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LTC4076 Datasheet(PDF) 9 Page - Linear Technology |
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LTC4076 Datasheet(HTML) 9 Page - Linear Technology |
9 / 16 page LTC4076 9 4076fa The LTC4076 is designed to efficiently manage charging of a single-cell lithium-ion battery from two separate power sources: a wall adapter and USB power bus. Using the constant-current/constant-voltage algorithm, the charger can deliver up to 950mA of charge current from the wall adapter supply or up to 650mA of charge current from the USB supply with a final float voltage accuracy of ±0.6%. The LTC4076 has two internal P-channel power MOSFETs and thermal regulation circuitry. No blocking diodes or external sense resistors are required. Power Source Selection The LTC4076 can charge a battery from either the wall adapterinputortheUSBportinput.TheLTC4076automati- cally senses the presence of voltage at each input. If both power sources are present, the LTC4076 defaults to the wall adapter source provided sufficient power is present at the DCIN input. “Sufficient power” is defined as: • Supply voltage is greater than the UVLO threshold. • Supply voltage is greater than the battery voltage by 50mV (180mV rising, 50mV falling). The open drain power status output (PWR) indicates that sufficientpowerisavailable.Table1describesthebehavior of this status output. Table 1. Power Source Selection VUSBIN > 3.95V and VUSBIN < 3.95V or VUSBIN > BAT + 50mV VUSBIN < BAT + 50mV VDCIN > 4.15V and Device powered from Device powered from VDCIN > BAT + 50mV wall adapter source; wall adapter source USBIN current < 25µA PWR: LOW PWR: LOW VDCIN < 4.15V or Device powered from No charging VDCIN < BAT + 50mV USB source; PWR: LOW PWR: Hi-Z Programming and Monitoring Charge Current The charge current delivered to the battery from the wall adaptersupplyisprogrammedusingasingleresistorfrom the IDC pin to ground. R V I I V R IDC CHRG DC CHRG DC IDC = = 1000 1000 ( ) ( ) , Similarly, the charge current from the USB supply is programmed using a single resistor from the IUSB pin to ground. Setting HPWR pin to its high state will select 100% of the programmed charge current, while setting HPWR to its low state will select 20% of the programmed charge current. R V I HPWR HIGH I IUSB CHRG USB CHRG USB = = 1000 ( ) ( ) ( ) == = = 1000 200 V R HPWR HIGH I V R IUSB CHRG USB IUS ( ) ( ) BB HPWR LOW ( ) = Charge current out of the BAT pin can be determined at any time by monitoring the IDC or IUSB pin voltage and using the following equations: I V R ch ing from wall adapter BAT IDC IDC = • , ( arg 1000 )) • , ( arg sup I V R ch ing from USB p BAT IUSB IUSB = 1000 lly HPWR HIGH I V R ch in BAT IUSB IUSB , ) • , ( arg = = 200 gg from USB ply HPWR LOW sup , ) = Programming Charge Termination The charge cycle terminates when the charge current falls below the programmed termination threshold during con- stant-voltage mode. This threshold is set by connecting an external resistor, RITERM, from the ITERM pin to ground. The charge termination current threshold (ITERMINATE) is set by the following equation: R V I I V R ITERM TERMINATE TERMINATE ITERM = = 100 100 , OPERATIO |
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