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LTC4089-1 Datasheet(PDF) 8 Page - Linear Technology |
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LTC4089-1 Datasheet(HTML) 8 Page - Linear Technology |
8 / 24 page LTC4089-1 8 40891f PI FU CTIO S GND (Pins 1, 2): Ground. Tie the GND pin to a local ground plane below the LTC4089-1 and the circuit components. HVOUT (Pins 3, 18): Voltage Output of the High Voltage Regulator. When sufficient voltage is present at HVOUT, the low voltage power path from IN to OUT will be discon- nected and the HVPR pin will be pulled low to indicate that a high voltage wall adapter has been detected. The LTC4089-1 high voltage regulator will provide a fixed 5V output to the battery charger MOSFET. HVOUT should be bypassed with at least 10µF to GND. Connect pins 3 and 18 with a resistance no greater than 1 . VC (Pin 4): Leave the VC pin floating or bypass to ground witha10pFcapacitor.Thisoptional10pFcapacitorreduces HVOUT ripple in discontinuous mode. NTC (Pin 5): Input to the NTC Thermistor Monitoring Circuits. The NTC pin connects to a negative temperature coeffcient thermistor which is typically co-packaged with the battery pack to determine if the battery is too hot or too cold to charge. If the battery’s temperature is out of range, charging is paused until the battery temperature re- enters the valid range. A low drift bias resistor is required from VNTC to NTC and a thermistor is required from NTC to ground. If the NTC function is not desired, the NTC pin should be grounded. VNTC (Pin 6): Output Bias Voltage for NTC. A resistor from this pin to the NTC pin will bias the NTC thermistor. HVPR (Pin 7): High Voltage Present Output. Active low open drain output pin. A low on this pin indicates that the high voltage regulator has sufficient voltage to charge the battery. This feature is disabled if no power is present on HVIN, IN or BAT (i.e., below UVLO thresholds). CHRG(Pin8):Open-DrainChargeStatusOutput.Whenthe battery is being charged, the CHRG pin is pulled low by an internal N-channel MOSFET. When the timer runs out or the charge current drops below 10% of the programmed charge current or the input supply is removed, the CHRG pin is forced to a high impedance state. PROG (Pin 9): Charge Current Program. Connecting a resistor, RPROG, to ground programs the battery charge current. The battery charge current is programmed as follows: I A V R CHG PROG ( ) , = 50 000 GATE (Pin 10): External ideal diode gate pin. This pin can be used to drive the gate of an optional external PFET con- nected between BAT (drain) and OUT (source). By doing so, the impedance of the ideal diode between BAT and OUT can be reduced. When not in use, this pin should be left floating. It is important to maintain a high impedance on this pin and minimize all leakage paths. BAT (Pin 11): Connect to a single cell Li-Ion battery. This pin is used as an output when charging the battery and as an input when supplying power to OUT. When the OUT pin potential drops below the BAT pin potential, an ideal diode function connects BAT to OUT and prevents VOUT from droppingmorethan100mVbelowVBAT.Aprecisioninternal resistor divider sets the final float (charging) potential on this pin. The internal resistor divider is disconnected when IN and HVIN are in undervoltage lockout. IN (Pin 12): Input Supply. Connect to USB supply, VBUS. Input current to this pin is limited to either 20% or 100% of the current programmed by the CLPROG pin as de- termined by the state of the HPWR pin. Charge current (to the BAT pin) supplied through the input is set to the current programmed by the PROG pin but will be limited by the input current limit if charge current is set greater than the input current limit. OUT (Pin 13): Voltage Output. This pin is used to provide controlled power to a USB device from either USB VBUS (IN), an external high voltage supply (HVIN), or the battery (BAT) when no other supply is present. The high voltage supply is prioritized over the USB VBUS input. OUT should be bypassed with at least 4.7µF to GND. |
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Similar Description - LTC4089-1 |
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