged to start another charge cycle. Two types of fault may occur during a charge cycle, namely, a TIMEOUT fault or a temperature fault (refer to Functional Pin Description on TIME, TOEN, and TEMP pins). If a fault occurs during the charge modes, the operation enters the fault state. The charger is in a standby state when the adapter is removed, or the EN pin of the IC is pulled to LOW. In the standby state, the charger IC draws less than 1µA current from the battery. The two open-drain pins, STATUS and FAULT, indicate the operation states of the charger (see Table 1). The charger starts a new charge cycle when a wall adapter is plugged in, a new battery is inserted, a battery voltage drops below the re-charge threshold, a temperature fault ends, or the EN pin is toggled from LOW to HIGH. Trickle Charge Mode A charge cycle always starts with the trickle charge mode. The trickle charge mode is to pre-condition the battery and prepare it for the fast charge (constant current or constant voltage charge). It is not recommended to fast charge a Li-ion battery when the battery is deeply discharged, indicated by a low battery voltage. When the ISL6291 sees a battery voltage lower than the VMIN given in the Electrical Specifications, it forces 1/10 of the current in the constant current mode into the battery. The charger stays in the trickle mode until the battery voltage is above VMIN for 15 consecutive oscillation cycles (TOSC). The 15-cycle delay is to avoid entering the constant current mode accidentally, caused by any transient voltage spike on the battery pack terminals. The charge time for the trickle mode is limited to 1/8 of the TIMEOUT interval (see TIME pin description and Figure 1). If the trickle charge time takes longer than 1/8 of the TIMEOUT interval, a TIMEOUT fault is issued and the charger is latched. The minimum trickle charge time is 15 TOSC, and the maximum time is 1/8 TIMEOUT. During the trickle mode, the STATUS pin is set to logic LOW, and the FAULT pin is set to logic HIGH. Constant Current Charge Mode The battery is charged with a constant current programmed by the IREF pin resistor (see IREF pin description) during the constant current mode. The constant current is trimmed to 10% accuracy. The battery voltage rises towards the charge termination voltage VCH in this mode. The constant current mode ends when the battery voltage reaches VCH. The internal clock counter limits the maximum time for the constant current mode to the TIMEOUT interval. The counter is reset at the beginning of the this charge mode. If the TABLE 1. STATUS INDICATIONS FAULT STATUS INDICATION HIGH HIGH Charge completed with no fault (Inhibit) or Standby HIGH LOW Charging in one of the three modes LOW HIGH Fault *Both outputs are pulled up with external resistors. FIGURE 1. MODES OF OPERATION V CH V RECHRG TIME 0 0 TIMEOUT Constant Voltage Mode Constant Current Mode Trickle Mode Inhibit CC Mode CV Mode V MIN Trickle time < 1/8 TIMEOUT Trickle Mode I REF I REF/10 I MIN |
Similar Part No. - ISL6291-2CR |
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Similar Description - ISL6291-2CR |
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