LT1304-5

LT1304-5_15 LINER

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LT1304/LT1304-3.3/LT1304-5 Micropower DC/DC Converters with Low-Battery Detector Active in Shutdown The LT®1304 is a micropower step-up DC/DC converter ideal for use in small, low voltage, battery-operated sys- tems. The devices operate from a wide input supply range of 1.5V to 8V. The LT1304-3.3 and LT1304-5 generate regulated outputs of 3.3V and 5V and the adjustable LT1304 can deliver output voltages up to 25V. Quiescent current, 120µA in active mode, decreases to just 10µA in shutdown with the low-battery detector still active. Peak switch current, internally set at 1A, can be reduced by adding a single resistor from the I LIM pin to ground. The high speed operation of the LT1304 allows the use of small, surface-mountable inductors and capacitors. The LT1304 is available in an 8-lead SO package. , LTC and LT are registered trademarks of Linear Technology Corporation. APPLICATIONSU n 2-, 3-, or 4-Cell to 5V or 3.3V Step-Up n Portable Instruments n Bar Code Scanners n Palmtop Computers n Diagnostic Medical Instrumentation n Personal Data Communicators/Computers n 5V at 200mA from Two Cells n 10µA Quiescent Current in Shutdown n Operates with VIN as Low as 1.5V n Low-Battery Detector Active in Shutdown n Low Switch VCESAT: 370mV at 1A Typical n 120µA Quiescent Current in Active Mode n Switching Frequency Up to 300kHz n Programmable Peak Current with One Resistor n 8-Lead SO Package FEATURES DESCRIPTIONU TYPICAL APPLICATIONU Efficiency LOAD CURRENT (mA) EFFICIENCY (%)

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0.1 1 10 500 100 VIN = 3.3V VIN = 2.5V VIN = 1.8V VIN SW SHDN GND SENSELBI LBOILIM LT1304-5+ + 100k 100µF NC 604k100µF2 CELLS 499k 22µH* D1** 200mA LBO LOW WHEN V BAT < 2.2V SUMIDA CD54-220 1N5817

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2-Cell to 5V Step-Up Converter with Low-Battery Detect

LT1304/LT1304-3.3/LT1304-5 ABSOLUTE MAXIMUM RATINGSW WW U PACKAGE/ORDER INFORMATIONW UU IN LT1304CS8 LT1304CS8-3.3 LT1304CS8-5 1304 13043 13045 S8 PART MARKING ORDER PART NUMBER TOP VIEW LBI LBO VIN SW FB (SENSE)* SHDN I LIM GND S8 PACKAGE 8-LEAD PLASTIC SO *FIXED OUTPUT VERSION TJMAX = 125°C, θJA = 150°C/W PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Operating Voltage l 1.5 1.65 V Operating Voltage Range l 8V Quiescent Current V SHDN = 2V, Not Switching l 120 200 µA Quiescent Current in Shutdown V SHDN = 0V, VIN = 2V l 71 5 µA VSHDN = 0V, VIN = 5V l 27 50 µA Comparator Trip Point LT1304 l 1.22 1.24 1.26 V FB Pin Bias Current LT1304 l 10 25 nA Sense Pin Leakage in Shutdown V SHDN = 0V, Fixed Output Versions l 0.002 1 µA Output Sense Voltage LT1304-3.3 l 3.17 3.3 3.43 V LT1304-5 l 4.80 5.05 5.25 V Line Regulation 1.8V ≤ VIN ≤ 8V l 0.04 0.15 %/V LBI Input Threshold Falling Edge l 1.10 1.17 1.25 V LBI Bias Current l 62 0 n A LBI Input Hysteresis l 35 65 mV LBO Output Voltage Low I SINK = 500µA l 0.2 0.4 V LBO Output Leakage Current LBI = 1.5V, LBO = 5V l 0.01 0.1 µA SHDN Input Voltage High l 1.4 V SHDN Input Voltage Low l 0.4 V SHDN Pin Bias Current V SHDN = 5V l 58 µA VSHDN = 0V l –5 –2 µA Switch OFF Time l 1 1.5 2 µs Switch ON Time Current Limit Not Asserted l 468 µs Maximum Duty Cycle Current Limit Not Asserted l 76 80 88 % Peak Switch Current I LIM Pin Open, VIN = 5V 0.8 1 1.2 A 20k from ILIM to GND 500 mA VIN = 2V, VSHDN = 2V unless otherwise noted.ELECTRICAL C CHARA TERISTICS Consult factory for Industrial and Military grade parts.

LT1304/LT1304-3.3/LT1304-5 VIN = 2V, VSHDN = 2V unless otherwise noted.ELECTRICAL C CHARA TERISTICS The l denotes specifications which apply over the 0°C to 70°C operating temperature range. PARAMETER CONDITIONS MIN TYP MAX UNITS Switch Saturation Voltage I SW = 1A 0.37 V ISW = 700mA l 0.26 0.35 V Switch Leakage Switch Off, V SW = 5V l 0.01 7 µA TYPICAL PERFORMANCE CHARACTERISTICS UW TEMPERATURE (°C) –50 –25 TIME (µs) 05 0 25 75 100

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SWITCH CURRENT (A) SATURATION VOLTAGE (mV) 500 400 300 200 100 0.2 0.4 0.6 0.8

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1.0 1.2 TA = 25°C TEMPERATURE (°C) –50 BIAS CURRENT (nA) –25 0 25 50

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Feedback Pin Bias CurrentFeedback Voltage TEMPERATURE (°C) –50 FEEDBACK VOLTAGE (V) 1.250 1.245 1.240 1.235 1.230 1.225 1.220 1.215 1.210 1.205 1.200 –25 02 5 5 0

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TEMPERATURE (°C) PEAK CURRENT (A) 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6

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–50 –25 0 25 50 75 100 Peak Switch Current LimitSwitch Saturation Voltage INPUT VOLTAGE (V) 01 3 5 7 SUPPLY CURRENT (µA) 24 6 8

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VSHDN = VIN NOT SWITCHING VSHDN = 0V TA = 25°C

LT1304/LT1304-3.3/LT1304-5 TYPICAL PERFORMANCE CHARACTERISTICS UW Load Transient Response VOUT 100mV/DIV AC COUPLED ILOAD 200mA VSW 5V/DIV 100µs/DIV 1304 G07 20µs/DIV 1304 G08 VOUT 100mV/DIV AC COUPLED Burst Mode TM Operation IL 500mA/DIV VIN = 2.5V VOUT = 5V ILOAD = 185mA L = 22µH PIN FUNCTIONSUU U LBI (Pin 1): Low-Battery Detector Input. When voltage on this pin is less than 1.17V, detector output is low. LBO (Pin 2): Low-Battery Detector Output. Open collector can sink up to 500µA. Low-battery detector remains active when device is shut down. VIN (Pin 3): Input Supply. Must be bypassed close (<0.2") to the pin. See required layout in the Typical Applications. SW (Pin 4): Collector of Power NPN. Keep copper traces on this pin short and direct to minimize RFI. GND (Pin 5): Device Ground. Must be low impedance; solder directly to ground plane. ILIM (Pin 6): Current Limit Set Pin. Float for 1A peak switch current; a resistor to ground will lower peak current. SHDN (Pin 7): Shutdown Input. When low, switching regulator is turned off. The low-battery detector remains active. The SHDN input should not be left floating. If SHDN is not used, tie the pin to V IN. FB/SENSE (Pin 8): On the LT1304 (adjustable) this pin goes to the comparator input. On the fixed-output ver- sions, the pin connects to the resistor divider which sets output voltage. The divider is disconnected from the pin during shutdown. Burst Mode is a trademark of Linear Technology Corporation.

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Figure 2. LT1304-3.3/LT1304-5 Block Diagram

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Figure 1. LT1304 Block Diagram. Independent Low-Battery Detector A3 Remains Alive When Device Is in Shutdown

LT1304/LT1304-3.3/LT1304-5 OPERATIOU The LT1304’s operation can best be understood by exam- ining the block diagram in Figure 1. Comparator A1 monitors the output voltage via resistor divider string R3/R4 at the FB pin. When V FB is higher than the 1.24V reference, A2 and the timers are turned off. Only the reference, A1 and A3 consume current, typically 120 µA. As VFB drops below 1.24V plus A1’s hysteresis (about 6mV), A1 enables the rest of the circuit. Power switch Q1 is then cycled on for 6µs, or until current comparator A2 turns off the ON timer, whichever comes first. Off-time is fixed at approximately 1.5µs. Q1’s switching causes cur- rent to alternately build up in inductor L1 and discharge into output capacitor C2 via D1, increasing the output voltage. As V FB increases enough to overcome C1’s hys- teresis, switching action ceases. C2 is left to supply current to the load until VOUT decreases enough to force A1’s output high, and the entire cycle repeats. If switch current reaches 1A, causing A2 to trip, switch ON time is reduced. This allows continuous mode opera- tion during bursts. A2 monitors the voltage across 7.2Ω resistor R1, which is directly related to the switch current. Q2’s collector current is set by the emitter-area ratio to 0.5% of Q1’s collector current. R1’s voltage drop exceeds 36mV, corresponding to 1A switch current, A2’s output goes high, truncating the ON time part of the switch cycle. The 1A peak current can be reduced by tying a resistor between the I LIM pin and ground, causing a voltage drop to appear across R2. The drop offsets some of the 36mV reference voltage, lowering peak current. A 22k resistor limits current to approximately 550mA. A capacitor con- nected between I LIM and ground provides soft start. Shut- down is accomplished by grounding the SHDN pin. The low-battery detector A3 has its own 1.17V reference and is always on. The open collector output device can sink up to 500µA. Approximately 35mV of hysteresis is built into A3 to reduce “buzzing” as the battery voltage reaches the trip level. Inductor Selection Inductors used with the LT1304 must be capable of handling the worst-case peak switch current of 1.2A without saturating. Open flux rod or drum core units may be biased into saturation by 20% with only a small reduc- tion in efficiency. For the majority of 2-cell or 3-cell input LT1304 applications, a 22µH or 20µH inductor such as the Sumida CD54-220 (drum) or Coiltronics CTX20-1 (toroid) will suffice. If switch current is reduced using the I LIM pin, smaller inductors such as the Sumida CD43 series or Coilcraft DO1608 series can be used. Minimizing DCR is important for best efficiency. Ideally, the inductor DCR should be less than 0.05Ω , although the physical size of such an inductor makes its use prohibitive in many space conscious applications. If EMI is a concern, such as when sensitive analog circuitry is present, a toroidal inductor such as the Coiltronics CTX20-1 is suggested. A special case exists where the V OUT/VIN differential is high, such as a 2V to 12V boost converter. If the required duty cycle for continuous mode operation is higher than the LT1304 can provide, the converter must be designed for discontinuous operation. This means that the inductor current decreases to zero during the switch OFF time. For a simple step-up (boost) converter, duty cycle can be calculated by the following formula: DC = 1 – [(V IN – VSAT)/(VOUT + VD)] where, V IN = Minimum input voltage VSAT = Switch saturation voltage (0.3V) VOUT = Output voltage VD = Diode forward voltage (0.4V) If the calculated duty cycle exceeds the minimum LT1304 duty cycle of 76%, the converter should be designed for discontinuous mode operation. The inductance must be low enough so that current in the inductor reaches the peak current in a single cycle. Inductor value can be calculated by: L = (V IN – VSAT)(tON/1A) where, t ON = Minimum on-time of LT1304 (4µs) One advantage of discontinuous mode operation is that inductor values are usually quite low so very small units can be used. Ripple current is higher than with continuous mode designs and efficiency will be somewhat less.

Table 1. Recommended Inductors gested capacitor sources are listed in Table 2. Table 2. Recommended Capacitors can be used in a pinch, although efficiency will suffer. Figure 3. Start-Up Response. Input Current Rises Quickly to Figure 4. 2-Cell to 5V/200mA Boost Converter Takes Four

2 CELLS

bypass is then required to restore low impedance at the IC. Figure 5. Start-Up Response with 1µF/1MΩ Components Figure 6. Peak Switch Current vs RLIM Value

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the detector. Hysteresis is clearly evident in the figure. Figure 7. Suggested Layout for Best Performance. Input Capacitor Placement as Shown Is Highly Recommended.

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Figure 10. Battery Life vs Load Current. Dots Specify

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Figure 11. Output Watt Hours vs Load Current. Note Figure 8. Low-Battery Detector Transfer Function.

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Figure 9. 2-Cell to 5V Converter Used in Battery Life Study ciency plot pictured on the first page of this data sheet.

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Super Burst is a trademark of Linear Technology Corporation. Figure 12. Overall System Efficiency Including Battery Efficiency

LT1304/LT1304-3.3/LT1304-5 TYPICAL APPLICATIONSU 2-Cell to 3.3V Boost Converter VIN SW GNDILIM NC SENSE LT1304-3.3 C2 100µF 10V C1 100µF L1* 22µH MBRS130L 3.3V 300mA *SUMIDA CD54-220 **AVX TPSD107M010R0100

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2-Cell to 3.3V Converter Efficiency LOAD CURRENT (mA) EFFICIENCY (%)

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0.1 1 10 1000 100 VIN = 3.3V VIN = 2.5V VIN = 2.5V LOAD CURRENT (mA) EFFICIENCY (%) 0.1 1 10 1000 100 VIN = 3.3V VIN = 2.5V VIN = 1.8V 3.3V SEPIC (Step-Up/Step-Down Converter) LOAD CURRENT (mA) EFFICIENCY (%) 10 100 500

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VIN = 4.5V VIN = 3.5V VIN = 2.5V 3.3V SEPIC Efficiency 5V SEPIC (Step-Up/Step-Down Converter) 5V SEPIC Efficiency LOAD CURRENT (mA) EFFICIENCY (%) 10 100 500

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VIN = 6V VIN = 5V VIN = 4V VIN = 3V VIN ILIM SW GND NC SENSE VIN 3V TO 8V LT1304-5 100µF†† 10V 47µF† 16V C1** 1µFL1A* MBRS130L 2 1 200mA * COILTRONICS CTX20-1 ** TOKIN 1E105ZY5U-C103-F † AVX TPSD476M016R0150 †† AVX TPSD107M010R0100

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L1B* VIN ILIM SW GND NC SENSE VIN 2.5V TO 8V LT1304-3.3 C3†† 100µF 10V C2† 47µF 16V C1** 1µFL1A* MBRS130L 2 1 3.3V 300mA * COILTRONICS CTX20-1 ** TOKIN 1E105ZY5U-C103-F † AVX TPSD476M016R0150 †† AVX TPSD107M010R0100

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L1B*

LT1304/LT1304-3.3/LT1304-5 TYPICAL APPLICATIONSU Single Li-Ion Cell to 5V Converter with Load Disconnect at VIN < 2.7V VIN SW GND FB LT1304 47µF 16V 47µF L1* 22µH D1† 1.07M 1% 12V 200mA 124k * SUMIDA CD54-220 ** AVX TPSD476M016R0150 † MOTOROLA MBRS130L

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5V to 12V DC/DC Converter 5V to 12V Converter Efficiency LOAD CURRENT (mA) EFFICIENCY (%) 10 100 300

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22µH** MBRS130LT3 (5V)(2.7V to 4.2V) SW GND SENSENC 220k * PRIMARY Li-Ion BATTERY PROTECTION MUST BE PROVIDED BY AN INDEPENDENT CIRCUIT ** SUMIDA CD54-220 † AVX TPSD107M010R0100 LBO VIN ILIM LBI 100µF† 10V SHDN LTC1477 VOUT VIN2 GND VOUT VIN1 VINS NC NCVIN3 EN 562k 432k SINGLE Li-Ion CELL* + 100µF 16V 1µF

LT1304/LT1304-3.3/LT1304-5 TYPICAL APPLICATIONSU Negative LCD Bias Generator Electroluminescent Panel Driver with 200Hz Oscillator VIN SW GND FB 22k ILIM LT1304+ 110k 90.9k VOLTAGE ADJUST 1kHz PWM INPUT 0V TO 5V 1.69M 1µF CERAMIC 47µF 3.3µF 10µF 35V1000pF L1* 10µH –VOUT –14V TO –22V 1mA TO 10mA * SUMIDA CD43-100 ** MOTOROLA MBR0530

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EFFICIENCY = 70% TO 75% AT I LOAD ≥ 2mA DANGER! HIGH VOLTAGEVIN SW GND 200Hz NC FB 3.3k ILIM LBI LBO LT1304 51k 22k 22k 22k 1/2 BAW56 FMMT458 MBR0530 50k INTENSITY ADJUST 10M (3.3M × 3) 1µF 200VMUR160 600V 1nF 0.01µF 47µF EL PANEL CPANEL ≤ 20nF 1:12* * DALE LPE3325-A205 TRANSFORMER MEASURES 6.5mm × 8.2mm × 5.2mm (H) (605) 665-9301

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5V = OPERATE 0V = SHUTDOWN 2N3906 75k 1/2 BAW56

LT1304/LT1304-3.3/LT1304-5 TYPICAL APPLICATIONSU 2- to 4-Cell to 5V Converter with Output Disconnect VIN VIN 2V TO 6V SW GNDILIM NC SENSE LT1304-5 22µF* 47µF* L1** 22µH MBRS130L ZTX788B *AVX TPS SERIES TANTALUM OR SANYO OS-CON **SUMIDA CD54-220

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220µF* 100mA VIN SW GND NC FB ILIM LT1304 MBR0530 0.01µF 0.01µF 0.01µF 0.01µF47µF T1*

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0.1µF VIN 2V TO 6V 620k R1** 500M VOUT 1kV 250µA V OUT = 1.24V 1+ R1 R2() * DALE LPE3325-A205 TRANSFORMER MEASURES 6.5mm × 8.2mm × 5.2mm (H) (605) 665-9301 ** IRC CGX-1/2 ALL 0.01µF CAPACITORS 250WVDC BAS21 OR MUR130 DANGER! HIGH VOLTAGE 2- to 4-Cell to 1kV Step-Up Converter

LT1304/LT1304-3.3/LT1304-5 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 circuits as described herein will not infringe on existing patent rights. TYPICAL APPLICATIONSU 2-Cell to 5V Converter with Auxiliary 10V Output 2-Cell to 5V Converter with Auxiliary – 5V Output VIN SW GNDILIM NC SENSE LT1304-5100µF2 CELLS L1* 22µH MBRS130L MBR0530 MBR0530 *SUMIDA CD54-220 1304 TA19 SHUTDOWN SHDN 100µF 10µF 1µF CERAMIC 150mA –5V 20mA VIN SW GNDILIM NC SENSE LT1304-5100µF 1µF CERAMIC L1* 22µH MBRS130L MBR0530 MBR0530 *SUMIDA CD54-220

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100µF 150mA 10V 20mA 10µF

LT1304/LT1304-3.3/LT1304-5 LT/GP 1195 10K • PRINTED IN USA  LINEAR TECHNOLOGY CORPORA TION 1995 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 l FAX: (408) 434-0507 l TELEX: 499-3977 PACKAGE DESCRIPTIONU Dimension in inches (millimeter) unless otherwise noted. 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 1 2 3 4 0.150 – 0.157** (3.810 – 3.988) 8 7 6 5 0.189 – 0.197* (4.801 – 5.004) 0.228 – 0.244 (5.791 – 6.197) 0.016 – 0.050 0.406 – 1.270 0.010 – 0.020 0°– 8° TYP 0.008 – 0.010 (0.203 – 0.254) SO8 0695 0.053 – 0.069 (1.346 – 1.752) 0.014 – 0.019 (0.355 – 0.483) 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) BSCDIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE **PART NUMBER DESCRIPTION COMMENTS LTC 1163 Triple High Side Driver for 2-Cell Inputs 1.8V Minimum Input, Drives N-Channel MOSFETs LT1239 Backup Battery Management System Easy-to-Use, Fail-Safe Backup Protection LT1301 Fixed 5V/12V Step-Up Micropower DC/DC Converter 12V/200mA from 5V, 120 µA IQ, 88% Efficiency LT1302 High Output Current Micropower DC/DC Converter 5V/600mA from 2V, 2A Internal Switch, 200 µA IQ LT1303 Micropower DC/DC Converter Low-Battery Detector Inactive in Shutdown LTC1477 Protected Switch Ultralow R DS(ON) Switch: 0.07Ω LT1521 300mA, 12 µA IQ Low Dropout Regulator 500mV Dropout at Full Load RELATED PARTS