LT1308A_1 LINER | Alldatasheet
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High Current, Micropower Single Cell, 600kHz DC/DC Converters ■ 5V at 1A from a Single Li-Ion Cell ■ 5V at 800mA in SEPIC Mode from Four NiCd Cells ■ Fixed Frequency Operation: 600kHz ■ Boost Converter Outputs up to 34V ■ Starts into Heavy Loads ■ Automatic Burst Mode TM Operation at Light Load (LT1308A) ■ Continuous Switching at Light Loads (LT1308B) ■ Low VCESAT Switch: 300mV at 2A ■ Pin-for-Pin Upgrade Compatible with LT1308 ■ Lower Quiescent Current in Shutdown: 1μA (Max) ■ Improved Accuracy Low-Battery Detector Reference: 200mV ± 2% ■ Available in 8-Lead SO and 14-Lead TSSOP Packages ■ GSM/CDMA Phones ■ Digital Cameras ■ LCD Bias Supplies ■ Answer-Back Pagers ■ GPS Receivers ■ Battery Backup Supplies ■ Handheld Computers The LT 1308A/LT1308B are micropower, fixed frequency step-up DC/DC converters that operate over a 1V to 10V input voltage range. They are improved versions of the LT1308 and are recommended for use in new designs. The LT1308A features automatic shifting to power saving Burst Mode operation at light loads and consumes just 140μA at no load. The LT1308B features continuous switching at light loads and operates at a quiescent current of 2.5mA. Both devices consume less than 1 μA in shutdown. Low-battery detector accuracy is significantly tighter than the LT1308. The 200mV reference is specified at ± 2% at room and ± 3% over temperature. The shutdown pin enables the device when it is tied to a 1V or higher source and does not need to be tied to V IN as on the LT1308. An internal VC clamp results in improved transient response and the switch voltage rating has been increased to 36V, enabling higher output voltage applications. The LT1308A/LT1308B are available in the 8-lead SO and the 14-lead TSSOP packages. Figure 1. LT1308B Single Li-Ion Cell to 5V/1A DC/DC Converter
FEATURES
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.
A UGWA WU WA RBSOLUTEX I T I S (Note 1) Operating Temperature Range (Note 6) TJMAX = 125°C, θJA = 80°C/W LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT1308ACS8#PBF LT1308ACS8#TRPBF 1308A 8-Lead Plastic SO 0°C to 70°C LT1308AIS8#PBF LT1308AIS8#TRPBF 1308AI 8-Lead Plastic SO –40°C to 85°C LT1308BCS8#PBF LT1308BCS8#TRPBF 1308B 8-Lead Plastic SO 0°C to 70°C LT1308BIS8#PBF LT1308BIS8#TRPBF 1308BI 8-Lead Plastic SO –40°C to 85°C LT1308ACF#PBF LT1308ACF#TRPBF LT1308ACF 14-Lead Plastic TSSOP 0°C to 70°C LT1308BCF#PBF LT1308BCF#TRPBF LT1308BCF 14-Lead Plastic TSSOP 0°C to 70°C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT1308ACS8 LT1308ACS8#TR 1308A 8-Lead Plastic SO 0°C to 70°C LT1308AIS8 LT1308AIS8#TR 1308AI 8-Lead Plastic SO –40°C to 85°C LT1308BCS8 LT1308BCS8#TR 1308B 8-Lead Plastic SO 0°C to 70°C LT1308BIS8 LT1308BIS8#TR 1308BI 8-Lead Plastic SO –40°C to 85°C LT1308ACF LT1308ACF#TR LT1308ACF 14-Lead Plastic TSSOP 0°C to 70°C LT1308BCF LT1308BCF#TR LT1308BCF 14-Lead Plastic TSSOP 0°C to 70°C Consult LTC Marketing for parts specified with wider operating temperature ranges. 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/ PI CO FIGURATIO UU U ORDER I FOR ATIOUU W TJMAX = 125°C, θJA = 190°C/W F PACKAGE 14-LEAD PLASTIC TSSOP TOP VIEW V C FB SHDN GND GND GND GND LBO LBI V IN VIN SW SW SW TOP VIEW LBO LBI V IN SW VC FB SHDN GND S8 PACKAGE 8-LEAD PLASTIC SO NOT RECOMMENDED FOR NEW DESIGNS Contact Linear Technology for Potential Replacement
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. Industrial Grade – 40°C to 85°C. VIN = 1.2V, VSHDN = VIN, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS IQ Quiescent Current Not Switching, LT1308A ● 140 240 μA Switching, LT1308B ● 2.5 4 mA VSHDN = 0V (LT1308A/LT1308B) ● 0.01 1 μA VFB Feedback Voltage ● 1.19 1.22 1.25 V IB FB Pin Bias Current (Note 3) ● 27 80 nA Reference Line Regulation 1.1V ≤ VIN ≤ 2V ● 0.05 0.4 %/V 2V ≤ VIN ≤ 10V ● 0.01 0.2 %/V Minimum Input Voltage 0.92 1 V gm Error Amp Transconductance ΔI = 5μA6 0 μmhos AV Error Amp Voltage Gain 100 V/V ELECTRICAL CHARACTERISTICSThe ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. Commercial Grade 0°C to 70°C. VIN = 1.1V, VSHDN = VIN, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS IQ Quiescent Current Not Switching, LT1308A 140 240 μA Switching, LT1308B 2.5 4 mA VSHDN = 0V (LT1308A/LT1308B) 0.01 1 μA VFB Feedback Voltage ● 1.20 1.22 1.24 V IB FB Pin Bias Current (Note 3) ● 27 80 nA Reference Line Regulation 1.1V ≤ VIN ≤ 2V ● 0.03 0.4 %/V 2V ≤ VIN ≤ 10V 0.01 0.2 %/V Minimum Input Voltage 0.92 1 V gm Error Amp Transconductance ΔI = 5μA6 0 μmhos AV Error Amp Voltage Gain 100 V/V fOSC Switching Frequency V IN = 1.2V ● 500 600 700 kHz Maximum Duty Cycle ● 82 90 % Switch Current Limit Duty Cyle = 30% (Note 4) 2 3 4.5 A Switch VCESAT ISW = 2A (25°C, 0°C), VIN = 1.5V 290 350 mV ISW = 2A (70°C), VIN = 1.5V 330 400 mV Burst Mode Operation Switch Current Limit V IN = 2.5V, Circuit of Figure 1 400 mA (LT1308A) Shutdown Pin Current V SHDN = 1.1V ● 25 μA VSHDN = 6V ● 20 35 μA VSHDN = 0V ● 0.01 0.1 μA LBI Threshold Voltage 196 200 204 mV
- 194 200 206 mV LBO Output Low I SINK = 50μA ● 0.1 0.25 V LBO Leakage Current V LBI = 250mV, VLBO = 5V ● 0.01 0.1 μA LBI Input Bias Current (Note 5) V LBI = 150mV 33 100 nA Low-Battery Detector Gain 3000 V/V Switch Leakage Current V SW = 5V ● 0.01 10 μA
TYPICAL PERFORMANCE CHARACTERISTICS UW LT1308B 3.3V Output Efficiency LT1308A 5V Output Efficiency LT1308A 3.3V Output Efficiency Note 4: Switch current limit guaranteed by design and/or correlation to static tests. Duty cycle affects current limit due to ramp generator (see Block Diagram). Note 5: Bias current flows out of LBI pin. Note 6: Connect the four GND pins (Pins 4–7) together at the device. Similarly, connect the three SW pins (Pins 8–10) together and the two V IN pins (Pins 11, 12) together at the device. Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LT1308ACS8, LT1308ACF, LT1308BCS8 and LT1308BCF are designed, characterized and expected to meet the industrial temperature limits, but are not tested at –40°C and 85°C. I grade devices are guaranteed over the –40°C to 85°C operating temperature range. Note 3: Bias current flows into FB pin. LOAD CURRENT (mA) 1 100 1000 1308A/B G01 EFFICIENCY (%) VIN = 1.8V VIN = 2.5V VIN = 1.2V LOAD CURRENT (mA) 1 100 1000 1308A/B G02 EFFICIENCY (%) VIN = 1.8V VIN = 2.5V VIN = 1.2V LOAD CURRENT (mA) EFFICIENCY (%) 10 100 1000 1308A/B G03 VIN = 4.2V VIN = 2.5V VIN = 3.6V VIN = 1.5V ELECTRICAL CHARACTERISTICSThe ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. Industrial Grade – 40°C to 85°C. VIN = 1.2V, VSHDN = VIN, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS fOSC Switching Frequency ● 500 600 750 kHz Maximum Duty Cycle ● 82 90 % Switch Current Limit Duty Cyle = 30% (Note 4) 2 3 4.5 A Switch VCESAT ISW = 2A (25°C, –40°C), VIN = 1.5V 290 350 mV ISW = 2A (85°C), VIN = 1.5V 330 400 mV Burst Mode Operation Switch Current Limit V IN = 2.5V, Circuit of Figure 1 400 mA (LT1308A) Shutdown Pin Current V SHDN = 1.1V ● 2 5 μA VSHDN = 6V ● 20 35 μA VSHDN = 0V 0.01 0.1 μA LBI Threshold Voltage 196 200 204 mV
- 193 200 207 mV LBO Output Low I SINK = 50μA ● 0.1 0.25 V LBO Leakage Current V LBI = 250mV, VLBO = 5V ● 0.01 0.1 μA LBI Input Bias Current (Note 5) V LBI = 150mV 33 100 nA Low-Battery Detector Gain 3000 V/V Switch Leakage Current V SW = 5V ● 0.01 10 μA
TYPICAL PERFORMANCE CHARACTERISTICS UW SHDN PIN VOLTAGE (V) SHDN PIN CURRENT (μA)
1308 G07
–4 0°C 25°C 85°C TEMPERATURE (°C) –50 –25 BIAS CURRENT (nA) 05 0 25 75 100 1308 • G08 LBI FB TEMPERATURE (°C) –50 –25 VREF (mV) 05 0 25 75 100 1308 • G09 203 202 201 200 199 198 197 196 195 TEMPERATURE (°C) –50 –2.5 FREQUENCY (kHz) 05 0 25 75 100 1308 • G10 800 750 700 650 600 550 500 450 400 TEMPERATURE (°C) –50 –25 QUIESCENT CURRENT (μA) 05 0 25 75 100 1308 • G11 180 170 160 150 140 130 120 110 100 TEMPERATURE (°C) –50 –25 VFB (V) 05 0 25 75 100 1308 • G12 1.25 1.24 1.23 1.22 1.21 1.20 1.19 1.18 SHDN Pin Bias Current vs Voltage FB, LBI Bias Current vs Temperature Low Battery Detector Reference vs Temperature Oscillator Frequency vs Temperature LT1308A Quiescent Current vs Temperature Feedback Pin Voltage vs Temperature LT1308B 12V Output Efficiency Switch Saturation Voltage vs Current Switch Current Limit vs Duty Cycle LOAD CURRENT (mA) 1 100 1000 1308A/B G04 EFFICIENCY (%) VIN = 5V VIN = 3.3V SWITCH CURRENT (A) SWITCH VCESAT (mV) 2.0 85°C
1308 G06
0.5 1.0 1.5 500 400 300 200 100 25°C –40°C DUTY CYCLE (%) CURRENT LIMIT (A) 3.0 3.5 1308 • G05 2.5 2.0 20 40 60 100 4.0
VC (Pin 1/Pin 1): Compensation Pin for Error Amplifier. Connect a series RC from this pin to ground. Typical values are 47kΩ and 100pF. Minimize trace area at VC. FB (Pin 2/Pin 2): Feedback Pin. Reference voltage is 1.22V. Connect resistive divider tap here. Minimize trace area at FB. Set VOUT according to: VOUT = 1.22V(1 + R1/R2). SHDN (Pin 3/Pin 3): Shutdown. Ground this pin to turn off switcher. To enable, tie to 1V or more. SHDN does not need to be at VIN to enable the device. GND (Pin 4/Pins 4, 5, 6, 7): Ground. Connect directly to local ground plane. Ground plane should enclose all components associated with the LT1308. PCB copper connected to these pins also functions as a heat sink. For the TSSOP package, connect all pins to ground copper to get the best heat transfer. This keeps chip heating to a minimum. PIN FUNCTIONSUU U (SO/TSSOP) SW (Pin 5/Pins 8, 9, 10): Switch Pins. Connect inductor/ diode here. Minimize trace area at these pins to keep EMI down. For the TSSOP package, connect all SW pins together at the package. V IN (Pin 6/Pins 11, 12): Supply Pins. Must have local bypass capacitor right at the pins, connected directly to ground. For the TSSOP package, connect both V IN pins together at the package. LBI (Pin 7/Pin 13): Low-Battery Detector Input. 200mV reference. Voltage on LBI must stay between –100mV and 1V. Low-battery detector does not function with SHDN pin grounded. Float LBI pin if not used. LBO (Pin 8/Pin 14): Low-Battery Detector Output. Open collector, can sink 50 μA. A 220k Ω pull-up is recom- mended. LBO is high impedance when SHDN is grounded.
Figure 3. LT1308A Exhibits Burst Mode Operation Output
- Q1 and Q2 form a bandgap reference core whose loop
high efficiency even at load currents of 1mA or less. pulls low when the LBI pin voltage drops below 200mV. and the device continues switching at constant frequency. ripple at the expense of efficiency. cated in Figure 1, set to a 5V output. Input voltage is 3V. switching by causing A1’s output to go low.
CESAT and VOUT plus the diode drop. causing interference problems. placement for an SO-8 package boost (step-up) converter. inability to regulate or oscillation. place only, to avoid introducing dI/dt in the ground plane.
1308 F04
Figure 6. Recommended Component Placement for SO-8 similar to the SO-8 package layout. Figure 5. Converter Waveforms in Discontinuous Mode Figure 4. 5V to 12V Boost Converter Waveforms in
Figure 9. Recommended Component Placement for SEPIC Figure 8. SEPIC (Single-Ended Primary
1308 F07
that spans (i.e., can be higher or lower than) the output. age SEPIC is shown in Figure 9.
1308 F09
Figure 7. Recommended Component Placement for TSSOP Boost Converter. Placement is Similar to Figure 4.
ence can also be accessed as shown in Figure 11.
1308 F10
1308 F11
Figure 12. Low-Battery Detector Figure 10. Setting Low-Battery Detector Trip Point Figure 11. Accessing 200mV Reference Figure 12. The LBI pin is swept with an input which varies current rises to 3.5A as the output capacitor is charged. After the output reaches 5V, inductor current is about 1A. voltage reaches 5V in 500μs after the device is enabled. reaches 5V in about 1ms after the device is enabled.
1308 F13
Figure 13. 5V Boost Converter of Figure 1.
causing a current to flow into R3 as V OUT increases.
- Without the soft-start circuit implemented, the inrush
adjusted to achieve any output slew rate desired.
1308 F16
Figure 16. 5V to 12V Boost Converter with Soft-Start Components Q1, C4, R3 and R4.
1308 F15
Figure 15. 5V SEPIC Start-Up from 9V Input into 10Ω Load
1308 F14
Figure 14. 5V Boost Converter of Figure 1.
VENDOR PART NO. VALUE PHONE NO. 220μF tantalum can be evaluated by referring to Figure 3. P, so the ESR of the output capacitor is 60mV/2A or 0.03Ω. Ripple can be further reduced by paralleling ceramic units. VENDOR SERIES PART NO. VALUE PHONE NO. performance similar to the MBRS130. Figure 17. Start-Up Waveforms of Figure 16’s Circuit Figure 18. Start-Up Waveforms of Figure 16’s Circuit
1308 F17
1308 F18
1308 F19
Figure 19. 5V to 12V Boost Converter the regulator loop. This zero is beneficial to loop stability. to optimum levels, as detailed in the following paragraphs. replaced by a 10 μF, X5R dielectric, ceramic capacitor. Without CPL, load step response is pictured in Figure 22. to optimize response using ceramic output capacitors. Figure 21. Load Step Response with 47μF Tantalum
1308 F20
Figure 20. Load Step Response of LT1308B 5V to 12V
1308 F21
1308 F22
Figure 22. Load Step Response with 10μF X5R
Figure 26. LT1308B Li-Ion to 5V Boost Figure 25. LT1308A Li-Ion to 5V Boost Converter Figure 24. Li-Ion to 5V Boost Converter Delivers 1A Burst Mode ripple at 10mA load.
1308 F23
Figure 23. Load Step Response with 10μF X5R
Triple Output TFTLCD Bias Supply 0.22μF 4.7μH VIN SW LT1308B GND VC FB SHDN 0.22μF 220k 10.7k
1308 TA02
76.8k 4.7μF VIN C2, C3 10μF 1μF 1μF 1μF 0.22μF AVDD 10V 500mA VON 27V 15mA VOFF –9V 10mA 100pF C1:TAIYO-YUDEN JMK212BJ475MG C2, C3:TAIYO-YUDEN LMK325BJ106MN C4, C5, C6:TAIYO-YUDEN EMK212BJ105MG D1: MBRM120 D2,D3,D4: BAT54S L1: TOKO 817FY-4R7M AVDD 500mV/DIV VON 500mV/DIV VOFF 500mV/DIV 100μs/DIV ILOAD 800mA 200mA TFTLCD Bias Supply Transient Response
1308 TA04
47μF 10nF 100pF D2D1 34.8k 10M 10nF 250V 10nF 250V 10nF 250V VOUT 350V 1.2mA V IN 2.7V TO 6V 1:12 SHUTDOWN D1, D2, D3: BAV21 200mA, 250V D4: MBR0540 T1: MIDCOM 31105R L P = 1.5μH VIN SW FB LT1308B L1A CTX10-2 L1B 47k 100k 309k 680pF 1308A/B TA05 47μF 220μF 6.3V 4.7μF CERAMIC V OUT 500mA VIN 3V TO 10V VC GND SHDNSHUTDOWN C1: AVX TAJC476M016 C2: TAIYO YUDEN EMK325BJ475(X5R) C3: AVX TPSD227M006 D1: IR 10BQ015 L1: COILTRONICS CTX10-2 SEPIC Converts 3V to 10V Input to a 5V/500mA Regulated Output 40nF EL Panel Driver High Voltage Supply 350V at 1.2mA TYPICAL APPLICATIO SU 47pF 10k 47k 17k 47μF VBAT 3V TO 6V 100pF D3D2 SHUTDOWN 4.3M 1μF 100k 150k 324k 3.3k 22nF 49.9k 400V
1308 TA03
1μF 200V EL PANEL ≤40nF + 3 VIN SW LT1308A GNDVC FBLBO LBI SHDN 3.3V REGULATED 1:12 C1: AVX TAJC476M010 C2: VITRAMON VJ225Y105KXCAT D1: BAT54 D2, D3: BAV21 Q1: MMBT3906 Q2: ZETEX FCX458 T1: MIDCOM 31105
.016 – .050 (0.406 – 1.270) .010 – .020 0°– 8° TYP .008 – .010 (0.203 – 0.254) SO8 0303 .053 – .069 (1.346 – 1.752) .014 – .019 (0.355 – 0.483) TYP .004 – .010 (0.101 – 0.254) .050 (1.270) BSC 1 2 3 4 .150 – .157 (3.810 – 3.988) NOTE 3 8 7 6 5 .189 – .197 (4.801 – 5.004) NOTE 3 .228 – .244 (5.791 – 6.197) .245 MIN .160 ±.005 RECOMMENDED SOLDER PAD LAYOUT .045 ±.005 .050 BSC .030 ±.005 TYP INCHES (MILLIMETERS) NOTE: 1. DIMENSIONS IN 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610)
14-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1650) PACKAGE DESCRIPTIONU F14 TSSOP 0204 0.09 – 0.20 (.0035 – .0079) 0° – 8° 0.25 REF 0.50 – 0.75 (.020 – .030) 4.30 – 4.50** (.169 – .177) 6.40 (.252) BSC 13 4 5 6 7 4.90 – 5.10* (.193 – .201) 14 13 12 11 10 9 1.10 (.0433) MAX 0.05 – 0.15 (.002 – .006) 0.65 (.0256) BSC 0.19 – 0.30 (.0075 – .0118) TYP MILLIMETERS (INCHES) DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED .152mm (.006") PER SIDE DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED .254mm (.010") PER SIDE NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ARE IN 3. DRAWING NOT TO SCALE 1.05 ± 0.10 0.65 BSC0.45 ± 0.05 RECOMMENDED SOLDER PAD LAYOUT 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.
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