LT1513-2CT7

LT1513-2CT7 LINEAR_DIMENSIONS | Alldatasheet

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Constant-Voltage Battery Charger The LT 1513 is a 500kHz current mode switching regula- tor specially configured to create a constant- or program- mable-current/constant-voltage battery charger. In addition to the usual voltage feedback node, it has a current sense feedback circuit for accurately controlling output current of a flyback or SEPIC (Single-Ended Primary Inductance Converter) topology charger. These topologies allow the current sense circuit to be ground referred and completely separated from the battery itself, simplifying battery switch- ing and system grounding problems. In addition, these topologies allow charging even when the input voltage is lower than the battery voltage. The LT1513 can also drive a CCFL Royer converter with high efficiency in floating or grounded mode. Maximum switch current on the LT1513 is 3A. This allows battery charging currents up to 2A for a single lithium-ion cell. Accuracy of 1% in constant-voltage mode is perfect for lithium battery applications. Charging current can be easily programmed for all battery types. DESCRIPTIONU n Charger Input Voltage May Be Higher, Equal to or Lower Than Battery Voltage n Charges Any Number of Cells Up to 20V n 1% Voltage Accuracy for Rechargeable Lithium Batteries n 100mV Current Sense Voltage for High Efficiency (LT1513) n 0mV Current Sense Voltage for Easy Current Programming (LT1513-2) n Battery Can Be Directly Grounded n 500kHz Switching Frequency Minimizes Inductor Size n Charging Current Easily Programmable or Shut Down

FEATURES

INPUT VOLTAGE (V) CURRENT (A) 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 LT1513 • TA02 10 15 20 30 12V INDUCTOR = 10mH ACTUAL PROGRAMMED CHARGING CURRENT WILL BE INDEPENDENT OF INPUT VOLTAGE IF IT DOES NOT EXCEED VALUES SHOWN SINGLE Li-Ion CELL (4.1V) DOUBLE Li-Ion CELL (8.2V) 16V 20V BATTERY VOLTAGE Maximum Charging Current , LTC and LT are registered trademarks of Linear Technology Corporation. n Charging of NiCd, NiMH, Lead-Acid or Lithium Rechargeable Cells n Precision Current Limited Power Supply n Constant-Voltage/Constant-Current Supply n Transducer Excitation n Universal Input CCFL Driver APPLICATIONSU Figure 1. SEPIC Charger with 1.25A Output Current

• 2 D1† CHARGE SHUTDOWN + TYPICAL APPLICATIONU

A UGWA WU WARBSOLUTEX I T I S Operating Junction Temperature Range ELECTRICAL C CHARA TERISTICS VIN = 5V, VC = 0.6V, VFB = VREF, IFB = 0V, VSW and S/S pins open, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VREF FB Reference Voltage Measured at FB Pin 1.233 1.245 1.257 V VC = 0.8V l 1.228 1.245 1.262 V FB Input Current V FB = VREF 300 550 nA l 600 nA FB Reference Voltage Line Regulation 2.7V £ VIN £ 25V, VC = 0.8V l 0.01 0.03 %/V VIREF IFB Reference Voltage (LT1513) Measured at I FB Pin –107 –100 –93 mV VFB = 0V, VC = 0.8V l –110 –100 –90 mV IFB Input Current V IFB = VIREF (Note 2) l 10 25 35 mA IFB Reference Voltage Line Regulation 2.7V £ VIN £ 25V, VC = 0.8V l 0.01 0.05 %/V IFBVOS IFB Voltage Offset (LT1513-2) (Note 3) I VFB = 60mA (Note 4) l –7.5 2.5 12.5 mV IFB Input Current V IFB = VIREF l –200 –10 0 nA VFB Source Current V IREF = – 10mV, VFB = 1.2V l –700 –300 –100 mA gm Error Amplifier Transconductance DIC = –25mA 1100 1500 1900 mmho l 700 2300 mmho Error Amplifier Source Current V FB = VREF – 150mV, VC = 1.5V l 120 200 350 mA Error Amplifier Sink Current V FB = VREF + 150mV, VC = 1.5V l 1400 2400 mA WU UPACKAGE/ORDER I FOR ATIO Consult factory for Military grade parts. ORDER PART NUMBER LT1513CR LT1513-2CR LT1513IR LT1513-2IR TJMAX = 125°C, qJA = 30°C/ W WITH PACKAGE SOLDERED TO 0.5INCH2 COPPER AREA OVER BACKSIDE GROUND PLANE OR INTERNAL POWER PLANE, qJA CAN VARY FROM 20°C/W TO > 40°C/W DEPENDING ON MOUNTING TECHNIQUE R PACKAGE 7-LEAD PLASTIC DD FRONT VIEW TAB IS GND VIN S/S V SW GND I FB FB V C ORDER PART NUMBER LT1513-2CT7 LT1513-2IT7 TJMAX = 125°C, qJA = 50°C/ W, qJC = 4°C/W T7 PACKAGE 7-LEAD TO-220 VIN S/S VSW GND I FB FB V C FRONT VIEW

ELECTRICAL C CHARA TERISTICS VIN = 5V, VC = 0.6V, VFB = VREF, IFB = 0V, VSW and S/S pins open, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Error Amplifier Clamp Voltage High Clamp, V FB = 1V 1.70 1.95 2.30 V Low Clamp, VFB = 1.5V 0.25 0.40 0.52 V AV Error Amplifier Voltage Gain 500 V/V VC Pin Threshold Duty Cycle = 0% 0.8 1 1.25 V f Switching Frequency 2.7V £ VIN £ 25V 450 500 550 kHz 0°C £ TJ £ 125°C 430 500 580 kHz TJ < 0°C 400 580 kHz Maximum Switch Duty Cycle l 85 95 % Switch Current Limit Blanking Time 130 260 ns BV Output Switch Breakdown Voltage 0 °C £ TJ £ 125°C4 0 4 7 V TJ < 0°C3 5 V VSAT Output Switch ON Resistance I SW = 2A l 0.25 0.45 W ILIM Switch Current Limit Duty Cycle = 50% l 3.0 3.8 5.4 A Duty Cycle = 80% (Note 1) l 2.6 3.4 5.0 A DIIN/DISW Supply Current Increase During Switch ON Time 15 25 mA/A Control Voltage to Switch Current 4A / V Transconductance Minimum Input Voltage l 2.4 2.7 V IQ Supply Current 2.7V £ VIN £ 25V l 4 5.5 mA Shutdown Supply Current 2.7V £ VIN £ 25V, VS/S £ 0.6V, TJ ‡ 0°C l 12 30 mA TJ < 0°C5 0 mA Shutdown Threshold 2.7V £ VIN £ 25V l 0.6 1.3 2 V Shutdown Delay l 51 2 2 5 ms S/S Pin Input Current 0V £ VS/S £ 5V l –10 15 mA Synchronization Frequency Range l 600 800 kHz The l denotes specifications which apply over the full operating temperature range. Note 1: For duty cycles (DC) between 50% and 85%, minimum guaranteed switch current is given by ILIM = 1.33 (2.75 – DC). Note 2: The IFB pin is servoed to its regulating state with VC = 0.8V. Note 3: Consult factory for grade selected parts. Note 4: The IFB pin is sevoed to regulate FB to 1.245V

TEMPERATURE (°C) –50 –50NEGATIVE FEEDBACK INPUT CURRENT (mA) –30 0 50 75 LT1513 • G06 –40 –10 –20 –25 25 100 125 150 CHARGING CURRENT (A) BATTERY VOLTAGE (V) 0.4 0.8 1.2 1.6

1513 G07

(A) 8.4V BATTERY ICHRG = 0.5A (B) 8.4V BATTERY ICHRG = 1A (C) 4.2V BATTERY ICHRG = 1.5A VIN = 12VMAXIMUM AVAILABLE CHARGING CURRENT WITH 12V INPUT (A) (B) (C) Negative Feedback Input Current vs Temperature Output Charging Characteristics Showing Constant-Current and Constant-Voltage Operation TEMPERATURE (°C) –50 MINIMUM SYNCHRONIZATION VOLTAGE (VP-P) 0.5 1.0 1.5 2.0 05 0 100 150 LT1513 • G04 2.5 3.0 –25 25 75 125 fSYNC = 700kHz Minimum Peak-to-Peak Synchronization Voltage vs Temperature TEMPERATURE (°C) –50 FEEDBACK INPUT CURRENT (nA) 400 500 600 150 LT1513 • G05 300 200 0 50 100 100 800 700 –25 25 75 125 VFB = VREF Feedback Input Current vs Temperature TYPICAL PERFORMANCE CHARACTERISTICS UW Switch Saturation Voltage vs Switch Current Minimum Input Voltage vs Temperature Switch Current Limit vs Duty Cycle TEMPERATURE (°C) –50 1.8 INPUT VOLTAGE (V) 2.0 2.2 2.4 2.6 05 0 100 150 LT1513 • G03 2.8 3.0 –25 25 75 125 DUTY CYCLE (%) SWITCH CURRENT LIMIT (A) 20 40 60 80 LT1513 • G02 100100 30 50 70 90 25°C AND 125°C –55°C SWITCH CURRENT (A) SWITCH SATURATION VOLTAGE (V) 0.6 0.8 1.0 3.2 LT1513 • G01 0.4 0.2 0.5 0.7 0.9 0.3 0.1 100°C 150°C 25°C –55°C

50k* *REMOVE ON LT1513-2 0.04W EA VC VIN LT1513 • BD 1.245V REF 500kHz OSCSYNC SHUTDOWN DELAY AND RESET LOW DROPOUT 2.3V REG ANTISAT LOGIC DRIVER SW SWITCH IA AV » 6 COMP The LT1513 is a current mode switcher. This means that switch duty cycle is directly controlled by switch current rather than by output voltage or current. Referring to the Block Diagram, the switch is turned “on” at the start of each oscillator cycle. It is turned “off” when switch current reaches a predetermined level. Control of output voltage and current is obtained by using the output of a dual feedback voltage sensing error amplifier to set switch current trip level. This technique has the advantage of simplified loop frequency compensation. A low dropout internal regulator provides a 2.3V supply for all internal circuitry on the LT1513. This low dropout design allows input voltage to vary from 2.7V to 25V. A 500kHz oscillator is the basic clock for all internal timing. It turns “on” the output switch via the logic and driver circuitry. Special adaptive antisat circuitry detects onset of saturation in the power switch and adjusts driver current instantaneously to limit switch saturation. This minimizes driver dissipation and provides very rapid turn-off of the switch. A unique error amplifier design has two inverting inputs which allow for sensing both output voltage and current. A 1.245V bandgap reference biases the noninverting input. The first inverting input of the error amplifier is brought out for positive output voltage sensing. The second inverting input is driven by a “current” amplifier which is sensing output current via an external current sense resistor. The current amplifier is set to a fixed gain of –12.5 which provides a –100mV current limit sense voltage. The LT1513-2 option removes the feedback resistors around the I FB amplifier and connects its output to the FB signal. This provides a ground referenced current sense voltage suitable for external current programming and makes amplifier input and output available for external loop compensation. The error signal developed at the amplifier output is brought out externally and is used for frequency compen- sation. During normal regulator operation this pin sits at a voltage between 1V (low output current) and 1.9V (high output current). Switch duty cycle goes to zero if the V C pin is pulled below the VC pin threshold, placing the LT1513 in an idle mode. OPERATIONU Figure 2

inductor core, although two separate inductors can be used. nominal 0.3mA typical value. to variations in bias current would be –0.42%. Figure 3. D2, C6 and R6 form a peak detector to drive the gate Diode Selection for a discussion of diode leakage.

1513 F03

Figure 3. Eliminating Divider Current switch voltage equal to input voltage plus output voltage.

APPLICATIONS INFORMATIONWU UU shown in the maximum charging current graph. Higher inductance values give slightly higher maximum charging current, but are larger and more expensive. A low loss toroid core such as Kool M m , Molypermalloy or Metglas is recommended. Series resistance should be less than 0.04W for each winding. “Open core” inductors, such as rods or barrels are not recommended because they generate large magnetic fields which may interfere with other electronics close to the charger. Input Capacitor The SEPIC topology has relatively low input ripple current compared to other topologies and higher harmonics are especially low. RMS ripple current in the input capacitor is less than 0.25A with L = 10 mH and less than 0.5A with L = 5mH. A low ESR 22mF, 25V solid tantalum capacitor (AVX type TPS or Sprague type 593D) is adequate for most applications with the following caveat. Solid tantalum capacitors can be destroyed with a very high turn-on surge current such as would be generated if a low impedance input source were “hot switched” to the charger input. If this condition can occur, the input capacitor should have the highest possible voltage rating, at least twice the surge input voltage if possible. Consult with the capacitor manufacturer before a final choice is made. A 4.7mF ceramic capacitor such as the one used for the coupling capacitor can also be used. These capacitors do not have a turn-on surge limitation. The input capacitor must be connected directly to the V IN pin and the ground plane close to the LT1513. Output Capacitor It is assumed as a worst case that all the switching output ripple current from the battery charger could flow in the output capacitor. This is a desirable situation if it is neces- sary to have very low switching ripple current in the battery itself. Ferrite beads or line chokes are often inserted in series with the battery leads to eliminate high frequency currents that could create EMI problems. This forces all the ripple current into the output capacitor. Total RMS current into the capacitor has a maximum value of about 1A, and this is handled with the two paralleled 22mF, 25V capacitors shown in Figure 1. These are AVX type TPS or Sprague type 593D surface mount solid tantalum units intended for switching applications. Do not substitute other types without ensuring that they have adequate ripple current ratings. See Input Capacitor section for details of surge limitation on solid tantalum capacitors if the battery may be “hot switched” to the output of the charger. Coupling Capacitor C2 in Figure 1 is the coupling capacitor that allows a SEPIC converter topology to work with input voltages either higher or lower than the battery voltage. DC bias on the capacitor is equal to input voltage. RMS ripple current in the coupling capacitor has a maximum value of about 1A at full charging current. A conservative formula to calculate this is: I IV V VCOUP RMS CHRG IN BAT IN () ( . ) ()= + 11 (1.1 is a fudge factor to account for inductor ripple current and other losses) With ICHRG = 1.2A, VIN = 15V and VBAT = 8.2V, ICOUP = 1.02A. The recommended capacitor is a 4.7mF ceramic type from Marcon or Tokin. These capacitors have extremely low ESR and high ripple current ratings in a small package. Solid tantalum units can be substituted if their ripple current rating is adequate, but typical values will increase to 22mF or more to meet the ripple current requirements. Diode Selection The switching diode should be a Schottky type to minimize both forward and reverse recovery losses. Average diode current is the same as output charging current, so this will be under 2A. A 3A diode is recommended for most applications, although smaller devices could be used at reduced charging current. Maximum diode reverse voltage will be equal to input voltage plus battery voltage. Diode reverse leakage current will be of some concern during charger shutdown. This leakage current is a direct drain on the battery when the charger is not powered. High Kool Mm is a registered trademark of Magnetics, Inc. Metglas is a registered trademark of AlliedSignal Inc.

to specify a low leakage current in high volume production. condition of higher than desired battery drain.

2 WINDING

Figure 4. LT1513 Suggested Partial Layout for Critical Thermal and Electrical Paths

Figure 5. In constant-current mode, I FB acts as a virtual voltage across R4 in the ratio R4/R5. final phase of charging lithium-ion and lead-acid batteries. Figure 6. Constant-Voltage Small-Signal Model

1513 F06

1513 F05

Figure 7. Constant-Current Small-Signal Model excellent even in the presence of subharmonic switching. at frequencies below 500kHz. of 25kHz or lower to avoid these excess phase regions. assigned to the battery model.

1513 F07

NUMBERS CORRESPOND TO THOSE USED IN FIGURE 1. P AND CP MODEL THE PHASE DELAY IN THE PowerPath. THE CURRENT AMPLIFIER HAS A FIXED VOLTAGE GAIN OF 12. GIVES BETTER PHASE MARGIN IN CONSTANT VOLTAGE MODE.

APPLICATIONS INFORMATIONWU UU The suggested way to control unity loop frequency is to increase the filter time constant on the IFB pin (R4/C4 in Figures 1 and 7). The filter resistor cannot be arbitrarily increased because high values will affect charging current accuracy. Charging current will increase by 1% for each 40W increase in R4. There is no inherent limitation on the value of C4, but if this capacitor is ceramic, it should be an X7R type to maintain its value over temperature. X7R dielectric requires a larger footprint. The formula for calculating the minimum value for the filter capacitor C4 is: C RV R fR V V IN IN BAT 4 3 4 12 1500 5 () ( ) ( ) m p VIN = Highest input voltage 1500m = Transconductance of error amplifier (EA)f = Desired unity-gain frequency VBAT = Battery voltage For example, assume VIN(MAX) = 15V, R3 = 0.4W (charging current set to 0.25A), R4 = 24W , R5 = 330W and VBAT = 8V, CF4 0 4 4 15 12 0 0015 330 15 8 )6.3(25000)(39)( m The value for C4 could be reduced to a more manageable size by increasing R4 to 75W and reducing R5 to 300W , yielding 0.47mF for C4. The 2% increase in charging current can be ignored or factored into the value for R3. More Help Linear Technology Field Application Engineers have a CAD spreadsheet program for detailed calculations of circuit operating conditions. In addition, our Applications Depart- ment is always ready to lend a helping hand. The LT1371 data sheet may also be helpful. The LT1513 is identical except for the current amplifier circuitry.

current, until IR4 is balanced by IR5. can be shut down with the S/S pin.

1513 F08

• 2 25µF 25V 910Ω 10k 3.3V 0.25W 78.7k 0.5% Li-Ion RECHARGABLE CELL GND 34k 0.5% CHARGE SHUTDOWN PRECHARGE CHARGE

Figure 8. Lithium-Ion Battery Charger

constant higher voltage input. input current is sensed with R2 and filtered with R3 and C6. also available from other LTC Application and Design Notes.

1513 F09

• Q2 Q1 C2: TOKIN MULTILAYER CERAMIC C3: MUST BE A LOW LOSS CAPACITOR, WIMA MKP-20 OR EQUIVALENT L1, L2: COILTRONICS CTX20-4 (MUST BE SEPARATE INDUCTORS) Q1, Q2: ZETEX ZTX849 OR FZT849 T1: COILTRONICS CTX110605 (67:1) LT1513-2 V FB VIN VSW IFB GND S/S VC

Figure 9. CCFL Power Supply for Floaing Lamp Configuration Operates on 2.7V

Dimensions in inches (millimeters) unless otherwise noted. 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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. R Package 7-Lead Plastic DD Pak (LTC DWG # 05-08-1462) R (DD7) 0396 0.026 – 0.036 (0.660 – 0.914) 0.143 +0.012 –0.020 ()3.632 +0.305 –0.508 0.040 – 0.060 (0.330 – 0.584) 0.095 – 0.115 (2.413 – 2.921) 0.004 +0.008 –0.004 ()0.102+0.203 –0.102 0.050 – 0.012 (1.270 – 0.305) 0.059 (1.499) TYP 0.045 – 0.055 (1.143 – 1.397) 0.165 – 0.180 (4.191 – 4.572) 0.330 – 0.370 (8.382 – 9.398) 0.060 (1.524) TYP 0.390 – 0.415 (9.906 – 10.541) 15° TYP 0.300 (7.620) 0.075 (1.905) 0.183 (4.648) 0.060 (1.524) 0.060 (1.524) 0.256 (6.502) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK 7-Lead Plastic TO-220 (Standard) (LTC DWG # 05-08-1422) 0.040 – 0.060 (1.016 – 1.524) 0.026 – 0.036 (0.660 – 0.914) T7 (TO-220) (FORMED) 1197 0.135 – 0.165 (3.429 – 4.191) 0.700 – 0.728 (17.780 – 18.491) 0.045 – 0.055 (1.143 – 1.397) 0.165 – 0.180 (4.191 – 4.572) 0.095 – 0.115 (2.413 – 2.921) 0.013 – 0.023 (0.330 – 0.584) 0.620 (15.75) TYP 0.155 – 0.195 (3.937 – 4.953) 0.152 – 0.202 (6.604 – 8.128) 0.147 – 0.155 (3.734 – 3.937) DIA 0.390 – 0.415 (9.906 – 10.541) 0.330 – 0.370 (8.382 – 9.398) 0.460 – 0.500 (11.684 – 12.700) 0.570 – 0.620 (14.478 – 15.748) 0.230 – 0.270 (5.842 – 6.858)

ª LINEAR TECHNOLOGY CORPORATION 1 996 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 l (408) 432-1900 FAX: (408) 434-0507 l TELEX: 499-3977 l www.linear-tech.com LT/TP 0198 REV A 4K • PRINTED IN THE USA PART NUMBER DESCRIPTION COMMENTS LT1239 Backup Battery Management System Charges Backup Battery and Regulates Backup Battery Output when Main Battery Removed LTC 1325 Microprocessor Controlled Battery Management System Can Charge, Discharge and Gas Gauge NiCd, NiMH and Pb-Acid Batteries with Software Charging Profiles LT1510 1.5A Constant-Current/Constant-Voltage Battery Charger Step-Down Charger for Li-Ion, NiCd and NiMH LT1511 3.0A Constant-Current/Constant-Voltage Battery Charger Step-Down Charger that Allows Charging During Computer Operation an d with Input Current Limiting Prevents Wall-Adapter Overload LT1512 SEPIC Constant-Current/Constant-Voltage Battery Charger Step-Up/Step-Down Charger for Up to 1A Current RELATED PARTS