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LTC4120 Datasheet(PDF) 9 Page - Linear Technology |
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LTC4120 Datasheet(HTML) 9 Page - Linear Technology |
9 / 32 page LTC4120/LTC4120-4.2 9 4120fe For more information www.linear.com/LTC4120 pin FuncTions INTVCC (Pin 1): Internal Regulator Output Pin. This pin is the output of an internal linear regulator that generates the internal INTVCC supply from IN. It also supplies power to the switch gate drivers and the low battery linear charge current ILOWBAT. Connect a 2.2µF low ESR capacitor from INTVCC to GND. Do not place any external load on INTVCC other than the NTC bias network. When the RUN pin is above VEN, and INTVCC rises above the UVLO threshold, and IN rises above BAT by ∆VDUVLO and its hysteresis, the charger is enabled. BOOST (Pin 2): Boosted Supply Pin. Connect a 22nF boost capacitor from this pin to the SW pin. IN (Pin 3): Positive Input Power Supply. Decouple to GND with a 10µF or larger low ESR capacitor. SW (Pin 4): Switch Pin. The SW pin delivers power from IN to BAT via the step-down switching regulator. An in- ductor should be connected from SW to CHGSNS. See the Applications Information section for a discussion of inductor selection. GND (Pin 5, Exposed Pad Pin 17): Ground Pin. Connect to exposed pad. The exposed pad must be soldered to PCB GND to provide a low electrical and thermal impedance connection to ground. DHC(Pin6):DynamicHarmonizationControlPin.Connect a Schottky diode from the DHC pin to the IN pin, and a capacitor from the DHC pin as shown in the Typical Ap- plication or the Block Diagram. When VIN is greater than VIN(DHC), this pin is high impedance. When VIN is below VIN(DHC) this pin is low impedance allowing the LTC4120 to modulate the resonance of the tuned receiver network. See Applications Information for more information on the tuned receiver network. FREQ (Pin 7): Buck Switching Frequency Select Input Pin. Connect to INTVCCtoselecta1.5MHzswitchingfrequency orGNDtoselecta750kHzswitchingfrequency.Donotfloat. CHGSNS (Pin 8): Battery Charge Current Sense Pin. An internal current sense resistor between CHGSNS and BAT pins monitors battery charge current. An inductor should be connected from SW to CHGSNS. BAT (Pin 9): Battery Output Pin. Battery charge current is delivered from this pin through the internal charge current sense resistor. In low battery conditions a small linear charge current, ILOWBAT, is sourced from this pin to precondition the battery. Decouple the BAT pin with a low ESR 22µF or greater ceramic capacitor to GND. BATSNS (Pin 10, LTC4120-4.2 Only): Battery Voltage Sense Pin. For proper operation, this pin must always be connectedphysicallyclosetothepositivebatteryterminal. FB (Pin 10, LTC4120 Only): Battery Voltage Feedback Pin. Thechargefunctionoperatestoachieveafinalfloatvoltage of 2.4V at this pin. Battery float voltage is programmed using a resistive divider from BAT to FB to FBG, and can be programmed up to 11V. The feedback pin input bias cur- rent, IFB, is 25nA. Using a resistive divider with a Thevenin equivalent resistance of 588k compensates for input bias current error (see curve of FB Pin Bias Current versus Temperature in the Typical Performance Characteristics). FBG (Pin 11, LTC4120 Only): Feedback Ground Pin. This pindisconnectstheexternalFBdividerloadfromthebattery when it is not needed. When sensing the battery voltage this pin presents a low resistance, RFBG, to GND. When in disabled or shutdown modes this pin is high impedance. NTC(Pin12):InputtotheNegativeTemperatureCoefficient Thermistor Monitoring Circuit. The NTC pin connects to a negative temperature coefficient thermistor which is typically co-packaged with the battery to determine if the battery is too hot or too cold to charge. If the battery’s temperature is out of range, the LTC4120 enters standby mode and charging is paused until the battery tempera- ture re-enters the valid range. A low drift bias resistor is required from INTVCC to NTC and a thermistor is required from NTC to GND. Tie the NTC pin to GND to disable NTC qualified charging if NTC functionality is not required. PROG(Pin13):ChargeCurrentProgramandChargeCurrent MonitorPin.Connecta1%resistorbetween3.01k(400mA) and 24.3k (50mA) from PROG to ground to program the charge current. While in constant-current mode, this pin regulates to 1.227V. The voltage at this pin represents the averagebatterychargecurrentusingthefollowingformula: IBAT = hPROG • VPROG RPROG where hPROG is typically 988. Keep parasitic capacitance on the PROG pin to a minimum. |
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Similar Description - LTC4120_15 |
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