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LTC4120/LTC4120-4.2 Rev. GFor more information www.analog.com Document Feedback TYPICAL APPLICATION FEATURES DESCRIPTION Wireless Power Receiver and 400mA Buck Battery Charger The LTC®4120 is a constant-current/constant-voltage wire- less receiver and battery charger . An external program- ming resistor sets the charge current up to 400mA. The LTC4120-4.2 is suitable for charging Li-Ion/Polymer batter- ies, while the programmable float voltage of the LTC4120 accommodates several battery chemistries. The LTC4120 uses a Dynamic Harmonization Control (DHC) technique that allows high efficiency contactless charging across an air gap. The LTC4120 regulates its input voltage via the DHC pin. This technique modulates the resonant frequency of a receiver tank to automatically adjust the power received as well as the power transmitted to provide an efficient solution for wirelessly charging battery-powered devices. Wireless charging with the LTC4120 provides a method to power devices in harsh environments without requiring expensive failure-prone connectors. This allows products to be charged while locked within sealed enclosures, or in moving or rotating equipment, or where cleanliness or sanitation is critical. This full featured battery charger includes accurate RUN pin threshold, low voltage battery preconditioning and bad battery fault detection, timer termination, auto-recharge, and NTC temperature qualified charging. The FAULT pin provides an indication of bad battery or temperature faults. Once charging is terminated, the LTC4120 signals end-of- charge via the CHRG pin, and enters a low current sleep mode. An auto-restart feature starts a new charging cycle if the battery voltage drops by 2.2%.
APPLICATIONS
n Dynamic Harmonization Control Optimizes Wireless Charging Over a Wide Coupling Range n Wide Input Voltage Range (12.5V to 40V) n Adjustable Float Voltage (3.5V to 11V) n Fixed 4.2V Float Voltage Option (LTC4120-4.2) n 50mA to 400mA Charge Current Programmed with a Single Resistor n ±1% Feedback Voltage Accuracy n Programmable 5% Accurate Charge Current n No Microprocessor Required n No T ransformer Core n Thermally Enhanced, Low Profile 16-Lead (3mm × 3mm × 0.75mm) QFN Package n Handheld Instruments n Industrial/Military Sensors and Devices n Harsh Environments n Portable Medical Devices n Physically Small Devices n Electrically Isolated Devices All registered trademarks and trademarks are the property of their respective owners. INTVCCIN FREQRUN BOOST SW CHGSNS NTC DHC FAULT CHRG 3.01k 22µF T
4120 TA01a
4.2V 22nF 26.7nF 6.5nF 47µH5µH Tx CIRCUITRY 10µF 2.2µF 33µH FB PROG FBG L TC4120 GND BAT 1.01M 1.35M Wireless Rx Voltage/Charge Current vs Spacing SPACING (cm) 0.4 VIN(RX) (V) CHARGE CURRENT (mA) 1.0 1.4
4120 TA01b
LTC4120/LTC4120-4.2 Rev. G For more information www.analog.com PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS (Note 1) ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC4120EUD#PBF LTC4120EUD#TRPBF LGHB 16-Lead (3mm × 3mm) Plastic QFN –40°C to 125°C LTC4120IUD#PBF LTC4120IUD#TRPBF LGHB 16-Lead (3mm × 3mm) Plastic QFN –40°C to 125°C LTC4120EUD-4.2#PBF LTC4120EUD-4.2#TRPBF LGMT 16-Lead (3mm × 3mm) Plastic QFN –40°C to 125°C LTC4120IUD-4.2#PBF LTC4120IUD-4.2#TRPBF LGMT 16-Lead (3mm × 3mm) Plastic QFN –40°C to 125°C Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container . Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix. LTC4120 OPTIONS FLOAT VOL TAGE LTC4120 Programmable LTC4120-4.2 4.2V Fixed LTC4120 LTC4120-4.2 16 15 14 13 5 6 7 8 TOP VIEW GND UD PACKAGE 16-LEAD (3mm × 3mm) PLASTIC QFN TJMAX = 125°C, θJA = 54°C/W EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB TO OBTAIN θJA
1 INTV
16-LEAD (3mm × 3mm) PLASTIC QFN TJMAX = 125°C, θJA = 54°C/W EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB TO OBTAIN θJA Operating Junction Temperature Range
LTC4120/LTC4120-4.2 Rev. GFor more information www.analog.com ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = VRUN = 15V, VCHGSNS = VBAT = 4V, RPROG = 3.01k, VFB = 2.29V (LTC4120), VBATSNS = 4V (LTC4120-4.2). Current into a pin is positive out of the pin is negative. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Operating Input Supply Range l 12.5 40 V Battery Voltage Range 0 11 V IIN DC Supply Current Switching, FREQ = GND 3.5 mA Standby Mode (Note 3) l 130 220 µA Sleep Mode (Note 3) LTC4120: VFB = 2.51V (Note 5), LTC4120-4.2: VBATSNS = 4.4V l 100 µA Disabled Mode (Note 3) l 37 70 µA Shutdown Mode (Note 3) l 20 40 µA ∆VDUVLO Differential Undervoltage Lockout VIN-VBAT Falling, VIN = 5V (LTC4120), VIN-VBATSNS Falling, VIN = 5V (LTC4120-4.2) l 20 80 160 mV Hysteresis VIN-VBAT Rising, VIN = 5V (LTC4120), VIN-VBATSNS Rising, VIN = 5V (LTC4120-4.2) 115 mV UVINTVCC INTVCC Undervoltage Lockout INTVCC Rising, VIN = INTVCC + 100mV, VBAT = NC l 4.00 4.15 4.26 V Hysteresis INTVCC Falling (Note 4) 220 mV Battery Charger IBAT BAT Standby Current Standby Mode (LTC4120) (Notes 3, 7, 8) Standby Mode (LTC4120-4.2) (Notes 3, 7, 8) l l 2.5 4.5 1000 µA nA BAT Shutdown Current Shutdown Mode (LTC4120) (Notes 3, 7, 8) Shutdown Mode (LTC4120-4.2) (Notes 3, 7, 8) l l 1100 2000 1000 nA nA I BATSNS BATSNS Standby Current (LTC4120-4.2) Standby Mode (Notes 3, 7, 8) l 5.4 10 µA BATSNS Shutdown Current (LTC4120-4.2) Shutdown Mode (Notes 3, 7, 8) l 1100 2000 nA IFB Feedback Pin Bias Current (LTC4120) VFB = 2.5V (Notes 5, 7) l 25 60 nA IFBG(LEAK) Feedback Ground Leakage Current (LTC4120) Shutdown Mode (Notes 3, 7) l 1 µA RFBG Feedback Ground Return Resistance (LTC4120) l 1000 2000 Ω VFB(REG) Feedback Regulation Voltage (LTC4120) (Note 5) l 2.393 2.370 2.400 2.407 2.418 V V V FLOAT Regulated Float Voltage (LTC4120-4.2) l 4.188 4.148 4.200 4.212 4.227 V V I CHG Battery Charge Current RPROG = 3.01k RPROG = 24.3k l l 383 402 421 mA mA VUVCL Undervoltage Current Limit VIN Falling 12.0 V VRCHG Battery Recharge Threshold VFB Falling Relative to VFB_REG (LTC4120) (Note 5) l –38 –50 –62 mV VRCHG_4.2 Battery Recharge Threshold VBATSNS Falling Relative to VFLOAT (LTC4120-4.2) l –70 –92 –114 mV hPROG Ratio of BAT Current to PROG Current VTRKL < VFB < VFB(REG) (LTC4120) (Note 5) VTRKL_4.2 < VBATSNS < VFLOAT (LTC4120-4.2) 988 mA/mA VPROG PROG Pin Servo Voltage l 1.206 1.227 1.248 V RSNS CHGSNS-BAT Sense Resistor IBAT = –100mA 300 mΩ
LTC4120/LTC4120-4.2 Rev. G For more information www.analog.com ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = VRUN = 15V, VCHGSNS = VBAT = 4V, RPROG = 3.01k, VFB = 2.29V (LTC4120), VBATSNS = 4V (LTC4120-4.2). Current into a pin is positive out of the pin is negative. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS ILOWBAT Low Battery Linear Charge Current 0V < VFB < VTRKL, VBAT = 2.6V (LTC4120), VBATSNS < VTRKL_4.2, VBAT = 2.6V (LTC4120-4.2) 6 9 16 mA VLOWBAT Low Battery Threshold Voltage VBAT Rising (LTC4120), VBATSNS Rising (LTC4120-4.2) l 2.15 2.21 2.28 V Hysteresis 147 mV ITRKL Switch Mode T rickle Charge Current VLOWBAT < VBAT, VFB < VTRKL (LTC4120) (Note 5), VLOWBAT < VBATSNS < VTRKL_4.2 (LTC4120-4.2) ICHG/10 mA PROG Pin Servo Voltage in Switch Mode T rickle Charge VLOWBAT < VBAT, VFB < VTRKL (LTC4120) (Note 5), VLOWBAT < VBATSNS < VTRKL_4.2 (LTC4120-4.2) 122 mV VTRKL T rickle Charge Threshold VFB Rising (LTC4120) (Note 5) l 1.64 1.68 1.71 V Hysteresis VFB Falling (LTC4120) (Note 5) 50 mV Hysteresis VBATSNS Falling (LTC4120-4.2) 88 mV hC/10 End of Charge Indication Current Ratio (Note 6) 0.1 mA/mA Safety Timer Termination Period 1.3 2.0 2.8 Hours Bad Battery Termination Timeout 19 30 42 Minutes Switcher fOSC Switching Frequency FREQ = INTVCC FREQ = GND l l 1.0 0.5 1.5 0.75 2.0 1.0 MHz MHz t MIN(ON) Minimum Controllable On-Time (Note 9) 120 ns Duty Cycle Maximum (Note 9) 94 % Top Switch RDS(ON) ISW = –100mA 0.8 Ω Bottom Switch RDS(ON) ISW = 100mA 0.5 Ω IPEAK Peak Current Limit Measured Across RSNS with a 15µH Inductor in Series with RSNS (Note 9) 585 750 1250 mA ISW Switch Pin Current (Note 8) VIN = Open-Circuit, VRUN = 0V, VSW = 8.4V (LTC4120) VIN = Open-Circuit, VRUN = 0V, VSW = 4.2V (LTC4120-4.2) l l µA µA Status Pins FAULT, CHRG Pin Output Voltage Low I = 2mA 500 mV Pin Leakage Current V = 43V, Pin High Impedance 0 1 µA NTC Cold Temperature V NTC/VINTVCC Fault Rising VNTC Threshold Falling VNTC Threshold l 73 74 %INTVCC %INTVCC Hot Temperature VNTC/VINTVCC Fault Falling VNTC Threshold Rising VNTC Threshold l 35.5 36.5 37.5 37.5 %INTVCC %INTVCC NTC Disable Voltage Falling VNTC Threshold Rising VNTC Threshold l 1 2 %INTVCC %INTVCC NTC Input Leakage Current VNTC = VINTVCC –50 50 nA
LTC4120/LTC4120-4.2 Rev. GFor more information www.analog.com The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = VRUN = 15V, VCHGSNS = VBAT = 4V, RPROG = 3.01k, VFB = 2.29V (LTC4120), VBATSNS = 4V (LTC4120-4.2). Current into a pin is positive out of the pin is negative. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS RUN VEN Enable threshold VRUN Rising l 2.35 2.45 2.55 V Hysteresis VRUN Falling 200 mV Run Pin Input Current VRUN = 40V 0.01 0.1 µA VSD Shutdown Threshold (Note 3) VRUN Falling l 0.4 1.2 V Hysteresis 220 mV FREQ FREQ Pin Input Low l 0.4 V FREQ Pin Input High VINTVCC-VFREQ l 0.6 V FREQ Pin Input Current 0V < VFREQ < VINTVCC ±1 µA Dynamic Harmonization Control VIN(DHC) Input Regulation Voltage 14 V DHC Pin Current VDHC = 1V, VIN < VIN(DHC) 330 mARMS Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LTC4120 is tested under pulsed load conditions such that TJ ≈ TA. The LTC4120E is guaranteed to meet performance specifications for junction temperatures from 0°C to 85°C. Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LTC4120I is guaranteed over the full –40°C to 125°C operating junction temperature range. Note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal impedance, and other environmental factors. Note 3: Standby mode occurs when the LTC4120 stops switching due to an NTC fault condition, or when the charge current has dropped low enough to enter Burst Mode operation. Disabled mode occurs when V RUN is between VSD and VEN. Shutdown mode occurs when VRUN is below VSD or when the differential undervoltage lockout is engaged. SLEEP mode occurs after a timeout while the battery voltage remains above the V RCHG or VRCHG_42 threshold. Note 4: The internal supply INTVCC should only be used for the NTC divider , it should not be used for any other loads. Note 5: The FB pin is measured with a resistance of 588k in series with the pin. Note 6: hC/10 is expressed as a fraction of measured full charge current as measured at the PROG pin voltage when the CHRG pin de-asserts. Note 7: In an application circuit with an inductor connected from SW to CHGSNS, the total battery leakage current when disabled is the sum of I BAT, IFBG(LEAK) and ISW (LTC4120), or IBATSNS and IBAT and ISW (LTC4120-4.2). Note 8: When no supply is present at IN, the SW powers IN through the body diode of the topside switch. This may cause additional SW pin current depending on the load present at IN. Note 9: Guaranteed by design and/or correlation to static test.
ELECTRICAL CHARACTERISTICS
LTC4120/LTC4120-4.2 Rev. G For more information www.analog.com TYPICAL PERFORMANCE CHARACTERISTICS Typical VFB(REG) vs Temperature IN Pin Disabled/Shutdown Current vs Temperature BAT Pin Sleep/Shutdown Current vs Temperature Typical Battery Charge Current vs Temperature Typical V FLOAT vs Temperature LTC4120-4.2 IN Pin Standby/Sleep Current vs Temperature T A = 25°C, unless otherwise noted. TEMPERATURE (°C) –40
2.36 VFB(REG) (V)
2.37 2.39 2.40 2.41 2.43 –25 35 65
4120 G01
2.38 2.42 20 95 125 DUT = DEVICE UNDER TEST 110–10 5 50 80
4 UNITS TESTED
FB(REG) (V) DUT2 VFB(REG) (V) DUT3 VFB(REG) (V) DUT4 VFB(REG) (V) LOW LIMIT TEMPERATURE (°C) 4.15 4.16 4.17 4.18 4.19VFLOAT (V) 4.25 4.24 4.23 4.22 4.21 4.20
4120 G20
–40 5 20 35 95 80 65–25 –10 50 110 125 TEMPERATURE (°C) –50 120 140 180 25 75
4120 G02
–25 0 50 100 125 160IIN (µA)
2 UNITS TESTED
V IN = 15V IIN STANDBY FREQ = INTVCC IIN STANDBY FREQ = INTVCC IIN STANDBY FREQ = GND IIN STANDBY FREQ = GND IIN SLEEP IIN SLEEP TEMPERATURE (°C) –50 IIN (µA) 25 75
4120 G03
–25 0 50 100 125 IIN SD IIN SD IIN DISABLED IIN DISABLED V IN = 15V TEMPERATURE (°C) –50 IBAT (µA)
4120 G04
–25 0 50 75 100 125 IBAT SLEEP IBAT SLEEP IBAT SHUTDOWN IBAT SHUTDOWN VBAT = 4.2V RFB2 = 1.01M RFB1 = 1.35M TEMPERATURE (°C) –50 399 400 402 25 75
4120 G05
–25 0 50 100 125 396 395 401ICHG (mA) FREQ = GND FREQ = GND FREQ = INTV CC FREQ = INTVCC RPROG = 3.01k Typical RSNS Current Limit vs Temperature TEMPERATURE (°C) –50 IPEAK (mA) 125
4120 G06
0 50 100–25 25 75 1120 DUT1 DUT2 DUT3
3 UNITS TESTED
LTC4120/LTC4120-4.2 Rev. GFor more information www.analog.com Switching Frequency vs Temperature Buck Efficiency vs Battery Current TEMPERATURE (°C) –50 0.8 1.0 1.4 25 75
4120 G07
0.6 –25 0 50 100 125 0.4 0.2 1.2 fOSC (MHz) FREQ = GND FREQ = GND FREQ = INTVCC FREQ = INTVCC IBAT (mA) EFFICIENCY (%) 400
4120 G08
VIN = 12.5V VIN = 14V VIN = 20V VIN = 30V LSW = 68µH, SLF12555T-680M1R3 FREQ = GND VBAT = 4.2V Burst Mode T rigger Current Typical Burst Mode Waveforms, IBAT = 38mA Typical tMIN(ON) vs Temperature TYPICAL PERFORMANCE CHARACTERISTICS Wireless Power T ransfer Efficiency, V IN_RX vs Battery Current BAT Pin Leakage Current/VBAT-VIN vs Temperature Typical Wireless Charging Cycle TA = 25°C, unless otherwise noted. TEMPERATURE (°C) –50 IBAT (µA) VBAT-VIN (mV)
4120 G09
–25 0 50 350 200 100 400 300 250 150 75 100 125 IBAT IBAT VBAT-VIN VBAT-VIN VIN = OPEN-CIRCUIT VBAT = 4.2V TEMPERATURE (°C) –50 tMIN(0N) (ns) 100 105 130 115 0 50 75 100
4120 G10
–22 25 125 IBAT (mA) 200
4120 G11
EFFICIENCY (%) VIN_RX (V) 9mm EFFICIENCY 10mm EFFICIENCY 11mm EFFICIENCY 9mm V_RX 10mm V_RX 11mm V_RX VFLOAT = 8.3V LSW = SLF6028-470MR59 RPROG = 4.64k TIME (HOURS) BATTERY CURRENT (mA) VBAT, VCHRG (V) 150 200 250 450
4120 G12
0.5 1.5 2.0 2.5 4.5 1.0 3.0 3.5 4.0 VCHRG VBAT IBAT BAT = 940mAhr LSW = TDK SLF4075 15µH RFB1 = 732k, RFB2 = 976k RPROG = 3.01k APPLICATION CCT OF FIGURE 10 SPACING = 14mm VIN (V) IBAT (mA)
4120 G13
RPROG = 6.2k RPROG = 3k VSW 5V/DIV VPROG 500mV/DIV ILSW 200mA/DIV 0mA 4µs/DIV
4120 G14
LTC4120/LTC4120-4.2 Rev. G For more information www.analog.com IN Pin Standby Current vs VIN IN Pin Disabled Current vs Input Voltage UVCL: ICHARGE vs Input Voltage IN Pin Shutdown Current vs Input Voltage IN Pin Switching Current vs Input Voltage TYPICAL PERFORMANCE CHARACTERISTICSTA = 25°C, unless otherwise noted. VIN (V) IIN (µA) 160 180 200 30 3515 20 25
4120 G15
VBAT = 4.21V NTC = GND IIN STBY FREQ HIGH 130°C IIN STBY FREQ LOW 130°C IIN STBY FREQ HIGH 25°C IIN STBY FREQ LOW 25°C IIN STBY FREQ HIGH –45°C IIN STBY FREQ LOW –45°C VIN (V) IIN (µA)40
4120 G16
IIN SD TEMP = 125°C IIN SD TEMP = 35°C IIN SD TEMP = –40°C VRUN = 0.4V VIN (V) IIN (µA) 100 10 20
4120 G17
IIN SD TEMP = 125°C IIN SD TEMP = 35°C IIN SD TEMP = –40°C VRUN = 1.6V VIN (V) 20 30
4120 G18
IIN (mA) UVCL IBAT = 0 130°C 25°C –45°C IICCQ(SWITCHING) FREQ HIGH FREQ = INTVCC IICCQ(SWITCHING) FREQ LOW FREQ = GND VIN (V) 11.90 ICHARGE (mA) 0.20
4120 G19
0.10 0.30 0.40 0.15 0.05 0.25 0.35 12.20 IBAT TEMP = 125°C IBAT TEMP = 35°C IBAT TEMP = –40°C
LTC4120/LTC4120-4.2 Rev. GFor more information www.analog.com 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. Overloading this pin can disrupt internal operation. When the RUN pin is above VEN, and INTV CC 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 inductor 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 imped- ance connection to ground. DHC (Pin 6) : Dynamic Harmonization Control Pin. Connect a Schottky diode from the DHC pin to the IN pin, and a capacitor from the DHC pin as shown in the Typical Application or the Block Diagram. When V IN is greater than VIN(DHC), this pin is high impedance. When V IN 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 informa- tion on the tuned receiver network. FREQ (Pin 7): Buck Switching Frequency Select Input Pin. Connect to INTV CC to select a 1.5MHz switching frequency or GND to select a 750kHz switching frequency. Do not float. 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 pre- condition 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 connected physically close to the positive battery terminal. FB (Pin 10, LTC4120 Only): Battery Voltage Feedback Pin. The charge function operates to achieve a final float voltage 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 pin disconnects the external FB divider load from the battery when it is not needed. When sensing the bat- tery voltage this pin presents a low resistance, R FBG, to GND. When in disabled or shutdown modes this pin is high impedance. NTC (Pin 12): Input to the Negative Temperature Coefficient 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 (Pin 13) : Charge Current Program and Charge Current Monitor Pin. Connect a 1% resistor between 3.01k (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 average battery charge current using the following formula: IBAT =hPROG • VPROG RPROG
on the PROG pin to a minimum. CHRG (Pin 14) : Open-Drain Charge Status Output Pin. value, the CHRG pin is forced to a high impedance state. FAULT (Pin 15) : Open-Drain Fault Status Output Pin. program the input voltage at which charging is enabled.
4120 F01
Figure 1. Block Diagram
4120 F02
Figure 2. LTC4120-4.2 BATSNS Connections
4120 F03
Figure 3. VIN(DHC) Test Circuit
put pins to indicate state of charge and fault status. Figure 4. DC-AC Converter , T ransmit/Receive Coils, Tuned Series Resonant Receiver and AC-DC Rectifier
4120 F04
Figure 5. Resonant Receiver Tank
4120 F05
refer to AN138: Wireless Power Users Guide. cally based on the power used to charge a battery. amount of power available at the input of the LTC4120. in excess of 30nF at this pin. conditions when the battery is fully charged.
the maximum power available at the input to the LTC4120. frequency so that more power is available. nant circuit refer to the applications section. where VFB(REG) is typically 2.4V. Figure 6. Programming the Float Voltage with the LTC4120
4120 F06
return for the battery float voltage divider . 1% resistor values for common battery float voltages. Table 1. Recommended 0.1% Resistors for Common VFLOAT Table 2. Recommended 1% Resistors for Common VFLOAT and limit stray capacitance at this node to less than 50pF.
charge current will be reduced to zero. if the NTC pin is pulled below about 85mV (VDIS). The LTC4120 uses a safety timer to terminate charging. timeout, the LTC4120 enters a low power sleep mode. Figure 7. NTC Connections
4120 F07
indicated by the pin voltages. Table 3. LTC4120 Open-Drain Indicator Outputs with Resistor is applied and the DC trickle charge current is turned off. the fault status pin is asserted to indicate a bad battery. condition less than 20µA is drawn from the supply at IN. frequency allows the use of smaller external components.
LTC4120/LTC4120-4.2 Rev. G For more information www.analog.com OPERATION improves efficiency by reducing internal gate charge and switching losses, but requires larger inductance values to maintain low output ripple. Operation at higher frequency allows the use of smaller components, but may require sufficient margin from the minimum on-time at the lowest duty cycle if fixed-frequency switching is required. PWM Dropout Detector If the input voltage approaches the battery voltage, the LTC4120 may require duty cycles approaching 100%. This mode of operation is known as dropout. In drop - out, the operating frequency may fall well below the pro- grammed fOSC value. If the top switch remains on for eight clock cycles, the dropout detector activates and forces the bottom switch on for the remainder of that clock cycle or until the inductor current decays to zero. This avoids a potential source of audible noise when using ceramic input or output capacitors and prevents the boost sup - ply capacitor for the top gate drive from discharging. In dropout operation, the actual charge current may not be able to reach the full-scale programmed value. In such a scenario the analog charge current monitor function does not represent actual charge current being delivered. Burst Mode Operation At low charge currents, for example during constant- voltage mode, the LTC4120 automatically enters Burst Mode operation. In Burst Mode operation the switcher is periodically forced into standby mode in order to improve efficiency. The LTC4120 automatically enters Burst Mode operation after it exits constant-current (CC) mode and as the charge current drops below about 80mA. Burst Mode operation is triggered at lower currents for larger PROG resistors, and depends on the input supply volt - age. Refer to graph Burst Mode T rigger Current and graph Typical Burst Mode Waveform, in the Typical Performance Characteristics , for more information on Burst Mode operation. Burst Mode operation has some hysteresis and remains engaged for battery currents up to about 150mA. While in Burst Mode operation, the PROG pin voltage to average charge current relationship is not well defined. This is due to the PROG pin voltage falling to 0V in between bursts, as shown in G14. If the PROG pin volt - age falls below 120mV for longer than 350µs this causes the CHRG pin to de-assert, indicating C/10. Burst current ripple depends on the selected switch inductor , and VIN/ VBAT. BOOST Supply Refresh The BOOST supply for the top gate drive in the LTC4120 switching regulator is generated by bootstrapping the BOOST flying capacitor to INTV CC whenever the bottom switch is turned on. This technique provides a voltage of INTVCC from the BOOST pin to the SW pin. In the event that the bottom switch remains off for a prolonged period of time, e.g., during Burst Mode operation, the BOOST supply may require a refresh. Similar to the PWM dropout timer , the LTC4120 counts the number of clock cycles since the last BOOST refresh. When this count reaches 32, the next PWM cycle begins by turning on the bottom side switch first. This pulse refreshes the BOOST flying capacitor to INTV CC and ensures that the topside gate driver has sufficient voltage to turn on the topside switch at the beginning of the next cycle. Operation Without an Input Supply or Wireless Power When a battery is the only available power source, care should be taken to eliminate loading of the IN pin. Load current on IN drains the battery through the body diode of the top side power switch as V IN falls below V SW. To prevent this possibility, place a diode between the input supply and the IN capacitor , CIN. The rectification diode (D9 in Figure 5 and Figure 11) in the wireless power appli- cations also eliminates this discharge path. Alternately, a P-channel MOSFET may be placed in series with the BAT pin provided care is taken to directly sense the positive battery terminal voltage with FB via the battery resistive divider . This is illustrated in Figure 15.
the load goes away (e.g, when the battery is fully charged). on the load without compromising available power . In the event that the coupling may become too large (e.g. Figure 9. Coupling Coefficient k vs Distance
0.50 NO MISALIGNMENT
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Figure 8. Wireless Power T ransfer
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and Figure 10) illustrates this connection. An example DC/AC transmitter is shown in Figure 10 .
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Figure 10. DC/AC Converter , T ransmit/Receive Coils, Tuned Series Resonant Receiver and AC/DC Rectifier Figure 11. High Voltage Pre-Regulator for T ransmitter
Table 4. Recommended T ransmitter and High Voltage Pre-Regulator Components 1CX = 300nF with 5µH LX coil, or CX = 233nF with 6.3µH LX coil. circuits is critical to achieving maximum power transfer . 40V, so adequate voltage ratings must also be observed.
Table 5. Recommended Receiver Components
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Figure 12. 4-Layer PCB Layout of Rx Coil
LTC4120/LTC4120-4.2 Rev. G For more information www.analog.com APPLICATIONS INFORMATION the operating frequency of the basic transmitter can vary with component selection. LTC4120 customers can also choose more advanced transmitter options such as the LTC4125. With addi - tional features such as: foreign metal detection; optimum power search and AutoResonant™ operating frequency. For more information on advanced transmitter options refer to the Wireless Power Users Guide. Maximum Battery Power Considerations Using one of the approved transmitter options with this wireless power design provides a maximum of 2W at the input to the LTC4120. It is optimized for supplying 400mA of charge current to a 4.2V Li-Ion battery. If a higher bat- tery voltage is selected, then a lower charge current must be used as the maximum power available is limited. The maximum battery charge current, I CHG(MAX), that may be programmed for a given float voltage, VFLOAT, can be cal- culated based on the charger efficiency, ηEFF, as: ICHG(MAX) ≤ ηEFF • 2W VFLOAT The charger efficiency, ηEFF, depends on the operating conditions and may be estimated using the Buck Efficiency curve in the Typical Performance Characteristics. Do not select a charge current greater than this limit when select- ing RPROG. Input Voltage and Minimum On-Time The LTC4120 can operate from input voltages up to 40V. The LTC4120 maintains constant frequency operation under most operating conditions. Under certain situa - tions with high input voltage and high switching frequency selected and a low battery voltage, the LTC4120 may not be able to maintain constant frequency operation. These factors, combined with the minimum on-time of the LTC4120, impose a minimum limit on the duty cycle to maintain fixed-frequency operation. The on-time of the top switch is related to the duty cycle (VBAT/VIN) and the switching frequency, fOSC in Hz: tON = VBAT fOSC • VIN When operating from a high input voltage with a low bat- tery voltage, the PWM control algorithm may attempt to enforce a duty cycle which requires an on-time lower than the LTC4120 minimum, t MIN(ON). This minimum duty cycle is approximately 18% for 1.5MHz operation or 9% for 750kHz operation. Typical minimum on-time is illustrated in graph G11 in the Typical Performance Characteristics section. If the on-time is driven below tMIN(ON), the charge current and battery voltage remain in regulation, but the switching duty cycle may not remain fixed, and/or the switching frequency may decrease to an integer fraction of its programmed value. The maximum input voltage allowed to maintain constant frequency operation is: VIN(MAX) = VLOWBAT fOSC • tMIN(ON) where VLOWBAT, is the lowest battery voltage where the switcher is enabled. Exceeding the minimum on-time constraint does not affect charge current or battery float voltage, so it may not be of critical importance in most cases and high switch- ing frequencies may be used in the design without any fear of severe consequences. As the sections on Inductor Selection and Capacitor Selection show, high switching frequencies allow the use of smaller board components, thus reducing the footprint of the applications circuit. Fixed-frequency operation may also be influenced by drop- out and Burst Mode operation as discussed previously. Switching Inductor Selection: LSW The primary criterion for switching inductor value selec- tion in an LTC4120 charger is the ripple current created in that inductor . Once the inductance value is determined, the saturation current rating for that inductor must be equal to or exceed the maximum peak current in the inductor , IL(PEAK). The peak value of the inductor current is the sum of the programmed charge current, ICHG, plus one-half of the ripple current, ∆I L. The peak inductor current must also remain below the current limit of the LTC4120, IPEAK: IL(PEAK) =ICHG + ∆IL <IPEAK
in the Typical Performance Characteristics. a value greater than IL(PEAK). tor is recommended to minimize voltage glitches at V IN. applications, with a voltage rating of 40V. blocking PFET connected with the LTC4120. Figure 15. Reverse Blocking with a P-Channel MOSFET in Series with the BAT Pin
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*ADD 4.99k WHEN MAX BAT VOL TAGE APPROACHES 85% OF VGS LIMIT FOR Si2343.
LTC4120/LTC4120-4.2 Rev. G For more information www.analog.com APPLICATIONS INFORMATION BAT Capacitor and Output Ripple: CBAT The LTC4120 charger output requires bypass capaci - tance connected from BAT to GND (CBAT). A 22µF ceramic capacitor is required for all applications. In systems where the battery can be disconnected from the charger out - put, additional bypass capacitance may be desired. In this type of application, excessive ripple and/or low ampli - tude oscillations can occur without additional output bulk capacitance. For optimum stability, the additional bulk capacitance should also have a small amount of ESR. For these applications, place a 100µF low ESR non-ceramic capacitor (chip tantalum or organic semiconductor capac- itors such as Sanyo OS-CONs or POSCAPs) from BAT to GND, in parallel with the 22µF ceramic bypass capacitor , or use large ceramic capacitors with an additional series ESR resistor of less than 1Ω. This additional bypass capacitance may also be required in systems where the battery is connected to the charger with long wires. The voltage rating of all capacitors applied to CBAT must meet or exceed the battery float voltage. Boost Supply Capacitor: CBST The BOOST pin provides a bootstrapped supply rail that provides power to the top gate drivers. The operating volt- age of the BOOST pin is internally generated from INTVCC whenever the SW pin pulls low. This provides a floating voltage of INTVCC above SW that is held by a capacitor tied from BOOST to SW . A low ESR ceramic capacitor of 10nF to 22nF is sufficient for CBST, with a voltage rating of 6V. INTVCC Supply and Capacitor: CINTVCC Power for the top and bottom gate drivers and most other internal circuitry is derived from the INTV CC pin. A low ESR ceramic capacitor of 2.2µF is required on the INTVCC pin. The INTVCC supply has a relatively low current limit (about 20mA) that is dialed back when INTV CC is low to reduce power dissipation. Do not use the INTVCC voltage to supply power for any external circuitry apart from the NTCBIAS network. When the RUN pin is above V EN the INTVCC supply is enabled, and when INTVCC rises above UVINTVCC the charger is enabled. APPLICATIONS INFORMATION Calculating Power Dissipation The user should ensure that the maximum rated junction temperature is not exceeded under all operating condi - tions. The thermal resistance of the LTC4120 package (θJA) is 54° C/W; provided that the exposed pad is sol - dered to sufficient PCB copper area. The actual thermal resistance in the application may depend on forced air cooling or other heat sinking means, and especially the amount of copper on the PCB to which the LTC4120 is attached. The actual power dissipation while charging is approximated by the following formula: PD ≅ VIN – VBAT( ) • ITRKL +VIN • IIN(SWITCHING) +RSNS • ICHG2 +RDS(ON)(TOP) • VBAT VIN
- ICHG2 +RDS(ON)(BOT) • 1– VBAT VIN ⎠⎟ • ICHG2 During trickle charge (VBAT < VTRKL) the power dissipation may be significant as I TRKL is typically 10mA, however during normal charging the ITRKL term is zero. The junction temperature can be estimated using the fol- lowing formula: TJ = TA + PD • θJA where TA is the ambient operating temperature. Significant power is also consumed in the transmitter electronics. The large AC voltage generated across the LX and CX tank results in power being dissipated in the DC resistance of the LX coil and the ESR of the CX capacitor . The large induced magnetic field in the L X coil may also induce heating in nearby metallic objects. PCB Layout To prevent magnetic and electrical field radiation and high frequency resonant problems, proper layout of the components connected to the LTC4120 is essential. For maximum efficiency, the switch node rise and fall times
LTC4120/LTC4120-4.2 Rev. GFor more information www.analog.com APPLICATIONS INFORMATION should be minimized. The following PCB design priority list will help insure proper topology. Layout the PCB using the guidelines listed below in this specific order . 1. Keep foreign metallic objects away from the transmit- ter coil. Metallic objects in proximity to the transmit coil will suffer from induction heating and will be a source of power loss. With the exception of a ferrite shield that can be used to improve the coupling from transmitter coil to receiver coil when placed behind the transmitter coil. Advanced transmitters using LTC4125 include features to detect the presence of foreign metallic objects that mitigates this issue. 2. VIN input capacitor should be placed as close as pos- sible to the IN and GND pins, with the shortest copper traces possible and a via connection to the GND plane 3. Place the switching inductor as close as possible to the SW pin. Minimize the surface area of the SW pin node. Make the trace width the minimum needed to support the programmed charge current, and ensure that the spacing to other copper traces be maximized to reduce capacitance from the SW node to any other node. 4. Place the BA T capacitor adjacent to the BAT pin and ensure that the ground return feeds to the same cop- per that connects to the input capacitor ground before connecting back to system ground. 5. Route analog ground (RUN ground and INT VCC capac- itor ground) as a separate trace back to the LTC4120 GND pin before connecting to any other ground. 6. Place the INT VCC capacitor as close as possible to the INTVCC pin with a via connection to the GND plane. 7. Route the DHC trace with sufficient copper and vias to support 350mA of RMS current, and ensure that the spacing from the DHC node to other copper traces be maximized to reduce capacitance and radiated EMI from the DHC node to other sensitive nodes. 8. It is important to minimize parasitic capacitance on the PROG pin. The trace connecting to this pin should be as short as possible with extra wide spacing from adjacent copper traces. 9. Minimize capacitive coupling to GND from the FB pin. 10. Maximize the copper area connected to the exposed pad. Place via connections directly under the exposed pad to connect a large copper ground plane to the LTC4120 to improve heat transfer . Design Examples The design example illustrated in Figure 17, reviews the design of the resonant coupled power transfer charger application. First the design of the wireless power receiver circuit is described. Then consider the design for the char- ger function given the maximum input voltage, a battery float voltage of 8.2V, and a charge current of 200mA for the LTC4120. This example also demonstrates how to select the switching inductance value to avoid discontinu- ous conduction; where switching noise increases. The wireless power receiver is formed by the tuned net - work LR and C2P, C2S. This tuned network automatically modulates the resonance of the tank with the DHC pin of the LTC4120 to optimize power transfer . The resonant frequency of the tank should match the oscillation fre - quency of the transmitter . Given the transmitter shown in Figure 4 this frequency is 130kHz. The tuned receiver resonant frequency is: fT = 1 2 • π • LR • (C2P +C2S) = 127 kHz In this design example, the de-tuned resonant frequency is: fD = 1 2 • π • LR • C2S = 142kHz fD should be set between 5% and 15% higher than f T. A higher level gives more control range but results in more power dissipation. A 47µH coil is selected for LR to obtain a turns ratio of 3:1 from the transmitter coil, LX = 5µH. Now C2S can be calculated to be 26.7nF. T wo standard parallel 50V rated capacitors, 22nF and 4.7nF, provide a value within 1% of the calculated C2S. Now C2P can be calculated to be 6.5nF which can be obtained with
LTC4120/LTC4120-4.2 Rev. G For more information www.analog.com APPLICATIONS INFORMATION 4.7nF and 1.8nF capacitors in parallel. All of the capacitors should be selected with 5% or better tolerance. The rectifier , D8, D9 and D5 are selected as 50V rated Schottky diodes. Now consider the design circuit for the LTC4120 charger function. First, the external feedback divider , RFB1/RFB2, is found using standard 1% values: RFB1 = 8.2V • 588k 2.4V ≅ 2.00M RFB2 = 2.00M • 588k 2.00M – 588k ≅ 825k With these resistors, and including the resistance of the FBG pin, the battery float voltage is 8.212V. With an 8.2V float voltage the maximum charge current available is limited by the maximum power available from the RCPT at ηEFF = 85% charger efficiency: ICHG(MAX) ≤ 85% • 2W 8.2V = 207mA A charge current of 200mA is achieved by selecting a standard 1% RPROG resistor of: RPROG = hPROG • VPROG ICHG =6.04k While charging a battery, the resonant receiver is loaded by the charge current, this load reduces the input voltage from the open-circuit value to a typical voltage in a range from 12V (at UVCL) up to about 26V. The amplitude of this voltage depends primarily on the amount of coupling between the transmitter and the receiver , typically this voltage is about 17V. The maximum loaded input voltage is used to select the operating frequency and influences the value of the switching inductor . The saturation current rating of the switching inductor is selected based on the worst case conditions at the maximum open-circuit voltage. A typical 2-cell Li-Ion battery pack engages pack pro - tection for V BAT less than 5V, this is the lowest voltage considered for determining the on-time and selecting the 1.5MHz operating frequency. tON = 5V 1.5MHz • 17V = 476ns > tMIN(ON) Now the switching inductor value is calculated. The induc- tor value is calculated based on achieving a 30% ripple current. The ripple current is calculated at the typical input operating voltage of 17V: 1.5MHz • 17V • 30% • 200mA( ) = 48µH 56µH is the next standard inductor value that is greater than this minimum. This inductor value results in a worst-case ripple current at the input open-circuit voltage, V IN(OC). VIN(OC) is estimated based on the transmitter design in Figure 4, at the largest coupling coefficient k = 0.37 as: VIN(OC) = k • n • π • VIN(TX) 1.5MHz • 56µH • 34.9V = 75mA This results in a worst-case peak inductor current of: IL(PEAK) =ICHG + ∆IL = 237mA Select an inductor with a saturation current rating greater than the worst-case peak inductor current of 237mA. Select a 50V rated capacitor for CIN = 10µF to achieve an input voltage ripple of 10mV at the typical operating input voltage of 17V: ∆VIN = 200mA • 8.2V 17V 10µF =10mV And select 6V rated capacitors for C INTVCC = 2.2µF, CBOOST = 22nF, and CBAT = 22µF. Optionally add diode D6, a 1W, 39V Zener diode if the coupling from trans - mitter to receiver coils is not well enough controlled to ensure that VIN remains below 39V when the battery is fully charged.
and R4 = 102k the RUN pin reaches 2.4V at VIN = 11.2V.
- 0.02A 2 +0.5Ω• 1– 3V 20V ⎟⎟ • 0.02A 2 = 0.27W This dissipated power results in a junction temperature rise of: PD • θJA = 0.27W • 54°C/W = 15°C During regular charging with V BAT > VTRKL, the power dissipation reduces to: PD = 20V • 5mA +0.3Ω• 0.2A 2 +0.8Ω• 8.2V 20V
- 0.2A 2 +0.5Ω• 1– 8.2V 20V ⎟ • 0.2A 2 = 0.14mW This dissipated power results in a junction temperature rise of 6°C over ambient. Design Example 2: Operation with the LTC4125 The LTC4125 is a 5W AutoResonant wireless power transmitter that offers several advantages over the simple transmitter shown in Figure 10, including foreign object detection, external overtemperature detection, automatic tuning of switching frequency and transmit power. When operating the LTC4120 receiver with the LTC4125, the DHC pin serves to enable an external shunt regulator that optimizes the input supply voltage to the LTC4120 as shown in Figure 16. For more information on using the LTC4125 see the LTC4125 data sheet.
Figure 16. LTC4125 Driving a 24μH T ransmit Coil at 103kHz, with 1.3A Input Current Threshold, 119kHz Frequency Limit
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LTC4120/LTC4120-4.2 Rev. G For more information www.analog.com PACKAGE DESCRIPTION 3.00 ±0.10 (4 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 1.45 ±0.05 (4 SIDES) NOTE: 1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2) 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE PIN 1 TOP MARK (NOTE 6) 0.40 ±0.10 BOTTOM VIEW—EXPOSED PAD 1.45 ± 0.10 (4-SIDES) 0.75 ±0.05 R = 0.115 TYP 0.25 ±0.05 PIN 1 NOTCH R = 0.20 TYP OR 0.25 × 45° CHAMFER 15 16
0.50 BSC
0.200 REF
2.10 ±0.05 3.50 ±0.05 0.70 ±0.05 0.00 – 0.05 (UD16) QFN 0904 0.25 ±0.05 16-Lead Plastic QFN (3mm × 3mm) (Reference LTC DWG # 05-08-1691 Rev Ø)
LTC4120/LTC4120-4.2 Rev. GFor more information www.analog.com Information furnished by Analog Devices is believed to be accurate and reliable. However , no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
REVISION HISTORY
A 12/13 Updated Table 4 component values and brands. 20 B 03/14 Removed word “battery” from float voltage range bullet. Modified various specification limits and removed some temp dots. Modified frequency range, resistor values and Note 3. Amended IIN curves. Modified text to reflect typical fOSC values. Updated text for VPROG servo. Amended equation for fD. Modified ICHG equation. Changed description of End-Of-Charge indication. Modified typical f OSC values. Modified Resonant Converter Selection. Added high voltage pre-regulator schematic. Added Table 4: Recommended T ransmitter and High Voltage Pre-Regulator Components. Added Table 5: Recommended Receiver Components. Added Figure 11, PCB Layout of Rx Coil. Added Figure 12, Tx layout: photo of Demo Circuit 1968A. Added Figure 13, Rx layout: photo of Demo Circuit 1967A-B Modified text of f OSC and fT. Modified fT equation. Modified equation for tON, L3, ∆IL, and IL(PEAK) and changed power dissipation calculations. C 05/14 Increased minimum V IN to 12.5V Added fixed 4.2V float version, throughout document, also added electrical parameters for –4.2 Increased IFB specification to TYP 25nA Reduced min RECHG threshold to –38mV Modified VPROG servo voltage spec by +3mV and –3mV Loosened VTRKL threshold voltage spec by –20mV and +10mV Increased TYP VTRKL hysteresis spec to 50mV Changed conditions on ISW specification to IN = Open-Circuit from IN = Float Revised RSNS current limit typical performance characteristics curve Added typical VFLOAT performance characteristics curve Corrected error in IIN(SWITCHING) Current curve (x-axis) Added Block Diagram of –4.2 BATSNS connections Changed V IN labels to IN in Figure 4, 5, and 10 Remove SW inductor selection Tables 6, 7, 8, and 9 Changed location of BAT decoupling cap in Figure 15 with reverse blocking diode Corrected error in L3 equation and substituted correct 56µH inductor 1, 3 1 to 32 12, 13, 20 N/A D 01/15 Change CBAT from 10µF to 22µF Add Würth P/N for RX coil Add INTER-TECH P/N for TX and RX coils Remove dos on 68µ bias inductor in basic TX schematic for clarity 26, 29 and 32 21, 22 12, 20 E 05/15 Clarified Battery Charge Current vs Temperature curve Clarified End-of-Charge and Battery Recharge sections Modified Operation without an Input Supply section Enhanced Reverse Blocking section Modified INTV CC Supply and Capacitor section 25,26 F 02/16 Removed INTV CC spec. Moved Note 4 to UV_INTVCC spec. Modified INTVCC pin definition. Included LTC4125 in Applications Information. Added 4.99k Note. Added paragraph and Figure 16 from LTC4125 data sheet. Renumbered Figure 17. Added to Related Parts Table. G 11/18 Removed references to PowerByProxi. 12, 27
Figure 17. Resonant Coupled Power T ransfer Charger Application