LT1303CS8

LT1303/LT1303-5 Micropower High Efficiency DC/DC Converters with Low-Battery Detector Adjustable and Fixed 5V FEATURES s s s s s s s s DESCRIPTION The LT®1303/LT1303-5 are micropower step-up high efficiency DC/DC converters using Burst ModeTM operation. They are ideal for use in small, low-voltage batteryoperated systems. The LT1303-5 accepts an input voltage between 1.8V and 5V and converts it to a regulated 5V. The LT1303 is an adjustable version that can supply an output voltage up to 25V. Quiescent current is only 120µA from the battery and the shutdown pin further reduces current to 10µA. The low-battery detector provides an opencollector output that goes low when the input voltage drops below a preset level. The on-chip NPN power switch has a low 170mV saturation voltage at a switch current of 1A. The LT1303/LT1303-5 are available in 8-lead PDIP or SO packages, easing board space requirements. For higher output current, please see the LT1305 or LT1302. , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation. 5V at 200mA from a 2V Input Supply Voltage As Low As 1.8V Up to 88% Efficiency 120µA Quiescent Current Low-Battery Detector Low VCESAT Switch: 170mV at 1A Typ Uses Inexpensive Surface Mount Inductors 8-Lead PDIP or SO Package APPLICATIONS s s s s s s s EL Panel Drivers 2-Cell and 3-Cell to 5V Conversion Palmtop Computers Portable Instruments Bar-Code Scanners PDAs Wireless Systems TYPICAL APPLICATION L1 22µH 316k 1% 1N5817 90 80 VIN LBI SW SENSE LT1303-5 100k LBO PGND 100µF EFFICIENCY (%) + 2 CELLS VOUT, 5V 200mA LOW BATTERY GOES LOW AT VBAT = 2.2V 100µF 412k 1% SHUTDOWN SHDN GND 70 60 50 40 + L1 = SUMDIA CD54-220 LT1303 TA02 30 Figure 1. 2-Cell to 5V DC/DC Converter with Low-Battery Detect U U U 5V Output Efficiency VIN = 4V VIN = 2V VIN = 2.5V VIN = 3V 0.1 1 10 100 1000 LT1303 TA01 LOAD CURRENT (mA) 1 LT1303/LT1303-5 ABSOLUTE MAXIMUM RATINGS VIN Voltage .............................................................. 10V SW1 Voltage ............................................................ 25V Sense Voltage (LT1303-5) ....................................... 20V FB Voltage (LT1303) ................................................ 10V Shutdown Voltage ................................................... 10V LBO Voltage ............................................................. 10V LBI Voltage .............................................................. 10V Maximum Power Dissipation ............................. 500mW Operating Temperature Range ..................... 0°C to 70°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C PACKAGE/ORDER INFORMATION TOP VIEW GND 1 LBO 2 SHDN 3 FB (SENSE)* 4 N8 PACKAGE 8-LEAD PDIP S8 PACKAGE 8-LEAD PLASTIC SO *FIXED VERSION TJMAX = 100°C, θJA = 130°C/W (N8) TJMAX = 100°C, θJA = 150°C/W (S8) 8 7 6 5 PGND SW VIN LBI ORDER PART NUMBER LT1303CN8 LT1303CS8 LT1303CN8-5 LT1303CS8-5 S8 PART MARKING 1303 13035 Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS SYMBOL IQ VIN PARAMETER Quiescent Current Input Voltage Range TA = 25°C, VIN = 2.0V, unless otherwise noted. MIN q q q CONDITIONS VSHDN = 0.5V, VSEL = 5V, VSENSE = 5.5V VSHDN = 1.8V DC tON VCESAT Feedback Voltage Output Sense Voltage Comparator Hysteresis Output Hysteresis Feedback Pin Bias Current Oscillator Frequency Oscillator TC Maximum Duty Cycle Switch On Time Output Line Regulation Switch Saturation Voltage Switch Leakage Current Peak Switch Current LBI Trip Voltage LBI Input Bias Current LBO Output Low LBO Leakage Current Shutdown Pin High Shutdown Pin Low Shutdown Pin Bias Current LT1303 LT1303-5 LT1303 (Note 1) LT1303-5 (Note 1) LT1303, VFB = 1V Current Limit Not Asserted q q q q q 1.8 2.0 1.22 4.8 TYP 120 7 1.55 1.24 5.0 6 22 7 155 0.2 86 5.6 0.06 130 0.1 1.0 0.9 1.24 7 0.11 0.1 MAX 200 15 120 q 1.26 5.2 12.5 50 20 185 95 0.15 200 10 1.25 1.15 1.27 20 0.4 5 0.5 20 1 75 Current Limit Not Asserted 1.8V < VIN < 6V ISW = 700mA VSW = 5V, Switch Off VIN = 2V VIN = 5V VLBI = 1V ILOAD = 100µA VLBI = 1.3V, VLBO = 5V q q q q q q q q q 0.75 0.65 1.21 VSHDNH VSHDNL ISHDN 1.8 8.0 3.0 0.1 VSHDN = 5V VSHDN = 2V VSHDN = 0V q q q UNITS µA µA V V V V mV mV nA kHz %/°C % µs %/V mV µA A A V nA V µA V V µA µA µA The q denotes specifications which apply over the 0°C to 70°C operating temperature range. Note 1: Hysteresis specified is DC. Output ripple may be higher if output capacitance is insufficient or capacitor ESR is excessive. 2 U W U U WW W LT1303/LT1303-5 TYPICAL PERFORMANCE CHARACTERISTICS VCESAT vs Switch Current 250 225 200 175 150 125 100 75 50 25 0 0.1 1.0 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 SWITCH CURRENT (A) LT1303 G01 160 150 140 130 120 110 100 –50 –25 25 50 0 TEMPERATURE (°C) 75 100 RESISTANCE (kΩ) VCESAT (mV) VCESAT (mV) LT1303 FB Voltage 1.250 1.245 1.240 FEEDBACK VOLTAGE (V) SENSE VOLTAGE (V) 1.230 1.225 1.220 1.215 1.210 1.205 1.200 –50 –25 25 50 0 TEMPERATURE (°C) 75 100 5.02 5.00 4.98 4.96 4.94 4.92 4.90 –50 –25 25 50 0 TEMPERATURE (°C) 75 100 LBI VOLTAGE (V) 1.235 LBI Pin Bias Current 20 18 16 BIAS CURRENT (nA) 14 12 10 8 6 4 2 0 –50 –25 25 50 0 TEMPERATURE (°C) 75 100 14 12 10 8 6 4 2 0 –50 –25 25 50 0 TEMPERATURE (°C) 75 100 SWITCH CURRENT (A) BIAS CURRENT (nA) UW LT1303 G07 VCESAT vs Temperature 200 190 180 170 800 700 600 500 400 LT1303-5 Sense Pin Resistance to Ground 1000 900 ISW = 700mA 300 –50 –25 50 25 0 TEMPERATURE (˚C) 75 100 LT1303 G02 LT1303 GO3 LT1303-5 Sense Voltage 5.10 5.08 5.06 5.04 1.250 1.245 1.240 1.235 1.230 1.225 1.220 1.215 1.210 1.205 Low Battery Detect Trip Point 1.200 –50 –25 25 50 0 TEMPERATURE (°C) 75 100 LT1330 G04 LT1303 G05 LT1303 G06 FB Pin Bias Current 20 18 16 1.50 1.40 1.30 1.20 1.10 1.00 0.90 0.80 0.70 Switch Current Limit VIN = 2V 0.60 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 LT1303 G08 LT1303 G09 3 LT1303/LT1303-5 TYPICAL PERFORMANCE CHARACTERISTICS Switch On-Time 8 7 6 5 4 3 2 –50 FREQUENCY (kHz) 200 190 180 160 150 140 130 120 110 DUTY CYCLE (%) –25 25 50 0 TEMPERATURE (°C) 75 100 ON-TIME (µs) –25 0 25 50 TEMPERATURE (°C) Quiescent Current 200 190 QUIESCENT CURRENT (µA) SWITCH OFF VIN = 2V QUIESCENT CURRENT (µA) 170 160 150 140 130 120 110 100 –50 300 SWITCH CURRENT (mA) 180 –25 25 50 0 TEMPERATURE (°C) Transient Response Figure 1 Circuit VOUT 100mV/DIV AC COUPLED 5V VOUT 1V/DIV ILOAD 200mA 0mA 200µs/DIV VIN = 2V VOUT = 5V 4 UW 75 Oscillator Frequency 100 95 90 85 80 75 70 65 60 55 Maximum Duty Cycle 170 100 100 –50 50 –50 –25 25 50 0 TEMPERATURE (°C) 75 100 LT1303 G10 LT1303 G11 LT1303 G12 Quiescent Current 500 TA = 25°C SWITCH OFF 1200 Switch Current Limit L = 33µH VL = 3V 400 1100 1000 200 900 100 800 0 75 100 0 2 6 4 INPUT VOLTAGE (V) 8 10 LT1303 G14 700 0 2 6 4 INPUT VOLTAGE (V) 8 10 LT1303 G15 LT1303 G13 Shutdown Pin Response VLBO 2V/DIV Low Battery Detector Transient Response VSHDN 5V/DIV LT1303 G16 VLBI 500µs/DIV VTRIP +10mV VTRIP –10mV 5µs/DIV RPULL-UP = 47k LT1303 G18 LT1303 G17 RLOAD = 100Ω VIN = 2V VOUT = 5V COUT = 100µF LT1303/LT1303-5 PIN FUNCTIONS GND (Pin 1): Signal Ground. Tie to PGND under the package. LBO (Pin 2): Open-Collector Output of Low-Battery Comparator. Can sink 100µA. Disabled when device is in shutdown. SHDN (Pin 3): Shutdown. Pull high to shut down the device. Ground for normal operation. FB/Sense (Pin 4): On 1303 (adjustable) this pin connects to the main comparator C1 input. On LT1303-5 this pin connects to the resistor string that sets output voltage at 5V. LBI (Pin 5): Low-Battery Comparator Input. When voltage on this pin below 1.24V, LBO is low. VIN (Pin 6): Supply Pin. Must be bypassed with a large value electrolytic to ground. Keep bypass within 0.2" of the device. SW (Pin 7): Switch Pin. Connect inductor and diode here. Keep layout short and direct to minimize radio frequency interference. PGND (Pin 8): Power ground. Tie to signal ground (pin1) under the package. Bypass capacitor from VIN should be tied directly to PGND within 0.2" of the device. BLOCK DIAGRA S VIN + C1 6 C2 4 FB – C1 OFF OSCILLATOR A3 DRIVER Q2 1× Q1 160× R2 REFERENCE 1.24V + – C3 + GND 1 5 LBI 2 LBO SHUTDOWN 3 8 PGND Figure 2. LT1303 Block Digram – R1 HYSTERETIC COMPARATOR + W U U U L1 VIN SW D1 + C2 7 CURRENT COMPARATOR 18mV R1 3Ω LT1303 BD01 5 LT1303/LT1303-5 BLOCK DIAGRA S 4 FB 6 VIN 7 CURRENT COMPARATOR C2 18mV SW R1 474k HYSTERETIC COMPARATOR – C1 R2 156k REFERENCE 1.24V OFF OSCILLATOR A3 DRIVER Q2 1× Q1 160× + – C3 + GND 1 5 LBI 2 LBO SHUTDOWN 3 8 PGND Figure 3. LT1303-5 Block Diagram OPERATION Operation of the LT1303 is best understood by referring to the Block Diagram in Figure 2. When C1’s negative input, related to the output voltage by the appropriate resistordivider ratio, is higher than the 1.24V reference voltage, C1’s output is low. C2, A3 and the oscillator are turned off, drawing no current. Only the reference and C1 consume current, typically 140µA. When C1’s negative input drops below 1.24V and overcomes C1’s 6mV hysteresis, C1’s output goes high, enabling the oscillator, current comparator C2 and driver A3. Quiescent current increases to 2mA as the device goes into active switching mode. Q1 then turns on in controlled saturation for nominally 6µs or until current comparator C2 trips, whichever comes first. The switch then turns off for approximately 1.5µs, then turns on again. The LT1303’s switching causes current to alternately build up in L1 and dump into output capacitor C4 via D1, increasing the output voltage. When the output is high enough to cause C1’s output to go high, switching action ceases. Capacitor C4 is left to supply current to the load until VOUT decreases enough to force C1’s output high, and the entire cycle repeats. Figure 4 details relevant waveforms. C1’s cycling causes low-to-mid-frequency ripple voltage on the output. Ripple can be reduced by making the output capacitor large. The 100µF unit specified results in ripple of 50mV to 100mV on the 5V output. A 220µF capacitor will decrease ripple by approximately 50%. VOUT 100mV/DIV AC COUPLED VSW 5V/DIV IL 1A/DIV 20µs/DIV LT1303 F04 Figure 4. Burst Mode Operation in Action If switch current reaches 1A, causing C2 to trip, switch ontime is reduced and off-time increases slightly. This allows continuous operation during bursts. C2 monitors the voltage across 3Ω resistor R1 which is directly related to the switch current. Q2’s collector current is set by the emitter-area ratio to 0.6% of Q1’s collector current. When R1’s voltage drop exceeds 18mV, corresponding to 1A switch current, C2’s output goes high, truncating the ontime portion of the oscillator cycle and increasing off-time 6 + – W R1 3Ω LT1303 BD02 U LT1303/LT1303-5 OPERATION to about 2µs. Response time of C2, which determines minimum on-time, is approximately 300ns. Low Battery Detector The low battery detector is enabled when SHDN is low and disabled when SHDN is high. The comparator has no VBAT LT1303 5V R1 R2 49.9k 1% R1 = (VTRIP –1.24V) (43.5k) HYSTERESIS ≈ 30mV Figure 5. R3 Adds Hysteresis to Low-Battery Detector APPLICATIONS INFORMATION Inductor Section Inductors suitable for use with the LT1303 usually fall in the 5µH to 50µH range. The inductor must: (1) handle current of 1.25A without saturating, (2) have enough inductance to provide a di/dt lower than 400mA/µs, and (3) have low enough DC resistance to avoid excessive heating or efficiency losses. Higher value inductors will deliver more power but tend to be physically larger. Most ferrite core drum or rod inductors such as those specified in Table 1 are suitable for use. It is acceptable to bias openflux inductors (e.g. Sumida CD54) into saturation by 10 to 20% without adverse effects. Table 1. Recommended Inductors VENDOR Coilcraft Coiltronics SERIES D03316 D01608 OCTAPAK CTX20-1 CTX20-2 CTX33-4 CD54 GA10 PHONE APPROPRIATE VALUES NUMBERS 10µH to 47µH (708) 639-6400 10µH (407) 241-7876 20µH 20µH 33µH 10µH to 33µH (708) 956-0666 10µH to 33µH (716) 532-2234 Sumida Gowanda U W U U U hysteresis built in, but hysteresis can be added by connecting a high-value resistor from LBI to LBO as shown in Figure 5. The internal reference can be accessed via the comparator as shown in Figure 6. VIN 100k 2N3906 VIN LBO LT1303 VREF OUTPUT R2 1.24V – + R3 2M R4 47k + LBI 2.2µF R1 GND LT1303 F05 VREF = 1.24V 1 + R2 R1 VIN ≥ VREF + 200mV R1 + R2 ≈ 33k () LT1303 F06 Figure 6. Accessing Internal Reference Figure 7 shows inductor current of a suitable inductor, di/dt is controlled at all times. The rapid rise in current shown in Figure 8 results from this inductor saturating at approximately 1A. Saturation occurs when the inductor cannot hold any more magnetic energy in the core. Current then increases rapidly, limited only by the resistance of the winding. Figure 9’s inductor has high DC resistance which results in the exponential time constant shape of the inductor current. IL 500mA/DIV 5µs/DIV LT1303 F07 Figure 7. Properly Chosen Inductor Does Not Saturate 7 LT1303/LT1303-5 APPLICATIONS INFORMATION Capacitor Selection Input and output capacitors should have low ESR for best efficiency. Recommended capacitors include AVX TPS series, Sprague 595D series, and Sanyo OS-CON. The output capacitor’s ESR determines the high frequency ripple amplitude. A 100µF capacitor is the minimum recommended for a 5V output. Higher output voltages can use lower capacitance values. For example, a 12V output can use a 33µF or 47µF capacitor. The VIN pin of the LT1303 should be decoupled with a 47µF or 100µF capacitor at the pin. When driving a transformer, an additional decoupling network of 10Ω and 0.1µF ceramic is recommended as shown in Figure 10. VIN 10Ω LT1303 F08 Figure 8. This Inductor Saturates at IL≈1A. A Poor Choice LT1303 F09 Figure 9. Slight Exponential Shape to Inductor Current Waveform Indicates Excessive DC Resistance Diode Selection The LT1303’s high switching speed demands a high speed rectifier. Schottky diodes are preferred for their low forward drop and fast recovery. Suitable choices include the 1N5817, MBRS120LT3, and MBR0520LT1. Do not use signal diodes such as 1N4148. They cannot carry 1A current. Also avoid “general-purpose” diodes such as 1N4001. These are far too slow and are unsuitable for any switching regulator application. For high temperature applications a silicon diode such as the MUR105 will have less leakage. 8 U W U U + 47µF 0.1µF CERAMIC VIN SW LT1303 ••• PGND GND LT1303 F10 Figure 10. 10Ω-1µF Network to LT1303 VIN Pin Provides Additional Decoupling. Recommended When Driving Transformers. Table 2. Recommended Capacitors VENDOR AVX Sanyo Panasonic Sprague SERIES TPS OS-CON HFQ 595D TYPE Surface Mount Through-Hole Through-Hole Surface Mount PHONE NUMBERS (803) 448-9411 (619) 661-6835 (201) 348-5200 (603) 224-1961 LT1303/LT1303-5 TYPICAL APPLICATIONS Setting Output Voltage on LT1303 L1 VIN VIN SW VOUT R2 FB GND PGND R1 1N5817 INPUT 1.8V TO 4.5V 100k 2N3906 VIN LBO 100µF LBI 2.2µF 33k GND VREF OUTPUT 1.24V * SUMIDA CD54-220MC U + + 100µF LT1303 + 100µF VOUT = 1.24V 1 + R2 R1 () 1303 TA03 5V Step-Up Converter with Reference Output 22µH* 1N5817 SW SENSE LT1303-5 SHDN PGND OUTPUT 5V + + 100µF 1303 TA04 9 LT1303/LT1303-5 TYPICAL APPLICATIONS 4-, 5-Cell to 5V Converter with Output Disconnect VIN 2V TO 8V VIN 3-Cell to 3.3V Boost/Linear Converter with Output Disconnect VIN 2V TO 6V VIN SHUTDOWN SHDN + 33µF *SUMIDA CD54-100MC **AVX TPS 330µF/6.3V † 1% METAL FILM 10 U 510Ω 10µH* MBRS130T3 ZTX788B SW SENSE VOUT 5V 100mA + 33µF GND LT1303-5 SHDN PGND SHUTDOWN + 33µF + 220µF** *SUMIDA CD54-100MC **AVX TPS 220µF/10V LT1303TA05 10µH* MBRS130T3 Si9433 100k SW LB0 LT1303 LBI GND FB PGND 1.96k† 100Ω + 33µF 200k† VOUT 3.3V/200mA + 121k† 330µF** ×2 LT1303 TA07 LT1303/LT1303-5 TYPICAL APPLICATIONS EL Panel Driver T1** 1:15 4,5 10Ω MUR160 C1* 50pF 1N5818 3.3M VIN 1.5V TO 8V + 47µF 0.1µF CERAMIC 100Hz TO 1000Hz SQUARE WAVE DRIVE *ADD C1 FOR OPEN-PANEL PROTECTION **DALE LPE5047-A132 1:15 TURNS RATIO (605) 666-9301 † R1 ADJUSTS VOUT 83VRMS TO 115VRMS 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 circuits as described herein will not infringe on existing patent rights. U •6 10 4.7µF 160V 1,2 • + 1k 1/2W 10k VIN SW 3.3M EL PANEL 3.3M 1N4148 LT1303 SHDN GND FB PGND MPSA42 51k SHUTDOWN R1† 25k LT1303 TA06 11 LT1303/LT1303-5 PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead Plastic DIP 0.300 – 0.325 (7.620 – 8.255) 0.045 – 0.065 (1.143 – 1.651) 0.130 ± 0.005 (3.302 ± 0.127) 0.400* (10.160) MAX 8 7 6 5 0.009 – 0.015 (0.229 – 0.381) 0.065 (1.651) TYP 0.005 (0.127) MIN 0.100 ± 0.010 (2.540 ± 0.254) 0.125 (3.175) MIN 0.018 ± 0.003 (0.457 ± 0.076) 0.015 (0.380) MIN ( +0.025 0.325 –0.015 8.255 +0.635 –0.381 ) *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm) 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0°– 8° TYP 0.053 – 0.069 (1.346 – 1.752) 0.016 – 0.050 0.406 – 1.270 *DIMENSION 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 RELATED PARTS PART NUMBER LT1129 LT1182/83/84 LT1301 LT1302 LT1305 LT1372 LTC ®1472 DESCRIPTION Micropower Low Dropout Regulator LCD and CCFL Backlight Controller 5V to 12V/200mA Step-Up DC/DC Converter 2-Cell to 5V/600mA Step-Up DC/DC Converter Micropower 2A Switch DC/DC Converter with Low-Battery Detect 500kHz Step-Up PWM, 1.5A Switch PCMCIA Host Switch with Protection COMMENTS 700mA Output Current in SO-8 Package High Efficiency and Excellent Backlight Control Range 120µA Quiescent Current 200µA Quiescent Current 2V to 5V at 400mA Low Noise, Fixed Frequency Operation Includes Current Limit and Thermal Shutdown 12 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977 U 0.255 ± 0.015* (6.477 ± 0.381) 1 2 3 4 N8 0695 S8 Package 8-Lead Plastic SOIC 0.189 – 0.197* (4.801 – 5.004) 0.004 – 0.010 (0.101 – 0.254) 8 7 6 5 0.014 – 0.019 (0.355 – 0.483) 0.050 (1.270) BSC 0.228 – 0.244 (5.791 – 6.197) 0.150 – 0.157** (3.810 – 3.988) 1 2 3 4 SO8 0695 LT/GP 0195 10K • PRINTED IN USA © LINEAR TECHNOLOGY CORPORATION 1995