LTC3331 Nanopower Buck-Boost DC/DC with Energy Harvesting Battery Charger DESCRIPTION FEATURES Dual Input, Single Output DC/DCs with Input Prioritizer nn Energy Harvesting Input: 3.0V to 19V Buck DC/DC nn Battery Input: Up to 4.2V Buck-Boost DC/DC nn 10mA Shunt Battery Charger with Programmable Float Voltages: 3.45V, 4.0V, 4.1V, 4.2V nn Low Battery Disconnect nn Ultra Low Quiescent Current: 950nA at no Load nn Integrated Supercapacitor Balancer nn Up to 50mA of Output Current nn Programmable DC/DC Output Voltage, Buck UVLO, and Buck-Boost Peak Input Current nn Integrated Low-Loss Full-Wave Bridge Rectifier nn Input Protective Shunt: Up to 25mA at V ≥ 20V IN nn 5mm × 5mm QFN-32 Package The LTC®3331 integrates a high voltage energy harvesting power supply plus a buck-boost DC/DC powered from a rechargeable battery to create a single output supply for alternative energy applications. A 10mA shunt allows simple charging of the battery with harvested energy while a low battery disconnect function protects the battery from deep discharge. The energy harvesting power supply, consisting of an integrated full-wave bridge rectifier and a high voltage buck DC/DC, harvests energy from piezoelectric, solar, or magnetic sources. Either DC/DC converter can deliver energy to a single output. The buck operates when harvested energy is available, reducing the quiescent current draw on the battery to the 200nA required by the shunt charger, thereby extending the life of the battery. The buck-boost powers VOUT only when harvested energy is unavailable. APPLICATIONS A supercapacitor balancer is also integrated, allowing for increased energy storage. Voltage and current settings for both inputs and outputs are programmable via pinstrapped logic inputs. The LTC3331 is available in a 5mm × 5mm QFN-32 package. nn Energy Harvesting Solar Powered Systems with Battery Backup nn Wireless HVAC Sensors and Security Devices nn Mobile Asset Tracking nn nn L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION + 3V TO 19V SOLAR PANEL – AC1 AC2 VIN SW 1µF 6.3V 22µF 25V 4.7µF, 6.3V 100k LTC3331 SWB VIN2 VOUT CHARGE SCAP BAL 4.7µF 6.3V PGVOUT 2 FLOAT[1:0] OUT[2:0] IPK[2:0] LBSEL SHIP UV[3:0] GND VIN3 47µF 6.3V 10mF 2.7V EH_ON BAT_IN Li-Ion BATTERY 1.8V TO 5V 50mA 10mF 2.7V BAT_OUT Charging a Battery with Harvested Energy VOUT 50mV/DIV AC-COUPLED BB_IN 4.7µF 6.3V + 22µH SWA CAP PIEZO MIDE V25W 22µH 3 OPTIONAL EH_ON 4V/DIV 0V IBB_IN 200mA/DIV 0A 0A ICHARGE 1mA/DIV ACTIVE ENERGY HARVESTER ENABLES CHARGING OF THE BATTERY IN SLEEP 3 BAT = 3.6V VOUT = 1.8V ILOAD = 50mA 4 100µs/DIV 3331 TA01b 0.1µF 6.3V 3331 TA01a 3331fc For more information www.linear.com/LTC3331 1 LTC3331 SHIP VIN3 CHARGE PGVOUT EH_ON OUT0 OUT1 TOP VIEW OUT2 32 31 30 29 28 27 26 25 BAL 1 24 FLOAT0 SCAP 2 23 FLOAT1 VIN2 3 22 LBSEL UV3 4 21 BAT_IN 33 GND UV2 5 20 BAT_OUT UV1 6 19 IPK2 UV0 7 18 IPK1 AC1 8 17 IPK0 BB_IN SWA SWB VOUT SW 9 10 11 12 13 14 15 16 CAP VIN Low Impedance Source...........................–0.3 to 19V* Current-Fed, ISW = 0A.........................................25mA AC1, AC2..............................................................0 to VIN BB_IN, VOUT, VIN3, BAT_IN, SCAP, PGVOUT, CHARGE, SHIP.................................................–0.3 to 6V BAT_OUT..... –0.3V to [Lesser of (BAT_IN + 0.3V) or 6V] VIN2.....................–0.3V to [Lesser of (VIN + 0.3V)] or 6V CAP....................... [Higher of –0.3V or (VIN – 6V)] to VIN BAL.............................................–0.3V to (SCAP + 0.3V) OUT[2:0]........... –0.3V to [Lesser of (VIN3 + 0.3V) or 6V] IPK[2:0]............ –0.3V to [Lesser of (VIN3 + 0.3V) or 6V] EH_ON.............. –0.3V to [Lesser of (VIN3 + 0.3V) or 6V] FLOAT[1:0].... –0.3V to [Lesser of (BB_IN + 0.3V) or 6V] LBSEL............ –0.3V to [Lesser of (BB_IN + 0.3V) or 6V] UV[3:0]............. –0.3V to [Lesser of (VIN2 + 0.3V) or 6V] IAC1, IAC2...............................................................±50mA ISWA, ISWB, IVOUT..................................................350mA ISW........................................................................500mA Operating Junction Temperature Range (Notes 2, 3)............................................. –40°C to 125°C Storage Temperature Range................... –65°C to 150°C PIN CONFIGURATION VIN (Note 1) AC2 ABSOLUTE MAXIMUM RATINGS UH PACKAGE 32-LEAD (5mm × 5mm) PLASTIC QFN TJMAX = 125°C, θJA = 44°C/W EXPOSED PAD (PIN 33) IS GND, MUST BE SOLDERED TO PCB *VIN has an internal 20V clamp ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3331EUH#PBF LTC3331EUH#TRPBF 3331 32-Lead (5mm × 5mm) Plastic QFN –40°C to 85°C LTC3331IUH#PBF LTC3331IUH#TRPBF 3331 32-Lead (5mm × 5mm) Plastic QFN –40°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. 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/ 2 3331fc For more information www.linear.com/LTC3331 LTC3331 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 5V, BAT_IN = BAT_OUT = BB_IN = 3.6V, SHIP = OV, SCAP = 0V unless otherwise specified. SYMBOL PARAMETER VIN Buck Input Voltage Range VBB_IN Buck-Boost Input Voltage Range (Note 7) IVIN VIN Quiescent Current VIN Input in UVLO VIN Input in UVLO Buck Enabled, Sleeping Buck Enabled, Sleeping Buck Enabled, Not Sleeping VIN = 2.5V, VBB_IN = 0V VIN = 16V, VBB_IN = 0V VIN = 4V, VBB_IN = 0V VIN = 18V, VBB_IN = 0V VIN = 5V, VBB_IN = 0V, ISW = 0A (Note 4) IBB_IN BB_IN Quiescent Current (Note 6) BB_IN Input with VIN Active VBB_IN = 3.6V, VIN = 5V Buck-Boost Enabled, Sleeping VBB_IN = 3.6V, VIN = 0V Buck-Boost Enabled, Not Sleeping VBB_IN = 3.6V, VIN = 0V, ISWA = ISWB = 0A (Note 4) VOUT Leakage Current 5V Output Selected, Sleeping IVOUT CONDITIONS MIN TYP UNITS 19 V 5.5 V 450 800 1300 1800 150 700 1400 2000 2700 225 nA nA nA nA µA 200 950 200 300 1500 300 nA nA µA l l MAX 1.8 100 150 nA VIN Undervoltage Lockout Thresholds 3V Level Selected (Rising or Falling) 4V Level Selected l 2.91 3.00 3.09 V l 3.88 4.00 4.12 V 5V Level Selected l 4.85 5.00 5.15 V 6V Level Selected l 5.82 6.00 6.18 V 7V Level Selected l 6.79 7.00 7.21 V 8V Level Selected l 7.76 8.00 8.24 V 9V Level Selected l 8.73 9.00 9.27 V 10V Level Selected l 9.70 10.0 10.30 V 11V Level Selected l 10.67 11.0 11.33 V 12V Level Selected l 11.64 12.0 12.36 V 13V Level Selected l 12.61 13.0 13.39 V 14V Level Selected l 13.58 14.0 14.42 V 15V Level Selected l 14.55 15.0 15.45 V 16V Level Selected l 15.52 16.0 16.48 V 17V Level Selected l 16.49 17.0 17.51 V 18V Level Selected l 17.46 18.0 18.54 V IVIN = 1mA l 19.0 20.0 21.0 V 800 1550 900 1750 mV mV 20 nA VSHUNT VIN Shunt Regulator Voltage ISHUNT Maximum Protective Shunt Current 25 Internal Bridge Rectifier Loss (|VAC1 – VAC2| – VIN) IBRIDGE = 10µA IBRIDGE = 50mA Internal Bridge Rectifier Reverse Leakage Current VREVERSE = 18V Internal Bridge Rectifier Reverse Breakdown Voltage IREVERSE = 1µA 700 1350 VSHUNT mA 30 V 3331fc For more information www.linear.com/LTC3331 3 LTC3331 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 5V, BAT_IN = BAT_OUT = BB_IN = 3.6V, SHIP = OV, SCAP = 0V unless otherwise specified. SYMBOL PARAMETER CONDITIONS VOUT Regulated Buck/Buck-Boost Output Voltage 1.8V Output Selected Sleep Threshold Wake-Up Threshold IPEAK_BB 4 MIN TYP MAX UNITS l l 1.728 1.806 1.794 1.872 V V 2.5V Output Selected Sleep Threshold Wake-Up Threshold l l 2.425 2.508 2.492 2.575 V V 2.8V Output Selected Sleep Threshold Wake-Up Threshold l l 2.716 2.809 2.791 2.884 V V 3.0V Output Selected Sleep Threshold Wake-Up Threshold l l 2.910 3.010 2.990 3.090 V V 3.3V Output Selected Sleep Threshold Wake-Up Threshold l l 3.200 3.311 3.289 3.400 V V 3.6V Output Selected Sleep Threshold Wake-Up Threshold l l 3.492 3.612 3.588 3.708 V V 4.5V Output Selected Sleep Threshold Wake-Up Threshold l l 4.365 4.515 4.485 4.635 V V 5.0V Output Selected Sleep Threshold Wake-Up Threshold l l 4.850 5.017 4.983 5.150 V V PGVOUT Falling Threshold As a Percentage of VOUT Target (Note 5) l 88 92 96 % Buck-Boost Peak Switch Current 250mA Target Selected 200 250 350 mA 150mA Target Selected 120 150 210 mA 100mA Target Selected 80 100 140 mA 50mA Target Selected 40 50 70 mA 25mA Target Selected 20 25 35 mA 15mA Target Selected 12 15 21 mA 10mA Target Selected 8 10 14 mA 5mA Target Selected 4 5 7 mA 50 Available Buck-Boost Current IPEAK_BB = 250mA, VOUT = 3.3V Buck-Boost PMOS Input and Output Switch On-Resistance IPK[2:0] = 111 IPK[2:0] = 110 IPK[2:0] = 101 IPK[2:0] = 100 IPK[2:0] = 011 IPK[2:0] = 010 IPK[2:0] = 001 IPK[2:0] = 000 0.8 1.0 1.4 2.4 4.5 7.3 10.7 20.5 mA Ω Ω Ω Ω Ω Ω Ω Ω Buck-Boost NMOS Input and Output Switch On-Resistance IPK2 = 1 IPK2 = 0 0.6 3.9 Ω Ω 3331fc For more information www.linear.com/LTC3331 LTC3331 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 5V, BAT_IN = BAT_OUT = BB_IN = 3.6V, SHIP = OV, SCAP = 0V unless otherwise specified. SYMBOL IPEAK_BUCK PARAMETER CONDITIONS MIN PMOS Switch Leakage Buck/Buck-Boost Regulators –20 20 nA NMOS Switch Leakage Buck/Buck-Boost Regulators –20 20 nA Maximum Buck Duty Cycle Buck/Buck-Boost Regulators l 200 Available Buck Output Current 100 UNITS % 250 500 mA mA Buck PMOS Switch On-Resistance 1.4 Ω Buck NMOS Switch On-Resistance 1.2 Ω Maximum Battery Shunt Current 10 Battery Disconnect Leakage Current Battery Disconnected SHIP Mode Engaged VFLOAT Shunt Charger Float Voltage (BAT_OUT Voltage) FLOAT[1:0] = 00, IBB_IN = 1mA FLOAT[1:0] = 01, IBB_IN = 1mA FLOAT[1:0] = 10, IBB_IN = 1mA FLOAT[1:0] = 11, IBB_IN = 1mA Low Battery Disconnect Threshold, BAT_IN Voltage (Falling) VLBC_BAT_IN Low Battery Connect Threshold, BAT_IN Voltage (Rising) VLBC_BAT_ OUT MAX 100 Buck Peak Switch Current IBAT_IN VLBD TYP mA –10 –10 0 0 10 10 nA nA 3.415 3.960 4.059 4.158 3.45 4.0 4.1 4.2 3.485 4.040 4.141 4.242 V V V V FLOAT[1:0] = 00, IBB_IN = 1mA FLOAT[1:0] = 01, IBB_IN = 1mA FLOAT[1:0] = 10, IBB_IN = 1mA FLOAT[1:0] = 11, IBB_IN = 1mA l l l l 3.381 3.920 4.018 4.116 3.45 4.0 4.1 4.2 3.519 4.080 4.182 4.284 V V V V LBSEL = 0, FLOAT[1:0] = 00, IBAT_IN = –1mA LBSEL = 1, FLOAT[1:0] = 00, IBAT_IN = –1mA LBSEL = 0, FLOAT[1:0] = 01, 10, 11, IBAT_IN = –1mA LBSEL = 1, FLOAT[1:0] = 01, 10, 11, IBAT_IN = –1mA l l l l 1.98 2.43 2.62 3.10 2.04 2.51 2.70 3.20 2.10 2.59 2.78 3.30 V V V V 2.26 2.74 2.91 3.39 2.35 2.85 3.03 3.53 2.44 2.96 3.15 3.67 V V V V LBSEL = 0, FLOAT[1:0] = 00, IBAT_IN = –1mA LBSEL = 1, FLOAT[1:0] = 00, IBAT_IN = –1mA LBSEL = 0, FLOAT[1:0] = 01, 10, 11, IBAT_IN = –1mA LBSEL = 1, FLOAT[1:0] = 01, 10, 11, IBAT_IN = –1mA Low Battery Connect Threshold, BAT_OUT Voltage (Rising) LBSEL = 0, FLOAT[1:0] = 00 LBSEL = 1, FLOAT[1:0] = 00 LBSEL = 0, FLOAT[1:0] = 01, 10, 11 LBSEL = 1, FLOAT[1:0] = 01, 10, 11 Battery Disconnect PMOS On-Resistance BAT_IN = 3.3V, IBAT_IN = 10mA Charge Pin Current Current Out of CHARGE Pin CHARGE Pin Voltage PMOS On-Resistance 2mA Out of CHARGE Pin 3.02 3.52 3.70 4.20 V V V V 5 Ω 1 2 l 60 Ω VSCAP Supercapacitor Balancer Input Range ISCAP Supercapacitor Balancer Quiescent Current SCAP = 5.0V Supercapacitor Balancer Source Current SCAP = 5.0V, BAL = 2.4V 10 mA Supercapacitor Balancer Sink Current SCAP = 5.0V, BAL = 2.6V 10 mA l 2.5 mA mA 150 5.5 V 225 nA 3331fc For more information www.linear.com/LTC3331 5 LTC3331 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 5V, BAT_IN = BAT_OUT = BB_IN = 3.6V, SHIP = OV, SCAP = 0V unless otherwise specified. SYMBOL PARAMETER CONDITIONS VBAL Supercapacitor Balance Point Percentage of SCAP Voltage VIH Digital Input High Voltage Pins: OUT[2:0], SHIP, FLOAT[1:0], LBSEL, IPK[2:0], UV[3:0] VIL Digital Input Low Voltage Pins: OUT[2:0], SHIP, FLOAT[1:0], LBSEL, IPK[2:0], UV[3:0] l IIH Digital Input High Current Pins: OUT[2:0], SHIP, FLOAT[1:0], LBSEL, IPK[2:0], UV[3:0] IIL Digital Input Low Current Pins: OUT[2:0], SHIP, FLOAT[1:0], LBSEL, IPK[2:0], UV[3:0] VOH PGVOUT, Output High Voltage EH_ON Output High Voltage BB_IN = 5V, 1µA Out of Pin VIN = 6V, 1µA Out of Pin VOL PGVOUT, EH_ON Output Low Voltage BB_IN = 5V, 1µA into Pin 6000 VIN Quiescent Current in Sleep vs VIN IVIN (nA) IVIN (nA) 85°C 800 25°C –40°C 0 3 6 9 VIN (V) 12 85°C 25°C 1000 15 18 3331 G01 0.4 V 0 10 nA 0 10 nA V V 0.4 V BAT_OUT TIED TO BB_IN 125°C 1750 3000 0 V 4.0 3.8 2500 3 6 12 9 VIN (V) 85°C 1250 1000 25°C 750 –40°C 250 18 15 1500 500 –40°C 200 0 % Buck-Boost Quiescent Current in Sleep vs BB_IN 125°C 2000 600 400 51 2000 4000 1400 1000 50 1.2 UNITS TA = 25°C, unless otherwise noted. 5000 1600 1200 49 l 2250 125°C 1800 l l IBB_IN (nA) 2000 MAX l l TYPICAL PERFORMANCE CHARACTERISTICS 2200 TYP Note 3: TJ is calculated from the ambient TA and power dissipation PD according to the following formula: TJ = TA + (PD • θJA). Note 4: Dynamic supply current is higher due to gate charge being delivered at the switching frequency. Note 5: The PGVOUT Rising threshold is equal to the sleep threshold. See VOUT specification. Note 6: These quiescent currents include the contribution from the internal resistor divider at the BAT_OUT pin as BAT_OUT must be tied to BB_IN for all applications. Note 7: The buck-boost operating voltage is further constrained to a narrower range by the programmed float voltage and the selected low battery disconnect and connect thresholds. 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 LTC3331 is tested under pulsed load conditions such that TJ ≈ TA. The LTC3331E is guaranteed to meet specifications from 0°C to 85°C. The LTC3331I is guaranteed over the –40°C to 125°C operating junction temperature range. Note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal impedance and other environmental factors. VIN Quiescent Current in UVLO vs VIN MIN 3331 G02 0 2.1 2.4 2.7 3.3 3 BB_IN (V) 3.6 3.9 4.2 3331 G03 6 3331fc For more information www.linear.com/LTC3331 LTC3331 TYPICAL PERFORMANCE CHARACTERISTICS VOUT Quiescent Current vs Temperature UVLO Threshold vs Temperature 130 IVOUT (nA) 120 110 100 90 80 70 60 50 –50 0 25 50 75 TEMPERATURE (°C) –25 100 APPLIES TO EACH UVLO SETTING 20.6 20.4 101 100 99 125 –25 0 25 50 75 TEMPERATURE (°C) 100 85°C 600 125°C 400 200 0 1µ 10µ 100µ 1m BRIDGE CURRENT (A) 10m 1.6 1.4 12 1.2 10 8 0.6 0.4 2 0.2 WAKE-UP THRESHOLD VOUT (V) VOUT (V) 2.75 2.40 2.35 1.70 100 125 3331 G10 2.25 –50 2.70 2.65 2.30 PGVOUT FALLING 10M 100M SLEEP THRESHOLD WAKE-UP THRESHOLD 1.72 10k 100k 1M FREQUENCY (Hz) 2.80 2.45 1.74 1k 2.8V Output vs Temperature SLEEP THRESHOLD 1.76 0 25 50 75 TEMPERATURE (°C) 100 2.85 2.50 WAKE-UP THRESHOLD –25 10 3331 G09 2.5V Output vs Temperature 1.80 VOUT (V) 0 170 35 80 125 TEMPERATURE (°C) 3331 G08 SLEEP THRESHOLD 1.66 0.8 4 2.55 1.68 1.0 6 1.8V Output vs Temperature 1.64 –50 4.8VP-P APPLIED TO AC1/AC2 INPUT 1.8 MEASURED IN UVLO 14 –10 125 Bridge Frequency Response 16 0 –55 1.84 1.78 100 2.0 VIN = 18V, LEAKAGE AT AC1 OR AC2 3331 G07 1.82 0 25 50 75 TEMPERATURE (°C) 3331 G06 VIN (V) BRIDGE LEAKAGE (nA) BRIDGE DROP (mV) 25°C –25 3331 G05 18 1200 800 19.0 –50 125 Bridge Leakage vs Temperature –40°C ISHUNT = 1mA 19.8 19.2 |VAC1 – VAC2| – VIN 1000 20.0 19.4 97 –50 20 1400 ISHUNT = 25mA 20.2 19.6 98 Total Bridge Rectifier Drop vs Bridge Current 1600 VSHUNT vs Temperature 20.8 102 3331 G04 1800 21.0 VSHUNT (V) VOUT IN REGULATION, SLEEPING 140 103 PERCENTAGE OF TARGET SETTING (%) 150 TA = 25°C, unless otherwise noted. 2.60 PGVOUT FALLING –25 0 25 50 75 TEMPERATURE (°C) 100 125 3331 G11 2.55 –50 PGVOUT FALLING –25 0 25 50 75 TEMPERATURE (°C) 100 125 3331 G12 3331fc For more information www.linear.com/LTC3331 7 LTC3331 TYPICAL PERFORMANCE CHARACTERISTICS 3V Output vs Temperature 3.3V Output vs Temperature 3.05 3.35 3.6V Output vs Temperature 3.65 SLEEP THRESHOLD SLEEP THRESHOLD WAKE-UP THRESHOLD VOUT (V) 2.90 2.85 2.80 WAKE-UP THRESHOLD 3.25 3.20 3.15 2.75 –25 0 25 50 75 TEMPERATURE (°C) 100 3.00 –50 125 –25 0 25 50 75 TEMPERATURE (°C) 300 SLEEP THRESHOLD SLEEP THRESHOLD 4.50 270 VOUT (V) 4.30 IPEAK_BB (mA) 4.90 4.35 4.80 4.70 4.25 4.10 –50 –25 210 0 25 50 75 TEMPERATURE (°C) 100 4.50 –50 125 –25 0 25 50 75 TEMPERATURE (°C) 3331 G16 200 –50 125 1.40 1.10 5.2 1.00 4.8 40 0.90 0.80 30 25 20 15 4.4 0.60 10 4.2 0.50 5 4.0 –50 0.40 –50 100 125 3331 G19 –25 50 25 0 75 TEMPERATURE (°C) 100 125 3331 G20 8 125 35 0.70 0 25 50 75 TEMPERATURE (°C) 100 PMOS, BB_IN = 2.1V NMOS, BB_IN = 2.1V PMOS, BB_IN = 4.2V NMOS, BB_IN = 4.2V 45 4.6 –25 0 25 50 75 TEMPERATURE (°C) RDS(ON) of Buck-Boost PMOS/NMOS vs Temperature, 5mA IPEAK Setting 50 RDS(ON) (Ω) 5.4 RDS(ON) (Ω) 1.20 55 PMOS, BB_IN = 2.1V NMOS, BB_IN = 2.1V PMOS, BB_IN = 4.2V NMOS, BB_IN = 4.2V 1.30 5.6 5.0 –25 3331 G18 RDS(ON) of Buck-Boost PMOS/NMOS vs Temperature, 250mA IPEAK Setting BB_IN = 3.6V 5.8 100 3331 G17 Buck-Boost Peak Current vs Temperature, 5mA IPEAK Setting 6.0 250 240 220 4.60 PGVOUT FALLING 4.15 260 230 PGVOUT FALLING 4.20 125 280 WAKE-UP THRESHOLD WAKE-UP THRESHOLD 100 BB_IN = 3.6V 290 5.00 4.40 0 25 50 75 TEMPERATURE (°C) Buck-Boost Peak Current vs Temperature, 250mA IPEAK Setting 5.10 4.45 –25 3331 G15 5V Output vs Temperature 4.60 VOUT (V) 3.25 –50 125 100 3331 G14 4.5V Output vs Temperature 4.55 PGVOUT FALLING 3.30 3331 G13 IPEAK_BB (mA) 3.45 3.35 PGVOUT FALLING 3.05 2.70 –50 3.50 3.40 3.10 PGVOUT FALLING WAKE-UP THRESHOLD 3.55 VOUT (V) 2.95 SLEEP THRESHOLD 3.60 3.30 3.00 VOUT (V) TA = 25°C, unless otherwise noted. 0 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 3331 G21 3331fc For more information www.linear.com/LTC3331 LTC3331 TYPICAL PERFORMANCE CHARACTERISTICS Buck Peak Current vs Temperature RDS(ON) of Buck PMOS/NMOS vs Temperature 300 2.0 VIN = 5V 290 Buck-Boost Load Regulation, VOUT = 3.3V 3.40 COUT = 100µF 3.38 L = 22µH IPK[2:0] = 111 3.36 VIN = 5V 1.8 280 270 3.34 1.6 260 250 240 PMOS 1.4 NMOS 1.2 230 220 VOUT (V) RDS(ON) (Ω) IPEAK_BUCK (mA) TA = 25°C, unless otherwise noted. BB_IN = 4.1V 3.30 BB_IN = 2.1V 3.28 3.26 3.24 1.0 210 3.22 200 –50 –25 0 25 50 75 TEMPERATURE (°C) 100 125 0.8 –50 –25 0 25 50 75 TEMPERATURE (°C) 100 3.400 OUTPUT VOLTAGE 50mV/DIV AC-COUPLED SWA VOLTAGE 0V 2V/DIV LOAD = 1mA LOAD = 50mA 3.250 INDUCTOR CURRENT 0mA 200mA/DIV 3.225 2.7 3.3 3 BB_IN (V) 3.6 10m 100m 3.350 SWB VOLTAGE 2V/DIV 0V 3.300 2.4 100µ 1m ILOAD (A) 3.9 8µs/DIV BAT = 2.1V, VOUT = 3.3V ILOAD = 10mA L = 22µH, COUT = 100µF 4.2 VIN = 4V COUT = 100µF L = 22µH 3.375 VOUT (V) COUT = 100µF 3.375 L = 22µH IPK[2:0] = 111 3.350 3.200 2.1 10µ Buck Load Regulation, 3.3V Buck-Boost Switching Waveforms 3.400 3.275 1µ 3331 G24 Buck-Boost Line Regulation, VOUT = 3.3V 3.325 3.20 125 3331 G23 3331 G22 VOUT (V) 3.32 3.325 3.300 3.275 3.250 3331 G26 3.225 3.200 1µ 10µ 100µ 1m ILOAD (A) 10m 100m 3331 G27 3331 G25 Buck Line Regulation, 3.3V 3.400 COUT = 100µF L = 22µH 3.375 VOUT (V) 3.350 3.325 OUTPUT VOLTAGE 50mV/DIV DC-COUPLED, OFFSET = 3.3V OUTPUT VOLTAGE 50mV/DIV AC-COUPLED EH_ON 5V/DIV SW VOLTAGE 10V/DIV 0V LOAD = 1mA 3.300 0V BUCK INDUCTOR CURRENT 200mA/DIV BUCK-BOOST 0mA INDUCTOR CURRENT 0mA 200mA/DIV LOAD = 100mA 3.275 INDUCTOR CURRENT 200mA/DIV 3.250 3.225 3.200 Prioritizer Buck to Buck-Boost Transition Buck Switching Waveforms 4 6 8 10 12 VIN (V) 14 16 18 3331 G28 0mA 8µs/DIV VIN = 18V, VOUT = 3.3V ILOAD = 10mA L = 22µH, COUT = 100µF 3331 G29 3331 G30 100µs/DIV VIN TRANSITIONS 18V TO 17V, UV[3:0] = 1110 BB_IN = 4.1V, VOUT = 3.3V ILOAD = 50mA, COUT = 100µF, LBUCK = 22µH, LBUCK-BOOST = 22µH 3331fc For more information www.linear.com/LTC3331 9 LTC3331 TYPICAL PERFORMANCE CHARACTERISTICS Buck-Boost Load Step Response LOAD CURRENT 25mA/DIV 1mA OUTPUT VOLTAGE 50mV/DIV DC-COUPLED, OFFSET = 3.3V LOAD CURRENT 25mA/DIV 1mA 2ms/DIV BB_IN = 3V, VOUT = 3.3V COUT = 100µF, L = 22µH LOAD STEP FROM 1mA TO 50mA 3331 G31 2ms/DIV VIN = 18V, VOUT = 3.3V COUT = 100µF, L = 22µH LOAD STEP FROM 1mA TO 50mA 100 80 3331 G33 100µs/DIV VIN TRANSITIONS 17V TO 18V, UV[3:0] = 1110 BB_IN = 4.1V, VOUT = 3.3V ILOAD = 50mA, COUT = 100µF, LBUCK = 22µH, LBUCK-BOOST = 22µH VOUT = 1.8V VOUT = 2.5V VOUT = 2.8V VOUT = 3V 95 Buck Efficiency vs VIN for ILOAD = 100mA, L = 100µH 100 VOUT = 3.3V VOUT = 3.6V VOUT = 4.5V VOUT = 5V VOUT = 1.8V VOUT = 2.5V VOUT = 2.8V VOUT = 3V 95 VOUT = 3.3V VOUT = 3.6V VOUT = 4.5V VOUT = 5V 60 50 40 VOUT = 1.8V VOUT = 2.5V VOUT = 3.3V VOUT = 5V 30 20 10 0 10µ 100µ 1m ILOAD (A) 10m 90 85 80 VIN = 6V, L = 22µH, DCR = 0.19Ω 1µ EFFICIENCY (%) 70 EFFICIENCY (%) 75 100m DCR = 0.19Ω 4 6 3331 G34 Buck Efficiency vs VIN, for VOUT = 3.3V 90 85 80 8 10 12 VIN (V) 14 16 75 18 Buck-Boost Efficiency vs ILOAD, 250mA IPEAK Setting 100 100 90 90 80 80 80 70 70 70 100 L = 22µH, DCR = 0.19Ω EFFICIENCY (%) 90 60 50 40 30 ILOAD = 100mA ILOAD =100µA ILOAD =50µA ILOAD =30µA 20 10 0 4 10 6 8 10 12 VIN (V) ILOAD =20µA ILOAD =10µA ILOAD =5µA 14 16 60 50 40 30 VOUT = 1.8V VOUT = 2.5V VOUT = 3.3V VOUT = 5.0V 20 18 3331 G37 BAT = 3.6V 10 L = 22µH RL = 0.36Ω 0 1µ 10µ 1m 100µ ILOAD (A) DCR = 0.45Ω 4 6 8 3331 G35 EFFICIENCY (%) EFFICIENCY (%) 3331 G32 EH_ON 5V/DIV 0V BUCK INDUCTOR CURRENT 200mA/DIV 0mA BUCK-BOOST INDUCTOR CURRENT 0mA 200mA/DIV Buck Efficiency vs VIN for ILOAD = 100mA, L = 22µH Buck Efficiency vs ILOAD 90 EFFICIENCY (%) Prioritizer Buck-Boost to Buck Transition Buck Load Step Response OUTPUT VOLTAGE 20mV/DIV AC-COUPLED OUTPUT VOLTAGE 20mV/DIV AC-COUPLED 100 TA = 25°C, unless otherwise noted. 10m 3331 G39 10 12 VIN (V) 14 16 18 3331 G36 Buck-Boost Efficiency vs ILOAD, 5mA IPEAK Setting 60 50 40 30 VOUT = 1.8V VOUT = 2.5V VOUT = 3.3V VOUT = 5.0V 20 BAT = 3.6V 10 L = 22µH DCR = 5.1Ω 0 10µ 1µ 100µ ILOAD (A) 1m 3331 G38 3331fc For more information www.linear.com/LTC3331 LTC3331 TYPICAL PERFORMANCE CHARACTERISTICS 90 80 70 ILOAD = 50mA ILOAD = 100µA ILOAD = 50µA ILOAD = 20µA ILOAD = 10µA ILOAD = 5µA 60 50 40 2.1 2.4 2.7 3.3 3 BB_IN (V) 3.9 90 70 ILOAD = 50mA ILOAD = 100µA ILOAD = 50µA ILOAD = 20µA ILOAD = 10µA ILOAD = 5µA 60 50 3.6 40 2.1 4.2 2.4 2.7 3.3 3 BB_IN (V) 3.6 3.9 90 80 70 ILOAD = 1mA ILOAD = 100µA ILOAD = 50µA ILOAD = 20µA ILOAD = 10µA ILOAD = 5µA 60 50 40 2.1 2.4 2.7 3.3 3 BB_IN (V) 3.9 100 L = 1000µH DCR = 5.1Ω 90 ILOAD = 1mA ILOAD = 100µA ILOAD = 50µA ILOAD = 20µA ILOAD = 10µA ILOAD = 5µA 60 40 2.1 4.25 3.55 4.20 2.4 2.7 3.3 3 BB_IN (V) 3.6 3.9 3.95 75 50 25 TEMPERATURE (°C) 100 125 3331 G46 2.4 2.7 3.3 3 BB_IN (V) 3.9 3.6 3.90 –50 –25 75 50 25 TEMPERATURE (°C) 0 4.2 3331 G45 8 IBB_IN = 1mA 4.05 3.30 0 ILOAD = 1mA ILOAD = 100µA ILOAD = 50µA ILOAD = 20µA ILOAD = 10µA ILOAD = 5µA 60 Shunt Float Voltage Load Regulation 4.10 4.00 4.2 70 40 2.1 4.2 4.15 3.35 3.25 –50 –25 3.9 3.6 L = 1000µH DCR = 5.1Ω 50 FLOAT VOLTAGE DEVIATION (mV) 3.60 FLOAT VOLTAGE (V) FLOAT VOLTAGE (V) 4.30 IBB_IN = 1mA 3.40 3.3 3 BB_IN (V) 80 4V, 4.1V, 4.2V Float Voltage vs Temperature 3.45 2.7 3331 G44 3.45V Float Voltage vs Temperature 3.50 2.4 Buck-Boost Efficiency vs BB_IN for VOUT = 5V, 5mA IPEAK Setting 3331 G43 3.65 ILOAD = 50mA ILOAD = 100µA ILOAD = 50µA ILOAD = 20µA ILOAD = 10µA ILOAD = 5µA 60 Buck-Boost Efficiency vs BB_IN for VOUT = 3.3V, 5mA IPEAK Setting 70 4.2 70 3331 G42 50 3.6 80 3331 G41 80 EFFICIENCY (%) EFFICIENCY (%) 90 100 L = 1000µH DCR = 5.1Ω L = 22µH DCR = 0.36Ω 40 2.1 4.2 EFFICIENCY (%) 100 Buck-Boost Efficiency vs BB_IN for VOUT = 5V, 250mA IPEAK Setting 50 3331 G40 Buck-Boost Efficiency vs BB_IN for VOUT = 1.8V, 5mA IPEAK Setting 100 L = 22µH DCR = 0.36Ω 80 EFFICIENCY (%) EFFICIENCY (%) 90 100 L = 22µH DCR = 0.36Ω Buck-Boost Efficiency vs BB_IN for VOUT = 3.3V, 250mA IPEAK Setting EFFICIENCY (%) 100 Buck-Boost Efficiency vs BB_IN for VOUT = 1.8V, 250mA IPEAK Setting TA = 25°C, unless otherwise noted. 100 125 3331 G47 ALL FLOAT SETTINGS IN SLEEP 7 6 5 4 3 2 1 0 1µ 10µ 100µ IBB_IN (A) 1m 10m 3331 G48 3331fc For more information www.linear.com/LTC3331 11 LTC3331 TYPICAL PERFORMANCE CHARACTERISTICS Battery Connect Voltage at BAT_IN vs IBAT_OUT 4.2 800 4.0 700 3.8 BAT_IN VOLTAGE (V) 4.4 900 PMOS BODY DIODE DROP (mV) 1000 –40°C 25°C 500 85°C 400 300 200 125°C Battery Connect Voltage at BAT_OUT vs IBAT_OUT 4.4 4.0, 4.1, 4.2 FLOAT, LBSEL = 1 4.0, 4.1, 4.2 FLOAT, LBSEL = 0 3.45 FLOAT, LBSEL = 1 3.45 FLOAT, LBSEL = 0 4.2 4.0 BAT_OUT VOLTAGE (V) Disconnect PMOS Body Diode Drop vs Current 600 TA = 25°C, unless otherwise noted. 3.6 3.4 3.2 3.0 2.8 3.4 3.2 3.0 2.8 2.6 100 2.4 2.4 0 2.2 1µ 100µ ID (A) 10µ 1m 10m 1µ 100µ 10µ 1m 3.4 BAT_IN VOLTAGE (V) 7 BAT_IN = 3.1V 5 BAT_IN = 4.1V 0 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 3.4 3.0 2.8 2.6 2.4 2.0 100µ IBAT_IN (A) 10µ 1m 10m CONNECT, BAT_OUT CONNECT, BAT_IN 0 25 50 75 TEMPERATURE (°C) 3.2 1m 10m 100 125 BAT_IN BATTERY CONNECTED 1V/DIV CONNECT, BAT_IN 2.8 0V 2.6 2.2 3331 G55 12 100µ IBAT_IN (A) 3331 G54 4.2V 3.0 2.4 DISCONNECT, BAT_OUT, BAT_IN –25 10µ Battery Connect Transient 3.4 2.6 2.0 –50 1µ CONNECT, BAT_OUT 3.6 2.8 2.2 1.8 3.8 3.0 2.4 2.4 Battery Connect/Disconnect vs Temperature 3.45 FLOAT LBSEL = 0 IBAT_OUT = 1mA 3.2 2.6 3331 G53 VOLTAGE (V) 3.4 2.8 2.2 Battery Connect/Disconnect vs Temperature 3.6 3.0 2.0 1µ 10m 3.2 2.2 3331 G50 3.8 1m 4.0, 4.1, 4.2 FLOAT, LBSEL = 1 4.0, 4.1, 4.2 FLOAT, LBSEL = 0 3.45 FLOAT, LBSEL = 1 3.45 FLOAT, LBSEL = 0 3.6 3.2 1.8 125 3.8 BAT_OUT VOLTAGE (V) BAT_IN = 2.1V 8 100µ IBAT_OUT (A) Battery Disconnect Voltage at BAT_OUT vs IBAT_IN 4.0, 4.1, 4.2 FLOAT, LBSEL = 1 4.0, 4.1, 4.2 FLOAT, LBSEL = 0 3.45 FLOAT, LBSEL = 1 3.45 FLOAT, LBSEL = 0 3.6 4 10µ 3331 G52 Battery Disconnect Voltage at BAT_IN vs IBAT_IN 3.8 6 1µ 3331 G51 10 9 2.2 10m 4.0, 4.1, 4.2 FLOAT, LBSEL = 1 4.0, 4.1, 4.2 FLOAT, LBSEL = 0 3.45 FLOAT, LBSEL = 1 3.45 FLOAT, LBSEL = 0 IBAT_OUT (A) RDS(ON) of Disconnect PMOS vs Temperature RDS(ON) (Ω) 3.6 2.6 3331 G49 VOLTAGE (V) 3.8 BAT_OUT DISCONNECT, BAT_OUT, BAT_IN 3.45 FLOAT LBSEL = 1 IBAT_OUT = 1mA 2.0 –50 –25 0 25 50 75 TEMPERATURE (°C) 100 125 3331 G57 2.5ms/DIV VIN = 18V, VOUT IN REGULATION, SLEEPING 10mA CHARGES BB_IN/BAT_OUT CBB_IN = 22µF FLOAT[1:0] = 11, LBSEL = 0 3331 G56 3331fc For more information www.linear.com/LTC3331 LTC3331 TYPICAL PERFORMANCE CHARACTERISTICS Battery Connect/Disconnect vs Temperature 4.4 4.2 Battery Connect/Disconnect vs Temperature 4.4 4.0, 4.1, 4.2 FLOAT LBSEL = 0 IBAT_OUT = 1mA 3.6 3.4 3.2 CONNECT, BAT_IN 3.0 2.8 2.6 –50 3.8 0 25 50 75 TEMPERATURE (°C) DISCONNECT, BAT_OUT, BAT_IN 3.2 0V 4.0, 4.1, 4.2 FLOAT LBSEL = 1 IBAT_OUT = 1mA 2.6 –50 125 –25 0 25 50 75 TEMPERATURE (°C) 500ms/DIV CBAT_IN = 1mF CBB_IN = 22µF, BB_IN TIED TO BAT_OUT 1mA LOAD AT VOUT FLOAT[1:0] = 11, LBSEL = 0 3331 G60 3331 G59 Supercapacitor Balancer Quiescent Current vs VSCAP Supercapacitor Balancer Source/Sink Current 50 BALANCER SOURCE/SINK CURRENT (mA) 250 125°C 200 85°C ISCAP (nA) 125 100 3331 G58 150 25°C 100 –40°C 50 0 BAT_OUT 3.4 2.8 100 VOUT 500mV/DIV CONNECT, BAT_IN 3.6 3.0 DISCONNECT, BAT_OUT, BAT_IN –25 BATTERY DISCONNECTED BAT_IN 4.0 CONNECT, BAT_OUT 3.8 Battery Connect Transient CONNECT, BAT_OUT 4.2 VOLTAGE (V) VOLTAGE (V) 4.0 TA = 25°C, unless otherwise noted. 2 2.5 3 3.5 4 VSCAP (V) 4.5 5 5.5 3330 G61 40 SCAP = 5V 30 20 10 SCAP = 2.5V 0 –10 –20 0 10 20 30 40 50 60 70 80 90 100 VBAL/VSCAP (%) 3330 G62 PIN FUNCTIONS BAL (Pin 1): Supercapacitor Balance Point. The common node of a stack of two supercapacitors is connected to BAL. A source/sink balancing current of up to 10mA is available. Tie BAL along with SCAP to GND to disable the balancer and its associated quiescent current. SCAP (Pin 2): Supply and Input for Supercapacitor Balancer. Tie the top of a 2-capacitor stack to SCAP and the middle of the stack to BAL to activate balancing. Tie SCAP along with BAL to GND to disable the balancer and its associated quiescent current. VIN2 (Pin 3): Internal Low Voltage Rail to Serve as Gate Drive for Buck NMOS Switch. Connect a 4.7µF (or larger) capacitor from VIN2 to GND. This pin is not intended for use as an external system rail. UV3, UV2, UV1, UV0 (Pins 4, 5, 6, 7): UVLO Select Bits for the Buck Switching Regulator. Tie high to VIN2 or low to GND to select the desired UVLO rising and falling thresholds (see Table 4). The UVLO falling threshold must be greater than the selected VOUT regulation level. Do not float. 3331fc For more information www.linear.com/LTC3331 13 LTC3331 PIN FUNCTIONS AC1 (Pin 8): Input Connection for piezoelectric element, other AC source, or current limited DC source (used in conjunction with AC2 for differential AC inputs). LBSEL (Pin 22): Low Battery Disconnect Select Pin. Connect LBSEL high to BB_IN or low to GND to select the low battery disconnect level. See Table 2. Do not float. AC2 (Pin 9): Input Connection for piezoelectric element, other AC source, or current limited DC source (used in conjunction with AC1 for differential AC inputs). FLOAT1, FLOAT0 (Pins 23, 24): Float Voltage Select Pins. Connect high to BB_IN or low to GND to select battery float voltages of 3.45V, 4.0V, 4.1V, and 4.2V (see Table 2). Do not float. VIN (Pin 10): Rectified Input Voltage. A capacitor on this pin serves as an energy reservoir and input supply for the buck regulator. The VIN voltage is internally clamped to a maximum of 20V (typical). CAP (Pin 11): Internal Rail Referenced to VIN to Serve as Gate Drive for Buck PMOS Switch. Connect a 1μF (or larger) capacitor between CAP and VIN. This pin is not intended for use as an external system rail. SW (Pin 12): Switch Node for the Buck Switching Regulator. Connect a 22µH or greater external inductor between this node and VOUT. VOUT (Pin 13): Regulated Output Voltage Derived from the Buck or Buck-Boost Switching Regulator. SWB (Pin 14): Switch Node for the Buck-Boost Switching Regulator. Connect an external inductor (value in Table 3) between this node and SWA. SWA (Pin 15): Switch Node for the Buck-Boost Switching Regulator. Connect an external inductor (value in Table 3) between this node and SWB. BB_IN (Pin 16): Input for the Buck-Boost Switching Regulator. BB_IN must be tied to BAT_OUT for proper operation. SHIP (Pin 25): Input to select SHIP mode. Tie SHIP to at least 1.2V to select SHIP mode in which the battery disconnect switch will be forced off, ensuring there is no drain on the battery. Do not float. VIN3 (Pin 26): Internal Low Voltage Rail Used by the Prioritizer. Logic high reference for IPK[2:0] and OUT[2:0]. Connect a 0.1µF capacitor from VIN3 to GND. This pin is not intended for use as an external system rail. CHARGE (Pin 27): Connect a resistor from CHARGE to the common BAT_OUT = BB_IN node to enable charging of the battery. The CHARGE pin is controlled to provide excess energy from the energy harvesting input when the output is in regulation and the BUCK converter is in SLEEP mode. PGVOUT (Pin 28): Power Good Output for VOUT. Logic level output referenced to an internal maximum rail (see Operation). PGVOUT transitioning high indicates regulation has been reached on VOUT (VOUT = Sleep Rising). PGVOUT remains high until VOUT falls to 92% (typical) of the programmed regulation point. IPK0, IPK1, IPK2 (Pins 17, 18, 19): IPEAK_BB Select Bits for the Buck-Boost Switching Regulator. Tie high to VIN3 or low to GND to select the desired IPEAK_BB (see Table 3). Do not float. EH_ON (Pin 29): Switcher Status. Logic level output referenced to VIN3. EH_ON is high when the buck switching regulator is in use (energy harvesting input). It is pulled low when the buck-boost switching regulator is in use (battery input). BAT_OUT (Pin 20): This is the output side of the battery disconnect switch. BAT_OUT must be connected to BB_IN to power the buck-boost regulator. OUT0, OUT1, OUT2 (Pins 30, 31, 32): VOUT Voltage Select Bits. Tie high to VIN3 or low to GND to select the desired VOUT (see Table 1). Do not float. BAT_IN (Pin 21): Input for backup battery and the input side to the battery disconnect switch. When the battery is disconnected there will be less than 10nA of quiescent current draw at BAT_IN. GND (Exposed Pad Pin 33): Ground. The Exposed Pad should be connected to a continuous ground plane on the second layer of the printed circuit board by several vias directly under the LTC3331. 14 3331fc For more information www.linear.com/LTC3331 LTC3331 BLOCK DIAGRAM 10 VIN 20V INTERNAL RAIL GENERATION UVLO AC1 8 UVLO_SET CAP SW AC2 9 26 VIN2 BANDGAP REFERENCE VREF PRIORITIZER GND SWA BB_IN VIN3 EH_ON ILIM_SET 27 3 BUCK CONTROL SWB 29 12 VIN3 SLEEP 16 11 CHARGE – VREF VIN2 VOUT BUCK-BOOST CONTROL 33 15 14 13 SLEEP + SLEEP-UVLO VIN2 BB_IN VOUT + SHUNT PMOS 20 VREF SLEEP 0.925*VREF – + PGVOUT – BAT_OUT SCAP BODY DIODE + – + 21 EA – VREF BAT_IN UVLO_SET BB_IN VIN3 BB_IN 2 SHIP 25 23, 24 VIN2 3 FLOAT[1:0] BAL LBSEL 22 32, 31, 30 4, 5, 6, 7 2 1 ILIM_SET VIN3 4 OUT[2:0] 28 3 UV[3:0] 19, 18, 17 IPK[2:0] 3331 BD 3331fc For more information www.linear.com/LTC3331 15 LTC3331 OPERATION Modes of Operation Table 3. IPEAK_BB Selection The following four tables detail all programmable settings on the LTC3331. Table 1. Output Voltage Selection OUT2 OUT1 OUT0 VOUT 0 0 0 1.8V 0 0 1 2.5V 0 1 0 2.8V 0 1 1 3.0V 1 0 0 3.3V 1 0 1 3.6V 1 1 0 4.5V 1 1 1 5.0V FLOAT1 FLOAT0 FLOAT CONNECT IPK1 IPK0 ILIM LMIN 0 0 0 5mA 1000µH 0 0 1 10mA 470µH 0 1 0 15mA 330µH 0 1 1 25mA 220µH 1 0 0 50mA 100µH 1 0 1 100mA 47µH 1 1 0 150mA 33µH 1 1 1 250mA 22µH Table 4.UVLO Selection UV3 UV2 UV1 UV0 UVLO RISING UVLO FALLING 0 0 0 0 4V 3V 0 0 0 1 5V 4V DISCONNECT 0 0 1 0 6V 5V 0 1 1 7V 6V 8V 7V Table 2. FLOAT Selection LBSEL IPK2 0 0 0 3.45V 2.35V 2.04V 0 0 0 1 4.0V 3.03V 2.70V 0 1 0 0 0 1 0 4.1V 3.03V 2.70V 0 1 0 1 8V 5V 1 1 0 10V 9V 0 1 1 4.2V 3.03V 2.70V 0 1 0 0 3.45V 2.85V 2.51V 0 1 1 1 10V 5V 0 0 0 12V 11V 1 0 1 4.0V 3.53V 3.20V 1 1 1 0 4.1V 3.53V 3.20V 1 0 0 1 12V 5V 1 1 1 4.2V 3.53V 3.20V 1 0 1 0 14V 13V 1 0 1 1 14V 5V 1 1 0 0 16V 15V 1 1 0 1 16V 5V 1 1 1 0 18V 17V 1 1 1 1 18V 5V 16 3331fc For more information www.linear.com/LTC3331 LTC3331 OPERATION Overview The LTC3331 combines a buck switching regulator and a buck-boost switching regulator to produce an energy harvesting solution with battery backup. The converters are controlled by a prioritizer that selects which converter to use based on the availability of a battery and/or harvestable energy. If harvested energy is available the buck regulator is active and the buck-boost is OFF. An onboard 10mA shunt battery charger with low battery disconnect enables charging of the backup battery to greatly extend the life of the battery. An optional supercapacitor balancer allows for significant energy storage at the output to handle a variety of load requirements. Energy Harvester The energy harvester is an ultralow quiescent current power supply designed to interface directly to a piezoelectric or alternative A/C power source, rectify the input voltage, and store harvested energy on an external capacitor while maintaining a regulated output voltage. It can also bleed off any excess input power via an internal protective shunt regulator. It consists of an internal bridge rectifier, an undervoltage lockout circuit, and a synchronous buck DC/DC. offers UVLO rising thresholds from 4V to 18V with large or small hysteresis windows. This allows for programming of the UVLO window near the peak power point of the input source. Extremely low quiescent current (450nA typical) in UVLO allows energy to accumulate on the input capacitor in situations where energy must be harvested from low power sources. Internal Rail Generation (CAP, VIN2, VIN3) Two internal rails, CAP and VIN2, are generated from VIN and are used to drive the high side PMOS and low side NMOS of the buck converter, respectively. Additionally the VIN2 rail serves as logic high for the UVLO threshold select bits UV[3:0]. The VIN2 rail is regulated at 4.8V above GND while the CAP rail is regulated at 4.8V below VIN. These are not intended to be used as external rails. Bypass capacitors are connected to the CAP and VIN2 pins to serve as energy reservoirs for driving the buck switches. When VIN is below 4.8V, VIN2 is equal to VIN and CAP is held at GND. Figure 1 shows the ideal VIN, VIN2 and CAP relationship. VIN3 is an internal rail used by the buck and the buck-boost. When the LTC3331 runs the buck VIN3 will be a Schottky diode drop below VIN2. When it runs the buck-boost VIN3 is equal to BB_IN. 18 Internal Bridge Rectifier Buck Undervoltage Lockout (UVLO) 16 14 VOLTAGE (V) An internal full-wave bridge rectifier accessible via the differential AC1 and AC2 inputs rectifies AC sources such as those from a piezoelectric element. The rectified output is stored on a capacitor at the VIN pin and can be used as an energy reservoir for the buck converter. The bridge rectifier has a total drop of about 800mV at typical piezo-generated currents (~10μA), but is capable of carrying up to 50mA. Either side of the bridge can be operated independently as a single-ended AC or DC input. VIN 12 10 8 6 VIN2 4 CAP 2 0 0 5 10 VIN (V) 15 3331 F01 Figure 1. Ideal VIN, VIN2 and CAP Relationship When the voltage on VIN rises above the UVLO rising threshold the buck converter is enabled and charge is transferred from the input capacitor to the output capacitor. When the input capacitor voltage is depleted below the UVLO falling threshold the buck converter is disabled. These thresholds can be set according to Table 4 which Buck Operation The buck regulator uses a hysteretic voltage algorithm to control the output through internal feedback from the VOUT sense pin. The buck converter charges an output 3331fc For more information www.linear.com/LTC3331 17 LTC3331 OPERATION capacitor through an inductor to a value slightly higher than the regulation point. It does this by ramping the inductor current up to IPEAK_BUCK through an internal PMOS switch and then ramping it down to 0mA through an internal NMOS switch. This efficiently delivers energy to the output capacitor. The ramp rate is determined by VIN, VOUT, and the inductor value. When the buck brings the output voltage into regulation the converter enters a low quiescent current sleep state that monitors the output voltage with a sleep comparator. During sleep load current is provided by the output capacitor. When the output voltage falls below the regulation point the buck regulator wakes up and the cycle repeats. This hysteretic method of providing a regulated output reduces losses associated with FET switching and maintains the output at light loads. The buck delivers a minimum of 100mA of average load current when it is switching. VOUT can be set from 1.8V to 5V via the output voltage select bits, OUT[2:0] (see Table 1). When the sleep comparator senses that the output has reached the sleep threshold the buck converter may be in the middle of a cycle with current still flowing through the inductor. Normally both synchronous switches would turn off and the current in the inductor would freewheel to zero through the NMOS body diode. Instead, the NMOS switch is kept on to prevent the conduction loss that would occur in the diode if the NMOS were off. If the PMOS is on when the sleep comparator trips the NMOS will turn on immediately in order to ramp down the current. If the NMOS is on it will be kept on until the current reaches zero. Though the quiescent current when the buck is switching is much greater than the sleep quiescent current, it is still a small percentage of the average inductor current which results in high efficiency over most load conditions. The buck operates only when sufficient energy has been accumulated in the input capacitor and the length of time the converter needs to transfer energy to the output is much less than the time it takes to accumulate energy. Thus, the buck operating quiescent current is averaged over a long period of time so that the total average quiescent current is low. This feature accommodates sources that harvest small amounts of ambient energy. 18 Buck-Boost Converter The buck-boost uses the same hysteretic voltage algorithm as the buck to control the output, VOUT, with the same sleep comparator. The buck-boost has three modes of operation: buck, buck-boost, and boost. An internal mode comparator determines the mode of operation based on BB_IN and VOUT. Figure 2 shows the four internal switches of the buck-boost converter. In each mode the inductor current is ramped up to IPEAK_BB, which is programmable via the IPK[2:0] bits and ranges from 5mA to 250mA (see Table 3). BB_IN M1 SWA M2 SWB M4 VOUT M3 3331 F02 Figure 2: Buck-Boost Power Switches In BUCK mode M4 is always on and M3 is always off. The inductor current is ramped up through M1 to IPEAK_BB and down to 0mA through M2. In boost mode M1 is always on and M2 is always off. The inductor current is ramped up to IPEAK_BB when M3 is on and is ramped down to 0mA when M4 is on as VOUT is greater than BB_IN in boost mode. Buck-boost mode is very similar to boost mode in that M1 is always on and M2 is always off. If BB_IN is less than VOUT the inductor current is ramped up to IPEAK_BB through M3. When M4 turns on the current in the inductor will start to ramp down. However, because BB_IN is close to VOUT and M1 and M4 have finite on-resistance the current ramp will exhibit a slow exponential decay, potentially lowering the average current delivered to VOUT. For this reason the lower current threshold is set to IPEAK_BB/2 in buck-boost mode to maintain high average current to the load. If BB_IN is greater than VOUT in buck-boost mode the inductor current still ramps up to IPEAK_BB and down to IPEAK_BB/2. It can still ramp down if BB_IN is greater than VOUT because the final value of the current in the inductor would be (VIN – VOUT)/(RON1 + RON4). If BB_IN is exactly IPEAK_BB/2 • (RON1 + RON4) above VOUT the inductor current will not reach the IPEAK_BB/2 threshold and switches M1 and M4 will stay on all the time. For higher BB_IN voltages the mode comparator will switch the converter to buck mode. M1 and M4 will remain on for BB_IN voltages up to VOUT + IPEAK_BB • (RON1 + RON4). At 3331fc For more information www.linear.com/LTC3331 LTC3331 OPERATION this point the current in the inductor is equal to IPEAK_BB and the IPEAK_BB comparator will trip turning off M1 and turning on M2 causing the inductor current to ramp down to IZERO, completing the transition from buck-boost mode to buck mode. VOUT Power Good A power good comparator is provided for the VOUT output. It transitions high the first time the LTC3331 goes to sleep, indicating that VOUT has reached regulation. It transitions low when VOUT falls to 92% (typical) of its regulation value. The PGVOUT output is referenced to an internal rail that is generated to be the highest of VIN2, BB_IN, and VOUT less a Schottky diode drop. Shunt Battery Charger The LTC3331 provides a reliable low quiescent current shunt battery charger to facilitate charging a battery with harvested energy. A low battery disconnect feature provides protection to the battery from overdischarge by disconnecting the battery from the buck-boost input at a programmable level. To use the charger connect the battery to the BAT_IN pin. An internal low battery disconnect PMOS switch is connected between the BAT_IN pin and the BAT_OUT pin. The BAT_OUT pin must be connected to BB_IN for proper operation. A charging resistor connected from VIN to BAT_OUT or from CHARGE to BAT_OUT will charge the battery through the body diode of the disconnect PMOS until the battery voltage rises above the low-battery connect threshold. Depending on the capacity of the battery and the input decoupling capacitor, the common BAT_OUT = BB_IN node voltage generally rises or falls to VBAT_IN when the PMOS turns on. Once the PMOS is on the charge current is determined by the charging resistor, the battery voltage, and the voltage of the charging source. As the battery voltage approaches the float voltage, the LTC3331 shunts current away from the battery thereby reducing the charging current. The LTC3331 can shunt up to 10mA. Float voltages of 3.45V, 4.0V, 4.1V, and 4.2V are programmable via the FLOAT[1:0] pins (see Table 2). Charging can occur through a resistor connected to VIN or the CHARGE pin. An internal set of back to back PMOS switches are connected between CHARGE and VIN2 and are turned on only when the energy harvesting buck converter is sleeping. In this way charging of the battery only happens when there is excess harvested energy available and the VOUT output is prioritized over charging of the battery. The charge current available from this pin is limited by the strength of the VIN2 LDO and an appropriate charging resistor must be selected to limit this current. The on resistance of the internal charge switches combined is approximately 60Ω. To charge with higher currents connect a resistor directly to VIN. Note that when charging from VIN the battery is always being charged. Care must be taken to ensure that enough power is available to bring up the VOUT output. Low Battery Disconnect/Connect: LBD/LBC The low battery disconnect (VLBD) and connect (VLBC) voltage levels are programmed by the LBSEL and FLOAT[1:0] pins (see Table 2). As shown in the Block Diagram the battery disconnects from the common BAT_OUT = BB_IN node by shutting off the PMOS switch when the BAT_IN voltage falls below VLBD. This disconnect function protects Li-Ion batteries from permanent damage due to deep discharge. Disconnecting the battery from the common BAT_OUT = BB_IN node prevents the load as well as the LTC3331 quiescent current from further discharging the battery. Once disconnected the common BAT_OUT = BB_IN node voltage collapses towards ground. When an input supply is reconnected the battery charges through the internal body diode of the disconnect PMOS. The input supply voltage should be larger than VLBC_BAT_OUT to ensure that the PMOS is turned on. When the voltage reaches VLBC_BAT_OUT, the PMOS turns on and connects the common BAT_OUT = BB_IN node to BAT_IN. While disconnected, the BAT_IN pin voltage is indirectly sensed through the PMOS body diode. Therefore VLBC_BAT_IN varies with charge current and junction temperature. See the Typical Performance Characteristics section for more information. Low Battery Select The low battery disconnect voltage level is programmed by the LBSEL pin for each float setting. The LBSEL pin allows the user to trade-off battery run time and maximum shelf life. A lower battery disconnect threshold maximizes run For more information www.linear.com/LTC3331 3331fc 19 LTC3331 OPERATION time by allowing the battery to fully discharge before the disconnect event. Conversely, by increasing the low battery disconnect threshold more capacity remains following the disconnect event which extends the shelf life of the battery. For maximum run time, tie LBSEL to GND. For extended shelf life, tie LBSEL to the common BAT_OUT = BB_IN node. If a high peak current event is expected, users may temporarily select the lower disconnect threshold. This avoids disconnecting the battery too early when the load works against the battery series resistance and temporarily reduces the common BAT_OUT = BB_IN node. Ship Mode A ship mode is provided which manually disconnects the battery. This may be useful to prevent discharge of the battery in situations when no harvestable energy is expected for a long period of time such as during shipping. Bring the SHIP pin high to engage ship mode. The low battery disconnect PMOS will turn off, disconnecting the battery at BAT_IN from the common BAT_OUT = BB_IN node. If no harvestable energy is present to hold up the common BAT_OUT = BB_IN node that voltage will collapse. Typically an additional 1µA of quiescent current will appear on BB_IN while SHIP mode is engaged. To exit SHIP mode first bring the SHIP pin low. If the BB_IN voltage had collapsed while in SHIP mode it must now be brought above the LBC threshold to reconnect the battery. This can be done manually or from an energy harvesting charging source. If harvestable energy had been propping up the common BAT_OUT = BB_IN node voltage above the LBC threshold then the battery will be connected immediately. Prioritizer The input prioritizer on the LTC3331 decides whether to use the energy harvesting input or the battery input to power VOUT. If a battery is powering the buck-boost converter and harvested energy causes a UVLO rising transition on VIN, the prioritizer will shut off the buck-boost and turn on the buck, orchestrating a smooth transition that maintains regulation of VOUT. 20 When harvestable energy disappears, the prioritizer will first poll the BB_IN voltage. If the BB_IN voltage is above 1.8V the prioritizer will switch back to the buck-boost while maintaining regulation. If the BB_IN voltage is below 1.8V the buck-boost is not enabled and VOUT cannot be supported until harvestable energy is again available. If the battery is connected then the BB_IN voltage will be above 1.8V for every float and LBSEL combination. If the battery is disconnected the BB_IN voltage will have collapsed below 1.8V and the prioritizer will not switch to the buck-boost when harvestable energy goes away. In the event that the battery is depleted and is disconnected while powering the buck-boost the prioritizer will not switch back to VIN until harvested energy is again available. If either BB_IN or VIN is grounded, the prioritizer allows the other input to run if its input is high enough for operation. The specified quiescent current in UVLO is valid upon start-up of the VIN input and when the battery has taken over regulation of the output. If the battery is less than 1.8V when UVLO is entered and the prioritizer does not enable the buck-boost several hundred nanoamperes of additional quiescent current will appear on VIN. When the prioritizer selects the VIN input the current on the BB_IN input drops to 200nA. However, if the voltage on BB_IN is higher than VIN2, a fraction of the VIN quiescent current will appear on BB_IN due to internal level shifting. This only affects a small range of battery voltages and UVLO settings. A digital output, EH_ON, is low when the prioritizer has selected the BB_IN input and is high when the prioritizer has selected the VIN input. The EH_ON output is referenced to VIN3. Supercapacitor Balancer An integrated supercapacitor balancer with 150nA of quiescent current is available to balance a stack of two supercapacitors. Typically the input, SCAP, will tie to VOUT to allow for increased energy storage at VOUT with supercapacitors. The BAL pin is tied to the middle of the stack and can source and sink 10mA to regulate the BAL pin’s voltage to half that of the SCAP pin’s voltage. To disable the balancer and its associated quiescent current the SCAP and BAL pins can be tied to ground. 3331fc For more information www.linear.com/LTC3331 LTC3331 APPLICATIONS INFORMATION When harvestable energy is available, it is transferred through the bridge rectifier where it accumulates on the VIN capacitor. A low quiescent current UVLO mode allows the voltage on the capacitor to increase towards a programmed UVLO rising threshold. When the voltage rises to this level, the buck converter turns on and transfers energy to VOUT. As energy is transferred the voltage at VIN may decrease to the UVLO falling threshold. If this happens, the buck converter turns off and the buck-boost then turns on to service the load from the battery input while more energy is harvested. When the buck is running the quiescent current on the BB_IN pin drops to the 200nA required by the shunt battery charger. The LTC3331 is well suited to wireless systems which consume low average power but occasionally need a higher concentrated burst of power to accomplish a task. If these bursts occur with a low duty cycle such that the total energy needed for a burst can be accumulated between bursts then the output can be maintained entirely by the harvester. If the bursts need to happen more frequently or if harvestable energy goes away the battery will be used. If enough energy is available the energy harvester will bring the output up and enter the low quiescent current sleep state and excess energy can be used to charge the battery. Piezo Energy Harvesting Ambient vibrational energy can be harvested with a piezoelectric transducer which produces a voltage and current in response to strain. Common piezoelectric elements are PZT (lead zirconate titanate) ceramics, PVDF (polyvinylidene fluoride) polymers, or other composites. Ceramic piezoelectric elements exhibit a piezoelectric effect when the crystal structure of the ceramic is compressed and internal dipole movement produces a voltage. Polymer elements comprised of long-chain molecules produce a voltage when flexed as molecules repel each other. Ceramics are often used under direct pressure while a polymer is commonly used as a cantilevered beam. A wide range of piezoelectric elements are available and produce a variety of open-circuit voltages and short-circuit currents. Typically the open-circuit voltage and short-circuit currents increase with available vibrational energy as shown in Figure 3. Piezoelectric elements can be placed in series or in parallel to achieve desired open-circuit voltages. 12 9 PIEZO VOLTAGE (V) The LTC3331 allows for energy harvesting from a variety of alternative energy sources in order to power a wireless sensor system and charge a battery. The extremely low quiescent current of the LTC3331 facilitates harvesting from sources generating only microamps of current. The onboard bridge rectifier is suitable for AC piezoelectric or electromagnetic sources as well as providing reverse protection for DC sources such as solar and thermoelectric generators. The LTC3331 powers the VOUT output continuously by seamlessly switching between the energy harvesting and battery inputs. INCREASING VIBRATION ENERGY 6 3 0 0 10 20 PIEZO CURRENT (µA) 30 3331 F03 Figure 3. Typical Piezoelectric Load Lines for Piezo Systems T220-A4-503X Piezos produce the most power when they operate at approximately half the open circuit voltage for a given vibration level. The UVLO window can be programmed to straddle this voltage so that the piezo operates near the peak power point. In addition to the normal configuration of connecting the piezo across the AC1 and AC2 inputs, a piezo can be connected from either AC1 or AC2 to ground. The resulting configuration is a voltage doubler as seen in Figure 4 where the intrinsic capacitance of the piezo is used as the doubling capacitor. 3331fc For more information www.linear.com/LTC3331 21 LTC3331 APPLICATIONS INFORMATION 500 AC1 IP sin(ωt) VIN CP 1500 SANYO 1815 SOLAR PANEL 1800 LUX 400 1200 CIN Figure 4. LTC3331 Voltage Doubler Configuration A second piezo may be connected from AC2 to ground. This may be of use if the second piezo is mechanically tuned to a different resonant frequency present in the system than the first piezo. To achieve maximum power transfer from the piezo with the doubler the UVLO window should be set to the open circuit voltage of the piezo. Piezoelectric elements are available from the manufacturers listed in Table 5. Table 5. Piezoelectric Element Manufacturers Advanced Cerametrics www.advancedcerametrics.com Piezo Systems www.piezo.com Measurement Specialties www.meas-spec.com PI (Physik Instrumente) www.pi-usa.us MIDE Technology Corporation www.mide.com Morgan Technical Ceramics www.morganelectroceramics.com Electromagnetic Energy Harvesting Another alternative AC source is an electromagnetic vibration harvester in which a magnet vibrating inside a coil induces an AC voltage and current in the coil that can then be rectified and harvested by the LTC3331. The vibration could be ambient to the system or it could be caused by an impulse as in a spring loaded switch. Solar Energy Harvesting The LTC3331 can harvest solar energy as the bridge rectifier can be used to provide reverse protection for a solar panel. A solar cell produces current in proportion to the amount of light falling on it. Figure 5 shows the relationship between current and voltage for a solar panel illuminated with several levels of light. The maximum power output occurs near the knee of each curve where the cell transitions from a constant current device to a constant voltage IPANEL (µA) 3331 F04 300 900 1000 LUX 200 600 WPANEL (µW) GND 22 PANEL CURRENT PANEL POWER LTC3331 PIEZO MODEL 500 LUX 100 0 300 200 LUX 0 1 2 3 VPANEL (V) 4 5 6 0 3331 F05 Figure 5. Typical Solar Panel Characteristics device. Fortunately, the peak power point doesn’t change much with illumination and an appropriate UVLO window can be selected so that the panel operates near the peak power point for a majority of light conditions. Two solar panels can be connected to the LTC3331, one from AC1 to ground and another from AC2 to ground. Each panel could be aimed in a different direction to capture light from different angles or at different times of the day as the sun moves. The panels should be similar so that the selected UVLO window is optimal for both panels. BB_IN/BAT_OUT, BAT_IN, VIN, and VOUT Capacitors The input to the buck-boost, BB_IN, must be connected to BAT_OUT for proper operation. BAT_OUT is the output side of the low battery disconnect switch. The series resistance of this switch must be considered when selecting a bypass capacitor for the common BAT_OUT = BB_IN node. At least 4.7μF to GND or greater should be used. For the higher IPEAK_BB settings the capacitor may need to be larger to smooth the voltage at the common BAT_OUT = BB_IN node. The goal is to average the input current to the buck boost so that the voltage droop at the common BAT_OUT = BB_IN node is minimized. A bypass capacitor of 1µF or greater can also be placed at the BAT_IN pin. In cases where the series resistance of the battery is high, a larger capacitor may be desired to handle transients. 3331fc For more information www.linear.com/LTC3331 LTC3331 APPLICATIONS INFORMATION The input capacitor to the buck on VIN and the VOUT capacitor can vary widely and should be selected to optimize the use of an energy harvesting source depending on whether storage of the harvested energy is needed at the input or the output. Storing energy at the input takes advantage of the high input voltage as the energy stored in a capacitor increases with the square of its voltage. Storage at the output may be necessary to handle load transients greater than the 100mA the buck can provide. The input or output capacitor should be sized to store enough energy to provide output power for the length of time required. If enough energy is stored so that the buck does not reach the UVLO falling threshold during a load transient then the battery current will always be zero. Spacing load transients so that the average power required to service the application is less than or equal to the power available from the energy harvesting source will then greatly extend the life of the battery. The VIN capacitor should be rated to withstand the highest voltage ever present at VIN. The following equation can be used to size the input capacitor to meet the power requirements of the output for the desired duration: 1 PLOAD t LOAD = ηCIN ( VIN2 – VUVLOFALLING2) 2 VUVLOFALLING ≤ VIN ≤ VSHUNT Here η is the average efficiency of the buck converter over the input voltage range and VIN is the input voltage when the buck begins to switch. Typically VIN will be the UVLO rising threshold. This equation may overestimate the input capacitor necessary as it may be acceptable to allow the load current to deplete the output capacitor all the way to the lower PGVOUT threshold. It also assumes that the input source charging has a negligible effect during this time. The duration for which the buck or buck-boost regulator sleeps depends on the load current and the size of the VOUT capacitor. The sleep time decreases as the load current increases and/or as the output capacitor decreases. The DC sleep hysteresis window is ±6mV for the 1.8V output and scales linearly with the output voltage setting (±12mV for the 3.6V setting, etc.). Ideally this means that the sleep time is determined by the following equation: tSLEEP = COUT 12mV • VOUT 1.8V I LOAD This is true for output capacitors on the order of 100μF or larger, but as the output capacitor decreases towards 10μF, delays in the internal sleep comparator along with the load current itself may result in the VOUT voltage slewing past the DC thresholds. This will lengthen the sleep time and increase VOUT ripple. A capacitor less than 10μF is not recommended as VOUT ripple could increase to an undesirable level. If transient load currents above 100mA are required then a larger capacitor should be used at the output. This capacitor will be continuously discharged during a load condition and the capacitor can be sized for an acceptable drop in VOUT: COUT = (ILOAD – IDC/DC ) tLOAD + VOUT – VOUT – Here VOUT+ is the value of VOUT when PGVOUT goes high and VOUT– is the acceptable lower limit of VOUT. IDC/DC is the average current being delivered from either the buck converter or the buck-boost converter. The buck converter typically delivers 125mA on average to the output as the inductor current is ramped up to 250mA and down to zero. The current the buck-boost delivers depends on the mode of operation and the IPEAK_BB setting. In buck mode the deliverable current is IPEAK_BB/2. In buck-boost and boost modes the deliverable current also depends on the VIN to VOUT ratio: Buck-boost mode: Boost mode: 3 V I DC/DC = I PEAK_BB IN 4 VOUT 1 V I DC/DC = I PEAK_BB IN 2 VOUT A standard surface mount ceramic capacitor can be used for COUT, though some applications may be better suited to a low leakage aluminum electrolytic capacitor or a supercapacitor. These capacitors can be obtained from manufacturers such as Vishay, Illinois Capacitor, AVX, or CAP-XX. 3331fc For more information www.linear.com/LTC3331 23 LTC3331 APPLICATIONS INFORMATION CAP, VIN2, and VIN3 Capacitors A 1μF or larger capacitor must be connected between VIN and CAP and a 4.7μF capacitor must be connected between VIN2 and GND. These capacitors hold up the internal rails during buck switching and compensate the internal rail generation circuits. In applications where the voltage at VIN is limited to less than 6V, the CAP pin can be tied to GND and the VIN2 pin can be tied to VIN as shown in Figure 6. An optional 5.6V Zener diode can be connected to VIN to clamp VIN in this scenario. The leakage of the Zener diode below its clamping voltage should be considered as it could be comparable to the quiescent current of the LTC3331. This circuit does not require the capacitors on VIN2 and CAP, saving two components and allowing for a lower voltage rating for the single VIN capacitor. A 0.1µF bypass capacitor must be connected from VIN3 to ground. VIN3 is an internal rail that is shared by both the buck and buck-boost. It is not intended for use as a system rail. It is used as a the logic high reference level for the IPK[2:0] and OUT[2:0] digital inputs. In the event that these pins are dynamically driven in the application, external inverters may be needed and they must use VIN3 as a rail. However, care must be taken not to overload VIN3 and the quiescent current of such logic should be kept minimal. The output resistance of the VIN3 pin is typically 15kΩ. + + SOLAR PANEL SOLAR PANEL – – AC2 AC1 VIN 5.6V (OPTIONAL) 22µF 6.3V VIN2 CAP UV3 UVLO RISING = 4V UVLO FALLING = 3V IPEAK_BB = 150mA SWA 33µH SWB LTC3331 SW 22µH VOUT UV2 SCAP UV1 BAL UV0 PGVOUT 1.8V 22µF 6.3V EH_ON 4.2V + BAT_IN Li-ION 1µF 6.3V VIN3 IPK2 IPK1 CHARGE 12k 22µF 6.3V IPK0 OUT2 BAT_OUT OUT1 BB_IN OUT0 FLOAT1 FLOAT0 LBSEL SHIP GND 0.1µF 6.3V 3331 F06 Figure 6. Low Voltage Solar Harvester with Reduced Component Count (VIN < 6V) 24 3331fc For more information www.linear.com/LTC3331 LTC3331 APPLICATIONS INFORMATION Inductor Selection The buck is optimized to work with a 22µH inductor in typical applications. A larger inductor will benefit high voltage applications by increasing the on-time of the PMOS switch and improving efficiency by reducing gate charge loss. Choose an inductor with a DC current rating greater than 500mA. The DCR of the inductor can have an impact on efficiency as it is a source of loss. Tradeoffs between price, size, and DCR should be evaluated. The buck-boost is optimized to work with a minimum inductor of 22μH for the 250mA IPEAK_BB setting. For the other seven IPEAK_BB settings the inductor value should increase as the IPEAK_BB selection decreases to maintain the same IPEAK_BB • L product. The minimum inductor values for the buck-boost for each IPEAK_BB setting are listed in Table 3. Larger inductors may increase efficiency. Choose an inductor with an ISAT rating at least 50% greater than the selected IPEAK value. Table 6 lists several inductors that work well with both the buck and the buck-boost. Table 6. Recommended Inductors for the LTC3331 PART NUMBER 744043102 LPS5030-105ML LPS4018-105ML LPS3314-105ML B82442T1105K050 L(µH) 1000 744043471 LPS4018-474ML LPS3314-474ML B82442T147K050 744042331 LPS4018-334ML LPS3314-334ML B82442T1334K050 744042221 LPS4018-224ML LPS3314-224ML B82442T1224K050 744031101 LPS4018-104ML LPS3314-104ML B82442T1104K050 744031470 LPS4018-473ML LPS3314-473ML B82442T1473K050 744031330 LPS4018-333ML LPS3314-333ML 1070BS-330ML B82442T1333K050 744031220 LPS5030-223ML LPS4018-223ML LPS3314-223ML 1070AS-220M B82442T1223K050 744029220 1069BS-220M 470 330 220 100 47 33 22 22 MANUFACTURER Würth Elektronik Coilcraft Coilcraft Coilcraft EPCOS Würth Elektronik Coilcraft Coilcraft EPCOS Würth Elektronik Coilcraft Coilcraft EPCOS Würth Elektronik Coilcraft Coilcraft EPCOS Würth Elektronik Coilcraft Coilcraft EPCOS Würth Elektronik Coilcraft Coilcraft EPCOS Würth Elektronik Coilcraft Coilcraft Toko EPCOS Würth Elektronik Coilcraft Coilcraft Coilcraft Toko EPCOS Würth Elektronik Toko SIZE (mm) (L × W × H) 4.8 × 4.8 × 2.8 5.51 × 5.51 × 2.9 3.9 × 3.9 × 1.7 3.3 × 3.3 × 1.3 5.6 × 5 × 5 4.8 × 4.8 × 2.8 3.9 × 3.9 × 1.7 3.3 × 3.3 × 1.3 5.6 × 5 × 5 4.8 × 4.8 × 1.8 3.9 × 3.9 × 1.7 3.3 × 3.3 × 1.3 5.6 × 5 × 5 4.8 × 4.8 × 1.8 3.9 × 3.9 × 1.7 3.3 × 3.3 × 1.3 5.6 × 5 × 5 3.8 × 3.8 × 1.65 3.9 × 3.9 × 1.7 3.3 × 3.3 × 1.3 5.6 × 5 × 5 3.8 × 3.8 × 1.65 3.9 × 3.9 × 1.7 3.3 × 3.3 × 1.3 5.6 × 5 × 5 3.8 × 3.8 × 1.65 3.9 × 3.9 × 1.7 3.3 × 3.3 × 1.3 3.2 × 3.2 × 2 5.6 × 5 × 5 3.8 × 3.8 × 1.65 5.51 × 5.51 × 2.9 3.9 × 3.9 × 1.7 3.3 × 3.3 × 1.3 3.2 × 3.2 × 2 5.6 × 5 × 5 2.8 × 2.8 × 1.35 3.2 × 3.2 × 1.8 MAX IDC (mA) 80 110 98 99 150 125 160 110 240 130 190 110 280 160 260 160 330 180 360 230 510 250 550 330 700 320 640 380 230 840 360 750 800 450 410 1040 300 290 MAX DCR (Ω) 7 5.1 18 31 9.5 2.6 7.8 12 4.73 4.5 5.9 9.3 3.29 3.2 3.7 6 2.2 2.4 1.4 2.75 0.99 1 0.65 1.4 0.519 0.66 0.42 0.92 0.61 0.36 0.45 0.19 0.36 0.72 0.64 0.238 0.97 0.495 3331fc For more information www.linear.com/LTC3331 25 LTC3331 APPLICATIONS INFORMATION Supercapacitor Balancer Battery Considerations If supercapacitors are used at VOUT the onboard supercapacitor balancer can be used to balance them with ±10mA of balance current. A list of supercapacitor suppliers is provided in Table 7. The shunt battery charger is designed to work with any single Li-Ion, LiFeP04, or other chemistry with a termination voltage compatible with the available levels. Table 9 lists some batteries, their capacities and their equivalent series resistance (ESR). The ESR causes BAT_OUT and BAT_IN to droop by the product of the load current amplitude multiplied by the ESR. This droop may trigger the low battery disconnect while the battery itself may still have ample capacity. An appropriate bypass capacitor placed at BAT_OUT will help prevent large, low duty cycle load transients from pulling down on BAT_OUT. The bypass capacitor used at BB_IN, which is tied to BAT_OUT, to bypass the buck-boost may be sufficient. Table 7. Supercapacitor Manufacturers CAP-XX www.cap-xx.com NESS CAP www.nesscap.com Maxwell www.maxwell.com Bussman www.cooperbussman.com AVX www.avx.com Illinois Capacitor www.illcap.com Tecate Group www.tecategroup.com By seamlessly combining a battery source and an energy harvesting source, the LTC3331 enables the use of supercapacitors in energy harvesting applications. The battery provides the initial current required to overcome the effects of the diffusion current when voltage is first applied to the supercapacitors. The energy harvesting source can then support the lower steady state leakage current and average load current. Summary of Digital inputs and outputs There are 14 digital pin-strapped logic inputs to the LTC3331 and two digital logic outputs. These and the rails they are referenced to are summarized in Table 8. Table 8. Digital Pin Summary INPUT PIN UV[3:0] IPK[2:0] OUT[2:0] FLOAT[1:0], LBSEL SHIP LOGIC HIGH LEVEL VIN2 VIN3 VIN3 BAT_OUT = BB_IN ≥ 1.2V OUTPUT PIN PGVOUT EH_ON LOGIC HIGH LEVEL MAX (BB_IN, VIN2, VOUT) VIN3 26 Table 9. Low Capacity Li-Ion and Thin-Film Batteries MANUFACTURER P/N CAPACITY RESISTANCE VMIN CYMBET CBC012 CYMBET CBC050 12μAh 5k to 10k 3.0V 50μAh 1500Ω to 3k 3.0V GM Battery GMB031009 8mAh 10Ω to 20Ω 2.75V GS NanoTech N/A 500μAh 40Ω 3.0V Power Stream LIR2032 40mAh 0.6Ω 3.0V Charging the Battery Charging the battery with the CHARGE pin allows the battery to be charged only when the energy harvester is sleeping, which prioritizes the VOUT output over the battery. The current that the CHARGE pin can supply is limited to 2mA and an appropriately chosen current limiting resistor should be used. Use the following equation to calculate the value of this resistor: RCHARGE = 4.8V – VLBD – 60Ω ICHARGE Here 4.8V is the output of the VIN2 LDO which is the supply to the CHARGE pin, VLBD is the selected low battery disconnect threshold, 60Ω is the resistance of the CHARGE pin PMOS, and ICHARGE is the desired charge current. For high charging currents approaching 2mA, a larger VIN2 capacitor may improve transient behavior. 3331fc For more information www.linear.com/LTC3331 LTC3331 APPLICATIONS INFORMATION For applications where more charging current is available a resistor tied to VIN or the circuit of Figure 7 can be used to provide up to 10mA to the battery. The circuit of Figure 7 uses the CHARGE pin to only allow charging when the energy harvester is sleeping. For applications VIN LTC3331 R1 56.2Ω Q2 CMPT3906E R2 1M Q1A NDC7001C CHARGE R3 1M R4 100k BB_IN Q1B NDC7001C Higher Efficiency Battery Powered Buck 3331 F07 MIDE V25W 22µF 25V AC2 VIN VIN2 4.7µF 6.3V UVLO RISING = 12V** UVLO FALLING = 11V IPEAK_BB = 250mA AC1 SWA CAP 22µH SW UV3 VOUT UV2 SCAP UV1 BAL UV0 PGVOUT + BAT_IN 1µF 6.3V Li-ION 22µH 5V 22µF 6.3V 1µF 6.3V VIN3 4.7µF 6.3V 22µF 6.3V BB_IN OUT0 FLOAT1 FLOAT0 LBSEL SHIP GND 22µH EN VOUT 22µF 6.3V D1 D0 OUT2 OUT1 PGOOD SW VIN2 IPK0 BAT_OUT LTC3388-3* CAP IPK1 CHARGE VIN 2.2µF 10V IPK2 68k If the battery voltage will always be higher than the regulated output of the LTC3331 then the battery powered buck-boost will always run in buck mode. In this case the inductor that is usually placed between SWA and SWB can go directly to VOUT from SWA, bypassing internal switch M4 of the buck-boost (Figure 9). This will reduce conduction losses in the converter and improve the efficiency at higher loads. SWB LTC3331 EH_ON 4.1V LTC3331 System Solutions The LTC3331 can be paired with other Linear Technology low quiescent current integrated circuits to form a multirail system. Figure 8 shows an LTC3331 powering an LTC3388-3 from its 5V output. The LTC3388-3, an 800nA Buck converter, is configured here to produce a negative 5V rail by tying the VOUT pin to ground and tying its GND pin to the regulated –5V output. The result is a ±5V energy harvesting power supply with battery backup. CMOSH-3 Figure 7 1µF 6.3V requiring even more charging current, the LTC3331 can be paired with the LTC4071 shunt battery charger connected at the BB_IN pin. GND STBY –5V 3331 F08 0.1µF 6.3V *EXPOSED PAD MUST BE ELECTRICALLY ISOLATED FROM SYSTEM GROUND AND CONNECTED TO THE –5V RAIL **FOR PEAK POWER TRANSFER, CENTER THE UVLO WINDOW AT HALF THE RECTIFIED OPEN CIRCUIT VOLTAGE OF THE PIEZO Figure 8. Dual ±5V Power Supply 3331fc For more information www.linear.com/LTC3331 27 LTC3331 APPLICATIONS INFORMATION MIDE V25W 22µF 25V 4.7µF AC2 VIN2 UVLO RISING = 12V* UVLO FALLING = 11V IPEAK_BB = 250mA 4.0V + Li-ION 1µF 6.3V LTC3331 SW UV3 UV2 BAL UV1 PGVOUT UV0 EH_ON BAT_IN 22µH VOUT SCAP 22µF 6.3V 100 1.8V 95 VIN3 VOUT = 1.8V, BYPASS SWB VOUT = 1.8V, INCLUDE SWB VOUT = 3.3V, BYPASS SWB VOUT = 3.3V, INCLUDE SWB 90 85 IPK2 80 IPK1 CHARGE 68k 22µF 6.3V 22µH SWA SWB CAP 6.3V AC1 EFFICIENCY (%) 1µF 6.3V VIN IPK0 75 2.6 OUT2 BAT_OUT OUT1 BB_IN OUT0 FLOAT0 0.1µF 6.3V FLOAT1 LBSEL SHIP GND 2.8 3 3.2 3.4 3.6 BB_IN (V) 3.8 4 4.2 3331 F09b Figure 9b. Efficiency Comparison Between Normal Buck-Boost and Bypassed SWB Configuration 3331 F09a *FOR PEAK POWER TRANSFER, CENTER THE UVLO WINDOW AT HALF THE RECTIFIED OPEN CIRCUIT VOLTAGE OF THE PIEZO Figure 9a. Higher Efficiency Battery-Powered Buck Regulator Alternative Power Sources The LTC3331 can accommodate a wide variety of input sources. Figure 10 shows the LTC3331 internal bridge rectifier connected to a 120V RMS AC line in series with four 3.9k current limiting resistors. This produces a peak current of 10mA with the LTC3331 shunt holding VIN at 20V. This current may be increased by reducing the resistor values since the shunt can sink 25mA and the bridge is rated for 50mA. An optional external Zener diode (shown) may be required if the current exceeds 25mA. A transformer may also be used to step down the voltage and reduce the power loss in the current limiting resistors. The 3.3k charging resistor charges the battery from VIN with approximately 5mA. This is a high voltage application and minimum spacing between the line, neutral, and any high voltage components should be maintained per the applicable UL specification. For general off-line applications refer to UL Regulation 1012. 28 Figure 11 shows an application where copper panels are placed near a standard fluorescent room light to capacitively harvest energy from the electric field around the light. The frequency of the emission will be double the line frequency for magnetic ballasts but could be higher if the light uses electronic ballast. The peak AC voltage and the total available energy will scale with the size of the panels used and with the proximity of the panels to the electric field of the light. The LTC3331 could also be used to wirelessly harvest energy and charge a battery by using a transmitter and receiver consisting of loosely coupled tuned resonant tanks as shown in Figure 12. Using EH_ON to Program VOUT The EH_ON output indicates whether the energy harvesting input or the battery is powering the output. The application 3331fc For more information www.linear.com/LTC3331 LTC3331 APPLICATIONS INFORMATION DANGEROUS AND LETHAL POTENTIALS ARE PRESENT IN OFFLINE CIRCUITS! BEFORE PROCEEDING ANY FURTHER, THE READER IS WARNED THAT CAUTION MUST BE USED IN THE CONSTRUCTION, TESTING AND USE OF OFFLINE CIRCUITS. EXTREME CAUTION MUST BE USED IN WORKING WITH AND MAKING CONNECTIONS TO THESE CIRCUITS. REPEAT: OFFLINE CIRCUITS CONTAIN DANGEROUS, AC LINE-CONNECTED HIGH VOLTAGE POTENTIALS, USE CAUTION. ALL TESTING PERFORMED ON AN OFFLINE CIRCUIT MUST BE DONE WITH AN ISOLATION TRANSFORMER CONNECTED BETWEEN THE OFFLINE CIRCUIT’S INPUT AND THE AC LINE. USERS AND CONSTRUCTORS OF OFFLINE CIRCUITS MUST OBSERVE THIS PRECAUTION WHEN CONNECTING TEST EQUIPMENT TO THE CIRCUIT TO AVOID ELECTRIC SHOCK. REPEAT: AN ISOLATION TRANSFORMER MUST BE CONNECTED BETWEEN THE CIRCUIT INPUT AND THE AC LINE IF ANY TEST EQUIPMENT IS TO BE CONNECTED. DANGER HIGH VOLTAGE 3.9k 3.9k 120VAC 60Hz 3.9k 3.9k 1µF 6.3V 22µF 25V 18V (OPTIONAL) VIN AC2 VIN2 UV3 4.0V + LTC3331 3.3V VOUT 22µF 6.3V SCAP BAL UV1 PGVOUT UV0 EH_ON BAT_IN VIN3 1µF 6.3V Li-ION 22µH SW UV2 UVLO RISING = 18V UVLO FALLING = 5V IPEAK_BB = 250mA 3.3k SWA SWB CAP 4.7µF 6.3V 22µH AC1 IPK2 IPK1 IPK0 22µF 6.3V CHARGE OUT2 BAT_OUT OUT1 BB_IN OUT0 FLOAT0 0.1µF 6.3V FLOAT1 LBSEL SHIP GND 3331 F10 Figure 10. AC Line Powered 5V UPS on the last page of this data sheet shows the EH_ON output tied to the OUT2 input. When EH_ON is low the output is programmed to 2.5V and the battery powers the output. When energy harvesting is available EH_ON is high and the output is programmed to 3.6V allowing for increased storage of harvested energy. If energy harvesting goes away, the output is again programmed to 2.5V and the buck-boost converter will be in sleep until the output is discharged to the wake-up threshold. If the energy stored at 3.6V is enough to ride through a temporary loss of energy harvesting then the only drain on the battery will be the quiescent current in sleep. 3331fc For more information www.linear.com/LTC3331 29 LTC3331 APPLICATIONS INFORMATION COPPER PANEL (12" × 24") AC2 AC1 VIN 1µF 6.3V 22µF 25V COPPER PANEL (12" × 24") CAP VIN2 4.7µF 6.3V LTC3331 UV2 UV1 UV0 4.2V + SWB UV3 UVLO RISING = 14V UVLO FALLING = 5V IPEAK_BB = 5mA 1µF 6.3V Li-ION BAT_IN SW 22µH 2.5V VOUT 100mF 2.7V SCAP 22µF 6.3V BAL PGVOUT EH_ON VIN3 100mF 2.7V IPK2 IPK1 CHARGE 300k 22µF 6.3V 100µH SWA IPK0 OUT2 BAT_OUT BB_IN FLOAT1 FLOAT0 OUT1 OUT0 LBSEL SHIP GND 0.1µF 6.3V 3331 F10 Figure 11. Electric Field Energy Harvester 30 3331fc For more information www.linear.com/LTC3331 LTC3331 APPLICATIONS INFORMATION TX + – DC 130kHz SOURCE TRANSMITTER GND 300nF 5µH 50V 270Ω 100nF 25V 47µH POWER TY LINEAR TECHNOLOGY DC1968A PART OF DC1969A-B KIT 1µF 6.3V 22µF 25V VIN AC2 CAP VIN2 4.7µF 6.3V UVLO RISING = 14V UVLO FALLING = 5V IPEAK_BB = 5mA AC1 SWB LTC3331 PGVOUT 22µF 6.3V 100mF 2.7V EH_ON VIN3 BAT_IN IPK2 IPK1 IPK0 CHARGE 4.3k 22µF 6.3V 2.5V 100mF 2.7V BAL UV1 1µF 6.3V 200F 22µH SCAP UV2 3.45V SW VOUT UV3 UV0 Li-ION CAPACITOR TAIYO YUDEN 100µH SWA OUT2 BAT_OUT BB_IN FLOAT1 FLOAT0 OUT1 OUT0 LBSEL SHIP GND 0.1µF 6.3V 3331 F12 Figure 12. Wireless Battery Charger 3331fc For more information www.linear.com/LTC3331 31 LTC3331 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. UH Package 32-Lead Plastic QFN (5mm × 5mm) (Reference LTC DWG # 05-08-1693 Rev D) 0.70 ±0.05 5.50 ±0.05 4.10 ±0.05 3.50 REF (4 SIDES) 3.45 ±0.05 3.45 ±0.05 PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC RECOMMENDED SOLDER PAD LAYOUT APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 5.00 ±0.10 (4 SIDES) BOTTOM VIEW—EXPOSED PAD 0.75 ±0.05 R = 0.05 TYP 0.00 – 0.05 R = 0.115 TYP PIN 1 NOTCH R = 0.30 TYP OR 0.35 × 45° CHAMFER 31 32 0.40 ±0.10 PIN 1 TOP MARK (NOTE 6) 1 2 3.50 REF (4-SIDES) 3.45 ±0.10 3.45 ±0.10 (UH32) QFN 0406 REV D 0.200 REF NOTE: 1. DRAWING PROPOSED TO BE A JEDEC PACKAGE OUTLINE M0-220 VARIATION WHHD-(X) (TO BE APPROVED) 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 0.20mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 32 0.25 ±0.05 0.50 BSC 3331fc For more information www.linear.com/LTC3331 LTC3331 REVISION HISTORY REV DATE DESCRIPTION PAGE NUMBER A 07/14 Clarified IQ on the LTC3330 in the Related Parts list 34 B 11/14 Clarified Description Clarified Available Buck-Boost Current Conditions Replaced PGOOD with PGVOUT in Graphs Clarified Table 2 Replaced PGOOD with PGVOUT in Text Clarified tSLEEP Formula Clarified Figure 6 Schematic Clarified Inductor Selection Paragraph Clarified Typical Application Schematic Clarified LTC3330 Comments in Related Parts 1 4 7, 8 16 23 23 24 25 34 34 C 08/15 Changed COUT Equation 23 3331fc 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 representaFor more information www.linear.com/LTC3331 tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. 33 LTC3331 TYPICAL APPLICATION UPS System for Wireless Mesh Networks with Output Supercapacitor Energy Storage MIDE V25W AC2 1µF 6.3V 22µF 25V AC1 VIN SWA SWB CAP UVLO RISING = 12V* UVLO FALLING = 11V IPEAK_BB = 50mA 3.45V + 1µF 6.3V LiFePO4 VOUT = 3.6V FOR EH_ON = 1 VOUT = 2.5V FOR EH_ON = 0 22µH SW LTC3331 VIN2 4.7µF 6.3V 100µH VOUT UV3 SCAP UV2 BAL UV1 PGVOUT UV0 EH_ON 1F 2.7V 1F 2.7V VIN3 BAT_IN IPK2 PGOOD IPK1 VSUPPLY TX IPK0 CHARGE EHORBAT OUT2 130k OUT1 BAT_OUT OUT0 BB_IN 22µF 6.3V 22µF 6.3V FLOAT1 FLOAT0 LBSEL 0.1µF 6.3V SHIP GND 3331 TA02 GND LINEAR TECHNOLOGY DC9003A-AB DUST MOTE FOR WIRELESS MESH NETWORKS *FOR PEAK POWER TRANSFER, CENTER THE UVLO WINDOW AT HALF THE RECTIFIED OPEN CIRCUIT VOLTAGE OF THE PIEZO RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3330 Nanopower Buck-Boost DC/DC with Energy Harvesting Battery Life Extender VIN: 3.0V to 19V; BAT: 1.8V to 5.5V, 750nA IQ 5mm × 5mm QFN-32 Package LTC3588-1/ LTC3588-2 Nanopower Energy Harvesting Power Supply with Up to 100mA of Output Current VIN: 2.7V to 20V; VOUT: Fixed 1.8V to 5V; IQ = 950nA; ISD = 450nA; MSOP-10, 3mm × 3mm DFN-10 Packages LT1389 Nanopower Precision Shunt Voltage Reference VREF: 1.25V, 2.25V, 4.096V; IQ = 800nA; ISD < 1µA; SO-8 Package LTC1540 Nanopower Comparator with Reference VIN: 2V to 11V; IQ = 0.3µA; ISD < 1µA; 3mm × 3mm DFN-8 Package LT3009 3μA IQ, 20mA Low Dropout Linear Regulator VIN: 1.6V to 20V; VOUT: 0.6V, Fixed 1.2V to 5V; IQ = 3µA; ISD < 1µA; SC-70-8, 2mm × 2mm DFN-8 Packages LTC3105 400mA Step-Up Converter with MPPC and 250mV VIN: 0.2V to 5V; VOUT: Max 5.25V; IQ = 22µA; ISD < 1µA; 3mm × 3mm DFN-10, MSOP-12 Package Start-Up LTC3108 Ultralow Voltage Step-Up Converter and Power Manager VIN: 0.02V to 1V; VOUT: Fixed 2.35V to 5V; IQ = 7µA; ISD < 1µA; TSSOP-16, 3mm × 4mm DFN-12 Packages LTC3109 Auto-Polarity, Ultralow Voltage Step-Up Converter and Power Manager VIN: 0.03V to 1V; VOUT: Fixed 2.35V to 5V; IQ = 7µA; ISD < 1µA; SSOP-20, 4mm × 4mm QFN-20 Packages LTC3388-1/ LTC3388-3 20V, 50mA High Efficiency Nanopower Step-Down Regulator VIN: 2.7V to 20V; VOUT: Fixed 1.1V to 5.5V; IQ = 720nA; ISD = 400nA; MSOP-10, 3mm × 3mm DFN-10 Packages LTC4070 50mA Micropower Shunt Li-Ion Charger VOUT(MIN): 4V, 4.1V, 4.2V; IQ = 450nA; ISD = 45nA; MSOP-8, 2mm × 3mm DFN-8 Packages LTC4071 50mA Micropower Shunt Li-Ion Charger with PowerPath™ Control VOUT(MIN): 4V, 4.1V, 4.2V; IQ = 450nA; ISD = 45nA; MSOP-8, 2mm × 3mm DFN-8 Packages LTC3129/ LTC3129-1 Micropower 200mA Synchronous Buck-Boost DC/DC Converter VIN: 2.42V to 15V; VOUT: 1.4V to 15V; IQ = 1.3µA; ISD = 10nA; MSOP-16E, 3mm × 3mm QFN-16 Packages 34 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 For more information www.linear.com/LTC3331 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LTC3331 3331fc LT 0815 REV C • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 2014