LTC3113 3A Low Noise Buck-Boost DC/DC Converter FEATURES DESCRIPTION n The LTC®3113 is a wide VIN range, highly efficient, fixed frequency, buck-boost DC/DC converter that operates from input voltages above, below or equal to the output voltage. The topology incorporated in the IC provides low noise operation, making it well suited for RF and precision measurement applications. n n n n n n n n n n n n Regulated Output with Input Voltage Above, Below or Equal to the Output Voltage 1.8V to 5.5V Input and Output Voltage Range 3A Continuous Output Current VIN > 3.0V, VOUT = 3.8V 1.5A Continuous Output Current for VIN ≥ 1.8V, VOUT = 3.3V Single Inductor Low Noise Buck-Boost Architecture Up to 96% Efficiency Programmable Frequency from 300kHz to 2MHz Selectable Burst Mode® Operation Output Disconnect in Shutdown Shutdown Current: <1μA Internal Soft-Start Small, Thermally Enhanced 16-Lead (4mm × 5mm × 0.75mm) DFN Package and 20-Lead TSSOP Package APPLICATIONS n n n n n The LTC3113 can deliver up to 3A of continuous output current to satisfy the most demanding applications. Higher output current is possible in stepdown (buck) mode. Integrated low RDS(ON) power MOSFETs and a programmable switching frequency up to 2MHz result in a compact solution footprint. Selectable Burst Mode operation improves efficiency at light loads. Other features include <1μA shutdown current, integrated soft-start, short-circuit protection, current limit and thermal overload protection. The LTC3113 is housed in the thermally enhanced 16-lead (4mm × 5mm × 0.75mm) DFN and 20-lead TSSOP packages. L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks and No RSENSE, PowerPath are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Wireless Modems Backup Power Systems Portable Inventory Terminals Portable Barcode Readers Portable Instrumentation TYPICAL APPLICATION Efficiency vs Input Voltage 100 Li-Ion to 3.8V/3A 95 2.2μH VIN 3V TO 4.2V SW2 VIN 47μF OFF ON PWM BURST VOUT 845k LTC3113 RUN FB BURST VC 6.49k 47pF 49.9k RT SGND ILOAD = 1A 90 680pF 158k VOUT 3.8V 100μF 3A EFFICIENCY (%) SW1 VOUT = 3.8V 85 ILOAD = 3A 80 75 70 65 60 55 PGND 3113 TA01a 90.9k 12pF 50 1.5 2.0 2.5 3.0 3.5 4.0 4.5 INPUT VOLTAGE (V) 5.0 5.5 3113 TA01b 3113f 1 LTC3113 ABSOLUTE MAXIMUM RATINGS (Notes 1, 3) VIN, VOUT, SW1, SW2 Voltage (DC).............. –0.3V to 6V SW1, SW2 Voltage, Pulsed (<100ns) (Note 4)............7V VC, RUN, BURST Voltage ............................. –0.3V to 6V FB ................................................................–0.3V to VIN RT Voltage.................................................... –0.3V to 1V Operating Junction Temperature Range (Notes 2, 5) ............................................ –40°C to 125°C Maximum Junction Temperature........................... 125°C Storage Temperature Range................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) TSSOP .............................................................. 300°C PIN CONFIGURATION TOP VIEW TOP VIEW PGND 1 20 PGND VOUT 1 16 SW2 VOUT 2 19 SW2 VOUT 2 15 SW2 VOUT 3 18 SW2 VIN 3 14 SW1 VIN 4 VIN 4 13 SW1 VIN 5 VIN 5 12 SW1 VIN 6 SGND 6 11 RUN SGND 7 14 RUN BURST 7 10 FB BURST 8 13 FB RT 8 9 RT 9 12 VC 17 PGND VC 17 SW1 21 PGND PGND 10 DHD PACKAGE 16-LEAD (5mm s 4mm) PLASTIC DFN TJMAX = 125°C, θJA = 36.5°C/W, θJC = 3.6°C/W EXPOSED PAD (PIN 17) IS PGND, MUST BE SOLDERED TO PCB 16 SW1 15 SW1 11 PGND FE PACKAGE 20-LEAD PLASTIC TSSOP TJMAX = 125°C, θJA = 31.5°C/W, θJC = 4.1°C/W EXPOSED PAD (PIN 21) IS PGND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3113EDHD#PBF LTC3113EDHD#TRPBF 3113 16-Lead (5mm × 4mm) Plastic DFN –40°C to 125°C LTC3113IDHD#PBF LTC3113IDHD#TRPBF 3113 16-Lead (5mm × 4mm) Plastic DFN –40°C to 125°C LTC3113EFE#PBF LTC3113EFE#TRPBF LTC3113FE 20-Lead Plastic TSSOP –40°C to 125°C LTC3113IFE#PBF LTC3113IFE#TRPBF LTC3113FE 20-Lead Plastic TSSOP –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. Consult LTC Marketing for information on non-standard lead based finish parts. 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/ 3113f 2 LTC3113 ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 3.3V, VOUT = 3.8V unless otherwise noted. PARAMETER CONDITION MIN TYP MAX UNITS Input Operating Range l 1.8 5.5 V Output Voltage Adjust Range l 1.8 5.5 V l 588 600 612 mV Feedback Voltage VBURST = 0V Feedback Input Current VFB = 0.7V 0 50 nA Quiescent Current–Burst Mode Operation VBURST = 3.3V 40 55 μA Quiescent Current–Shutdown VOUT = 0V, VRUN = 0V, Not Including Switch Leakage 0.1 1 μA Quiescent Current–Active VFB = 0.7V, VBURST = 0V, RT = 90.9k 300 500 μA 5.8 7.8 9.8 A Peak Current Limit 6.5 11.1 16.0 A Burst Mode Peak Current Limit 0.9 1.9 2.9 A Reverse Current Limit –1.6 –1 –0.4 A l Input Current Limit NMOS Switch Leakage Switch B, SW1 = 5.5V, VIN = 5.5V, VOUT = 5.5V Switch C, SW2 = 5.5V, VIN = 5.5V, VOUT = 5.5V 0.01 0.01 10 10 μA μA PMOS Switch Leakage Switch A, VIN = 5.5V, VOUT = 5.5V, SW1 = 0V Switch D, VIN = 5.5V, VOUT = 5.5V, SW2 = 0V 0.01 0.01 20 20 μA μA NMOS Switch On-Resistance Switch B, VOUT = 3.8V Switch C, VOUT = 3.8V 25 35 mΩ mΩ PMOS Switch On-Resistance Switch A, VIN = 3.3V Switch D, VOUT = 3.8V 30 40 mΩ mΩ Maximum Duty Cycle Boost (% Switch C On) Buck (% Switch A On) 90 % % 80 100 l Minimum Duty Cycle Frequency Accuracy l l RT = 90.9k l 0 0.8 Error Amp AVOL Error Amp Source Current VC = 0V, VFB = 0V Error Amp Sink Current VC = 1.2V, VFB = 0.7V BURST Input Logic Threshold BURST Input Current RUN Input Current VRUN = 5.5V Soft-Start Time 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 LTC3113 is tested under pulsed load conditions such that TJ ≈ TA . The LTC3113E is guaranteed to meet performance specifications from 0°C to 85°C junction temperature. Specifications over the –40°C to 125°C operating temperature range are assured by design, characterization and correlation with statistical process controls. The LTC3113I is guaranteed to meet performance specifications over the –40°C to 125°C operating junction temperature range. 1.2 MHz 100 dB 500 μA 160 l 0.3 0.7 l 0.3 0 VBURST = 5.5V RUN Input Logic Threshold 1 % μA 1.2 V 0 1 μA 0.7 1.2 V 1 μA 2 ms Note 3: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. The maximum rated junction temperature will be exceeded when the protection is active. Continuous operation above the specified absolute maximum operating junction temperature may impair device reliability or permanently damage the device. Note 4: Voltage transients on the switch pins beyond the DC limit specified in the absolute maximum ratings are non-disruptive to normal operation when using good layout practices, as shown on the demo board or described in the data sheet and application notes. Note 5: The junction temperature (TJ in °C) is calculated from the ambient temperature (TA in °C) and the power dissipation (PD in Watts) as follows: TJ = TA + (PD) • (θJA°C/W) 3113f 3 LTC3113 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C, VIN = 3.3V, VOUT = 3.8V unless otherwise specified) Efficiency 3.3V ±10% to 3.8V Burst Mode No-Load Input Current vs VIN Efficiency 1.8V, 3.6V, 5.5V to 3.8V 100 100 100 90 VIN = 2.97V VIN = 3.3V VIN = 3.63V VIN = 2.97V BURST VIN = 3.3V BURST VIN = 3.63V BURST 60 50 0.001 0.01 0.1 1 LOAD CURRENT (A) 70 VIN = 1.8V VIN = 3.6V VIN = 5.5V VIN = 1.8V BURST VIN = 3.6V BURST VIN = 5.5V BURST 60 50 0.001 10 0.01 0.1 1 LOAD CURRENT (A) 60 60 50 50 20 VOUT = 5.5V 40 30 VOUT = 3.8V 20 10 10 VOUT = 1.8V 0 –45 –25 –5 15 35 55 75 TEMPERATURE (°C) 0 1.5 95 115 2.0 2.5 3.0 3.5 4.0 VIN (V) 4.5 30 10 0 1.5 2.0 2.5 3.0 4.5 3.5 4.0 VIN (V) 5.0 5.0 1.4 Normalized P-Channel Switch Resistance vs VIN 1.3 T = 125°C 1.2 1.1 T = 25°C 1.0 T = –40°C 0.9 0.8 0.7 1 1.5 2 5.5 2.5 3 3.5 4 VIN (V) 4.5 5 1.6 5.5 6 3113 G06 Feedback Voltage vs Temperature Normalized N-Channel Switch Resistance vs VIN 5.5 3113 G03 3113 G05 3113 G04 Maximum Load Current in PWM Mode vs VIN (Input Current limit 5.8A) 6 0.601 1.5 1.3 T = 125°C 1.2 1.1 T = 25°C 1.0 0.9 T = –40°C 0.8 MAXIMUM LOAD CURRENT (A) 0.600 1.4 FEEDBACK VOLTAGE (V) NORMALIZED N-CHANNEL SWITCH RESISTANCE VOUT = 1.8V 40 10 PWM Mode No-Load Input Current vs VIN INPUT CURRENT (mA) INPUT CURRENT (μA) Burst Mode No-Load Input Current vs Temperature 30 50 3113 G02 3113 G01 40 70 V OUT = 3.8V 60 20 NORMALIZED P-CHANNEL SWITCH RESISTANCE 70 80 INPUT CURRENT (μA) EFFICIENCY (%) EFFICIENCY (%) 80 VOUT = 5.5V 80 90 90 0.599 0.598 0.597 0.596 5 4 3 2 0.7 0.6 1 1.5 2 2.5 3 3.5 4 VIN (V) 4.5 5 5.5 6 3113 G07 0.595 –45 –25 –5 15 35 55 75 TEMPERATATURE (°C) 95 115 3113 G08 1 1.5 2.0 2.5 3.0 3.5 4.0 VIN (V) 4.5 5.0 5.5 3113 G09 3113f 4 LTC3113 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C, VIN = 3.3V, VOUT = 3.8V unless otherwise specified) Maximum Load Current in Burst Mode Operation vs VIN (Burst Mode Peak Current Limit 0.9A) Output Voltage Regulation vs Load Current OUTPUT VOLTAGE REGULATION (%) MAXIMUM LOAD CURRENT (mA) 300 250 200 150 100 50 0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 0 VOUT 200mV/DIV Burst Mode OPERATION –0.2 ILOAD 2A/DIV –0.4 –0.6 –0.8 0.001 VIN (V) 0.01 0.1 LOAD CURRENT (A) 1 10 3113 G11 3113 G10 Output Voltage Ripple in Burst Mode Operation Output Voltage Ripple in PWM Mode Burst to PWM Mode Transient VOUT 20mV/DIV VOUT 20mV/DIV VOUT 50mV/DIV VIN = 3.3V VOUT 20mV/DIV VIN = 4V VOUT 20mV/DIV INDUCTOR CURRENT 1A/DIV BURST 2V/DIV VIN = 4.55V 20μs/DIV ILOAD = 50mA FRONT PAGE TYPICAL APPLICATION 3113 G14 ILOAD = 1A 3113 G14 1μs/DIV Normalized Peak Current Limit vs Temperature (11.1A Typical) 500μs/DIV 3113 G16 1.10 NORMALIZED PEAK CURRENT LIMIT VIN = 3.3V VOUT = 3.8V COUT = 100μF NORMALIZED INPUT CURRENT LIMIT 1.10 RUN 5V/DIV 1.05 1.00 0.95 0.90 –45 –25 –5 3113 G15 ILOAD = 50mA 500μs/DIV FRONT PAGE TYPICAL APPLICATION Normalized Input Current Limit vs Temperature (7.8A Typical) Soft-Start VOUT 2V/DIV 3113 G12 100μs/DIV BACK PAGE TYPICAL APPLICATION –1.0 0.0001 5.5 5.0 Load Step, 0A to 3A PWM MODE 15 35 55 75 TEMPERATURE (°C) 95 115 3113 G17 1.05 1.00 0.95 0.90 –45 –25 –5 15 35 55 75 TEMPERATURE (°C) 95 115 3113 G18 3113f 5 LTC3113 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C, VIN = 3.3V, VOUT = 3.8V unless otherwise specified) Minimum Start-Up Voltage vs Temperature Negative Inductor Current vs Oscillator Frequency Oscillator Frequency vs RT 2.5 1.705 0 VOUT PULLED UP TO 5.5V L = 2.2μH START-UP VOLTAGE (V) 1.701 1.699 1.697 1.695 1.693 1.691 1.689 2.0 REVERVE CURRENT LIMIT (A) OSCILLATOR FREQUENCY (MHz) 1.703 1.5 1.0 0.5 –1 –2 –3 –4 –5 1.687 1.685 –45 –25 –5 0 15 35 55 75 TEMPERATURE (°C) 0 95 115 50 100 150 200 RT (kΩ) 250 300 3113 G20 3113 G19 Junction Temperature Rise vs Continuous Load Current for VOUT = 1.8V 60 50 40 30 20 VIN = 1.8V VIN = 2.4V VIN = 3.3V VIN = 5.5V 10 0 0.5 1 1.5 2 2.5 3 3.5 LOAD CURRENT (A) 4 JUNCTION TEMPERATURE RISE (°C) JUNCTION TEMPERATURE RISE (°C) 3113 G21 Junction Temperature Rise vs Continuous Load Current for VOUT = 3.3V 60 0 –6 0.25 0.45 0.65 0.85 1.05 1.25 1.45 1.65 1.85 OSCILLATOR FREQUENCY (MHz) 350 50 40 30 20 0 4.5 VIN = 1.8V VIN = 2.4V VIN = 3.3V VIN = 5.5V 10 0 0.5 1 1.5 2 2.5 3 3.5 LOAD CURRENT (A) 4 3113 G22 3113 G23 Junction Temperature Rise vs Continuous Load Current for VOUT = 5.5V Junction Temperature Rise vs Continuous Load Current for VOUT = 3.8V 60 50 40 30 20 VIN = 1.8V VIN = 2.4V VIN = 3.3V VIN = 5.5V 10 0 0.5 1 1.5 2 2.5 3 3.5 LOAD CURRENT (A) 4 4.5 3113 G24 JUNCTION TEMPERATURE RISE (°C) JUNCTION TEMPERATURE RISE (°C) 60 0 4.5 50 40 30 20 VIN = 1.8V VIN = 2.4V VIN = 3.3V VIN = 5.5V 10 0 0 0.5 1 1.5 2 2.5 LOAD CURRENT (A) 3 3.5 3113 G25 3113f 6 LTC3113 PIN FUNCTIONS (DFN/TSSOP) VOUT (Pins 1, 2/Pins 2, 3): Buck-Boost Output Voltage. A low ESR capacitor should be placed from VOUT to PGND. The capacitor should be placed as close to the IC as possible and have a short return path to ground. VIN (Pins 3, 4, 5/Pins 4, 5, 6): Power Input for the Converter. A 47μF or larger bypass capacitor should be connected between VIN and PGND. The bypass capacitor should located as close to VIN and PGND as possible and should via directly to the ground plane. SGND (Pin 6/Pin 7): Signal Ground. Terminate the frequency setting resistor and output voltage divider to SGND. BURST (Pin 7/Pin 8): Pulse Width Modulation/Burst Mode Selection Input. Forcing this pin low causes the switching converter to operate in low noise fixed frequency PWM mode. Forcing this pin high enables constant Burst Mode operation for the converter. During Burst Mode operation, the converter can only support a reduced maximum load current. RT (Pin 8/Pin 9): Programs the Frequency of the Internal Oscillator. Connect a resistor from RT to ground (SGND). The RT resistor value for a given frequency is given by the following equation. RT ≅ 90 (kΩ) f (MHz ) VC (Pin 9/Pin 12): Error Amp Output. An R-C network is connected from this pin to FB for loop compensation. Refer to the Closing the Feedback Loop section for component selection guidelines. FB (Pin 10/Pin 13): Feedback Voltage for the Buck-Boost Converter Derived from a Resistor Divider on the BuckBoost Output Voltage. The buck-boost output voltage is given by the following equation: ⎛ R2 ⎞ VOUT = 0.600 ⎜ 1+ ⎟ ( V ) ⎝ R1⎠ where R1 is a resistor connected between FB and SGND, and R2 is a resistor connected between FB and VOUT . The buck-boost output voltage can be adjusted from 1.8V to 5.5V. RUN (Pin 11/Pin 14): Active High Converter Enable Input. Applying a voltage <0.3V to this pin shuts down the LTC3113. Applying a voltage >1.2V to this pin enables the LTC3113. SW1 (Pins 12, 13, 14/Pins 15, 16, 17): Switch Pin Where Internal Switches A and B are Connected. Connect the inductor from SW1 to SW2. Minimize trace length to reduce EMI. SW2 (Pins 15, 16/Pins 18, 19): Switch Pin Where Internal Switches C and D are Connected. Connect the inductor from SW1 to SW2. Minimize trace length to reduce EMI. PGND (Exposed Pad Pin 17/Pins 1, 10, 11, 20, Exposed Pad Pin 21): The exposed pad must be soldered to the PCB and electrically connected to ground through the shortest and lowest impedance connection possible. In most applications the bulk of the heat flow out of the LTC3113 is through this pad, so printed circuit board design has an impact on the thermal performance of the part. See the PCB Layout and Thermal Considerations section for more details. 3113f 7 LTC3113 DETAILED BLOCK DIAGRAM (DFN Package) 2.2μH 12 VIN 1.8V TO 5.5V 3 + VIN 13 14 SW1 SW2 SWA GATE DRIVERS AND ANTICROSS CONDUCTION 5 SWB PEAK CURRENT LIMIT 11.1A 1.6V RT + – + – UVLO + – PWM LOGIC AND OUTPUT PHASING – + 7.8A REVERSE CURRENT LIMIT INPUT CURRENT + LIMIT RZ2 6.49k CZ1 47pF – ERROR AMP + + – SOFT-START 0.6V + – FB VC 10 CP1 RZ 680pF 49.9k CL 100μF 9 CP2 12pF SLEEP 7 PWM COMPARATORS R2 845k 2 –1.0A SWC 1 OSC RT 90.9k 1 = BURST 0 = PWM VOUT SWD 4 8 15 16 Burst Mode CONTROL R1 158k BURST PGND SGND 17 RUN RUN LOGIC RUN 11 1 = ON 0 = OFF 6 3113 BD 3113f 8 LTC3113 OPERATION INTRODUCTION The LTC3113 is a low noise, high power synchronous buck-boost DC/DC converter optimized for demanding applications. The LTC3113 utilizes a proprietary switching algorithm, which allows its output voltage to be regulated above, below or equal to the input voltage. The error amplifier output (VC) determines the output duty cycle of each switch. The low RDS(ON), low gate charge, synchronous power switches provide high frequency pulse width modulation control. High efficiency is achieved at light loads when Burst Mode operation is commanded. LOW NOISE FIXED FREQUENCY OPERATION Oscillator The frequency of operation can be programmed between 300kHz and 2MHz by an external resistor from the RT pin to ground, according to the following equation: RT ≅ 90 (kΩ) f (MHz ) Error Amplifier The error amplifier is a high gain voltage mode amplifier. The loop compensation components are configured around the amplifier (from FB to VC) to obtain stable converter operation. For improved bandwidth, an additional RC feedforward network can be placed across the upper feedback divider resistor. Refer to the Applications Information section of this data sheet under Closing the Feedback Loop for information on selecting compensation type and components. Current Limit Operation The buck-boost converter has two current limit circuits. The primary current limit is an average current limit circuit which sources current into FB to reduce the output voltage, should the input current exceed 7.8A. Due to the high gain of the feedback loop, the injected current forces the error amplifier output to decrease until the average current through switch A decreases approximately to the current limit value. The average current limit utilizes the error amplifier in an active state and thereby provides a smooth recovery with little overshoot once the current limit fault condition is removed. Since the current limit is based on the average current through switch A, the peak inductor current in current limit will have a dependency on the duty cycle (i.e., on the input and output voltages) in the overcurrent condition. For this current limit feature to be most effective, the Thevenin resistance from FB to ground should exceed 100k. The speed of the average current limit circuit is limited by the dynamics of the error amplifier. On a hard output short, it is possible for the inductor current to increase substantially beyond current limit before the average current limit circuit would react. For this reason, there is a second current limit circuit which turns off switch A if the current ever exceeds approximately 142% of the average current limit value. This provides additional protection in the case of an instantaneous hard output short. Should the output voltage become less then 1.2V nominally, both the current limits are reduced compared to the normal operating current limits. Reverse Current Limit During fixed frequency operation, a reverse-current comparator on switch D monitors the current entering VOUT . When this current exceeds 1A (typical) switch D will be turned off for the remainder of the switching cycle. This feature protects the buck-boost converter from excessive reverse current if the buck-boost output is held above the regulation voltage by an external source. In applications where the oscillator frequency is programmed above 1MHz and the output voltage is held above its programmed regulation value, reverse currents greater than 1A (typical) may be observed. In conjunction with oscillator frequencies higher than 1MHz, higher output voltages will also increase the magnitude of observed reverse current. Refer to the Negative Inductor Current vs Oscillator Frequency graph in the Typical Performance Characteristics section for typical variations. 3113f 9 LTC3113 OPERATION Internal Soft-Start Inductor Damping The LTC3113 buck-boost converter has an independent internal soft-start circuit with a nominal duration of 2ms. The converter remains in regulation during soft-start and will therefore respond to output load transients which occur during this time. In addition, the output voltage rise time has minimal dependency on the size of the output capacitor or load current during start-up. During soft-start, the buck-boost is forced into PWM mode operation regardless of the state of the BURST pin. When the LTC3113 is in burst operation and sleep mode, active circuits “damp” the inductor voltage through 165Ω (typical) impedance from both SW1 and SW2 to ground minimizing EMI. Thermal Shutdown If the die temperature exceeds 155°C the LTC3113 buckboost converter will be disabled. All power devices are turned off and the switch nodes will be forced into a high impedance state. The soft-start circuit for the converter is reset during thermal shutdown to provide a smooth recovery once the overtemperature condition is eliminated. When the die temperature drops to approximately 145°C the LTC3113 will restart. For recommendations regarding thermal design of the LTC3113 PCB, refer to the PCB Thermal Considerations section in Applications Information. Undervoltage Lockout If the supply voltage decreases below 1.6V (typical) then the LTC3113 buck-boost converter will be disabled and all power devices are turned off. The soft-start circuit is reset during undervoltage lockout to provide a smooth restart once the input voltage rises above 1.7V (typical) the undervoltage lockout increasing threshold. When operating the LTC3113 at low input voltages, care must be taken under heavy loads to prevent the part from cycling into and out of UVLO. When operating at low input voltages the voltage drop created by the source resistance can trigger the UVLO, resetting the part. Operation near the undervoltage lockout is not recommended, but if requirements dictate, the source resistance should be less than 100mV/IIN(MAX) (where IIN(MAX) is the maximum input current) to ensure proper operation. PWM Mode Operation When the BURST pin is held low, the LTC3113 buckboost converter operates in a fixed-frequency pulse width modulation (PWM) mode using voltage mode control. Full output current is only available in PWM mode. A proprietary switching algorithm allows the converter to transition between buck, buck-boost, and boost modes without discontinuity in inductor current. The switch topology for the buck-boost converter is shown in Figure 1. VOUT VIN A D L B C 3113 F01 Figure 1. Buck-Boost Switch Topology When the input voltage is significantly greater than the output voltage, the buck-boost converter operates in buck mode. Switch D turns on continuously and switch C remains off. Switches A and B are pulse width modulated to produce the required duty cycle to support the output regulation voltage. As the input voltage decreases, switch A remains on for a larger portion of the switching cycle. When the duty cycle reaches approximately 85%, the switch pair AC begins turning on for a small fraction of the switching period. As the input voltage decreases further, the AC switch pair remains on for longer durations and the duration of the BD phase decreases proportionally. As the input voltage drops below the output voltage, the 3113f 10 LTC3113 OPERATION AC phase will eventually increase to the point that there is no longer any BD phase. At this point, switch A remains on continuously while switch pair CD is pulse width modulated to obtain the desired output voltage. At this point, the converter is operating solely in boost mode. This switching algorithm provides a seamless transition between operating modes and eliminates discontinuities in average inductor current, inductor current ripple, and loop transfer function throughout all three operational modes. These advantages result in increased efficiency and stability in comparison to the traditional four-switch buck-boost converters. Burst Mode Operation With the BURST pin held high, the buck-boost converter operates utilizing a variable frequency switching algorithm designed to improve efficiency at light load and reduce the standby current at zero load. In Burst Mode operation, the inductor is charged with fixed peak amplitude current pulses and as a result only a fraction of the maximum output current can be delivered when in this mode. These current pulses are repeated as often as necessary to maintain the output regulation voltage. The maximum output current, IMAX, which can be supplied in Burst Mode operation is dependent upon the input and output voltage as given by the following formula: IMAX ≅ IPK VIN • • η (A) 2 VIN + VOUT where IPK is the Burst Mode peak current limit in amps and is the η efficiency. If the buck-boost load exceeds the maximum Burst Mode current capability, the output rail will lose regulation. In Burst Mode operation, the error amplifier is configured in a low power mode of operation and used to hold the compensation pin, VC, to reduce transients that may occur during transitions from Burst Mode to PWM mode operation. 3113f 11 LTC3113 APPLICATIONS INFORMATION The basic LTC3113 application circuit is shown as the typical application on the front page of this data sheet. The external component selection is dependent upon the required performance of the IC in each particular application given considerations and trade-offs such as PCB area, output voltage, output current, output ripple voltage and efficiency. 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 application circuit. OUTPUT VOLTAGE PROGRAMMING The buck-boost output voltage is set via an external resistor divider connected to the FB pin as shown in Figure 2. 1.8V ≤ VOUT ≤ 5.5V R2 formulas, where f is the frequency in MHz and L is the inductance in μH: ΔIL,P-P,BUCK = VOUT ⎛ VIN – VOUT ⎞ ⎟⎠ ( A ) f • L ⎜⎝ VIN ΔIL,P-P,BOOST = VIN ⎛ VOUT – VIN ⎞ (A) f • L ⎜⎝ VOUT ⎟⎠ To ensure operation without triggering the reverse current comparator under no load conditions it is recommended that the peak-to-peak inductor ripple not exceed 800mA taking into account the maximum reverse current limit of –0.4A specified in the Electrical Characteristics section. Utilizing this recommendation for applications operating at a switching frequency of 300kHz requires a minimum inductance of 6.8μH, similarly an application operation at a frequency of 2MHz would require a minimum of 1μH. FB LTC3113 R1 SGND 3113 F02 Figure 2. Setting the Output Voltage The resistor divider values determine the buck-boost output voltage according to the following formula: ⎛ R2 ⎞ VOUT = 0.600 ⎜ 1+ ⎟ ⎝ R1⎠ (V) As noted in the Current Limit Operation section: “for the current limit feature to be most effected, the Thevenin resistance (R1||R2) from FB to ground should exceed 100k.” INDUCTOR SELECTION To achieve high efficiency, a low ESR inductor should be selected for the buck-boost converter. In addition, the inductor must have a saturation current rating that is greater than the worst-case average inductor current plus half the ripple current. The peak-to-peak inductor current ripple will be larger in buck and boost mode than in the buck-boost region. The peak-to-peak inductor current ripple for each mode can be calculated from the following In addition to affecting output current ripple, the value of the inductor can also impact the stability of the feedback loop. In boost and buck-boost mode, the converter transfer function has a right half plane zero at a frequency that is inversely proportional to the value of the inductor. As a result, a large inductor can move this zero to a frequency that is low enough to degrade the phase margin of the feedback loop. In addition to affecting the efficiency of the buck-boost converter, the inductor DC resistance can also impact the maximum output capability of the buck-boost converter at low input voltage. In buck mode, the buck-boost output current is limited only by the inductor current reaching the current limit value. However, in boost mode, especially at large step-up ratios, the output current capability can also be limited by the total resistive losses in the power stage. These include switch resistances, inductor resistance and PCB trace resistance. Use of an inductor with high DC resistance can degrade the output current capability from that shown in the graph in the Typical Performance Characteristics section of this data sheet. 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. 3113f 12 LTC3113 APPLICATIONS INFORMATION The choice of inductor style depends upon the price, sizing, and EMI requirements of a particular application. Table 1 provides a small sampling of inductors that are well suited to many LTC3113 buck-boost converter applications. All inductor specifications are listed at an inductance value of 2.2μH for comparison purposes but other values within these inductor families are generally well suited to this application. Within each family (i.e. at a fixed size), the DC resistance generally increases and the maximum current generally decreases with increased inductance. f is the frequency in MHz, COUT is the capacitance in μF, L is the inductance in μH, VIN is the input voltage in volts, VOUT is the output voltage in volts. ∆VP-P is the output ripple in volts and ILOAD is the output current in amps. Table 1. Representative Buck-Boost Surface Mount Inductors Given that the output current is discontinuous in boost mode, the ripple in this mode will generally be much larger than the magnitude of the ripple in buck mode. PART NUMBER VALUE (μH) DCR (mΩ) MAX DC CURRENT (A) SIZE (mm) W×L×H COUT ≥ COUT ≥ 1 ΔVP-P,BUCK • 8 • L • f 2 • ILOAD ( VOUT – VIN ) ΔVP-P,BOOST • VOUT • f ( VIN – VOUT ) • VOUT (µF ) V IN (µF ) CoilCraft (www.coilcraft.com) MSS1048 2.2 7.2 8.4 10 × 10.3 × 4 MSS1260 2.2 12 13.9 12.3 × 12.3 × 6 SER1052 2.2 4 10 10.6 × 10.6 × 5.2 Toko (www.toko.com) D106C 2.4 7.7 10 10.3 × 10.3 × 6.7 FDA1055 2.2 4.8 10.5 11.6 × 10.8 × 5.5 FDA1254 2.2 4.5 14.7 13.5 × 12.6 × 5.4 Cooper (www.cooperbussmann.com) HCP0703 2.2 18 14 7 × 7.3 × 3 HCP0704 2.3 16.5 11.5 6.8 × 6.8 × 4.2 HC8 2.6 11.4 10 10.9 × 10.4 × 4 9.7 × 10 × 4 INPUT CAPACITOR SELECTION It is recommended that a low ESR ceramic capacitor with a value of at least 47μF be located as close to VIN as possible. In addition, the return trace from the pin to the ground plane should be made as short as possible. It is important to minimize any stray resistance from the converter to the battery or other power sources. If cabling is required to connect the LTC3113 to the battery or power supply, a higher ESR capacitor or a series resistor with low ESR capacitor in parallel with the low ESR capacitor may be needed to damp out ringing caused by the cable inductance. TDK (www.component.tdk.com) VLF100040 2.2 7.9 8.2 RLF12560 2.7 4.5 12 13 × 13 × 6 VLF12060 2.7 6.4 10 11.7 × 12 × 6 Wurth (www.we-online.com) 744066 2.2 10.5 6.8 10 × 10 × 3.8 744355 2 8 13 13.2 × 12.8 × 6.2 744324 2.4 4.8 17 10.5 × 10.2 × 4.7 OUTPUT CAPACITOR SELECTION A low ESR output capacitor should be utilized at the buckboost converter output in order to minimize output voltage ripple. Multilayer ceramic capacitors are an excellent choice as they have low ESR and are available in small footprints. The capacitor should be chosen large enough to reduce the output voltage ripple to acceptable levels. Neglecting the capacitor ESR and ESL, the peak-to-peak output voltage ripple can be calculated by the following formulas, where CAPACITOR VENDOR INFORMATION Both the input bypass capacitors and output capacitors used with the LTC3113 must be low ESR and designed to handle the large AC currents generated by switching converters. This is important to maintain proper functioning of the IC and to reduce output ripple. Many modern low voltage ceramic capacitors experience significant loss in capacitance from their rated value with increased DC bias voltages. For example, it is not uncommon for a small surface mount ceramic capacitor to lose 50% or more of its rated capacitance when operated near its rated voltage. As a result, it is sometimes necessary to use a larger value capacitance or a capacitor with a higher voltage rating than required in order to actually realize the intended capacitance at the full operating voltage. For details, consult the capacitor vendor’s curve of capacitance versus DC bias voltage. 3113f 13 LTC3113 APPLICATIONS INFORMATION The capacitors listed in Table 2 provide a sampling of small surface mount ceramic capacitors that are well suited to LTC3113 application circuits. All listed capacitors are either X5R or X7R dielectric in order to ensure that capacitance loss over temperature is minimized. Table 2. Representative Buck-Boost Surface Input Mount Bypass and Output Capacitors VALUE (μF) VOLTAGE (V) SIZE (mm) W × L × H (FOOTPRINT) 1812D476KAT2A 47 6.3 3.2 × 4.5 × 2.5 (1812) 18126D107KAT2A 100 6.3 3.2 × 4.5 × 2.8 (1812) GRM43ER60J476ME01 47 6.3 3.2 × 4.5 × 2.5 (1812) GRM43SR60J107ME20 100 6.3 3.2 × 4.5 × 2.8 (1812) GRM55FR60J107KA01L 100 6.3 5 × 5.7 × 3.2 (2220) PART NUMBER AVX (www.avx.com) Murata (www.murata.com) Taiyo Yuden (www.t-yuden.com) JMK432BJ476MM-T 47 6.3 3.2 × 4.5 × 2.5 (1812) JMK432C107MM-T 100 6.3 3.2 × 4.5 × 2.8 (1812) TDK (www.component.tdk.com) C4532X5R0J476M 47 6.3 3.2 × 4.5 × 2.5 (1812) C4532X5R0J107M 100 6.3 3.2 × 4.5 × 2.5 (1812) C5750X5R1C476M 47 16 5 × 5.7 × 2.5 (2220) C5750X5R1A686M 68 10 5 × 5.7 × 2.5 (2220) C5750X5R0J107M 100 6.3 5 × 5.7 × 2.5 (2220) PCB LAYOUT CONSIDERATIONS The LTC3113 switches large currents at high frequencies. Special attention should be paid to the PCB layout to ensure a stable, noise-free and efficient application circuit. Figure 3 presents a representative 4-layer PCB layout to outline some of the primary considerations. A few key guidelines are outlined below: 1. All circulating high current paths should be kept as short as possible. This can be accomplished by keeping the routes to all highlighted components in Figure 3 as short and as wide as possible. Capacitor ground connections should via down to the ground plane in the shortest route possible. The bypass capacitors on VIN should be placed as close to the IC as possible and should have the shortest possible paths to ground. 2. The Exposed Pad is the power ground connection for the LTC3113. Multiple vias should connect the backpad directly to the ground plane. In addition maximization of the metallization connected to the backpad will improve the thermal environment and improve the power handling capabilities of the IC. Refer to Figure 3d bottom layer as an example of proper exposed pad power ground and via layout to provide good thermal and ground connection performance. 3. The components shown highlighted and their connections should all be placed over a complete ground plane to minimize loop cross-sectional areas. This minimizes EMI and reduces inductive drops. 4. Connections to all of the components shown highlighted should be made as wide as possible to reduce the series resistance. This will improve efficiency and maximize the output current capability of the buck-boost converter. 5. To prevent large circulating currents from disrupting the output voltage sensing, the ground for each resistor divider should be returned to the ground plane using a via placed close to the IC and away from the power connections. 6. Keep the connection from the resistor dividers to the feedback pins, FB, as short as possible and away from the switch pin connections. 7. Crossover connections should be made on inner copper layers if available. If it is necessary to place these on the ground plane, make the trace on the ground plane as short as possible to minimize the disruption to the ground plane. Thermal Considerations The LTC3113 output current may need to be derated if it is required to operate in a high ambient temperature or delivering a large amount of continuous power. The amount of current derating is dependent upon the input voltage, output voltage and ambient temperature. The temperature rise curves given in the Typical Performance Characteristics section can be used as a guide. These curves were generated by mounting the LTC3113 to a 4-layer FR4 demo board shown in Figure 3. Boards of other sizes and layer count can exhibit different thermal behavior, so 3113f 14 LTC3113 APPLICATIONS INFORMATION L1 2.2μH 12 VIN E3 1.8V TO 5.5V 13 14 15 3 4 C5 1μF 5 11 C7 68μF 10V VOUT VIN VIN VIN VOUT R8 90.9k 1% FB VC SGND 6 OFF 1 2 3 R2 715k 1% VOUT 3.3V E2 GND 10 9 C8 R5 680pF 10k C9 10pF 17 E4 ON 1 2 PGND R7 158k 1% GND GND JP2 R3 10k C3 1μF 6.3V LTC3113EDHD RUN 7 BURST 8 RT R4 1M C2 100μF 6.3V C1 33pF 16 SW1 SW1 SW1 SW2 SW2 VIN E1 VOUT Burst Mode OPERATION FIXED FREQUENCY 3113 F03a JP1 PWM 1 2 3 R9 1.0M VIN Figure 3a Figure 3b. Fabrication Layer of Example PCB 3113f 15 LTC3113 APPLICATIONS INFORMATION THERMAL AND PGND VIAS Figure 3c. Top Layer of Example PCB Figure 3d. Bottom Layer of Example PCB it is incumbent upon the user to verify proper operation over the intended system’s line, load and environmental operating conditions. Consequently, a poor printed circuit board design can cause excessive heating, resulting in impaired performance or reliability. Refer to the PCB Layout Considerations section for printed circuit board design suggestions. The junction-to-air (θJA) and junction-to-case (θJC) thermal resistance given in the “Pin Configuration” diagram may also be used to estimate the LTC3113 internal temperature. These thermal coefficients are determined using a 4-layer PCB. Bear in mind that the actual thermal resistance of the LTC3113 to the printed circuit board depends upon the design of the circuit board. The die temperature of the LTC3113 must be lower than the maximum rating of 125°C, so care should be taken in the layout of the circuit board to ensure good heat sinking of the LTC3113. The bulk of the heat flow is through the bottom exposed pad of the part into the printed circuit board. As described in the Thermal Shutdown section, the LTC3113 is equipped with a thermal shutdown circuit that will inhibit power switching at high junction temperatures. The activation threshold of this function, however, is above the 125°C rating to avoid interfering with normal operation. Thus, it follows that prolonged or repetitive operation under a condition in which the thermal shutdown activates necessarily means that the die is subjected to temperatures above the 125°C rating for prolonged or repetitive intervals, which may damage or impair the reliability of the device. 3113f 16 LTC3113 APPLICATIONS INFORMATION CLOSING THE FEEDBACK LOOP The LTC3113 incorporates voltage mode PWM control. The control-to-output gain varies with the operation region (buck, buck-boost, boost), but is usually no greater than 15. The output filter exhibits a double pole response, as given by: fFILTER _ POLE = 1 2π LCOUT (Hz ) (In Buck Region) fFILTER _ POLE = 1 2π LCOUT VIN (Hz ) VOUT (In Boost Region) where L is in Henries and COUT is in Farads. The output filter zero is given by: fFILTER _ ZERO = 1 2πRESRCOUT (Hz ) where RESR is the equivalent series resistance out the output capacitor in ohms. A troublesome feature in the boost and buck-boost region is the right-half plane (RHP) zero, given by: fRHPZ Most applications demand an improved transient response to allow a smaller output capacitor. To achieve a higher bandwidth, Type III compensation is required, providing two zeros to compensate for the double-pole response of the output filter. Referring to Figure 5, the location of the poles and zeros are given by: 1 (Hz ) 2π105 R2CP1 1 fZERO1 = (Hz ) 2πR Z CP1 1 fZERO2 = (Hz ) 2πR2CZ1 1 fPOLE2 = (Hz ) 2πR Z CP2 1 fPOLE3 = (Hz ) 2πRP C Z1 fPOLE1 = where resistance is in Ohms and capacitance is in Farads. VOUT A simple Type I compensation network can be incorporated to stabilize the loop at the cost of reduced bandwidth and slower transient response. To ensure proper phase margin using Type I compensation, the loop must be crossed over a decade before the LC double pole. Referring to Figure 4, the unity-gain frequency of the error amplifier with the Type I compensation is given by: ERROR AMP FB VIN2 = (Hz ) 2πIOUT LVOUT The loop gain is typically rolled off before the RHP zero frequency. + 0.6V R2 – VC CP1 R1 3113 F04 Figure 4. Error Amplifier with Type I Compensation VOUT 0.6V RP CZ1 R2 FB + ERROR AMP VC – R1 CP1 RZ CP2 3113 F05 1 fUG = (Hz ) 2πR2CP1 Figure 5. Error Amplifier with Type III Compensation 3113f 17 LTC3113 TYPICAL APPLICATIONS Li-Ion to 3.3V/3A 2.2μH VIN 2.5V TO 4.2V Li-Ion SW1 SW2 VIN VOUT 47μF 825k LTC3113 OFF ON PWM BURST RUN FB BURST VC 47pF 49.9k RT SGND 6.49k VOUT 3.3V 100μF 3A 680pF PGND 182k 3113 TA02a 90.9k 12pF Efficiency Li-Ion (3V, 3.7V, 4.2V) to 3.3V 100 EFFICIENCY (%) 90 80 VIN = 3V VIN = 3.7V VIN = 4.2V VIN = 3V BURST VIN = 3.7V BURST VIN = 4.2V BURST 70 60 0.001 0.1 1 0.01 LOAD CURRENT (A) 10 3113 TA02b Power Loss Li-Ion (3V, 3.7V, 4.2V) to 3.3V 10 PWM MODE POWER LOSS (W) 1 0.1 0.01 Burst Mode OPERATION 0.001 0.0001 0.001 VIN = 3V VIN = 3.7V VIN = 4.2V 0.1 1 0.01 LOAD CURRENT (A) 10 3113 TA02c 3113f 18 LTC3113 TYPICAL APPLICATIONS Supercap Powered Backup Supply 2.2μH SW1 VIN 1.8V TO 4.5V SW2 VIN 30F 30F 0.1μF VOUT 825k LTC3113 OFF ON PWM BURST RUN FB BURST VC SGND 100μF 47pF 49.9k RT 6.49k VOUT 3.3V 680pF PGND 182k 3113 TA03a 90.9k 12pF Typical Output Response with 1.5A Load VIN 2V/DIV VOUT 2V/DIV RUN 2V/DIV 5 SEC/DIV 3113 TA03b 3113f 19 LTC3113 TYPICAL APPLICATIONS 3.3V to 5V/2.5A Boost Converter with Output Disconnect 2.2μH VIN 3.3V ±10% SW2 SW1 VIN VOUT 47μF 5V 887k LTC3113 OFF ON PWM BURST RUN FB BURST VC SGND 100μF 47pF 49.9k RT 6.49k 680pF PGND 121k 3113 TA04a 90.9k 12pF Efficiency vs Load Current 100 PWM MODE EFFICIENCY (%) 90 Burst Mode OPERATION 80 70 60 50 0.001 0.01 0.1 1 LOAD CURRENT (A) 10 3113 TA04b Power Loss vs Load Current 10 PWM MODE POWER LOSS (W) 1 0.1 Burst Mode OPERATION 0.01 0.001 0.001 0.1 1 0.01 LOAD CURRENT (A) 10 3113 TA04c 3113f 20 LTC3113 TYPICAL APPLICATIONS 3.3V to 1.8V/5A Buck Converter 2.2μH SW2 SW1 VIN 47μF VOUT 665k LTC3113 OFF ON PWM BURST RUN FB BURST VC SGND 6.49k 100μF VOUT 1.8V 47pF 49.9k RT 680pF PGND 332k 3113 TA05a 90.9k 12pF Efficiency vs Load Current 100 PWM MODE EFFICIENCY (%) 90 Burst Mode OPERATION 80 70 60 50 0.001 0.01 0.1 1 LOAD CURRENT (A) 10 3113 TA05b Power Loss vs Load Current 10 1 PWM MODE POWER LOSS (W) VIN 3.3V ±10% 0.1 0.01 Burst Mode OPERATION 0.001 0.0001 0.001 0.01 0.1 1 LOAD CURRENT (A) 10 3113 TA06 3113f 21 LTC3113 PACKAGE DESCRIPTION DHD Package 16-Lead Plastic DFN (5mm × 4mm) (Reference LTC DWG # 05-08-1707) 0.70 p0.05 4.50 p0.05 3.10 p0.05 2.44 p0.05 (2 SIDES) PACKAGE OUTLINE 0.25 p 0.05 0.50 BSC 4.34 p0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 5.00 p0.10 (2 SIDES) R = 0.20 TYP 4.00 p0.10 (2 SIDES) 9 0.40 p 0.10 16 2.44 p 0.10 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 6) PIN 1 NOTCH (DHD16) DFN 0504 8 0.200 REF 1 0.25 p 0.05 0.50 BSC 0.75 p0.05 0.00 – 0.05 4.34 p0.10 (2 SIDES) BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WJGD-2) IN JEDEC PACKAGE OUTLINE MO-229 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 0.15mm 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 3113f 22 LTC3113 PACKAGE DESCRIPTION FE Package 20-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663) Exposed Pad Variation CA 6.40 – 6.60* (.252 – .260) 4.95 (.195) 4.95 (.195) 20 1918 17 16 15 14 13 12 11 6.60 p0.10 2.74 (.108) 4.50 p0.10 6.40 2.74 (.252) (.108) BSC SEE NOTE 4 0.45 p0.05 1.05 p0.10 0.65 BSC 1 2 3 4 5 6 7 8 9 10 RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 (.0035 – .0079) 0.25 REF 0.50 – 0.75 (.020 – .030) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 3. DRAWING NOT TO SCALE 1.20 (.047) MAX 0o – 8o 0.65 (.0256) BSC 0.195 – 0.30 (.0077 – .0118) TYP 0.05 – 0.15 (.002 – .006) FE20 (CA) TSSOP 0204 4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE 3113f Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 23 LTC3113 TYPICAL APPLICATION Pulsed Load or Portable RF Power Amplifier Application 2.2μH VIN 3.3V ±10% SW1 Typical Output Response SW2 VIN VOUT 4.7μF 47μF 845k LTC3113 OFF ON PWM BURST RUN FB BURST VC SGND 4.7μF VOUT 200mV/DIV 33pF 68k RT 10k 200μF VOUT 3.8V 0A TO 3A 220pF PGND ILOAD 2A/DIV 158k 100μs/DIV 3113 TA06a 90.9k 3113 TA06b 10pF RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3112 15V, 2.5A (IOUT) Synchronous Buck-Boost DC/DC Converter VIN: 2.7V to 15V, VOUT: 2.5V to 14V, IQ = 50μA, ISD < 1μA, DFN Package LTC3127 1A Buck-Boost DC/DC Converter with Programmable Input Current Limit VIN: 1.8V to 5.5V, VOUT: 1.8V to 5.25V, IQ = 35μA, ISD < 1μA, DFN Package LTC3531 200mA Buck-Boost Synchronous DC/DC Converter VIN: 1.8V to 5.5V, VOUT = 3.3V, IQ =16μA, ISD < 1μA, DFN Package LTC3533 2A (IOUT), 2MHz Synchronous Buck-Boost DC/DC Converter VIN: 1.8V to 5.5V, VOUT : 1.8V to 5.25V, IQ = 40μA, ISD < 1μA, DFN Package LTC3534 7V, 500mA Synchronous Buck-Boost DC/DC Converter VIN: 2.4V to 7V, VOUT : 1.8V to 7V, IQ = 25μA, ISD < 1μA, DFN Package LTC3440 600mA (IOUT), 2MHz Synchronous Buck-Boost DC/DC Converter VIN: 2.5V to 5.5V, VOUT : 2.5V to 5.25V, IQ = 25μA, ISD < 1μA, MSOP and DFN Packages LTC3441 1.2A (IOUT), 1MHz Synchronous Buck-Boost DC/DC Converter VIN: 2.4V to 5.5V, VOUT : 2.4V to 5.25V, IQ = 25μA, ISD < 1μA, DFN Package LTC3442 1.2A (IOUT), 2MHz Synchronous Buck-Boost DC/DC Converter with Programmable Burst Mode Operation VIN: 2.4V to 5.5V, VOUT : 2.4V to 5.25V, IQ = 35μA, ISD < 1μA, DFN Package LTC3785 10V, High Efficiency, Synchronous, No RSENSE™ Buck-Boost Controller VIN: 2.7V to 10V, VOUT : 2.7V to 10V, IQ = 86μA, ISD < 15μA, QFN Package LTC3101 Wide VIN, Multi-Output DC/DC Converter and PowerPath™ Controller VIN: 1.8V to 5.5V, VOUT : 1.5V to 5.25V, IQ = 38μA, ISD < 15μA, QFN Package LTC3530 Wide Input Voltage Synchronous Buck-Boost DC/DC Converter VIN: 1.8V to 5.5V, VOUT : 1.8V to 5.25V, IQ = 40μA, ISD < 1μA, DFN Package 3113f 24 Linear Technology Corporation LT 1110 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2010