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LTC4009-1 Datasheet(PDF) 12 Page - Linear Technology |
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LTC4009-1 Datasheet(HTML) 12 Page - Linear Technology |
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12 / 28 page  LTC4009 LTC4009-1/LTC4009-2 12 4009fb Charge Current Monitoring When the LTC4009 is charging, the voltage on the PROG pin varies in direct proportion to the charge current. Referring to Figure 1, the nominal PROG voltage is given by V IR R R μA R PROG CHRG SENSE PROG IN PROG =+ •• .• 11 67 Voltage tolerance on PROG is limited by the charge current accuracy specified in the Electrical Characteristics table. Refer to the Applications Information section on program- ming charge current for additional details. Adapter Input Current Limit The LTC4009 can monitor and limit current from the input DC supply, which is normally an AC adapter. When the programmed adapter input current is reached, charge current is reduced to maintain the desired maximum input current. The ITH and PROG pins will reflect the reduced charge current. This limit function avoids overloading the DC input source, allowing the product to operate at the same time the battery is charging without complex load management algorithms. The battery will automatically be charged at the maximum possible rate that the adapter will support, given the application’s operating condition. The LTC4009 can only limit input current by reducing charge current, and in this case the charger uses nonsynchro- nous PWM operation to prevent boosting if the average charge current falls below about 25% of the maximum programmed current. Note that the ICL indicator output becomes active (low) at an adapter input current level just slightly less than that required for the internal amplifier to begin to assert control over the PWM loop. If system load current equals or exceeds the input adapter current limit for more than a few milliseconds, the bootstrap capacitor between BOOST and SW can fully discharge due to normal pin leakage currents. In this case, the PWM will not restart until the system current has dropped to about 85% of the programmed input adapter limit value. Charger Status Indicator Outputs The LTC4009 open-drain indicator outputs provide valu- able information about the IC’s operating state and can OPERATION Figure 1. PWM Circuit Diagram – + EA CA – + CC 19 2 11 PWM LOGIC OSCILLATOR WATCHDOG TIMER LOOP COMPENSATION TGATE SYSTEM POWER L1 RIN + – 16 BGATE 15 CSP 14 CSN 13 PROG 10 VFB 12 ITH RPROG R1 FROM ICL 1.2085V RSENSE VSENSE ICHRG 4009 F01 CPROG Q S CLOCK LTC4009 CLP BAT RD RIN + |
Similar Part No. - LTC4009-1 |
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Similar Description - LTC4009-1 |
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