LTC3130EUDC-1#PBF

LTC3130/LTC3130-1 25V, 600mA Buck-Boost DC/DC Converter with 1.6µA Quiescent Current DESCRIPTION FEATURES Regulates VOUT Above, Below or Equal to VIN Wide VIN Range: 2.4V to 25V, 3.15V, RUN > 1.1V EXTVCC > 3.15V, RUN > 1.1V MIN l l l l For External FB Resistor Applications From –40°C to +85°C (Note 3) Feedback Input Current (LTC3130) FB = 1.1V VS1 = VS2 = 0V Fixed VOUT Voltages (LTC3130-1) VS1 = VCC, VS2 = 0V VS1 = 0V, VS2 = VCC VS1 = VS2 = VCC VIN Quiescent Current – Shutdown RUN < 0.2V 0.85V < RUN < 0.9V, EXTVCC = 0V VIN Quiescent Current – UVLO VIN Quiescent Current – Burst Mode Operation FB > 1.02V (LTC3130), VOUT > VREG (LTC3130-1), (Sleeping) MODE = 0V, RUN = VIN, MPPC > 1.05V SW1 = SW2 = 0V, VIN = VOUT = 25V NMOS Switch Leakage on VIN and VOUT NMOS Switch On-Resistance VCC = 4V Inductor Average Current Limit LTC3130-1 (Note 4), LTC3130: ILIM = VCC (Note 4) LTC3130: ILIM = 0V (Note 4) Inductor Peak Current Limit LTC3130-1 (Note 4), LTC3130: ILIM = VCC (Note 4) LTC3130: ILIM = 0V (Note 4) Maximum Boost Duty Cycle LTC3130-1: VOUT < VREG (Note 7), LTC3130: FB < 0.975V (Note 7) (Percentage of Period SW2 is Low) Minimum Duty Cycle LTC3130-1: VOUT > VREG (Note 7), LTC3130: FB > 1.02V (Note 7) Switching Frequency SW1 and SW2 Minimum Low Time (Note 3) MPPC Reference Voltage MPPC Input Current MPPC = 5V RUN Logic Threshold to Enable Reference RUN Threshold to Enable Switching (Rising) VIN > 2.4V or EXTVCC > 3.15V RUN Threshold Hysteresis RUN Input Current RUN = 25V RUN = 1V ILIM Input Logic High (LTC3130) ILIM Input Logic Low (LTC3130) ILIM Input Current (LTC3130) ILIM = 5V VS1, VS2 Input Logic High (LTC3130-1) VS1, VS2 Input Logic Low (LTC3130-1) VS1, VS2 Input Current (LTC3130-1) VS1, VS2 = 5V MODE Input Logic High MODE Input Logic Low MODE Input Current MODE = 5V (If RUN is Low or VCC is in UVLO) MODE = 5V (If Switching is Enabled) l l l l l l l l l l 0.6 1.0 0.975 0.980 1.75 3.20 4.85 11.64 660 250 0.9 0.6 91 TYP 2.30 0.6 1.000 1.000 0.1 1.80 3.3 5.0 12.0 500 1.4 1.6 5 0.35 850 450 1.3 0.85 94 l l 1.00 l 0.95 l l 0.2 1.01 90 l 1.1 l 1.20 70 1.00 1 0.6 1.05 100 1 0.1 1200 650 1.7 1.15 97 0 % 1.40 1.05 20 0.85 1.09 110 30 5 1 0.35 20 1 1.7 0.35 20 4 1.1 1.1 l UNITS V V V V V V nA V V V V nA µA µA nA Ω mA mA A A % 0.35 20 l l 100 1 l l MAX 2.40 1.0 25 25 1.020 1.020 10 1.85 3.39 5.125 12.30 850 2.4 2.7 MHz ns V nA V V mV nA nA V V nA V V nA V V nA µA 3130f For more information www.linear.com/LTC3130 3 LTC3130/LTC3130-1 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). PVIN = VIN = 12V, VOUT = 5V unless otherwise noted. PARAMETER Soft-Start Time VCC Voltage VCC Voltage -– Shutdown VCC Dropout Voltage (VIN – VCC) VCC Current Limit VCC UVLO Threshold (Rising) VCC UVLO Hysteresis EXTVCC Enable Threshold EXTVCC Enable Hysteresis EXTVCC Input Operating Range EXTVCC Quiescent Current – Burst Mode Operation (Sleeping) EXTVCC Quiescent Current – Shutdown EXTVCC Current Limit VIN Sleep Current When Powered by EXTVCC VOUT UV Threshold VOUT UV Hysteresis VOUT Quiescent Current – Shutdown CONDITIONS For Average Inductor Current to Reach Limit (EXTVCC or VIN) > 4.7V, RUN > 0.85V RUN ≤ 0.2V VIN = 3.0V, Switching VCC = 0V l 2.20 100 2.85 l 3.15 l EXTVCC > 3.15V, FB >1.02V (LTC3130), MPPC > 1.05V VOUT > VREG (LTC3130-1), MODE = 0V, RUN > 1.10V EXTVCC = 5V, RUN < 0.2V VCC = 0V, EXTVCC = 15V FB > 1.02V (LTC3130), VOUT > VREG (LTC3130-1), EXTVCC > 3.15V, MODE = 0V, RUN >1.10V, VIN = 12V, MPPC > 1.05V Rising VOUT Quiescent Current – Burst Mode Operation (Sleeping) MODE = 0V, FB > 1.02V, MPPC > 1.05V PGOOD Threshold, Rising PGOOD Hysteresis PGOOD Voltage Low PGOOD Leakage Referenced to Programmed VOUT Voltage Referenced to Programmed VOUT Voltage ISINK = 1mA PGOOD = 25V 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 LTC3130/LTC3130-1 is tested under pulsed load conditions such that TJ ≈ TA. The LTC3130E/LTC3130E-1 is guaranteed to meet specifications from 0°C to 85°C junction temperature. Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LTC3130I/LTC3130I-1 is guaranteed over the –40°C to 125°C operating junction temperature range. The junction temperature (TJ) is calculated from the ambient temperature (TA) and power dissipation (PD) according to the formula: TJ = TA + (PD • θJA°C/W), where θJA is the package thermal impedance. Note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated thermal package thermal resistance and other environmental factors. 4 MIN TYP 12 4 3.25 50 17 2.3 120 3.0 260 1.6 l 0.35 100 34 2.40 135 3.15 25 2.5 UNITS ms V V mV mA V mV V mV V µA 400 32 600 750 68 nA mA nA 0.7 55 (VOUT–1) 0.95 V mV µA 27 (VOUT–1) –7.0 MAX 27 –5.0 2.5 165 1 (VOUT) 17 (VOUT) 17 –3.0 250 50 µA % % mV nA Note 3: Specification is guaranteed by design and not 100% tested in production. Note 4: Current measurements are made when the output is not switching. Note 5: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 165°C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may result in device degradation or failure. Note 6: Failure to solder the exposed backside of the package to the PC board ground plane will result in a much higher thermal resistance. Note 7: Switching time measurements are made in an open-loop test configuration. Timing in the application may vary somewhat from these values due to differences in the switch pin voltage during non-overlap durations when switch pin voltage is influenced by the magnitude and duration of the inductor current. Note 8: Voltage transients on the switch pin(s) beyond the DC limits specified in the Absolute Maximum Ratings are non-disruptive to normal operation when using good layout practices as described elsewhere in the data sheet and application notes and as seen on the product demo board. 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 TYPICAL PERFORMANCE CHARACTERISTICS 70 Efficiency, VOUT = 3.3V, PWM ModeOUT 80 60 50 40 30 70 50 40 30 60 50 40 30 20 10 10 10 1 10 100 LOAD CURRENT (mA) 1k 0.1 3130 G01 Efficiency, VOUT = 12V, PWM ModeOUT 100 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 80 70 40 30 50 40 10 0 0.01 1k VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 30 20 1 10 100 LOAD CURRENT (mA) 0.1 3130 G04 1k 1 10 100 LOAD CURRENT (mA) 10 1 0.1 1k 0.001 0.01 Power Loss, VOUT = 3.3V, Burst Mode OUT Operation (LTC3130-1) 100 40 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 30 20 10 0 0.01 0.1 1 10 100 LOAD CURRENT (mA) 10 1 0.1 3130 G07 0.001 0.01 1k Efficiency, VOUT = 5V, Burst Mode Operation (LTC3130-1) OUT 80 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 0.01 1k 1 10 100 LOAD CURRENT (mA) 90 EFFICIENCY (%) POWER LOSS (mW) 50 0.1 3130 G06 100 60 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 0.01 90 80 1k Power Loss, VOUT = 1.8V, Burst Mode OUT Operation (LTC3130-1) 3130 G05 Efficiency, VOUT = 3.3V, Burst Mode OUT Operation (LTC3130-1) 70 1 10 100 LOAD CURRENT (mA) 100 60 10 100 1k 70 20 0.1 Efficiency, VOUT = 1.8V, Burst Mode OUT Operation (LTC3130-1) 80 50 0.1 3130 G03 90 60 0 0.01 0 0.01 1k POWER LOSS (mW) 90 1 10 100 LOAD CURRENT (mA) 3130 G02 EFFICIENCY (%) 100 EFFICIENCY (%) 70 20 0.1 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 80 60 0 0.01 Efficiency, VOUT = 5V, vs Load, VOUT = 5V, PWM Mode PWM Mode 90 20 0 0.01 EFFICIENCY (%) 100 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 90 EFFICIENCY (%) 80 EFFICIENCY (%) 100 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 90 EFFICIENCY (%) 100 Efficiency, VOUT = 1.8V, vs Load, VOUT = 1.8V, PWM Mode PWM Mode TA = 25°C, unless otherwise noted. 0.1 1 10 100 LOAD CURRENT (mA) 70 60 50 40 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 30 20 10 1k 3130 G08 0 0.01 0.1 1 10 100 LOAD CURRENT (mA) 1k 3130 G09 3130f For more information www.linear.com/LTC3130 5 LTC3130/LTC3130-1 TYPICAL PERFORMANCE CHARACTERISTICS 1k Power Loss, VOUT = 5V, Burst Mode (LTC3130-1) VOUT =Operation 5V, Burst Mode 100 TA = 25°C, unless otherwise noted. Efficiency, VOUT = 12V, Burst Mode OUT Operation (LTC3130-1) 1k Power Loss, VOUT = 12V, Burst Mode OUT Operation (LTC3130-1) 90 80 1 0.1 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 0.01 0.001 0.01 0.1 1 10 100 LOAD CURRENT (mA) 70 60 50 40 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 30 20 10 0 0.01 1k 0.1 1 10 100 LOAD CURRENT (mA) Efficiency, VOUT = 8V, PWM OUT Mode (LTC3130) 80 70 50 40 30 1k 50 40 20 10 1 10 100 LOAD CURRENT (mA) 0 0.01 1k VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 30 1k Power Loss , VOUT = 8V, Burst Mode (LTC3130) VOUT =Operation 8V, Burst Mode 0.1 1 10 100 LOAD CURRENT (mA) 10 1 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 0.1 0.01 0.01 1k 0.1 1 10 100 LOAD CURRENT (mA) Efficiency, VOUT = 15V V(LTC3130) OUT = 15V 1k 1k 3130 G15 3130 G14 Power Loss, VOUT = 15V, Burst Mode OUT Operation (LTC3130) 100 90 Efficiency, VOUT = 24V (LTC3130) OUT 90 80 80 60 50 40 30 EFFICIENCY (%) 100 70 POWER LOSS (mW) EFFICIENCY (%) 1 10 100 LOAD CURRENT (mA) 100 3130 G13 10 1 20 VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 10 0 0.01 6 0.1 3130 G12 Efficiency, VOUT = 8V, Burst Mode Operation VOUT = 8V, (LTC3130) Burst Mode 60 10 100 0.01 0.01 1k 70 20 0.1 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 0.1 80 60 0 0.01 1 90 EFFICIENCY (%) EFFICIENCY (%) 100 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 90 10 3130 G11 3130 G10 100 POWER LOSS (mW) EFFICIENCY (%) 10 100 POWER LOSS (mW) POWER LOSS (mW) 100 0.1 1 10 100 LOAD CURRENT (mA) Burst Mode OPERATION: VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V PWM: 1k 3130 G16 0.1 0.01 0.1 1 10 100 LOAD CURRENT (mA) 60 50 40 30 20 10 1k 3130 G17 VIN = 3.6V VIN = 5V VIN = 12V VIN = 24V 70 0 0.01 0.1 1 10 100 LOAD CURRENT (mA) Burst Mode OPERATION: VIN = 5V VIN = 12V VIN = 24V PWM: 1k 3130 G18 VIN = 5V VIN = 12V VIN = 24V 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 TYPICAL PERFORMANCE CHARACTERISTICS Power Loss, VOUT = 24V, Burst Mode Operation (LTC3130) 1k TA = 25°C, unless otherwise noted. VIN Shutdown Current vs VIN (RUN = 0V, EXTVCC = 0V) Maximum Output Current vs VIN and VOUT VOUT = 24V, Burst Mode IN 700 OUT 0.90 600 0.80 10 400 300 VOUT = 1.8V VOUT = 3.3V VOUT = 5V VOUT = 12V VOUT = 25V 200 1 0.1 0.01 VIN = 5V VIN = 12V VIN = 24V 0.1 100 1 10 100 LOAD CURRENT (mA) 0 1k 0 5 10 15 VIN (V) VIN UVLO Current vs VIN (0.85V ≤ RUN ≤ 1.01V, EXTVCC = 0V) CC 0.30 0.10 0 25 1.00 0.80 0.40 10 15 20 25 3130 G21 No-Load Input Current in Burst Mode Operation vs VIN and VOUT (LTC3130-1, MODE = 0V) and V (LTC3130-1, MODE = 0V) 15 OUT 5.0 VOUT = 1.8V VOUT = 3.3V VOUT = 5V VOUT =1 2V 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 5 0.20 5 3130 G20 10 0.60 0 VIN (V) IIN (μA) 20 IIN (μA) 0.5 0 5 10 15 VIN (V) 20 0 25 IN 10 15 VIN (V) 20 25 3130 G25 0 5 3130 G23 10 15 VIN (V) 20 25 3130 G24 Average Inductor Current Limit vs MPPC Voltage vs MPPC Voltage 0.80 0.70 0.09 0.06 VOUT = 1.8V VOUT = 3.3V VOUT = 5V VOUT = 12V VOUT = 25V 0.03 5 5 0 25 OUT 10 0 20 0.12 IOUT (A) 15 IN 0.15 VOUT = 1.8V VOUT = 3.3V VOUT = 5V VOUT = 12V VOUT = 25V 20 10 15 VIN (V) Burst Mode Operation, Load Current Threshold vs VIN and VOUT (MODE = 0V) OUT 25 5 3130 G22 No-Load Input Current in Fixed Frequency vs VIN and VOUT (MODE = VCC) 30 0 INDUCTOR CURRENT LIMIT (A) VIN CURRENT (μA) 0.40 IOUT = 2μA (FB DIVIDER) VOUT = 1.8V VOUT = 3.3V VOUT = 5V VOUT = 12V VOUT = 25V 25 1.20 IIN (mA) 0.50 OUT 30 1.40 0 0.60 No-Load Input Current in Burst Mode Operation vs VIN and VOUT (LTC3130, MODE = 0V) 1.60 0 0.70 0.20 20 3130 G19 1.80 VIN CURRENT (μA) 500 IOUT (mA) POWER LOSS (mW) 100 CC 1.00 0 0 5 10 15 VIN (V) 20 0.60 0.50 0.40 0.30 0.20 0.10 25 3130 G26 0 0.95 0.98 1.01 1.04 MPPC (V) 1.07 1.10 3130 G27 3130f For more information www.linear.com/LTC3130 7 LTC3130/LTC3130-1 TYPICAL PERFORMANCE CHARACTERISTICS Average Current Limit vs Temperature (Normalized to 25°C) FB Voltage vs Temperature LTC3130 (Normalized to 25°C) LTC3130–1 (Normalized to 25 C) 0.00 0.00 –1.00 –0.10 –0.10 –2.00 –0.20 –3.00 –4.00 –5.00 –6.00 –7.00 –8.00 CHANGE IN OUTPUT VOLTAGE (%) 0 CHANGE IN FB VOLTAGE (%) CHANGE IN AVERAGE CURRENT LIMIT (%) Output Voltage vs Temperature LTC3130–1 (Normalized to 25°C) LTC3130 (Normalized to 25 C) (Normalized to 25 C) –0.30 –0.40 –0.50 –0.60 –0.70 –0.80 –0.90 –9.00 –10.00 –50 –25 0 –1.00 –50 –25 25 50 75 100 125 150 TEMPERATURE (° C) 0 –4.00 –5.00 –6.00 –7.00 –8.00 –9.00 –10.00 –50 –25 0 –0.90 –1.00 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (° C) 3130 G30 Accurate RUN Threshold vs Temperature (Normalized to 25°C) 99 98 97 2.4 Switch Temperature DS(ON)vsvsTemperature Switch R Rdson 2.8 3.2 VCC (V) 3.6 4.0 –0.20 –0.30 –0.40 –0.50 –0.60 –0.70 –0.80 –0.90 –1.00 –50 –25 3130 G32 0.50 SW2 (5V/DIV) 0.42 0.45 RDSON (Ω) 25 50 75 100 125 150 TEMPERATURE (° C) Fixed Frequency PWM Waveforms (Buck Region) CC 0.45 0 3130 G33 Switch vsVVCC DS(ON)vs Switch R Rdson 0.55 RDSON (Ω) –0.80 0.00 3130 G31 0.35 –0.70 –0.10 25 50 75 100 125 150 TEMPERATURE (° C) 0.40 –0.60 CHANGE IN RUN THRESHOLD (%) –3.00 –0.50 CC 100 NORMALIZED OSCILLATOR FREQUENCY (%) –2.00 –0.40 Oscillator Frequency vs VCC (Normalized to VCC = 4V) Oscillator Frequency vs V (Normalized to 25 C) –1.00 –0.30 3130 G29 Oscillator Frequency vs Temperature (Normalized to 25°C) 0 –0.20 25 50 75 100 125 150 TEMPERATURE (° C) 3130 G28 CHANGE IN OSCILLATOR FREQUENCY (%) TA = 25°C, unless otherwise noted. SW1 (10V/DIV) 0.39 INDUCTOR CURRENT (0.5A/DIV) 0.36 0.30 0.20 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (° C) 3131 G34 8 200nsec/DIV 0.33 0.25 0.30 2.5 3 3.5 VCC (V) 3130 G36 4 3134 G35 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 TYPICAL PERFORMANCE CHARACTERISTICS Fixed Frequency PWM Waveforms (Buck-Boost Region) Fixed Frequency PWM Waveforms (Boost Region) SW2 (5V/DIV) SW2 (10V/DIV) SW1 (5V/DIV) SW1 (5V/DIV) INDUCTOR CURRENT (0.5A/DIV) INDUCTOR CURRENT (0.5A/DIV) 200nsec/DIV TA = 25°C, unless otherwise noted. Fixed Frequency Output Voltage Ripple VOUT (50mV/DIV) INDUCTOR CURRENT (0.2A/DIV) 0 3130 G37 3130 G38 200nsec/DIV PWM to Burst Mode Operation Transition Burst Mode Operation Waveforms VIN (10V/DIV) VCC (2V/DIV) MODE PIN (2V/DIV) VOUT (2V/DIV) INDUCTOR CURRENT (0.2A/DIV) INDUCTOR CURRENT (0.2A/DIV) INDUCTOR CURRENT (0.2A/DIV) 20μsec/DIV 3130 G40 1msec/DIV 3130 G41 2msec/DIV Start-Up Sequence When Raising RUN Pin (VIN = 12V) RUN (5V/DIV) VCC Response to a Step on EXTVCC (VIN = 3V) VCC Response to a Step on EXTVCC (VIN > 4V) VCC (2V/DIV) VCC (2V/DIV) VCC (2V/DIV) VOUT (2V/DIV) 0 0 INDUCTOR CURRENT (0.2A/DIV) EXTVCC (5V/DIV) 0 EXTVCC 2msec/DIV 3138 G43 3130 G42 COUT = 22µF 12VIN, 5VOUT, ILOAD = 20mA, COUT = 22µF 5VOUT ILOAD =10mA COUT = 22µF 3130 G39 Start-Up Sequence When Applying VIN (RUN Tied to VIN) VOUT (100mV/ DIV) VOUT (50mV/DIV) 500nsec/DIV 12VIN, 5VOUT, ILOAD = 0.5A, COUT = 22µF (5V/DIV) 0 1msec/DIV 3130 G44 1msec/DIV 3130 G45 3130f For more information www.linear.com/LTC3130 9 LTC3130/LTC3130-1 TYPICAL PERFORMANCE CHARACTERISTICS Step Load Transient Response in Fixed Frequency TA = 25°C, unless otherwise noted. VOUT (2V/DIV) PGOOD (2V/DIV) VOUT (100mV/DIV) VOUT (100mV/DIV) INDUCTOR CURRENT (0.2A/DIV) INDUCTOR CURRENT (0.5A/DIV) 3130 G46 500μsec/DIV 12VIN, 5VOUT, 50mA to 500mA LOAD STEP COUT = 22µF, L = 10μH PGOOD Response to a Drop in VOUT Due to a Step Overload Step Load Transient Response in Burst Mode Operation INDUCTOR CURRENT (0.5A/DIV) 500μsec/DIV 3130 G47 1msec/DIV 12VIN, 5VOUT, 10mA to 250mA LOAD STEP COUT = 22µF, L = 10μH MPPC Response to an Overload (VMPPC Set to 5V at VIN) 3130 G48 VIN Line Step Response in Fixed Frequency VOUT (5V/DIV) VIN (5V/DIV) VOUT (1V/DIV) VIN (10V/DIV) INDUCTOR CURRENT (0.2A/DIV) INDUCTOR CURRENT (0.2A/DIV) 3130 G49 2msec/DIV VOC = 9V VOUT = 12V RIN = 20Ω CIN = 33μF VOUT (2V/DIV) VOUT (1V/DIV) VIN (10V/DIV) INDUCTOR CURRENT (0.2A/DIV) 50μsec/DIV 3130 G51 5VOUT, 5V TO 25V VIN STEP, COUT = 22µF, L = 10μH, LIGHT LOAD 10 3130 G50 Output Voltage Short-Circuit Waveforms VIN Line Step Response in Burst Mode Operation INDUCTOR CURRENT (0.2A/DIV) 50μsec/DIV 5VOUT, 5V TO 25V VIN STEP, COUT = 22µF, L = 10μH, LIGHT LOAD 10μsec/DIV 3130 G52 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 PIN FUNCTIONS (QFN/MSOP) BST1 (Pin 1/Pin 2): Boot-Strapped Floating Supply for High Side NMOS Gate Drive. Connect to SW1 through a 22nF capacitor, as close to the part as possible. PVIN (Pin 2/Pin 4): Power Input for the Buck-Boost Converter. A 4.7μF or larger bypass capacitor should be connected between this pin and the ground plane. The capacitor should be located as close to the IC as possible. When powered through long leads or from a high ESR source, a larger bulk input capacitor (typically 47μF or larger) may be required. VIN (Pin 3/Pin 5): Input Voltage for the VCC Regulator. Connect a minimum of 1µF ceramic decoupling capacitor from this pin to the ground plane. RUN (Pin 4/Pin 6): Input to the Run Comparator. Raising this pin above 1.05V enables the converter. Pull this pin above 0.6V (typical) to put the converter in “standby mode”, where the internal reference will be enabled, but the part will not be switching. Connecting this pin to a resistor divider from VIN to ground allows programming an accurate VIN start threshold. To enable the converter all the time, tie RUN to VIN. See the Operation section of this data sheet for more guidance. VCC (Pin 5/Pin 7): Output Voltage of the Internal 4V Voltage Regulator. This is the supply pin for the internal circuitry. Bypass this output with a minimum of 4.7µF ceramic capacitor. This internal regulator is powered by VIN or EXTVCC. Note that VCC should not be back-driven. VCC can be used to power external circuitry as long as the peak load current doesn’t exceed 2mA. Note that this added load will increase the minimum required operating VIN voltage by up to 60mV. NC (Pin 17, QFN Only): Unused. This pin should be grounded. MPPC (Pin 6/Pin 8): Maximum Power Point Control Programming Input. Connect this pin to a resistor divider from VIN to ground to enable MPPC functionality. If the divider voltage drops below 1.0V (typical), the inductor current will be reduced to servo VIN to the programmed minimum voltage, as set by the divider. Note that this pin is very noise sensitive, therefore minimize trace length and stray capacitance. Refer to the Applications Information section of this data sheet for more detail on programming the MPPC. If this function is not needed, tie the pin to VCC. GND (Pins 7-8, Exposed Pad Pin 21/Pin 1, Exposed Pad Pin 17): Ground. Provide a short direct PCB path between GND and the ground plane that the exposed pad is soldered to. The exposed pad must be soldered to the PCB ground plane. It serves as a power ground connection, and as a means of conducting heat away from the die. FB (Pin 9/Pin 9 (LTC3130)): Feedback input to the error amplifier. Connect to a resistor divider from VOUT to ground. The output voltage can be adjusted from 1.0V to 25V by:  R1 VOUT = 1.00V •  1+   R2  (Re fer to Figure 2) Note that this pin is very noise sensitive, therefore minimize trace length and stray capacitance. Please refer to the Applications Information section of this data sheet for more detail on setting the FB voltage divider, and the optional use of an optional feed-forward capacitor. VS2 (Pin 9/Pin 9 (LTC3130-1)): Output Voltage Select Pin. Connect this pin to ground or VCC to program the output voltage (see Table 1). This pin can also be dynamically driven by any logic signal that satisfies the specified thresholds. ILIM (Pin 10/Pin 10 (LTC3130)): Programming pin to select between 250mA or 660mA average minimum inductor current limit. Please see the Maximum Output Current curve in the Typical Performance Characteristics section. ILIM = Low (ground): Sets the average inductor current limit to 250mA (minimum) for low current applications ILIM = High (tie to VCC): Sets the average inductor current limit to 660mA (minimum) This pin can also be dynamically driven by any logic signal that satisfies the specified thresholds. 3130f For more information www.linear.com/LTC3130 11 LTC3130/LTC3130-1 PIN FUNCTIONS (QFN/MSOP) VS1 (Pin 10/Pin 10 (LTC3130-1)): Output Voltage Select Pin. Connect this pin to ground or VCC to program the output voltage (see Table 1). This pin can also be dynamically driven by any logic signal that satisfies the specified thresholds. Table 1. VOUT Program Settings for the LTC3130-1 VS2 VS1 VOUT 0 0 1.8V 0 VCC 3.3V VCC 0 5.0V VCC VCC 12V MODE (Pin 11/Pin 11): Mode Select Pin. MODE = Low (ground): Enables automatic Burst Mode operation MODE = High (tie to VCC): Fixed frequency PWM operation This pin can also be dynamically driven by any logic signal that satisfies the specified thresholds. There is an internal 3MΩ pull-down resistor connected to MODE once switching is enabled, to prevent it from floating. EXTVCC (Pin 12/Pin 12): Second Input to the Internal VCC Regulator. This pin can be tied to VOUT or another voltage between 3V and 25V. If this input is used, it will power the IC, reducing the quiescent current draw on VIN in buck applications and allowing the converter to operate from a VIN voltage down to 1V or less. A 4.7µF decoupling capacitor is recommended on this pin unless it is tied directly to the VOUT decoupling capacitor. If not used, this pin should be grounded. 12 PGOOD (Pin 13/Pin 13): Open-drain output that pulls to ground when FB (LTC3130) or VOUT (LTC3130-1) drops too far below its regulated voltage. Connect a pull-up resistor from this pin to a positive supply. Note that if a supply voltage is present on VIN or EXTVCC, this pin will be forced low in shutdown or UVLO. VOUT (Pin 14/Pin 14): Output Voltage of the Converter. Connect a minimum value of 4.7µF ceramic capacitor from this pin to the ground plane. See the Applications Information section of this data sheet for guidance. BST2 (Pin 16/Pin 15): Boot-Strapped Floating Supply for High Side NMOS Gate Drive. Connect to SW2 through a 22nF capacitor, as close to the part as possible. SW2 (Pin 15/Pin 16): Switch Pin. Connect to the other side of the inductor. Keep PCB trace lengths as short and wide as possible to reduce EMI and parasitic resistance. PGND (Pins 18-19)/(Pin 1): Power Ground. Provide a short direct PCB path between PGND and the ground plane. SW1 (Pin 20/Pin 3): Switch Pin. Connect to one side of the inductor. Keep PCB trace lengths as short and wide as possible to reduce EMI and parasitic resistance. 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 LTC3130 BLOCK DIAGRAM PVIN EXTVCC VIN BST SW1 SW2 BST2 VREF VCC_GD LDO VCC 1.05V 1.0V VREF_GD B DRIVER VSENSE C DRIVER START + – VSENSE + – 1.2A ON + – IPK UV LOGIC FB 0.7V VSENSE ENABLE VSENSE 50mA MPPC MODE DRIVER D + – 1.0V RESET IZERO THERMAL SHUTDOWN + – SOFT-START 3M VCC_GD + – 100mV – + + – 0.6V A VC + – RUN DRIVER VOUT ISENSE 4V VREF VOUT VCC VCC + – VIN 1.0V OSC – + 600mA SLEEP GND 200mA PGND CLAMP –7.5% – + PGOOD ILIM 3130 BD VCC 3130f For more information www.linear.com/LTC3130 13 LTC3130/LTC3130-1 LTC3130-1 BLOCK DIAGRAM PVIN EXTVCC VIN BST SW1 SW2 BST2 VCC 1.0V VCC_GD LDO VCC 1.05V DRIVER B VSENSE C VS2 DRIVER VOUT SELECT INPUTS START + – VSENSE + – 1.2A ON + – IPK UV LOGIC 0.7V VSENSE ENABLE VSENSE 50mA MPPC MODE VS1 DRIVER + – 1.0V RESET IZERO THERMAL SHUTDOWN 100mV – + + – PWM SOFT-START 3M VCC_GD + – + – 0.6V D VC + – RUN A ISENSE 1.0V VREF_GD VOUT VCC DRIVER 4V VREF VOUT + – VIN FB 1.0V OSC 600mA SLEEP GND – + CLAMP –7.5% – + PGOOD PGND 31301 BD 14 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 OPERATION INTRODUCTION The LTC3130/LTC3130-1 are 1.6µA quiescent current, monolithic, current mode, buck-boost DC/DC converters that can operate over a wide input voltage range of 0.6V (2.4V to start) to 25V and provide up to 600mA to the load. The LTC3130 has a FB pin for programming VOUT anywhere from 1V to 25V, while the LTC3130-1 features four fixed, user-selectable output voltages which can be selected using the two digital programming pins. Internal, low RDS(ON) N-channel power switches reduce solution complexity and maximize efficiency. A proprietary switch control algorithm allows the buck-boost converter to maintain output voltage regulation with input voltages that are above, below or equal to the output voltage. Transitions between the step-up or step-down operating modes are seamless and free of transients and sub-harmonic switching, making this product ideal for noise sensitive applications. The LTC3130/LTC3130-1 operate at a fixed nominal switching frequency of 1.2MHz, which provides an ideal trade-off between small solution size and high efficiency. Current mode control provides inherent input line voltage rejection, simplified compensation and rapid response to load transients. Burst Mode capability is included in the LTC3130/ LTC3130‑1 and is user-selected via the MODE pin. In Burst Mode operation, exceptional light-load efficiency is achieved by operating the converter only when necessary to maintain voltage regulation. The Burst Mode quiescent current is a miserly 1.6µA. When Burst Mode operation is selected, the converter automatically switches to fixed frequency PWM mode at higher loads. (Please refer to the Typical Performance Characteristic curves for the mode transition point at different input and output voltages.) If the application requires extremely low noise under all load conditions, continuous PWM operation can also be selected via the MODE pin by pulling it high. A MPPC (maximum power point control) function is also provided that prevents the converter from pulling enough current to drop VIN below a user-programmed threshold under load. This servos the input voltage of the converter to a programmable point for maximum power extraction when operating from various non-ideal power sources such as photovoltaic cells. The LTC3130/LTC3130-1 also feature an accurate RUN comparator threshold with hysteresis, allowing the buck/boost DC/DC converter to turn on and off at userprogrammed VIN voltage thresholds. With a wide voltage range, 1.6µA Burst Mode current and programmable RUN and MPPC pins, these highly integrated monolithic converters are well suited for many diverse applications. PWM MODE OPERATION If the MODE pin is high (or if the load current on the converter is high enough to command PWM mode operation with MODE low), the LTC3130/LTC3130-1 operate in a fixed 1.2MHz PWM mode using an internally compensated average current mode control loop. PWM mode minimizes output voltage ripple and yields a low noise switching frequency spectrum. A proprietary switching algorithm provides seamless transitions between operating modes and eliminates discontinuities in the average inductor current, inductor ripple current and loop transfer function throughout all modes of operation. These advantages result in increased efficiency, improved loop stability and lower output voltage ripple in comparison to the traditional buck-boost converter. Figure 1 shows the topology of the power stage which is comprised of four N-channel DMOS switches and their associated gate drivers. In PWM mode operation both switch pins transition on every cycle independent of the input and output voltages. In response to the internal control loop command, an internal pulse width modulator generates the appropriate switch duty cycle to maintain regulation of the output voltage. CBST1 BST1 CBST2 L PVIN SW1 SW2 VOUT BST2 VCC VCC A D VCC VCC B PGND C PGND Figure 1. Power Stage Schematic LTC3130 3130 F01 3130f For more information www.linear.com/LTC3130 15 LTC3130/LTC3130-1 OPERATION When stepping down from a high input voltage to a lower output voltage, the converter operates in buck mode and switch D remains on for the entire switching cycle except for the minimum switch low duration (typically 70ns). During the switch low duration, switch C is turned on which forces SW2 low and charges the flying capacitor, CBST2. This ensures that the switch D gate driver power supply rail on BST2 is maintained. The duty cycle of switches A and B are adjusted to maintain output voltage regulation in buck mode. If the input voltage is lower than the output voltage, the converter operates in boost mode. Switch A remains on for the entire switching cycle except for the minimum switch low duration (typically 70ns). During the switch low duration, switch B is turned on which forces SW1 low and charges the flying capacitor, CBST1. This ensures that the switch A gate driver power supply rail on BST1 is maintained. The duty cycle of switches C and D are adjusted to maintain output voltage regulation in boost mode. Oscillator The LTC3130/LTC3130-1 operate from an internal oscillator with a nominal fixed frequency of 1.2MHz. This allows the DC/DC converter efficiency to be maximized while still using small external components. Current Mode Control The LTC3130/LTC3130-1 utilizes average current mode control for the pulse width modulator. Current mode control, both average and the better known peak method, enjoy some benefits compared to other control methods including: simplified loop compensation, rapid response to load transients and inherent line voltage rejection. Referring to the Block Diagrams, a high gain, internally compensated transconductance voltage error amplifier monitors VOUT through a voltage divider connected to the FB pin (LTC3130) or via the internal VOUT voltage divider (LTC3130-1). The error amplifier output is used by the current mode control loop to command the appropriate inductor current level. The inverting input of the internally compensated average current amplifier is connected to the inductor current sense circuit. The average current amplifier’s output is compared to the oscillator ramps, 16 and the comparator outputs are used to control the duty cycle of the switch pins on a cycle-by-cycle basis. The voltage error amplifier makes adjustments to the current command as necessary to maintain VOUT in regulation. The voltage error amplifier therefore controls the outer voltage regulation loop. The average current amplifier makes adjustments to the inductor current as directed by the voltage error amplifier, and is commonly referred to as the inner current loop amplifier. The average current mode control technique is similar to peak current mode control except that the average current amplifier, by virtue of its configuration as an integrator, controls average current instead of the peak current. This difference eliminates the peak to average current error inherent to peak current mode control, while maintaining most of the advantages inherent to peak current mode control. The compensation components required to ensure proper operation have been carefully selected and are integrated within the LTC3130/LTC3130-1. Inductor Current Sense and Maximum Average Output Current As part of the current control loop required for current mode control, the LTC3130/LTC3130-1 include a pair of current sensing circuits that measure the buck-boost converter inductor current. The voltage error amplifier output (VC) is internally clamped to an accurate threshold. Since the average inductor current is proportional to VC, the clamp level sets the maximum average inductor current that can be programmed by the inner current loop. Taking into account the current sense amplifier’s gain, the maximum average inductor current is approximately 850mA typical (660mA minimum, assuming the ILIM pin is pulled high for the LTC3130). In buck mode, the output current is approximately equal to 90% of the inductor current IL (due to the forced low time of the B and C switches, where no current is delivered to the output): IOUT(BUCK) ≈ 0.9 • IL 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 OPERATION In boost mode, the output current is related to average inductor current and duty cycle by: IOUT(BOOST)  V  ≈ IL •  IN  • η  VOUT  Since the output current in boost mode is reduced by the step-up ratio of VIN/VOUT, the output current rating in buck mode is always greater than in boost mode. Also, because boost mode operation requires a higher inductor current for a given output current compared to buck mode, the efficiency (η) in boost mode will generally be lower due to higher IL2 • RDS(ON) losses in the power switches. This will further reduce the output current capability in boost mode. In either operating mode, however, the inductor peak-to-peak ripple current does not play a major role in determining the output current capability, unlike peak current mode control. The LTC3130/LTC3130-1 measure and control average inductor current, and therefore, the inductor ripple current magnitude has little effect on the maximum current capability (in contrast to an equivalent peak current mode converter). Under most conditions in buck mode, the LTC3130/LTC3130-1 are capable of providing a minimum of 600mA to the load. Refer to the Typical Performance Characteristics section for more details. In boost mode, as described previously, the output current capability is related to the boost ratio. For example, for a 5V VIN to 15V output application, the LTC3130/LTC3130-1 can provide up to 150mA typical to the load. Refer to the Typical Performance Characteristics section for more detail on output current capability. Programming VOUT (LTC3130) The output voltage of the LTC3130 is programmed using an external resistor divider from VOUT to ground with the divider tap connected to the FB pin, as shown in Figure 2, according to the equation:  R1 VOUT = 1.00V •  1+   R2  (Re fer to Figure 2) The output voltage can be set anywhere from 1.0V to 25V. An optional feed-forward capacitor can be added in parallel with R1 (as shown in Figure 2) to reduce Burst Mode ripple and improve transient response of the voltage loop. The typical feed-forward capacitor value can be calculated by: CFF (pF ) = 40 R1 (Meg) In some applications, where the voltage-loop bandwidth is high, it may prove beneficial to add a resistor in series with the feed-forward capacitor to limit the high frequency gain. The value isn’t critical, and resistor values of VOUT COUT LTC3130 R1 CFF OPTIONAL FEED-FORWARD RFF FB R2 GND 3130 F02 Figure 2. VOUT Feedback Divider (Showing Optional Feed-Forward Capacitor) approximately R1/20 are generally recommended. VOUT Programming Pins (LTC3130-1) The LTC3130-1 has a precision internal voltage divider on VOUT, eliminating the need for high value external feedback resistors. This not only eliminates two external components, it minimizes no-load quiescent current by using very high resistance values that would not be practical when used externally due to the effects of noise and board leakages that would cause VOUT regulation errors. The tap point on this divider is digitally selected by using the VS1 and VS2 pins to program one of four fixed output voltages. The VS1 and VS2 pins can be grounded or connected to VCC to select the desired output voltage, according to Table 1. They can also be driven dynamically from external logic signals, as long as the pin’s specified logic levels are satisfied and the absolute maximum ratings for the pins are not exceeded. 3130f For more information www.linear.com/LTC3130 17 LTC3130/LTC3130-1 OPERATION Note that driving VS1 or VS2 to a logic high that is below the VCC voltage can result in an increase of up to 1µA of current draw from VCC per VS pin. This does not occur in shutdown or if VCC is below its UVLO threshold, in which case these inputs are disabled and will not cause any extra current draw. Table 1. VOUT Program Settings for the LTC3130-1 VS2 VS1 VOUT 0 0 1.8V 0 VCC 3.3V VCC 0 5.0V VCC VCC 12V Programming the ILIM Threshold (LTC3130 only) The LTC3130 has two average current limit settings, which are set by the ILIM pin. If ILIM is pulled high (tied to VCC), the average inductor current limit will be set to 660mA (minimum). If the ILIM pin is pulled low (tied to ground), the average inductor current limit will be reduced to 250mA (minimum). This setting can be used in low power applications to reduce the maximum current draw from sources that may suffer excessive voltage drop at the full 600mA current limit setting, or to simply reduce the maximum output current. VOUT Undervoltage and Foldback Current Limit The LTC3130/LTC3130-1 include a foldback current limit feature to reduce power dissipation into a shorted output. When VOUT is less than 0.7V (typical), the average current limit is reduced to about half of its normal value. In the case of the LTC3130 with the ILIM pin set low, the average inductor current limit has already been cut in half and will not be further reduced during undervoltage. Overload Peak Current Limit The LTC3130/LTC3130-1 also have peak overload current (IPEAK) and zero current (IZERO) comparators. The IPEAK current comparator turns off switch A for the remainder of the switching cycle if the inductor current exceeds the maximum threshold of 1.3A (typical). An inductor current 18 level of this magnitude may occur during a fault, such as an output short circuit, or possibly for a few cycles during large load or input voltage transients. Note that it may also occur if there is excessive inductor ripple current (or inductor saturation) due to an improperly sized inductor. Note that if a peak current limit is reached while VOUT is also less than 0.7V typical (which would be indicative of a shorted output), a soft-start cycle will be triggered. IZERO Comparator The LTC3130/LTC3130-1 feature near discontinuous inductor current operation at light output loads by virtue of the IZERO comparator circuit. By limiting the reverse current magnitude in PWM mode, a balance between low noise operation and improved efficiency at light loads is achieved. The IZERO threshold is set near the zero current level in PWM mode, and as a result the reverse current magnitude will be a function of inductance value and output voltage due to the comparator’s propagation delay. In general, higher output voltages and lower inductor values will result in increased peak reverse current. In automatic Burst Mode operation (MODE pin low), the IZERO threshold is increased so that reverse inductor current does not normally occur. This maximizes efficiency at light loads. Note that reverse current is also inhibited during softstart (regardless of the MODE pin setting) to prevent VOUT discharge when starting up into pre-biased outputs. Burst Mode OPERATION When the MODE pin is held low, the LTC3130/LTC3130-1 are configured for automatic Burst Mode operation. As a result, the buck-boost DC/DC converter will operate with normal continuous PWM switching above a predetermined minimum output load and will automatically transition to power saving Burst Mode operation below this output load level. Refer to the Typical Performance Characteristics section of this data sheet to determine the Burst Mode transition threshold for various combinations of VIN and VOUT. 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 OPERATION If MODE is low, at light output loads, the LTC3130/ LTC3130‑1 go into a standby or sleep state when the output voltage achieves its nominal regulation level. The sleep state halts PWM switching and powers down all non-essential functions of the IC, significantly reducing the quiescent current of the converter to just 1.6µA typical. This greatly improves overall power conversion efficiency when the output load is light. Since the converter is not operating in sleep, the output voltage will slowly decay at a rate determined by the output load current and the output capacitor value. When the output voltage has decayed by a small amount, the LTC3130/LTC3130-1 wake and resume normal PWM switching operation until the voltage on VOUT is restored to the previous level. If the load is very light, the converter may only need to switch for a few cycles to restore VOUT and may sleep for extended periods of time, significantly improving efficiency. If the load is suddenly increased above the burst transition threshold, the part will automatically resume continuous PWM operation until the load is once again reduced. Note that Burst Mode operation is inhibited until soft-start is done, the MPPC pin is greater than 1.05V and VOUT has reached 95% of regulation. Soft-Start The LTC3130/LTC3130-1 soft-start circuit minimizes input current transients and output voltage overshoot on initial power up. The required timing components for soft-start are internal to the IC and produce a nominal average current limit soft-start duration of approximately 12ms. The internal soft-start circuit slowly ramps the error amplifier output. In doing so, the maximum average inductor current is also slowly increased, starting from zero. Soft-start is reset if the RUN pin drops below the accurate run threshold, VCC drops below its UVLO threshold, a thermal shutdown occurs, or a peak current limit occurs while VOUT is less than 0.7V typical. Note that because the average current limit is being softstarted, the VOUT rise time will be load dependent, and is typically less that 12ms. VCC Regulator and EXTVCC Input An internal low dropout regulator (LDO) generates a nominal 4V VCC rail from VIN, or from EXTVCC if a valid EXTVCC voltage is present. The VCC rail powers the internal control circuitry and the gate drivers of the LTC3130/LTC3130-1. The VCC regulator is enabled even in shutdown, but will regulate to a lower voltage. The VCC regulator includes current-limit protection to safeguard against accidental short-circuiting of the VCC rail. VCC should be decoupled with a 4.7µF ceramic capacitor located close to the IC. During start-up, the IC will choose the higher of VIN or EXTVCC to generate VCC. Once VCC is above its rising UVLO threshold, EXTVCC will continue to be used if it is above 3.0V typical, otherwise VIN will be used. This allows startup from low VIN sources (in applications where a valid EXTVCC voltage is present), while minimizing LDO power dissipation after start-up in applications where VIN may be much higher than VCC. Use of the EXTVCC input allows the converter to operate from VIN voltages less than 1V, as long as EXTVCC is held in its operating range of 3.0V minimum and 25V maximum. If EXTVCC is tied to VOUT in buck applications, it will also reduce the input current drawn from VIN, thereby increasing converter efficiency, especially at light loads. If an independent source, such as a battery or another supply rail, is used to power EXTVCC, then the IC can start up and operate at any input voltage, from 25V down to (theoretically) 0V (assuming the RUN pin is held above 1.05V). In practice, the minimum VIN voltage capability will be application specific, determined by the required output voltage and output current of the converter. Due to the rapid drop in efficiency at very low input voltages, the practical VIN limit is usually around 0.6V, assuming a low resistance source, and that the step-up ratio to VOUT doesn’t become duty cycle limited. Refer to the Typical Performance Characteristic curves for the output voltage and current capability versus VIN. If not used, EXTVCC should be grounded. 3130f For more information www.linear.com/LTC3130 19 LTC3130/LTC3130-1 OPERATION Undervoltage Lockout (UVLO) The VCC UVLO has a falling voltage threshold of 2.175V (typical). If the VCC voltage falls below this threshold, IC operation is disabled until VCC rises above 2.30V (typical). Therefore, if a valid voltage source is not present on EXTVCC, the minimum VIN for the part to start up is 2.30V (typical). Note that until VCC is above the UVLO threshold, the part will remain in a low quiescent current state (1.4µA typical). This facilitates start-up from very weak sources. RUN Pin Comparator When RUN is driven above its logic threshold (0.6V typical), the internal voltage reference and the PGOOD circuit are enabled (assuming VCC is above 2.30V typical). If the voltage on RUN is increased further so that it exceeds the RUN comparator’s accurate rising threshold (1.05V typical), all functions of the buck-boost converter will be enabled and a start-up sequence will ensue. The RUN pin comparator has 100mV of hysteresis, so operation will be inhibited if the pin drops below 0.95V. Therefore, with the addition of an optional resistor divider as shown in Figure 3, the RUN pin can be used to establish user-programmable turn-on and turn-off (UVLO) thresholds. This feature can be utilized to minimize battery drain below a programmed input voltage, or to operate the converter in a hiccup mode from very low current sources. LTC3130 VIN 1.05V R3 – + ACCURATE THRESHOLD ENABLE SWITCHING RUN R4 0.6V + – ENABLE VREF AND PGOOD LOGIC THRESHOLD 3130 F03 Figure 3. Accurate RUN Pin Comparator 20 If RUN is brought below the accurate comparator falling threshold, the buck-boost converter will inhibit switching, but the VCC regulator and control circuitry will remain powered. In this state, the typical VIN quiescent current is only 1.4µA, in order to completely shut down the IC and reduce the VIN current to 500nA (typical), it is necessary to ensure that RUN is brought below its minimum low logic threshold of 0.2V. RUN can be tied directly to VIN to continuously enable the IC when the input supply is present. Also note that RUN can be driven above VIN or VOUT as long as it stays within the absolute maximum rating of 25V. The converter is enabled when the voltage on RUN exceeds 1.05V (nominal). Therefore, the turn-on voltage threshold on VIN is given by:  R3  VIN(TURNON) = 1.05V •  1+   R4  Once the converter is enabled, the RUN comparator includes a built-in hysteresis of 100mV, so that the turnoff threshold will be :  R3  VIN(TURNOFF) = 0.95V •  1+   R4  The RUN comparator is designed to be relatively noise insensitive, but there may be cases due to PCB layout, very large value resistors for R3 and R4, or proximity to noisy components where noise pickup is unavoidable and may cause the turn-on or turn-off of the IC to be intermittent. In these cases, a small filter capacitor can be added across R4. PGOOD Comparator The LTC3130/LTC3130-1 provide an open-drain PGOOD output that pulls low if FB (LTC3130) or VOUT (LTC3130‑1) falls more than 7.5% (typical) below its programmed value. When VOUT rises to within 5% (typical) of its programmed value, the internal PGOOD pull-down will turn off and PGOOD will go high if an external pull-up resistor has been provided. An internal filter prevents 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 OPERATION nuisance trips of PGOOD due to short transients on VOUT. PGOOD can be pulled up to any voltage, as long as the absolute maximum rating of 25V is not exceeded, and as long as the absolute maximum sink current rating of 12mA is not exceeded when PGOOD is low. The MPPC divider resistor values can be in the MΩ range so as to minimize the input current in very low power applications. However, stray capacitance and noise pickup on the MPPC pin must also be minimized. If the MPPC function is not required, the MPPC pin should be tied to VCC. Note that PGOOD will be driven low if VCC is below its UVLO threshold or if the part is in shutdown (RUN below its logic threshold). PGOOD is not affected by the accurate RUN threshold. Therefore, if PGOOD is pulled up to VIN or VCC, this will add to the VIN quiescent current in shutdown and UVLO, when PGOOD is low. For the lowest possible VIN current in shutdown or UVLO, PGOOD should be pulled up to VOUT or some other source. Beware of adding a noise filter capacitor to the MPPC pin, as the added filter pole may cause the MPPC control loop to be unstable. Maximum Power Point Control (MPPC) The MPPC input of the LTC3130/LTC3130-1 can be used with an optional external voltage divider to dynamically adjust the commanded inductor current in order to maintain a minimum input voltage when using high resistance sources, such as photovoltaic panels, so as to maximize input power transfer and prevent VIN from dropping too low under load. Referring to Figure 4, the MPPC pin is internally connected to the noninverting input of a gm amplifier, whose inverting input is connected to the 1.0V reference. If the voltage at MPPC, using the external voltage divider, falls below the reference voltage, the output of the amplifier pulls the internal VC node low. This reduces the commanded average inductor current so as to reduce the input current and regulate VIN to the programmed minimum voltage, as given by: Note that because Burst Mode operation will be inhibited if the MPPC loop takes control, the converter will be operating in fixed frequency mode, and will therefore require a minimum of about 6mA of continuous input current to operate. For operation from weaker sources, such as small indoor solar panels, refer to the Applications Information section to see how the RUN pin may be programmed to control the converter in a hysteretic manner while providing an effective MPPC function by maintaining VIN at the desired voltage. This technique can be used with sources as weak as 3µA (enough to power the IC in UVLO and the external RUN divider). VIN RS CIN R5 + – VSOURCE MPPC + – R6 VIN LTC3130 1.0V FB + – VC CURRENT COMMAND VOLTAGE ERROR AMP 3130 F04  R5  VIN(MPPC) = 1.00V •  1+   R6  Figure 4. MPPC Amplifier with External Resistor Divider Note that external compensation should not be required for MPPC loop stability if the input filter capacitor, CIN, is at least 22µF. 3130f For more information www.linear.com/LTC3130 21 LTC3130/LTC3130-1 APPLICATIONS INFORMATION A standard application circuit for the LTC3130-1 is shown on the front page of this data sheet. There are numerous other application examples for both the LTC3130-1 and LTC3130 shown in the Typical Applications section of this data sheet. The appropriate selection of external components is dependent upon the required performance of the IC in each particular application given considerations and trade-offs such as PCB area, input and output voltage range, output voltage ripple, transient response, required efficiency, thermal considerations and cost. This section of the data sheet provides some basic guidelines and considerations to aid in the selection of external components and the design of the applications circuit, as well as more application circuit examples. VCC Capacitor Selection The VCC output of the LTC3130/LTC3130-1 is generated from VIN or EXTVCC by a low dropout linear regulator. The VCC regulator has been designed for stable operation with a wide range of output capacitors. For most applications, a low ESR capacitor of at least 4.7µF should be used. The capacitor should be located as close to the VCC pin as possible and connected to the VCC pin and ground through the shortest traces possible. VCC is the regulator output and is also the internal supply pin for the IC control circuitry as well as the gate drivers and boost rail charging diodes. Inductor Selection The choice of inductor used in LTC3130/LTC3130-1 application circuits influences the maximum deliverable output current, the converter bandwidth, the magnitude of the inductor current ripple and the overall converter efficiency. The inductor must have a low DC series resistance or output current capability and efficiency will be compromised. Larger inductor values reduce inductor current ripple but do not increase output current capability as is the case with peak current mode control. Larger value inductors also tend to have a higher DC series resistance 22 for a given case size, which will have a negative impact on efficiency. Larger values of inductance will also lower the right half plane (RHP) zero frequency when operating in boost mode, which can compromise loop stability. Nearly all LTC3130/LTC3130-1 application circuits deliver the best performance with an inductor value between 3.3µH and 15µH, depending on VIN and VOUT. Buck mode only applications can use the larger inductor values as they are unaffected by the RHP zero, while mostly boost applications generally require inductance on the low end of this range depending on how large the step-up ratio is. Regardless of inductor value, the saturation current rating should be selected such that it is greater than the worst-case average inductor current plus half of the ripple current. The peak-to-peak inductor current ripple for each operational mode can be calculated from the following formula, where f is the switching frequency (1.2MHz), L is the inductance in µH and tLOW is the switch pin minimum low time in µs. The switch pin minimum low time is typically 0.07µs. ∆IL(P-P)(BUCK) = VOUT  VIN – VOUT   1   – tLOW  Amps   L  VIN  f ∆IL(P-P)(BOOST) = VIN  VOUT – VIN   1   – tLOW  Amps   L  VOUT  f It should be noted that the worst-case peak-to-peak inductor ripple current occurs when the duty cycle in buck mode is minimum (highest VIN) and in boost mode when the duty cycle is 50% (VOUT = 2 • VIN). As an example, if VIN (minimum) = 2.5V and VIN (maximum) = 15V, VOUT = 5V and L = 10µH, the peak-to-peak inductor ripples at the voltage extremes (15V VIN for buck and 2.5V VIN for boost) are: Buck = 251mA peak-to-peak Boost = 94mA peak-to-peak One-half of this inductor ripple current must be added to the highest expected average inductor current in order to select the proper saturation current rating for the inductor. 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 APPLICATIONS INFORMATION To minimize core losses and to prevent high inductor current ripple from tripping the peak current limit before the average current limit is reached, an inductor value with a �IL of less than 500mA P-P should be chosen. For loads that operate well below current limit, higher inductor ripple can be tolerated to allow the use of a lower value inductor. To avoid the possibility of inductor saturation during load transients, an inductor with a saturation current rating of at least 1200mA is recommended for all applications (unless the ILIM pin of the LTC3130 is set low, in which case a 650mA rated inductor may be used). Note that in boost mode, especially at large step-up ratios, the output current capability is often limited by the total  resistive losses in the power stage. These losses include switch resistances, inductor DC resistance and PCB trace resistance. Avoid inductors with a high DC resistance (DCR) as they can degrade the maximum output current capability from what is shown in the Typical Performance Characteristics section and from the Typical Application circuits. As a guideline, the inductor DCR should be significantly less than the typical power switch resistance of 350mΩ. The only exceptions are applications that have a maximum output current much less than what the LTC3130/ LTC3130-1 are capable of delivering. Generally speaking, inductors with a DCR in the range of 0.05Ω to 0.15Ω are recommended. Lower values of DCR will improve the efficiency at the expense of size, while higher DCR values will reduce efficiency (typically by a few percent) while allowing the use of a physically smaller inductor. Different inductor core materials and styles have an impact on the size and price of an inductor at any given current rating. Shielded construction is generally preferred as it minimizes the chances of interference with other circuitry. The choice of inductor style depends upon the price, sizing, and EMI requirements of a particular application. Table 2 provides a wide sampling of inductor families from different manufacturers that are well suited to LTC3130/ LTC3130-1 applications. However, be sure to check the current rating and DC resistance for the particular value you need, as not all of the inductor values in a given family will be suitable. Table 2. Recommended Inductors VENDOR PART NUMBER FAMILY Coilcraft coilcraft.com EPL3015, LPS3314, LPS4012, LPS4018, XFL3012, XFL4020, MSS4020 Coiltronics cooperindustries.com SD3814, SD3118, SD52 Murata murata.com LQH43P, LQH44P Sumida sumida.com CDRH2D18, CDRH3D14, CDRH3D16, CDRH4D14 Taiyo-Yuden t-yuden.com NR3012T, NR3015T, NRS4012T, NR4018T TDK tdk.com VLF252015MT, VLF302510MT, VLF302512MT, VLS3015ET, VLCF4018T, VLCF4020T, SPM4012T Toko tokoam.com DB318C, DB320C, DEM2815C, DEM3512C, DEM3518C Wurth we-online.com WE-TPC 2818, WE-TPC 3816 Recommended maximum inductor values and minimum output capacitor values, for different output voltage ranges are given in Table 3 as a guideline. These values were chosen to minimize inductor size while ensuring loop stability over the entire load range of the converter. Table 3. Recommended Inductor and Output Capacitor Values MINIMUM RECOMMENDED OUTPUT CAPACITANCE (μF) VOUT (V) LMAX LTC3130-1/LTC3130 LTC3130 (μH) WITH FEED FORWARD PWM AND NO FEED-FORWARD 1 – 2.4 4.7 40 20 2.5 – 3.9 6.8 30 15 4 – 6.5 10 20 10 6.6 – 14 15 20 10 14 – 25 15 10 5 Note that many applications will be able to use a lower inductor value, depending on the input voltage range and resulting inductor current ripple. Lower inductor values will also allow the use of a smaller output capacitor value without compromising loop stability. 3130f For more information www.linear.com/LTC3130 23 LTC3130/LTC3130-1 APPLICATIONS INFORMATION Output Capacitor Selection A low effective series resistance (ESR) output capacitor of 10µF minimum should be connected at the output of the buck-boost converter in order to minimize output voltage ripple. Multilayer ceramic capacitors are an excellent option as they have low ESR and are available in small footprints. The capacitor value should be chosen large enough to reduce the output voltage ripple to acceptable levels. Neglecting the capacitor’s ESR and ESL (effect series inductance), the peak-to-peak output voltage ripple can be calculated by the following formula, where f is the frequency in MHz (1.2MHz), COUT is the capacitance in µF, tLOW is the switch pin minimum low time in µs (0.07µs) and ILOAD is the output current in Amps: ∆VP-P(BUCK) = ILOAD t LOW ∆VP-P(BOOST) = COUT Volts ILOAD  VOUT – VIN + tLOW fVIN   Volts fCOUT  VOUT Examining the previous equations reveal that the output voltage ripple increases with load current and is generally higher in boost mode than in buck mode. Note that these equations only take into account the voltage ripple that occurs from the inductor current to the output being discontinuous. They provide a good approximation of the ripple at any significant load current but underestimate the output voltage ripple at very light loads where the output voltage ripple is dominated by the inductor current ripple. In addition to the output voltage ripple generated across the output capacitance, there is also output voltage ripple produced across the internal resistance of the output capacitor. The ESR-generated output voltage ripple is proportional to the series resistance of the output capacitor and is given by the following expressions where RESR is 24 the series resistance of the output capacitor and all other terms as previously defined: ∆VP-P(BUCK) = ILOADRESR ∆VP-P(BOOST) = 1– tLOW f ≅ ILOADRESR Volts ILOADRESR VOUT ( VIN 1– t LOW f ) V  ≅ ILOADRESR  OUT  Volts  VIN  In most LTC3130/LTC3130-1 applications, an output capacitor between 10µF and 47µF will work well. To minimize output ripple in Burst Mode operation, or transients incurred by large step loads, values of 22µF or larger are recommended. Input Capacitor Selection The PVIN pin carries the full inductor current, while the VIN pin provides power to internal control circuits in the IC. To minimize input voltage ripple and ensure proper operation of the IC, a low ESR bypass capacitor with a value of at least 4.7µF should be located as close to the PVIN pin as possible. The VIN pin should be bypassed with a 1μF ceramic capacitor located close to the pin, and Kelvined to “quiet side” of the primary VIN decoupling capacitor. Do not tie the VIN pin directly to PVIN pin. When powered through long leads or from a power source with any significant resistance, an additional, larger value bulk input capacitor may be required and is generally recommended. In such applications, a 47µF to 100µF low ESR electrolytic capacitor in parallel with the 4.7µF ceramic capacitor generally yields a high performance, low cost solution. For applications using the MPPC feature, a minimum CIN capacitor value of 22µF is recommended. Larger values can be used without limitation. 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 APPLICATIONS INFORMATION Recommended Input and Output Capacitor Types The capacitors used to filter the input and output of the LTC3130/LTC3130-1 must have low ESR and must be rated to handle the AC currents generated by the switching converter. This is important to maintain proper functioning of the IC and to reduce output voltage ripple. There are many capacitor types that are well suited to these applications including multilayer ceramic, low ESR tantalum, OS-CON and POSCAP technologies. In addition, there are certain types of electrolytic capacitors such as solid aluminum organic polymer capacitors that are designed for low ESR and high AC currents and these are also well suited to some LTC3130/LTC3130-1 applications. value capacitance or a higher voltage rated capacitor than would ordinarily be required to actually realize the intended capacitance at the operating voltage of the application. X5R and X7R dielectric types are recommended as they exhibit the best performance over the wide operating range and temperature of the LTC3130/LTC3130-1. To verify that the intended capacitance is achieved in the application circuit, be sure to consult the capacitor vendor’s curve of capacitance versus DC bias voltage. Using the Programmable RUN Function to Operate from Extremely Weak Input Sources Beware of Capacitor DC Bias Effect Another application of the programmable RUN pin is that it can be used to operate the converter in a “hiccup” mode from extremely weak sources. This allows operation from sources that can only generate microamps of output current, and would be far too weak to sustain normal steady-state operation, even with the use of the MPPC pin. Because the LTC3130/LTC3130-1 draw only 1.4µA typical from VIN until they are enabled, the RUN pin can be programmed to keep the ICs disabled until VIN reaches the programmed voltage level. In this manner, the input source can trickle-charge an input storage capacitor, even if it can only supply microamps of current, until VIN reaches the turn-on threshold set by the RUN pin divider. The converter will then be enabled, using the stored charge in the input capacitor to power the converter and bring up VOUT, until VIN drops below the turn-off threshold, at which point the converter will turn off and the process will repeat. Ceramic capacitors are often utilized in switching converter applications due to their small size, low ESR and low leakage currents. However, many ceramic capacitors intended for power applications experience a significant loss in capacitance from their rated value as the DC bias voltage on the capacitor increases. It is not uncommon for a small surface mount capacitor to lose more than 50% of its rated capacitance when operated at even half of its maximum rated voltage. This effect is generally reduced as the case size is increased for the same nominal value capacitor. As a result, it is often necessary to use a larger This approach allows the converter to run from weak sources as small, thin-film solar cells using indoor lighting. Although the converter will be operating in bursts, it is enough to charge an output capacitor to power low duty cycle loads, such as in wireless sensor applications, or to trickle-charge a battery. In addition, note that the input voltage will be cycling (with 10% ripple as set by the UVLO hysteresis) about a fixed voltage, as determined by the divider. This allows the high impedance source to operate about the programmed optimal voltage for maximum power transfer. The choice of capacitor technology is primarily dictated by a trade-off between size, leakage current and cost. In backup power applications, the input or output capacitor might be a super or ultra capacitor with a capacitance value measuring in the Farad range. The selection criteria in these applications are generally similar except that voltage ripple is generally not a concern. Some capacitors exhibit a high DC leakage current which may preclude their consideration for applications that require a very low quiescent current in Burst Mode operation. Note that ultra capacitors may have a rather high ESR, therefore a 4.7µF (minimum) ceramic capacitor is recommended in parallel, close to the IC pins. 3130f For more information www.linear.com/LTC3130 25 LTC3130/LTC3130-1 APPLICATIONS INFORMATION In these “trickle-charge” applications, a larger input capacitor is generally required. If the load on VOUT is extremely light, such that the available steady-state input power can sustain VOUT, then the input capacitor simply has to have enough charge to bring VOUT into regulation before VIN discharges below the falling UVLO threshold (assuming that the goal is to charge up VOUT in a single “burst” and then maintain VOUT regulation). In this case, the minimum value required for CIN can be determined by: CIN(MIN) > COUT • VOUT 2 ( η( V – (0.9 • V ))) IN 2 IN 2 where VIN is the programmed rising UVLO threshold and η is the average conversion efficiency, given VIN and VOUT. It can be seen that a larger COUT capacitor will require a larger CIN capacitor to charge it. The time required for the CIN capacitor to charge up to the VIN rising UVLO threshold (starting from zero volts) is: tCHARGE ( sec ) = CIN (µF ) • VIN(UVLO) (ICHARGE (µA ) – 1.4µA –ILEAK (µA )) where ILEAK is the leakage of the input capacitor in µA at the programmed VIN UVLO voltage. For applications where VOUT must remain in regulation during a pulsed load for a given period of time, the input capacitor value required will be dictated by the programmed VIN and VOUT, and the duration and magnitude of the output load current, as given by: CIN(MIN) > IOUT • VOUT • 2 • t ( η( V – (0.9 • V ))) IN 2 IN 2 where CIN is in micro Farads, IOUT is the average load current in milliamps for duration t in milliseconds. VIN is the programmed rising UVLO threshold and η is the average conversion efficiency, given VIN and VOUT. This calculation assumes that the VOUT capacitor has already been charged, and that the load on VOUT before and after the load pulse is low enough as to be sustained by the available steady-state input power. 26 For example, if VOUT is 5V, with a pulsed load of 25mA for a duration of 5ms, and VIN has been programmed for a rising UVLO threshold of 12V, then the minimum CIN capacitor required, assuming a conversion efficiency of 85%, would be 53.7µF, so a 68µF input capacitor would be recommended. When using high value RUN pin divider resistors (in the MΩ range) to minimize current draw on VIN, a small noise filter capacitor may be necessary across the lower divider resistor to prevent noise from erroneously tripping the RUN comparator. The capacitor value should be minimized (10pF may do) so as not to introduce a time delay long enough for the input voltage to drop significantly below the desired VIN threshold. Note that larger VIN decoupling capacitor values will minimize this effect by providing more holdup time on VIN. Use of the EXTVCC Input As discussed in the Operation section of this data sheet, the LTC3130/LTC3130-1 include an EXTVCC input that can be used to provide VCC for the IC, allowing start-up and/ or operation in applications where VIN is below the VCC UVLO threshold, all the way down to less than 1V. Possible sources that could be used to power the EXTVCC input would include VOUT (if VOUT is programmed for at least 3.15V and if VIN is at least 2.4V to start), or an independent voltage rail that may be available in the system, or even a battery. The requirements for the EXTVCC voltage are that it is a minimum of 3.0V typical, and an absolute maximum of 25V. It must also be able to supply a minimum of 6mA of current. If the source of EXTVCC is not very close to the IC, then a decoupling capacitor of 4.7µF minimum is recommended at the EXTVCC pin. In the case of using a battery to power EXTVCC, the battery life for continuous steady-state operation in fixed frequency mode can be estimated by: Battery Life (Hours) = Battery Capacity (mA-Hr)/6mA 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 APPLICATIONS INFORMATION For example, a 3.6V battery with a capacity of 2600mA‑Hr (2.6A-Hr) could power the IC continuously in fixed frequency mode for ~433 hours (only about 18 days). However, if the IC is in Burst Mode operation at light load, the battery life time will be extended, possibly by orders of magnitude (depending on the load) since the current demand when the IC is sleeping will be only 1.6µA typical. In shutdown, the current draw will be only 0.5µA typical. For applications where VOUT will be greater than the battery voltage, and at least 3.6V, a battery and a dual Schottky diode can be used to get the part started at low VIN. After start-up, the IC will be powered from VOUT, so there will be no steady-state current draw on the battery. In this case, the battery life may approach its shelf life (even in continuous fixed frequency operation). In shutdown, there will be about 0.5uA of current draw from the battery. An example of this configuration is shown in Figure 5. + V – PVIN VIN 1V TO 25V EXTVCC VOUT VIN LTC3130/ LTC3130-1 RUN COUT VOUT 4V TO 25V BAT54C EXTVCC SGND 4.7µF + 3.6V 3031 F05 Figure 5. Using a Battery Just for Start-Up from Low VIN Note that during start-up, when VCC is still in UVLO, the IC chooses the higher of VIN or EXTVCC to power VCC (even if EXTVCC is below 3.0V). After start-up however, when VCC has risen above its rising UVLO threshold, the IC will choose to use the EXTVCC input to power VCC only if EXTVCC is above 3.0V, typical. This is done to avoid using EXTVCC at a very low voltage when a higher voltage may be available at VIN. Therefore, there could be a situation where the IC would switch between using EXTVCC during start-up, and VIN as the source for VCC after start-up. However, if VIN is below the UVLO threshold, VCC will drop and revert to using EXTVCC again. This cycling will only occur if VIN is below the UVLO falling threshold and EXTVCC is greater than the UVLO rising threshold of 2.4V, but less than 3.0V (and the part is enabled, with the RUN pin above the accurate rising threshold). Note that during this time, the IC will be periodically trying to start switching, as it goes in and out of UVLO. If EXTVCC is held above 3.0V, this will not occur. In applications where the VIN and EXTVCC voltages are such that this scenario could occur, the RUN pin can be used to monitor the EXTVCC input and inhibit operation whenever EXTVCC is below 3.15V. An example of this is shown in Figure 6. EXTVCC + V – 2M VEXT LTC3130 1.05V RUN – + ENABLE SWITCHING 1M 3130 F06 Figure 6. Using the RUN Pin to Set the Minimum Voltage for EXTVCC to 3.15V Programming the MPPC Voltage As discussed in the previous section, the LTC3130/ LTC3130-1 include an MPPC function to optimize performance when operating from voltage sources with relatively high source resistance. Using an external voltage divider from VIN, the MPPC function takes control of the average inductor current when necessary to maintain a minimum input voltage, as programmed by the user. Referring to Figure 3:  R5  VIN(MPPC) = 1.0V •  1+   R6  This is useful for such applications as photovoltaic powered converters, since the maximum power transfer point occurs when the photovoltaic panel is operated at about 75% of its open-circuit voltage. For example, when operating from a photovoltaic panel with an open-circuit voltage of 5V, the maximum power transfer point will be when the panel is loaded such that its output voltage is about 3.75V. Referring to Figure 4, choosing values of 2MΩ for R5 and 732k for R6 will program the MPPC function to regulate the maximum input current so as to maintain VIN at a minimum of 3.73V (typical). Note that if the panel can provide more power than the application requires, the input voltage will rise above the programmed MPPC point. This is fine as long as the input voltage doesn’t exceed 25V. 3130f For more information www.linear.com/LTC3130 27 LTC3130/LTC3130-1 APPLICATIONS INFORMATION For weak input sources with very high resistance (hundreds of Ohms or more), the LTC3130/LTC3130-1 may still draw more current than the source can provide, causing VIN to drop below the UVLO threshold. For these applications, it is recommended that the programmable RUN feature be used, as described in a previous section. MPPC Compensation and Gain When using MPPC, there are a number of variables that affect the gain and phase of the input voltage control loop. Primarily these are the input capacitance, the MPPC resistor divider ratio and the VIN source resistance. To simplify the design of the application circuit, the MPPC control loop in the LTC3130/LTC3130-1 is designed with a relatively low gain, such that external MPPC loop compensation is generally not required when using a VIN capacitor of at least 22µF. The gain from the MPPC pin to the internal control voltage is about ten, and the gain of the internal control voltage to average inductor current is about one. Therefore, a change of 60mV a the MPPC pin will result in a change of average inductor current of about 600mA, which is close to the full current capability of the IC. So the programmed input voltage will be maintained within about 6% over the full current range of the IC (which may be more than that required by the load). Sources of Small Photovoltaic Panels A list of companies that manufacture small solar panels (sometimes referred to as modules or solar cell arrays), suitable for use with the LTC3130/LTC3130-1 is provided in Table 4. Table 4. Small Photovoltaic Panel Manufacturers Sanyo panasonic.net PowerFilm powerfilmsolar.com Ixys Corporation ixys.com G24 Innovations gcell.com 28 Thermal Considerations The power switches of the LTC3130/LTC3130-1 are designed to operate continuously with currents up to the internal current limit thresholds. However, when operating at high current levels, there may be significant heat generated within the IC. As a result, careful consideration must be given to the thermal environment of the IC in order to provide a means to remove heat from the IC and ensure that the LTC3130/LTC3130-1 is able to provide its full-rated output current. Specifically, the exposed die attach pad of both the QFN and MSE packages must be soldered to a copper layer on the PCB to maximize the conduction of heat out of the IC package. This can be accomplished by utilizing multiple vias from the die attach pad connection underneath the IC package to other PCB layer(s) containing a large copper plane. A typical board layout incorporating these concepts in show in Figure 7. As described elsewhere in this data sheet, the EXTVCC pin may be used to reduce the VCC power dissipation term significantly in high VIN applications, lowering die temperature and improving efficiency. If the IC die temperature exceeds approximately 165°C, overtemperature shutdown will be invoked and all switching will be inhibited. The part will remain disabled until the die temperature cools by approximately 10°C. The soft-start circuit is re-initialized in overtemperature shutdown to provide a smooth recovery when the IC die temperature cools enough to resume operation. Applications with Low VIN and VOUT Applications which must operate from input voltages of less that 3V and have an output voltage of 1.8V or less, while operating at heavy loads, will benefit significantly from the addition of Schottky diode from SW2 to VOUT. Diodes such as an MBR0530 or equivalent are recommended for these applications. 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 APPLICATIONS INFORMATION LTC3130 L1 CBST2 CBST1 RPGD VIN VOUT GND GND CIN PGOOD ILIM R2 R1 MODE MPPC RUN COUT CEXT CVCC LTC3130-1 L1 CBST2 CBST1 RPGD VIN VOUT GND GND CIN COUT VS1 MODE VS2 RUN MPPC PGOOD CEXT CVCC 8603 F07 Figure 7. Typical 2-Layer PC Board Layout (QFN Package Shown) 3130f For more information www.linear.com/LTC3130 29 LTC3130/LTC3130-1 APPLICATIONS INFORMATION 22nF VOC = 5V VOP = 3.5V VIN BST1 PVIN 22nF 4.7µH SW1 SW2 PV PANEL RUN EXTVCC LTC3130 1µF VCC 2M 3.4M PGOOD MPPC 47µF + 4.7µF VIN 4.99M BST2 VOUT ILIM + 100F VOUT 4.4V 100k 100F 100k FB VCC MODE GND PGND 4.7µF 1M TECATE TPL-100/22x45F 3130 F08 Figure 8. Outdoor Solar Panel Powered, 600mA Supercapacitor Charger Using MPPC 22nF BST1 PVIN VIN 22nF 10µH SW1 SW2 VIN 3.6V Li-SOCI2 + RUN 10µF VCC 1µF LTC3130 BST2 VOUT EXTVCC PGOOD MPPC ILIM 1M 10µF 10pF VOUT 24V 20mA 4.02M 200k PGOOD FB VCC MODE GND PGND 174k 4.7µF 3130 F09 Figure 9. Battery-Powered 24V Converter with 200mA ILIM to Limit Battery Droop 30 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 APPLICATIONS INFORMATION 22nF BST1 PVIN VIN 2.4V TO 25V 22nF 10µH SW1 SW2 VIN RUN 10µF VCC 1µF BST2 VOUT 10µF EXTVCC LTC3130 VOUT 15V 500mA 10pF (V > 15V) IN 4.99M 249k PGOOD MPPC ILIM FB VCC MODE GND PGND 4.7µF 357k 3130 F10 Figure 10. Wide VIN Range 15V Converter with Burst Mode Operation 22nF BST1 PVIN VIN 0.95V TO 25V (2.4V TO START) 22nF 6.8µH SW1 SW2 22µF VIN RUN 10µF VCC LTC3130-1 EXTVCC 1M MPPC MODE 1µF VOUT 5V 500mA (VIN > 5V) BST2 VOUT PGOOD PGOOD VS1 VS2 VCC GND PGND 4.7µF 3130 F11 Figure 11. Low Noise, Wide VIN Range 5V Converter 3130f For more information www.linear.com/LTC3130 31 LTC3130/LTC3130-1 APPLICATIONS INFORMATION MBR0520 22nF 12V WALL ADAPTER INPUT IOUT UP TO 600mA WHEN OPERATING FROM WALL ADAPTER IOUT UP TO 500mA WHEN OPERATING FROM USB 3.0 INPUT IOUT UP TO 300mA WHEN OPERATING FROM BATTERY 22nF 6.8µH B130 USB 3.0 INPUT BST1 PVIN VIN BSS314 RUN GATE VIN 10µF LTC4412 Li-Ion + VCC SW1 SW2 STAT GND 1M MPPC PGOOD PGOOD VS1 1µF CTL VOUT 5V 22µF EXTVCC LTC3130-1 MODE SENSE BST2 VOUT VCC VS2 VCC GND PGND 4.7µF 3130 F12 Figure 12. Multiple VIN 5V Out Application, Using the LTC4412 PowerPath™ Controller 22nF VMPPC = 8V BST1 PVIN VIN VIN + 10V TO 14V 698k 10Ω RUN 22nF 6.8µH SW1 SW2 LTC3130-1 BST2 VOUT 10µF VOUT 12V 100mA MIN EXTVCC MPPC 22µF 1µF VCC 100k MODE PGOOD VS1 VS2 VCC GND PGND 4.7µF 3130 F13 Figure 13. 12V Converter Uses MPPC Function to Maintain a Minimum VIN from a Current Limited Source 32 3130f For more information www.linear.com/LTC3130 LTC3130/LTC3130-1 APPLICATIONS INFORMATION 22nF DC SOURCE