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LTC4075X Datasheet(PDF) 9 Page - Linear Technology |
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LTC4075X Datasheet(HTML) 9 Page - Linear Technology |
9 / 16 page LTC4075/LTC4075X 9 4075Xf The LTC4075 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 LTC4075 has two internal P-channel power MOSFETs and thermal regulation circuitry. No blocking diodes or external sense resistors are required. Power Source Selection The LTC4075 can charge a battery from either the wall adapter input or the USB port input. The LTC4075 automati- cally senses the presence of voltage at each input. If both power sources are present, the LTC4075 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 outputs (⎯P⎯W⎯R and USBPWR) indicate which power source has been selected. Table 1 describes the behavior of these status outputs. 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 ⎯P⎯W⎯R: LOW ⎯P⎯W⎯R: LOW USBPWR: LOW USBPWR: LOW VDCIN < 4.15V or Device powered from No charging VDCIN < BAT + 50mV USB source; ⎯P⎯W⎯R: LOW ⎯P⎯W⎯R: Hi-Z USBPWR: Hi-Z USBPWR: LOW Programming and Monitoring Charge Current The charge current delivered to the battery from the wall adapter supply is programmed using a single resistor from the IDC pin to ground. Likewise, the charge current from the USB supply is programmed using a single resis- tor from the IUSB pin to ground. The program resistor and the charge current (ICHRG) are calculated using the following equations: R V I I V R R V I I V R IDC CHRG DC CHRG DC IDC IUSB CHRG USB CHRG USB IUSB == == − − − − 1000 1000 1000 1000 , , 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 fromwall adapter I V R ch ing fromUSB ply BAT IDC IDC BAT IUSB IUSB = = • , ( arg ) • , ( arg sup ) 1000 1000 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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