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ISL6299 Datasheet(PDF) 6 Page - Intersil Corporation |
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ISL6299 Datasheet(HTML) 6 Page - Intersil Corporation |
6 / 8 page 6 FN9184.0 March 17, 2005 GND (Pin 8) System ground. ICDL (Pin 9) The ICDL pin has two functions. The first function is to program the cradle charge current during the constant- current mode. The voltage of this pin is 1.22V during the constant-current mode of the cradle charger. The constant- current mode current is programmed by the following equations: where RICDL is the resistor in Ω, connected to the ICDL pin (see the Typical Application). It is recommended that the charge current be programmed in the range of 350mA to 650mA. The second function of the ICDL pin is to monitor the actual charge current. The voltage of this pin, VICDL, is proportional to the actual charge current, ICHG. The cradle charge current should be programmed equal or higher than the USB current; otherwise, the ICDL pin voltage will be higher than 1.22V during the constant current mode when the USB charger is working. The charger still works properly but the accuracy of the current monitoring voltage degrades and saturates at approximately 2.1V. BAT (Pin 10) Charger output pin. Connect this pin to the battery pack or the battery cell. A 1µF or larger value ceramic capacitor is recommended for decoupling. The charger relies on the battery for stability so a battery should always be connected to the BAT pin. Description The ISL6299 is designed for a single-cell Li-ion or Li-polymer battery charging circuit that accepts both a USB port and a desktop cradle as its power source. While the charge current from the USB input source is fixed at 380mA, the charge current from the cradle input is programmable between 0.1A and 1.0A by the resistor RICDL. Similarly, the end-of-charge current is fixed at typically 80mA for the USB input and programmable for the cradle input by the resistor RIMIN. Input Auto Selection When both input sources are present, the charger selects only one power source to charge the battery. When the CRDL input is higher than the POR threshold, CRDL is selected as the power source. Otherwise the USB input is selected. If the CRDL input voltage is below the battery voltage but the USB input voltage is higher than the battery voltage, then the USB input is used to charge the battery. The control circuit always breaks both internal power devices before switching from one power source to the other to avoid a cross conduction of both power MOSFETs. USB Charge Current When the USB port is selected as the power source, the charge current enabled by the logic input at the USBON pin. When the USBON is driven to logic LOW, the charger is disabled. When the USBON is driven to logic HIGH, the charge current is fixed at a typical value of 380mA. Thus for the USB input, the USBON pin has a similar function as the EN pin. The following table describes the USB charge control by both the USBON pin and EN pin: The USBON pin is equivalent to a logic LOW when left floating. Typically the P-channel MOSFET for the USB input has an rDS(ON) of 700mΩ at room temperature. With a 380mA charge current, the typical head room is 260mV. Thus, if the input voltage drops to a level that the voltage difference between the USB pin and the BAT pin is less than 260mV, the rDS(ON) becomes a limiting factor of the charge current; and the charger drops out the constant current regulation. Cradle Charge Current The cradle charge current is enabled by the EN pin only, the USBON pin has no control on the cradle charge current. The cradle charge current is programmed with the external resistor connected between the ICDL pin and the GND pin. The current can be calculated with one of the equations given in the ICDL pin description. Two equations are used for the cradle current calculation, each corresponds to a different range of currents. The typical rDS(ON) of the P-channel MOSFET for the CRDL input is 600m Ω at room temperature. When the head room between the input and output voltages is small, the actual charge current, similar to the USB case, could be limited by the rDS(ON). On the other hand, if the head room between the input and output voltages is large, the charge current may be limited by the thermal foldback threshold. Floating Charge Voltage The floating voltage during the constant voltage phase is 4.2V. The floating voltage has an 1% accuracy over the ambient temperature range of -40°C to 70°C. ICLD 16685.5 RICDL --------------------- 0.026 0.1A ICLD 0.7A << – = ICDL 21242.1 RICDL --------------------- 0.188 0.7A ICDL 1.1A << – = TABLE 1. USB CHARGE CONTROL EN = LOW EN = HIGH USBON = LOW Disabled Disabled USBON = HIGH Enabled Disabled ISL6299 |
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