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ISL9220B Datasheet(PDF) 9 Page - Intersil Corporation |
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ISL9220B Datasheet(HTML) 9 Page - Intersil Corporation |
9 / 15 page ISL9220B 9 FN7652.1 July 2, 2010 If the battery voltage is less than the pre-charge voltage (VPCHG), the charger operates in LDO mode, with an output current fixed at 50mA typical. In this mode, the output voltage can go to 0V. This provides the ability to recover a battery that has entered a safety-circuit undervoltage fault mode. When the cell voltage exceeds the pre-charge voltage threshold (VPCHG), fast charging will commence. If this threshold is not reached within the precharge timer period, a TIME-OUT-FAULT condition is asserted, and the charger is disabled. Charge Safety Timer An internal oscillator establishes a timing reference. The oscillation period is programmable with an external capacitor at the TIME pin, CTime, as shown in the “Typical Application” diagram on page 6. The oscillator charges the timing capacitor to 1.5V and then discharges it to 0.5V in one period, both with 10μA current. The period tOSC is: Where CTime is in F. A 1nF capacitor provides 0.2ms oscillation period. The allowable range of CTime value is 100pF to 1μF, providing a programmable charge safety-timeout range of about 1.4 minutes to almost 10 days. Total charge time, excluding any time required for precharge, is limited to a length of TIMEOUT. This can be calculated using Equation 3: Total charge time for battery precharge is limited to a length of 1/8 TIMEOUT. This can be calculated using Equation 4: The TIME pin can be grounded to disable the safety timer functions if not needed. Fast Charge The fast charge current is programmed by the resistor between the ISET1 pin and ground, and by the value of the RSNS resistor. Where RISET1 is in kΩ and RSNS is in Ω. For best accuracy, select RSNS value that provides between 40mV to 80mV differential voltage across RSNS at the desired maximum peak current (DC plus ripple). Charge Termination Output current is continuously monitored during charge. When current falls below the taper current threshold, charging will stop, and BATFUL is asserted to indicate a successful charge completion. This taper current threshold is programmed by a single external resistor between ISET2 and ground. Where RISET2 is in kΩ and RSNS is in Ω. A secondary charge termination method is provided via the safety timer. The timeout period of this timer is programmable via a single external capacitor between the TIME pin and ground. To disable the charge safety timer, tie the TIME pin to ground. Charge Current Sensing Charge current is sensed with an external current sense resistor. A low-inductance, precision resistor should be used for best performance. Input Current Sensing Input current is sensed with an external sense resistor. A low-inductance, precision resistor should be used for accurate input current limit. An internal amplifier compares the voltage between CSIP and CSIN, and limits the current when this differential voltage exceeds the threshold voltage. The effective input current limit threshold is thus set by the value of the RICS resistor as calculated by Equation 7. Where RICS is in Ω. The ISL9220, ISL9220A limits the battery charge current when the input current limit threshold is exceeded. This allows the most efficient use of AC-adapter power without overloading the adapter output. A low pass filter is suggested to eliminate the switching noise, as shown in “Typical Application” on page 6. Status Outputs STAT1 and STAT2 are configured to indicate various charging conditions as given in Table 1. A fault status is triggered under one of these conditions: 1. VBAT > VOUT_OVP threshold 2. Timeout occurs before the EOC current has been reached IPCHG 50mA = (EQ. 1) tOSC 0.2 10 6 × CTime × Sec () = (EQ. 2) TIMEOUT 2 22 TOSC × Sec () = (EQ. 3) TIMEOUT PCHG () 2 19 TOSC × Sec () = (EQ. 4) ICHG 1946 RISET1 RSNS × ------------------------------------------- mA () = (EQ. 5) TABLE 1. STAT1 AND STAT2 TRUE TABLE STAT1 STAT2 CHARGING CONDITION L L Precharge, or fast charge in progress L H Charge Complete H L Fault H H Suspend IEOC 1170 RISET2 RSNS × ------------------------------------------- mA () = (EQ. 6) IIN LIM () 0.1 RICS -------------- A () = (EQ. 7) |
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