LTC4090EDJC-TRPBF

FEATURES ■ ■ ■ LTC4090/LTC4090-5 USB Power Manager with 2A High Voltage Bat-Track Buck Regulator DESCRIPTION The LTC®4090/LTC4090-5 are USB power managers plus high voltage Li-Ion/Polymer battery chargers. The devices control the total current used by the USB peripheral for operation and battery charging. Battery charge current is automatically reduced such that the sum of the load current and the charge current does not exceed the programmed input current limit. The LTC4090/LTC4090-5 also accommodate high voltage power supplies, such as 12V AC/DC wall adapters, FireWire, or automotive power. The LTC4090 provides a Bat-Track adaptive output that tracks the battery voltage for high efficiency charging from the high voltage input. The LTC4090-5 provides a fixed 5V output from the high voltage input to charge single cell Li-Ion bateries. The charge current is programmable and an end-of-charge status output (⎯C⎯H⎯R⎯G) indicates full charge. Also featured are programmable total charge time, an NTC thermistor input used to monitor battery temperature while charging and automatic recharging of the battery. , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Bat-Track is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. ■ ■ ■ ■ ■ Seamless Transition Between Power Sources: LiIon Battery, USB, and 6V to 36V Supply (60V Max) 2A Output High Voltage Buck Regulator with BatTrackTM Adaptive Output Control (LTC4090) Internal 215mΩ Ideal Diode Plus Optional External Ideal Diode Controller Provides Low Loss Power Path When External Supply / USB Not Present Load Dependent Charging from USB Input Guarantees Current Compliance Full Featured Li-Ion Battery Charger 1.5A Maximum Charge Current with Thermal Limiting NTC Thermistor Input for Temperature Qualified Charging Tiny (3mm × 6mm × 0.75mm) 22-Pin DFN Package APPLICATIONS ■ ■ ■ ■ HDD-Based Media Players Personal Navigation Devices Other USB-Based Handheld Products Automotive Accessories TYPICAL APPLICATION 0.47μF HIGH (6V-36V) VOLTAGE INPUT 5V WALL ADAPTER IN USB 4.7μF VC TIMER RT 0.1μF 40.2k CLPROG 2k GND LTC4090 OUT 4.7μF BAT PROG 100k HVIN 1μF HVOUT HVPR 1k BOOST SW 22μF 6.8μH LTC4090/LTC4090-5 High Voltage Battery Charger Efficiency 90 FIGURE 12 SCHEMATIC WITH RPROG = 52k 80 NO OUTPUT LOAD LTC4090 EFFICIENCY (%) LOAD 70 LTC4090-5 60 50 40 30 HVIN = 8V HVIN = 12V HVIN = 24V HVIN = 36V 2.5 3.5 3.0 VBAT (V) 4.0 4.5 4090 TA01b 59k 270pF + Li-Ion BATTERY VOUT (TYP) VBAT + 0.3V 5V 5V VBAT AVAILABLE INPUT HV INPUT (LTC4090) HV INPUT (LTC4090-5) USB ONLY BAT ONLY 20 2.0 4090 TAO1 4090fa 1 LTC4090/LTC4090-5 ABSOLUTE MAXIMUM RATINGS (Notes 1, 2, 3, 4) PIN CONFIGURATION TOP VIEW SYNC PG RT VC NTC VNTC HVPR CHRG PROG 1 2 3 4 5 6 7 8 9 23 22 HVEN 21 HVIN 20 SW 19 BOOST 18 HVOUT 17 TIMER 16 SUSP 15 HPWR 14 CLPROG 13 OUT 12 IN HVIN, HVEN (Note 9) ................................................60V BOOST ......................................................................56V BOOST above SW .....................................................30V PG, SYNC ..................................................................30V IN, OUT, HVOUT t < 1ms and Duty Cycle < 1% .................. –0.3V to 7V Steady State............................................. –0.3V to 6V BAT, HPWR, SUSP, VC, ⎯C⎯H⎯R⎯G, ⎯H⎯V⎯P⎯R ........... –0.3V to 6V NTC, TIMER, PROG, CLPROG ..........–0.3V to VCC + 0.3V IIN, IOUT, IBAT (Note 5) ..............................................2.5A Operating Temperature Range ..................... –40 to 85°C Junction Temperature ........................................... 110°C Storage Temperature Range....................... –65 to 125°C GATE 10 BAT 11 DJC PACKAGE 22-LEAD (6mm × 3mm) PLASTIC DFN TJMAX = 110°C, θJA = 47°C/W EXPOSED PAD (PIN 23) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH LTC4090EDJC#PBF LTC4090EDJC-5#PBF TAPE AND REEL LTC4090EDJC#TRPBF LTC4090EDJC-5#TRPBF PART MARKING 4090 40905 PACKAGE DESCRIPTION 22-Lead (6mm × 3mm) Plastic DFN 22-Lead (6mm × 3mm) Plastic DFN TEMPERATURE RANGE –40°C to 85°C –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ ELECTRICAL CHARACTERISTICS SYMBOL VIN IIN ILIM IIN(MAX) RON VCLPROG ISS PARAMETER USB Input Supply Voltage Input Bias Current Current Limit Maximum Input Current Limit On-Resistance VIN to VOUT CLPROG Servo Voltage in Current Limit Soft-Start Inrush Current USB Input Current Limit The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. HVIN = HVEN = 12V, BOOST = 17V, VIN = HPWR = 5V, VBAT = 3.7V, RPROG = 100k, RCLPROG = 2k and SUSP = 0V, unless otherwise noted. CONDITIONS ● MIN 4.35 TYP MAX 5.5 UNITS V mA μA mA mA A Ω IBAT = 0 (Note 6) Suspend Mode; SUSP = 5V HPWR = 5V HPWR = 0V (Note 7) IOUT = 80mA RCLPROG = 2k RCLPROG = 1k ● ● ● ● 0.5 50 475 90 500 100 2.4 0.215 1 100 525 110 ● ● 0.98 0.98 1.00 1.00 10 1.02 1.02 V V mA/μs 4090fa 2 LTC4090/LTC4090-5 ELECTRICAL CHARACTERISTICS SYMBOL VCLEN VUVLO ΔVUVLO VHVIN VOVLO IHVIN VOUT VOUT fSW PARAMETER Input Current Limit Enable Threshold Voltage (VIN - VOUT) Input Undervoltage Lockout Input Undervoltage Lockout Hysteresis HVIN Supply Voltage HVIN Overvoltage Lockout Threshold HVIN Bias Current Output Voltage with HVIN Present Output Voltage with HVIN Present Switching Frequency Shutdown; HVEN = 0.2V Not Switching, HVOUT = 3.6V Assumes HVOUT to OUT Connection, 0 ≤ VBAT ≤ 4.2V (LTC4090) Assumes HVOUT to OUT Connection (LTC4090-5) RT = 8.66k RT = 29.4k RT = 187k ● The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. HVIN = HVEN = 12V, BOOST = 17V, VIN = HPWR = 5V, VBAT = 3.7V, RPROG = 100k, RCLPROG = 2k and SUSP = 0V, unless otherwise noted. CONDITIONS (VIN - VOUT) Rising (VIN - VOUT) Falling VIN Rising VIN Rising – VIN Falling ● ● ● ● MIN 20 –80 3.6 TYP 50 –50 3.8 130 MAX 80 –20 4 UNITS mV mV V mV High Voltage Regulator 6 36 41.5 0.01 130 3.45 4.85 2.1 0.9 160 3.0 VBAT + 0.3 5 2.4 1.0 200 60 3.5 500 0.02 ● 60 45 0.5 200 4.6 5.15 2.7 1.15 240 150 4.0 2 2.1 35 27 35 100 4.235 4.242 535 1080 1.02 1.02 0.11 60 3.0 V V μA μA V V MHz MHz kHz ns A mV μA V mA μA μA μA V V mA mA A V V mA/mA mA V mV mV tOFF ISW(MAX) VSAT IR VB(MIN) IBST IBAT Minimum Switch Off-Time Switch Current Limit Switch VCESAT Boost Schottky Reverse Leakage Minimum Boost Voltage (Note 8) BOOST Pin Current Battery Drain Current ISW = 1A VBAT = 4.3V, Charging Stopped Suspend Mode, SUSP = 5V VIN = 0V, BAT Powers OUT, No Load IBAT = 2mA IBAT = 2mA; 0 ≤ TA ≤ 85°C Duty Cycle = 5% ISW = 2A SW = 10V, HVOUT = 0V 1.5 22 Battery Management ● ● ● 15 22 60 4.165 4.158 4.200 4.200 500 1000 1.5 1.00 1.00 0.1 50 2.9 55 80 VFLOAT ICHG ICHG(MAX) VPROG kEOC ITRKL VTRKL VCEN ΔVRECHRG VBAT Regulated Output Voltage Constant-Current Mode Charge Current, RPROG = 100k No Load RPROG = 50k, 0 ≤ TA ≤ 85°C Maximum Charge Current PROG Pin Servo Voltage Ratio of End-of-Charge Indication Current to Charge Current Trickle Charge Current Trickle Charge Threshold Voltage Charge Enable Threshold Voltage Recharge Battery Threshold Voltage RPROG = 100k RPROG = 50k VBAT = VFLOAT (4.2V) BAT = 2V BAT Rising (VOUT – VBAT) Falling; VBAT = 4V (VOUT – VBAT) Rising; VBAT = 4V Threshold Voltage Relative to VFLOAT ● 465 900 0.98 0.98 0.085 35 ● ● ● ● 2.75 ● –65 –100 –135 mV 4090fa 3 LTC4090/LTC4090-5 ELECTRICAL CHARACTERISTICS SYMBOL tTIMER PARAMETER TIMER Accuracy Recharge Time Low Battery Trickle Charge Time TLIM Junction Temperature in Constant Temperature Mode Incremental Resistance, VON Regulation IOUT = 100mA On-Resistance VBAT to VOUT Voltage Forward Drop (VBAT – VOUT) IOUT = 600mA IOUT = 5mA IOUT = 100mA IOUT = 600mA ● The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. HVIN = HVEN = 12V, BOOST = 17V, VIN = HPWR = 5V, VBAT = 3.7V, RPROG = 100k, RCLPROG = 2k and SUSP = 0V, unless otherwise noted. CONDITIONS VBAT = 4.3V Percent of Total Charge Time Percent of Total Charge Time, VBAT 41.5V (typical), the LTC4090/LTC4090-5 will stop switching, allowing the output to fall out of regulation. While the high voltage regulator output is in start-up, short-circuit, or other overload conditions, the switching frequency should be chosen according to the following discussion. For safe operation at inputs up to 60V the switching frequency must be low enough to satisfy VHVIN(MAX) ≥ 45V according to the following equation. If lower VHVIN(MAX) is desired, this equation can be used directly. VHVIN(MAX ) = VHVOUT + VD –V +V fSW • tON(MIN) D SW may enter pulse skipping operation where some switching pulses are skipped to maintain output regulation. In this mode the output voltage ripple and inductor current ripple will be higher than in normal operation. Above 41.5V, switching will stop. The minimum input voltage is determined by either the high voltage regulator’s minimum operating voltage of ~6V or by its maximum duty cycle (see equation in previous section). The minimum input voltage due to duty cycle is: VHVIN(MIN) = VHVOUT + VD −V +V 1− fSW tOFF(MIN) D SW where VHVIN(MIN) is the minimum input voltage, and tOFF(MIN) is the minimum switch off time (150ns). Note that higher switching frequency will increase the minimum input voltage. If a lower dropout voltage is desired, a lower switching frequency should be used. Inductor Selection and Maximum Output Current A good choice for the inductor value is L = 6.8μH (assuming a 800kHz operating frequency). With this value the maximum load current will be ~2.4A. The RMS current rating of the inductor must be greater than the maximum load current and its saturation current should be about 30% higher. Note that the maximum load current will be programmed charge current plus the largest expected application load current. For robust operation in fault conditions, the saturation current should be ~3.5A. To keep efficiency high, the series resistance (DCR) should be less than 0.1Ω. Table 2 lists several vendors and types that are suitable. Table 2. Inductor Vendors VENDOR URL Murata TDK Toko www.murata.com www.componenttdk.com www.toko.com PART SERIES LQH55D SLF7045 SLF10145 D62CB D63CB D75C D75F CR54 CDRH74 CDRH6D38 CR75 TYPE Open Shielded Shielded Shielded Shielded Shielded Open Open Shielded Shielded Open 4090fa where VHVIN(MAX) is the maximum operating input voltage, VHVOUT is the high voltage regulator output voltage, VD is the catch diode drop (~0.5V), VSW is the internal switch drop (~0.5V at max load), fSW is the switching frequency (set by RT), and tON(MIN) is the minimum switch-on time (~150ns). Note that a higher switching frequency will depress the maximum operating input voltage. Conversely, a lower switching frequency will be necessary to achieve safe operation at high input voltages. If the output is in regulation and no short-circuit, startup, or overload events are expected, then input voltage transients of up to 60V are acceptable regardless of the switching frequency. In this mode, the LTC4090/LTC4090-5 Sumida www.sumida.com 19 LTC4090/LTC4090-5 APPLICATIONS INFORMATION Catch Diode The catch diode conducts current only during switch-off time. Average forward current in normal operation can be calculated from: ID( AVG) = IHVOUT • COUT = 100 VOUT fSW ( VHVIN – VHVOUT ) VHVIN where IHVOUT is the output load current. The only reason to consider a diode with a larger current rating than necessary for nominal operation is for the worst-case condition of shorted output. The diode current will then increase to the typical peak switch current. Peak reverse voltage is equal to the regulator input voltage. Use a Schottky diode with a reverse voltage rating greater than the input voltage. The overvoltage protection feature in the high voltage regulator will keep the switch off when VHVIN > 45V which allows the use of 45V rated Schottky even when VHVIN ranges up to 60V. Table 3 lists several Schottky diodes and their manufacturers. Table 3. Diode Vendors PART NUMBER On Semiconductor MBRM120E MBRM140 Diodes Inc. B130 B220 B230 B360 DFLS240L International Rectifier 10BQ030 20BQ030 VR (V) 20 40 30 20 30 60 40 30 30 IAVE (A) 1 1 1 2 2 3 2 1 2 VF AT 1A (MV) 530 550 500 500 500 500 550 500 470 470 VF AT 2A (MV) 595 where fSW is in MHz, and COUT is the recommended output capacitance in μF. Use X5R or X7R types. This choice will provide low output ripple and good transient response. Transient performance can be improved with a higher value capacitor if the compensation network is also adjusted to maintain the loop bandwidth. A lower value of output capacitor can be used to save space and cost but transient performance will suffer. See the High Voltage Regulator Frequency Compensation section to choose an appropriate compensation network. When choosing a capacitor, look carefully through the data sheet to find out what the actual capacitance is under operating conditions (applied voltage and temperature). A physically larger capacitor, or one with a higher voltage rating, may be required. High performance tantalum or electrolytic capacitors can be used for the output capacitor. Low ESR is important, so choose one that is intended for use in switching regulators. The ESR should be specified by the supplier, and should be 0.05Ω or less. Such a capacitor will be larger than a ceramic capacitor and will have a larger capacitance, because the capacitor must be large to achieve low ESR. Ceramic Capacitors Ceramic capacitors are small, robust and have very low ESR. However, ceramic capacitors can cause problems when used with the high voltage switching regulator due to their piezoelectric nature. When in Burst Mode operation, the LTC4090/LTC4090-5’s switching frequency depends on the load current, and at very light loads the LTC4090/LTC4090-5 can excite the ceramic capacitor at audio frequencies, generating audible noise. Since the LTC4090/LTC4090-5 operate at a lower current limit during Burst Mode operation, the noise is typically very quiet to a casual ear. If this is unacceptable, use a high performance tantalum or electrolytic capacitor at the output. High Voltage Regulator Frequency Compensation The LTC4090/LTC4090-5 high voltage regulator uses current mode control to regulate the output. This simplifies loop compensation. In particular, the high voltage 4090fa 420 High Voltage Regulator Output Capacitor Selection The high voltage regulator output capacitor has two essential functions. Along with the inductor, it filters the square wave generated at the switch pin to produce the DC output. In this role it determines the output ripple, and low impedance at the switching frequency is important. The second function is to store energy in order to satisfy transient loads and stabilize the LTC4090/LTC4090-5’s control loop. Ceramic capacitors have very low equivalent series resistance (ESR) and provide the best ripple performance. A good starting value is: 20 LTC4090/LTC4090-5 APPLICATIONS INFORMATION regulator does not require the ESR of the output capacitor for stability, so you are free to use ceramic capacitors to achieve low output ripple and small circuit size. Frequency compensation is provided by the components tied to the VC pin, as shown in Figure 1. Generally a capacitor (CC) and a resistor (RC) in series to ground are used. In addition, there may be a lower value capacitor in parallel. This capacitor (CF) is not part of the loop compensation but is used to filter noise at the switching frequency, and is required only if a phase-lead capacitor is used or if the output capacitor has high ESR. Loop compensation determines the stability and transient performance. Designing the compensation network is a bit complicated and the best values depend on the application and in particular the type of output capacitor. A practical approach is to start with the front page schematic and tune the compensation network to optimize performance. Stability should then be checked across all operating conditions, including load current, input voltage and temperature. The LTC1375 datasheet contains a more thorough discussion of loop compensation and describes how to test the stability using a transient load. Figure 5 shows the transient response when the load current is stepped from 500mA to 1500mA and back to 500mA. Low Ripple Burst Mode Operation and Pulse-Skip Mode The LTC4090/LTC4090-5 are capable of operating in either low ripple Burst Mode operation or pulse-skip mode which are selected using the SYNC pin. Tie the SYNC pin below VSYNC,L (typically 0.5V) for low ripple Burst Mode operation or above VSYNC,H (typically 0.8V) for pulse-skip mode. FIGURE 12 SCHEMATIC HVOUT 50mV/DIV VSW 5V/DIV To enhance efficiency at light loads, the LTC4090/LTC4090-5 can be operated in low ripple Burst Mode operation which keeps the output capacitor charged to the proper voltage while minimizing the input quiescent current. During Burst Mode operation, the LTC4090/LTC4090-5 deliver single cycle bursts of current to the output capacitor followed by sleep periods where the output power is delivered to the load by the output capacitor. Because the LTC4090/ LTC4090-5 deliver power to output with single, low current pulses, the output ripple is kept below 15mV for a typical application. As the load current decreases towards a no load condition, the percentage of time that the high voltage regulator operates in sleep mode increases and the average input current is greatly reduced resulting in high efficiency even at very low loads. See Figure 6. At higher output loads (above 70mA for the front page application) the LTC4090/LTC4090-5 will be running at the frequency programmed by the RT resistor, and will be operating in standard PWM mode. The transition between PWM and low ripple Burst Mode operation is seamless, and will not disturb the output voltage. If low quiescent current is not required, the LTC4090/ LTC4090-5 can operate in pulse-skip mode. The benefit of this mode is that the LTC4090/LTC4090-5 will enter full frequency standard PWM operation at a lower output load current than when in Burst Mode operation. The front page application circuit will switch at full frequency at output loads higher than about 60mA. VIN = 12V; FIGURE 12 SCHEMATIC ILOAD = 10mA IL 0.5A/DIV IL 1A/DIV VOUT 10mV/DIV 5μs/DIV 25μs/DIV 4090 F05 4090 F06 Figure 6. High Voltage Regulator Burst Mode Operation Figure 5. Transient Load Response of the LTC4090 High Voltage Regulator Front Page Application as the Load Current is Stepped from 500mA to 1500mA. 4090fa 21 LTC4090/LTC4090-5 APPLICATIONS INFORMATION Boost Pin Considerations Capacitor C2 (see Block Diagram) and an internal diode are used to generate a boost voltage that is higher than the input voltage. In most cases, a 0.47μF capacitor will work well. The BOOST pin must be at least 2.3V above the SW pin for proper operation. High Voltage Regulator Soft-Start The HVEN pin can be used to soft-start the high voltage regulator of the LTC4090/LTC4090-5, reducing maximum input current during start-up. The HVEN pin is driven through an external RC filter to create a voltage ramp at this pin. Figure 7 shows the start-up and shutdown waveforms with the soft-start circuit. By choosing a large RC time constant, the peak start-up current can be reduced to the current that is required to regulate the output, with no overshoot. Choose the value of the resistor so that it can supply 20μA when the HVEN pin reaches 2.3V. lower than the external synchronization frequency to ensure adequate slope compensation. While synchronized, the high voltage regulator will turn on the power switch on positive going edges of the clock. When the power good (PG) output is low, such as during start-up, short-circuit, and overload conditions, the LTC4090/LTC4090-5 will disable the synchronization feature. The SYNC pin should be grounded when synchronization is not required. Alternate NTC Thermistors and Biasing The LTC4090/LTC4090-5 provide temperature qualified charging if a grounded thermistor and a bias resistor are connected to NTC (see Figure 8). By using a bias resistor whose value is equal to the room temperature resistance of the thermistor (R25C) the upper and lower temperatures are pre-programmed to approximately 50°C and 0°C, respectively (assuming a Vishay “Curve 2” thermistor). The upper and lower temperature thresholds can be adjusted by either a modification of the bias resistor value or by adding a second adjustment resistor to the circuit. If only the bias resistor is adjusted, then either the upper or the lower threshold can be modified but not both. The other trip point will be determined by the characteristics of the thermistor. Using the bias resistor in addition to an adjustment resistor, both the upper and the lower temperature trip points can be independently programmed with the constraint that the difference between the upper and lower temperature thresholds cannot decrease. Examples of each technique are given below. NTC thermistors have temperature characteristics which are indicated on resistance-temperature conversion tables. The Vishay-Dale thermistor NTHS0603N02N1002J, used in the following examples, has a nominal value of 10k and follows the Vishay “Curve 2” resistance-temperature characteristic. The LTC4090/LTC4090-5’s trip points are designed to work with thermistors whose resistance-temperature characteristics follow Vishay Dale’s “R-T Curve 2.” The Vishay NTHS0603N02N1002J is an example of such a thermistor. However, Vishay Dale has many thermistor products that follow the “R-T Curve 2” characteristic in a variety of sizes. Furthermore, any thermistor whose ratio of RCOLD to RHOT is about 7.0 will also work (Vishay Dale R-T Curve 2 shows a ratio of 2.815/0.409 = 6.89). 4090fa RUN 15k 0.22μF HVEN GND IL 1A/DIV VRUN/SS 2V/DIV VOUT 2V/DIV 2ms/DIV 4090 F07 Figure 7. To Soft-Start the High Voltage Regulator, Add a Resistor and Capacitor to the HVEN Pin Synchronization and Mode The SYNC pin allows the high voltage regulator to be synchronized to an external clock. Synchronizing the LTC4090/LTC4090-5 internal oscillator to an external frequency can be done by connecting a square wave (with 20% to 80% duty cycle) to the SYNC pin. The square wave amplitude should be such that the valleys are below 0.3V and the peaks are above 0.8V (up to 6V). The high voltage regulator may be synchronized over a 300kHz to 2MHz range. The RT resistor should be chosen such that the LTC4090/LTC4090-5 oscillate 25% 22 LTC4090/LTC4090-5 APPLICATIONS INFORMATION In the explanation below, the following notation is used. R25C = Value of the Thermistor at 25°C RNTC|COLD = Value of Thermistor at the Cold Trip Point RNTC|HOT = Value of the Thermistor at the Hot Trip Point rcold = Ratio of RNTC|COLD to R25C rHOT= Ratio of RNTC|HOT to R25C RNOM = Primary Thermistor Bias Resistor (see Figure 8) R1 = Optional Temperature Range Adjustment resistor (see Figure 9) The trip points for the LTC4090/LTC4090-5’s temperature qualification are internally programmed at 0.29 • VNTC for the hot threshold and 0.74 • VNTC for the cold threshold. Therefore, the hot trip point is set when: RNTCHOT | RNOM + RNTCHOT | • VNTC = 0.29 • VNTC Solving these equations for RNTC|COLD and RNTC|HOT results in the following: RNTC|HOT = 0.409 • RNOM and RNTC|COLD = 2.815 • RNOM By setting RNOM equal to R25C, the above equations result in rHOT = 0.409 and rCOLD = 2.815. Referencing these ratios to the Vishay Resistance-Temperature Curve 2 chart gives a hot trip point of about 50°C and a cold trip point of about 0°C. The difference between the hot and cold trip points is approximately 50°C. By using a bias resistor, RNOM, different in value from R25C, the hot and cold trip points can be moved in either direction. The temperature span will change somewhat due to the non-linear behavior of the thermistor. The following equations can be used to easily calculate a new value for the bias resistor: rHOT •R 0.409 25C r RNOM = COLD • R25C 2.815 RNOM = and the cold trip point is set when: RNTC|COLD RNOM + RNTC|COLD VNTC 6 RNOM 10k NTC 5 0.738 • VNTC • VNTC = 0.74 • VNTC NTC BLCOK VNTC 6 NTC BLCOK – TOO_COLD RNOM 13.2k NTC 5 0.738 • VNTC – TOO_COLD + + RNTC 10k 0.29 • VNTC – TOO_HOT R1 1.97k 0.29 • VNTC RNTC 10k – TOO_HOT + + + NTC_ENABLE 0.1V + NTC_ENABLE 0.1V – 4090 F08 – 4090 F09 Figure 8. Typical NTC Thermistor Circuit Figure 9. NTC Thermistor Circuit with Additional Bias Resistor 4090fa 23 LTC4090/LTC4090-5 APPLICATIONS INFORMATION where rHOT and rCOLD are the resistance ratios at the desired hot and cold trip points. Note that these equations are linked. Therefore, only one of the two trip points can be chosen, the other is determined by the default ratios designed in the IC. Consider an example where a 40°C hot trip point is desired. From the Vishay Curve 2 R-T characteristics, rHOT is 0.5758 at 40°C. Using the above equation, RNOM should be set to 14.0k. With this value of RNOM, the cold trip point is about -7°C. Notice that the span is now 47°C rather than the previous 50°C. This is due to the increase in “temperature gain” of the thermistor as absolute temperature decreases. The upper and lower temperature trip points can be independently programmed by using an additional bias resistor as shown in Figure 9. The following formulas can be used to compute the values of RNOM and R1: rCOLD – rHOT • R25C 2.815 R1= 0.409 • RNOM – rHOT • R25C RNOM = For example, to set the trip points to -5°C and 55°C with a Vishay Curve 2 thermistor choose RNOM = 3.532 – 0.3467 • 10k = 13.2k 2.815 – 0.409 In general, if the LTC4090/LTC4090-5 is being powered from IN the power dissipation can be calculated as follows: PD = (VIN – VBAT) • IBAT + (VIN – VOUT) • IOUT where PD is the power dissipated, IBAT is the battery charge current, and IOUT is the application load current. For a typical application, an example of this calculation would be: PD = (5V – 3.7V) • 0.4A + (5V – 4.75V) • 0.1A = 545mW This examples assumes VIN = 5V, VOUT = 4.75V, VBAT = 3.7V, IBAT = 400mA, and IOUT = 100mA resulting in slightly more than 0.5W total dissipation. If the LTC4090 is being powered from HVIN, the power dissipation can be estimated by calculating the regulator power loss from an efficiency measurement, and subtracting the catch diode loss. PD = (1− η) • ⎡ VHVOUT •(IBAT + IOUT )⎤ ⎣ ⎦ ⎛V ⎞ − VD • ⎜ 1− HVOUT ⎟ • (IBAT + IOUT ) + 0.3V • IBAT ) VHVIN ⎠ ⎝ where η is the efficiency of the high voltage regulator and VD is the forward voltage of the catch diode at I = IBAT + IOUT. The first term corresponds to the power lost in converting VHVIN to VHVOUT, the second term subtracts the catch diode loss, and the third term is the power dissipated in the battery charger. For a typical application, an example of this calculation would be: PD = (1− 0.87) • [ 4V •(1A + 0.6 A)] 4V ⎞ ⎛ −0.4V • ⎜ 1− • (1A + 0.6 A ) + 0.3V • 1A = 0.7 W ⎠ ⎝ 12V ⎟ This example assumes 87% efficiency, VHVIN = 12V, VBAT = 3.7V (VHVOUT is about 4V), IBAT = 1A, IOUT = 600mA resulting in about 0.7W total dissipation. If the LTC4090-5 is being powered from HVIN, the power dissipation can be estimated by calculating the regulator power loss from an efficiency measurement, and subtracting the catch diode loss. the nearest 1% value is 13.3k. R1 = 0.409 • 13.3k – 0.3467 • 10k = 1.97k the nearest 1% value is 1.96k. The final solution is shown in Figure 9 and results in an upper trip point of 55°C and a lower trip point of -5°C. Power Dissipation and High Temperature Considerations The die temperature of the LTC4090/LTC4090-5 must be lower than the maximum rating of 110°C. This is generally not a concern unless the ambient temperature is above 85°C. The total power dissipated inside the LTC4090/ LTC4090-5 depend on many factors, including input voltage (IN or HVIN), battery voltage, programmed charge current, programmed input current limit, and load current. 4090fa 24 LTC4090/LTC4090-5 APPLICATIONS INFORMATION PD = 1 – η • 5V • IBAT + IOUT )( ( )) (IBAT + IOUT ) + (5V – VBAT ) • IBAT ( ⎛ 5V ⎞ – VD • ⎜ 1 – ⎟• ⎝ VHVIN ⎠ thermal resistance from die (i.e., junction) to ambient can be reduced to θJA = 40°C/W. Board Layout Considerations As discussed in the previous section, it is critical that the exposed metal pad on the backside of the LTC4090/ LTC4090-5 package be soldered to the PC board ground. Furthermore, proper operation and minimum EMI requires a careful printed circuit board (PCB) layout. Note that large, switched currents flow in the power switch (between the HVIN and SW pins), the catch diode and the HVIN input capacitor. These components, along with the inductor and output capacitor, should be placed on the same side of the circuit board, and their connections should be made on that layer. Place a local, unbroken ground plane below these components. The loop formed by these components should be as small as possible. Additionally, the SW and BOOST nodes should be kept as small as possible. Figure 10 shows the recommended component placement with trace and via locations. High frequency currents, such as the high voltage input current of the LTC4090/LTC4090-5, tend to find their way along the ground plane on a mirror path directly beneath the incident path on the top of the board. If there are slits or cuts in the ground plane due to other traces on that layer, the current will be forced to go around the slits. If high frequency currents are not allowed to flow back through their natural least-area path, excessive voltage will build up and radiated emissions will occur. See Figure 11. The difference between this equation and that for the LTC4090 is the last term, which represents the power dissipation in the battery charger. For a typical application, an example of this calculation would be: ⎛ 5V ⎞ PD = 1 – 0.87 • 5V • 1A + 0.6 A – 0.4V • ⎜ 1 – • ⎝ 12V ⎟ ⎠ )( ( )) (1A + 0.6A ) + (5V – 3.7V ) • 1A = 1.97W ( Like the LTC4090 example, this examples assumes 87% efficiency, VHVIN = 12V, VBAT = 3.7V, IBAT = 1A and IOUT = 600mA resulting in about 2W total power dissipation. It is important to solder the exposed backside of the package to a ground plane. This ground should be tied to other copper layers below with thermal vias; these layers will spread the heat dissipated by the LTC4090/LTC4090-5. Additional vias should be placed near the catch diode. Adding more copper to the top and bottom layers and tying this copper to the internal planes with vias can reduce thermal resistance further. With these steps, the C1 AND D1 GND PADS SIDE-BY-SIDE AND SEPERATED WITH C3 GND PAD MINIMIZE D1, L1, C3, U1, SW PIN LOOP U1 THERMAL PAD SOLDERED TO PCB. VIAS CONNECTED TO ALL GND PLANES WITHOUT THERMAL RELIEF 4090 F11 MINIMIZE TRACE LENGTH 4090 F10 Figure 10. Suggested Board Layout Figure 11. Ground Currents Follow Their Incident Path at High Speed. Slices in the Ground Plane Cause High Voltage and Increased Emissions. 4090fa 25 LTC4090/LTC4090-5 APPLICATIONS INFORMATION IN and HVIN Bypass Capacitor Many types of capacitors can be used for input bypassing; however, caution must be exercised when using multilayer ceramic capacitors. Because of the self-resonant and high Q characteristics of some types of ceramic capacitors, high voltage transients can be generated under some start-up conditions, such as from connecting the charger input to a hot power source. For more information, refer to Application Note 88. Battery Charger Stability Considerations The constant-voltage mode feedback loop is stable without any compensation when a battery is connected with low impedance leads. Excessive lead length, however, may add enough series inductance to require a bypass capacitor of at least 1μF from BAT to GND. Furthermore, a 4.7μF capacitor with a 0.2Ω to 1Ω series resistor to GND is recommended at the BAT pin to keep ripple voltage low when the battery is disconnected. TYPICAL APPLICATIONS HIGH (6V TO 36V) VOLTAGE INPUT C1 1μF 50V 1206 4.7μF 6.3V HVIN HVEN IN 680Ω 59k 1% HPWR VC 270pF 0.1μF 2.1k 1% 71.5k 1% 40.2k 1% SUSP TIMER OUT CLPROG GATE PROG BAT RT PG SYNC VNTC 10k 1% NTC T 10k 680Ω CHRG 4090 F12 BOOST SW 0.47μF 16V D1 L1 6.8μH C3 22μF 6.3V 1206 USB LTC4090 HVOUT HVPR 1k Q1 LOAD 4.7μF 6.3V Q2 + Li-Ion BATTERY D: DIODES INC. B360A L: SUMIDA CDR6D28MN-GR5 Q1, Q2: SILICONIX Si2333DS Figure 12. 800kHz Switching Frequency 0.47μF HIGH (6V TO 36V) TRANSIENT TO 60V* BOOST HVIN 1μF HVOUT USB 4.7μF VC RT TIMER CLPROG 2.1k GND IN LTC4090 HVPR 1k OUT BAT PROG 71.5k 4.7μF LOAD VC RT TIMER Li-Ion BATTERY 30k 330pF L: SUMIDA CDRH4D22/HP-2R2 4090 TAO3 4090 TAO4 L 10μH 4.7μF HIGH (6V TO 16V) VOLTAGE INPUT BOOST SW HVIN 1μF 0.47μF SW L 2.2μH 22μF HVOUT Q1 USB 4.7μF IN LTC4090 HVPR 1k OUT BAT PROG 71.5k LOAD 4.7μF Q1 35k 330pF 88.7k 0.1μF + CLPROG 2.1k GND 11.5k 0.1μF + Li-Ion BATTERY L: SUMIDA CDRH8D28/HP-100 * USE SCHOTTKY DIODE RATED AT VR > 45V Figure 13. 400kHz Switching Frequency Figure 14. 2MHz Switching Frequency 4090fa 26 LTC4090/LTC4090-5 PACKAGE DESCRIPTION DJC Package 22-Lead Plastic DFN (6mm × 3mm) (Reference LTC DWG # 05-08-1714) 0.889 0.70 ± 0.05 R = 0.10 0.889 PACKAGE OUTLINE 3.60 ± 0.05 1.65 ± 0.05 2.20 ± 0.05 (2 SIDES) 0.25 ± 0.05 0.50 BSC 5.35 ± 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 3. DRAWING IS NOT TO SCALE 6.00 ± 0.10 (2 SIDES) R = 0.10 TYP R = 0.115 TYP 22 0.40 ± 0.05 0.889 12 3.00 ± 0.10 (2 SIDES) PIN 1 TOP MARK (NOTE 6) 1.65 ± 0.10 (2 SIDES) 0.889 11 0.200 REF 0.75 ± 0.05 5.35 ± 0.10 (2 SIDES) 1 0.25 ± 0.05 0.50 BSC (DJC) DFN 0605 PIN #1 NOTCH R0.30 TYP OR 0.25mm × 45° CHAMFER 0.00 – 0.05 NOTE: 1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WXXX) IN JEDEC PACKAGE OUTLINE M0-229 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 TOP AND BOTTOM OF PACKAGE BOTTOM VIEW—EXPOSED PAD 4090fa Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 27 LTC4090/LTC4090-5 RELATED PARTS PART NUMBER Battery Chargers LTC1733 LTC1734 LTC4002 LTC4053 LTC4054 Monolithic Lithium-Ion Linear Battery Charger Lithium-Ion Linear Battery Charger in ThinSOTTM Switch Mode Lithium-Ion Battery Charger USB Compatible Monolithic Li-Ion Battery Charger Standalone Linear Li-Ion Battery Charger with Integrated Pass Transistor in ThinSOT Lithium-Ion Linear Battery Charger Standalone Charger with Programmable Timer, Up to 1.5A Charge Current Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed Standalone, 4.7V ≤ VIN ≤ 24V, 500kHz Frequency, 3 Hour Charge Termination Standalone Charger with Programmable Timer, Up to 1.25A Charge Current Thermal Regulation Prevents Overheating, C/10 Termination, C/10 Indicator, Up to 800mA Charge Current Up to 800mA Charge Current, Thermal Regulation, ThinSOT Package DESCRIPTION COMMENTS LTC4057 LTC4058 LTC4059 Standalone 950mA Lithium-Ion Charger C/10 Charge Termination, Battery Kelvin Sensing, ±7% Charge Accuracy in DFN 900mA Linear Lithium-Ion Battery Charger 2mm 2mm DFN Package, Thermal Regulation, Charge Current Monitor Output 4.2V, ±0.6% Float Voltage, Up to 750mA Charge Current, 2mm 2mm DFN, “A” Version has ACPR Function. 950mA Charge Current, Timer Termination + C/10 Detection Output, 4.2V, 0.6% Accurate Float Voltage, 4 ⎯C⎯H⎯R⎯G Pin Indicator States 95% Efficiency, VIN = 2.5V to 5.5V, VOUT = 0.6V, IQ = 20μA, ISD < 1μA, ThinSOT Package 95% Efficiency, VIN = 2.5V to 5.5V, VOUT = 0.8V, IQ = 60μA, ISD < 1μA, MS10 Package 95% Efficiency, VIN = 2.5V to 5.5V, VOUT = 2.5V, IQ = 25μA, ISD < 1μA, MS Package Seamless Transition Between Power Sources: USB, Wall Adapter and Battery; 95% Efficient DC/DC Conversion 88% Efficiency, VIN = 3.6V to 36V (40V Maximum), VOUT = 0.8V, ISD < 2μA, 2mm 3mm DFN Package Charges Single Cell Li-Ion Batteries Directly from a USB Port, Thermal Regulation, 200m Ideal Diode, 4mm 4mm QFN16 Package LTC4065/LTC4065A Standalone Li-Ion Battery Chargers in 2mm 2mm DFN LTC4095 Power Management LTC3406/LTC3406A 600mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter LTC3411 LTC3440 LTC3455 LT3493 LTC4055 LTC4066 LTC4067 LTC4085 LTC4089/ LTC4089-5 1.25A (IOUT), 4MHz, Synchronous Step-Down DC/DC Converter 600mA (IOUT), 2MHz, Synchronous Buck-Boost DC/DC Converter Dual DC/DC Converter with USB Power Manager and Li-Ion Battery Charger 1.2A, 750kHz Step-Down Switching Regulator USB Power Controller and Battery Charger Standalone USB Lithium-Ion/Polymer Battery Charger in in 2mm 2mm DFN USB Power Controller and Li-Ion Battery Charges Single Cell Li-Ion Batteries Directly from a USB Port, Thermal Regulation, 50m Charger with Low-Loss Ideal Diode Ideal Diode, 4mm 4mm QFN24 Package USB Power Controller with OVP, Ideal Diode and Li-Ion Battery Charger USB Power Manager with Ideal Diode Controller and Li-Ion Charger USB Power Manager with Ideal Diode Controller and High Efficiency Li-Ion Battery Charger Low Loss PowerPath Controller in ThinSOT High Voltage Power Path Controllers in ThinSOT 13V Overvoltage Transient Protection, Thermal Regulation, 200mΩ Ideal Diode with