LTC3104

LTC3104_15 LINER

Document overview

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Technical content

2.6µA Quiescent Current, 15V, 300mA Synchronous Step-Down DC/DC Converter and 10mA LDO The L TC®3104 is a high efficiency, monolithic synchronous step-down converter using a current mode architecture capable of supplying 300mA of output current. The L TC3104 includes an integrated, adjustable 10mA LDO to power noise sensitive functions. The L TC3104 offers two operational modes: automatic Burst Mode operation and forced continuous mode allow- ing the user to optimize output voltage ripple, noise and light load efficiency. With Burst Mode operation enabled, the typical DC input supply current at no load drops to 2.6µA, maximizing the efficiency for light loads. Selec - tion of forced continuous mode provides very low noise constant frequency, 1.2MHz operation. Additionally, the L TC3104 includes an accurate RUN com- parator , thermal overload protection, a power good output and an integrated soft-start feature to guarantee that the power system start-up is well controlled. Efficiency vs Output Current

APPLICATIONS

n Ultralow Quiescent Current: 2.6µA n Synchronous Rectification Efficiency Up to 95% n Wide VIN Range: 2.5V to 15V n Wide VOUT Range: 0.6V to 13.8V n 300mA Output Current n User-Selectable Automatic Burst Mode® or Forced Continuous Operation n Accurate and Programmable RUN Pin Threshold n 1.2MHz Fixed Frequency PWM n Internal Compensation n Power Good Status Output for VOUT n 10mA Adjustable LDO n Available in Thermally Enhanced 3mm × 4mm × 0.75mm, 14-Pin DFN and 16-Pin MSOP Packages n Remote Sensor Networks n Distributed Power Systems n Multicell Battery or SuperCap Regulator n Energy Harvesters n Portable Instruments n Low Power Wireless Systems L, L T , L TC, L TM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. VIN 22nF BST3V TO 15V ON OFF RUN SW RUNLDO MODE VCC PGOOD FBLDO VINLDO VLDO FB L TC3104 GND 412k 10µH 2.2V 300mA 1.8V 10mA

3104 TA01a

12pF 47µF 4.7µF 1µF 10µF 825k 1.78M 665kON OFF OUTPUT CURRENT (A) EFFICIENCY (%) POWER LOSS (mW) 100 0.0001 0.01 0.1 1

3104 TA01b

50 0.1 100 0.001 VIN = 3V VIN = 5V VIN = 10V VIN = 15V

(Note 1) ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE L TC3104EDE#PBF L TC3104EDE#TRPBF 3104 14-Lead (4mm × 3mm) Plastic DFN –40°C to 125°C L TC3104IDE#PBF L TC3104IDE#TRPBF 3104 14-Lead (4mm × 3mm) Plastic DFN –40°C to 125°C L TC3104EMSE#PBF L TC3104EMSE#TRPBF 3104 16-Lead Plastic MSOP –40°C to 125°C L TC3104IMSE#PBF L TC3104IMSE#TRPBF 3104 16-Lead Plastic MSOP –40°C to 125°C Consult L TC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container . Consult L TC 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/ V INLDO VLDO FBLDO FB RUN V CC NC MODE VIN SW BST GND RUNLDO PGOOD TOP VIEW GND DE PACKAGE 14-LEAD (4mm × 3mm) PLASTIC DFN TJMAX = 125°C, θJA = 53°C/W , θJC = 10°C/W EXPOSED PAD (PIN 15) IS GND, MUST BE SOLDERED TO PCB NC MODE V IN SW BST GND RUNLDO PGOOD NC V INLDO VLDO FBLDO FB RUN V CC NC TOP VIEW GND MSE PACKAGE 16-LEAD PLASTIC MSOP TJMAX = 125°C, θJA = 40°C/W , θJC = 10°C/W EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB PIN CONFIGURATION Operating Junction Temperature Range Lead Temperature (Soldering, 10 sec)

ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = VINLDO = 10V unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Step-Down Converter Input Voltage Range l 2.5 15 V Input Undervoltage Lockout Threshold VIN Rising VIN Rising, TJ = 0°C to 85°C (Note 4) l 2.1 2.1 2.6 2.5 V V Input Undervoltage Lockout Hysteresis (Note 4) 0.4 V Feedback Voltage (Note 5) l 0.588 0.6 0.612 V Feedback Voltage Line Regulation VIN = 2.5V to 15V (Note 5) 0.02 0.05 %/V Feedback Input Current (Note 5) l 1 20 nA Oscillator Frequency T J = 0°C to 85°C (Note 4) l 0.93 1.0 1.2 1.2 1.55 1.45 MHz MHz Quiescent Current, V IN—Active RUN = VIN, RUNLDO = VIN, MODE = 0V , FB > 0.612, Nonswitching 600 µA Quiescent Current, VIN—Sleep TJ = 0°C to 85°C, RUN = MODE = VIN, FB > 0.612 RUNLDO = VIN (Note 4) RUNLDO = 0V (Note 4) 2.6 1.8 3.3 2.6 µA µA RUN = MODE = V IN, FB > 0.612 RUNLDO = VIN RUNLDO = 0V l l 2.8 1.8 5.5 4.5 µA µA Quiescent Current, VIN—Shutdown RUN = 0V , RUNLDO = 0V , T J = 0°C to 85°C (Note 4) RUN = 0V , RUNLDO = 0V l 1.7 3.3 µA µA N-Channel MOSFET Synchronous Rectifier Leakage Current V IN = VSW =15V , VRUN = 0V 0.01 0.3 µA N-Channel MOSFET Switch Leakage Current VIN =15V , VSW = 0V , VRUN = 0V 0.01 0.3 µA N-Channel MOSFET Synchronous Rectifier RDS(ON) ISW = 200mA 0.85 Ω N-Channel MOSFET Switch RDS(ON) ISW = –200mA 0.65 Ω Peak Current Limit l 0.40 0.50 0.75 A PGOOD Threshold FB Falling, Percentage Below FB –14 –10 –5 % PGOOD Hysteresis Percentage of FB 2 % PGOOD Voltage Low IPGOOD = 100µA 0.2 V PGOOD Leakage Current VPGOOD = 5V 0.01 0.3 µA Maximum Duty Cycle l 89 92 % Switch Minimum Off Time (tOFF(MIN)) (Note 4) 65 ns Synchronous Rectifier Minimum On Time (tON(MIN)) (Note 4) 70 ns RUN Pin Threshold RUN Pin Rising l 0.76 0.8 0.85 V RUN Pin Hysteresis 0.06 V RUN Input Current RUN = 1.2V l 0.01 0.4 µA MODE Threshold l 0.5 0.8 1.2 V MODE Input Current MODE = 1.2V 0.1 4 µA Soft-Start Time 0.7 1.4 2.5 ms LDO Regulator LDO Input Voltage Range (VIN(LDO)) l 2.5 15 V LDO Output Voltage Range (VLDO) ILDO = 1mA l 0.6 14.5 V LDO Feedback Voltage l 0.576 0.6 0.624 V LDO Feedback Input Current l 1 20 nA

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 L TC3104 is tested under pulsed load conditions such that T J ≈ TA. The L TC3104E 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 L TC3104I is guaranteed over the full –40°C to 125°C operating junction temperature range. The junction temperature (T J) 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 the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal resistance and other environmental factors. ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = VINLDO = 10V unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Dropout Voltage (VDO) ILDO = 10mA 150 mV Output Current l 10 mA Output Current—Short Circuit VLDO = 0V l 15 20 mA Quiescent Current, VINLDO VIN = VINLDO = RUNLDO = 10V 0.3 µA Line Regulation VINLDO = 2.5V to 15V , ILDO = 1mA 0.1 % Load Regulation ILDO = 1mA to 10mA 0.75 % RUNLDO Threshold l 0.5 0.8 1.2 V RUNLDO Input Current RUNLDO = 1.2V 0.01 0.3 µA 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 this protection is active. Continuous operation above the specified absolute maximum operating junction temperature may impair device reliability or permanently damage the device. Note 4: Specification is guaranteed by design. Note 5: The L TC3104 has a proprietary test mode that allows testing in a feedback loop which servos V FB to the balance point for the error amplifier . TYPICAL PERFORMANCE CHARACTERISTICS Efficiency vs Output Current Efficiency vs Input Voltage (Automatic Burst Mode Operation) Application No-Load Input Current vs Supply Voltage (Automatic Burst Mode Operation) T A = 25°C unless otherwise noted OUTPUT CURRENT (A) EFFICIENCY (%) 100 0.0001 0.01 0.1 1

3104 G01

0.001 VIN = 4V VIN = 7V VIN = 10V VIN = 15V VOUT = 3.3V L = 15µH INPUT VOLTAGE (V) EFFICIENCY (%)

3104 G02

VOUT = 2.2V L = 10µH ILOAD = 300mA ILOAD = 100mA ILOAD = 10mA ILOAD = 1mA ILOAD = 100µA INPUT VOLTAGE (V) 2.0 INPUT CURRENT (µA)2.5 3.0 3.5 4.0 2 4 6 8

3104 G03

TYPICAL PERFORMANCE CHARACTERISTICS Efficiency vs Output Current (Forced Continuous Operation) Efficiency vs Input Voltage (Forced Continuous Operation) Feedback Voltage vs Temperature Oscillator Frequency vs Temperature R DS(ON) vs Temperature TA = 25°C unless otherwise noted Application No-Load Input Current vs Supply Voltage (Forced Continuous Operation) Application No-Load Input Current vs Temperature (Automatic Burst Mode Operation)SW Leakage vs Temperature Peak Current Limit vs Temperature OUTPUT CURRENT (A) EFFICIENCY (%) 100 0.0001 0.01 0.1 1

3104 G04

0.001 VIN = 3.7V VIN = 5V VIN = 7V VIN = 10V VIN = 15V VOUT = 3.3V L = 10µH INPUT VOLTAGE (V) EFFICIENCY (%) 100 7 11 13 15

3104 G05

VOUT = 3.3V, L = 10µH ILOAD = 300mA ILOAD = 100mA ILOAD = 10mA ILOAD = 1mA INPUT VOLTAGE (V) 2.0 2.5 3.5 8 12

3104 G06

1.5 1.0 4 6 10 14 16 0.5 3.0 INPUT CURRENT (mA) FRONT PAGE APPLICATION LDO ENABLED TEMPERATURE (°C) – 60 CHANGE IN VFB (%) 0.25 0.50 0.75 100

3104 G07

–0.25 –0.50 – 20 – 40 20 0 60 80 12040 140 NORMALIZED TO 25°C TEMPERATURE (°C) –50 –10 FREQUENCY CHANGE (%) 0 50 75

3104 G08

–25 25 100 125 150 NORMALIZED TO 25°C TEMPERATURE (°C) –50 CHANGE IN RESISTANCE (%)

3104 G09

–10 –25 0 50 –20 –30 75 100 125 NORMALIZED TO 25°C VIN = 10V SYNCHRONOUS RECTIFIER MAIN SWITCH TEMPERATURE (°C) –50 LEAKAGE CURRENT (nA) 350

3104 G10

–25 0 50 400 300 250 150 75 100 150 125 VIN = 10V MAIN SWITCH SYNCHRONOUS RECTIFIER TEMPERATURE (°C) –50 PEAK CURRENT LIMIT CHANGE (%) –2.5 2.5 40 100

3104 G11

–5.0 –7.5 –10.0 –20 10 70 5.0 7.5 10.0 130 VIN = 10V VOUT = 2.5V TEMPERATURE (°C) –50 2.0 INPUT CURRENT (µA) 2.5 3.0 3.5 4.0 –10 30 70 110

3104 G12

4.5 5.0 –25 10 50 90 VIN = 10V VOUT = 2.5V

Automatic Burst Mode Operation Forced Continuous Operation Start-Up into Pre-Biased Output (Automatic Burst Mode Operation) Start-Up into Pre-Biased Output (Forced Continuous Operation) Start-Up from Shutdown (Automatic Burst Mode Operation) Start-Up from Shutdown (Forced Continuous Operation) TYPICAL PERFORMANCE CHARACTERISTICSTA = 25°C unless otherwise noted Load Step (Automatic Burst Mode Operation) Load Step (Forced Continuous Operation) Minimum Input Voltage at Maximum Duty Cycle vs Load Current VOUT 50mV/DIV AC-COUPLED IL 100mA/DIV 10µs/DIV

3104 G13

ILOAD = 25mA VIN = 10V CIN = 10µF L = 10µH VOUT = 2.5V COUT = 22µF VOUT 20mV/DIV AC-COUPLED IL 100mA/DIV 1µs/DIV

3104 G14

ILOAD = 25mA VIN = 10V CIN = 10µF L = 10µH V OUT = 2.5V COUT = 22µF RUN 5V/DIV VOUT 1V/DIV PGOOD 5V/DIV IL 100mA/DIV 500µs/DIV

3104 G15

ILOAD = 2mA VIN = 10V CIN = 10µF L = 10µH V OUT = 2.5V COUT = 47µF BURST CURRENT PULSES SOFT-START PERIOD VBST REFRESH CURRENT PULSES RUN 5V/DIV VOUT 1V/DIV IL 100mA/DIV PGOOD 5V/DIV 500µs/DIV

3104 G16

ILOAD = 2mA VIN = 10V L = 10µH V OUT = 2.5V VBST REFRESH CURRENT PULSES RUN 5V/DIV PGOOD 5V/DIV VOUT 1V/DIV IL 100mA/DIV 500µs/DIV

3104 G17

ILOAD = 25mA VIN = 10V L = 10µH V OUT = 2.5V RUN 5V/DIV PGOOD 5V/DIV VOUT 1V/DIV IL 100mA/DIV 500µs/DIV

3104 G18

ILOAD = 25mA VIN = 10V L = 10µH V OUT = 2.5V SOFT-START/ FOLDBACK PERIOD VOUT 200mV/DIV AC-COUPLED IL 200mA/DIV ILOAD 200mA/DIV 200µs/DIV

3104 G19

ILOAD = LOAD STEP , 5mA TO 300mA VIN = 10V CIN = 10µF L = 10µH V OUT = 2.5V COUT = 47µF VOUT 50mV/DIV AC-COUPLED IL 100mA/DIV ILOAD 100mA/DIV 200µs/DIV

3104 G20

ILOAD = LOAD STEP , 50mA TO 200mA VIN = 10V L = 10µH V OUT = 2.5V COUT = 22µF LOAD CURRENT (mA) 2.5 INPUT VOLTAGE (V) 3.0 3.5 4.0 4.5 5.5 50 100 150 200

3104 G21

5.0 VOUT = 4.2V VOUT = 3.3V VOUT = 2.5V VOUT = 2.2V VOUT = 1.8V VOUT = 1.5V

Automatic Burst Mode Threshold vs Supply Voltage LDO Feedback Voltage vs Temperature LDO Output Voltage vs V IN(LDO) Supply Voltage LDO Output Voltage vs Load Current Minimum Input Voltage at Maximum Duty Cycle vs Load Current Load Regulation (Automatic Burst Mode Operation) Load Regulation (Automatic Burst Mode Operation) Load Regulation (Automatic Burst Mode Operation) Maximum Duty Cycle vs Input Voltage TYPICAL PERFORMANCE CHARACTERISTICSTA = 25°C unless otherwise noted TEMPERATURE (°C) – 60 CHANGE IN VFB (%) 0.50 1.00 1.50 100

3104 G28

–0.50 0.25 0.75 1.25 –0.25 –0.75 –1.00 – 20 – 40 20 0 60 80 12040 140 NORMALIZED TO 25°C INPUT VOLTAGE (V) 0.04 0.06 0.10 8 12

3104 G29

0.02 4 6 10 14 16 –0.02 –0.04 0.08 CHANGE IN LDO OUTPUT VOLTAGE (%) NORMALIZED TO VIN = 3.3V NOMINAL VLDO = 1.8V ILDO = 5mA VIN = VINLDO LDO LOAD CURRENT (mA) CHANGE IN OUTPUT VOLTAGE (%) 0.01 0.02 0.03 6 10

3104 G30

–0.01 –0.02 2 4 8 0.04 0.05 0.06 NORMALIZED TO ILDO = 5mA NOMINAL VLDO = 1.8V VIN = VINLDO = 10V LOAD CURRENT (mA) INPUT VOLTAGE (V) 50 100 150 200

3104 G22

VOUT = 12V VOUT = 9V VOUT = 5V ILOAD (mA) –2.0 CHANGE IN VOUT (%) –1.5 –1.0 –0.5 0.5 1.0 10 20 30 40

3104 G23

NORMALIZED AT ILOAD = 100mA VIN = 10V VOUT = 5V CFF = 12pF COUT = 68µF COUT = 47µF COUT = 22µF ILOAD (mA) –2.0 CHANGE IN VOUT (%) –1.5 –1.0 –0.5 20 40 60 80

3104 G24

0.5 1.0 10 30 50 70 NORMALIZED AT ILOAD = 100mA VIN = 10V VOUT = 3.3V CFF = 12pF COUT = 68µF COUT = 47µF COUT = 33µF ILOAD (mA) CHANGE IN VOUT (%) –1.5 –1.0 –0.5 60 100

3104 G25

–2.0 –2.5 –3.0 20 40 80 0.5

1.0 NORMALIZED AT ILOAD = 100mA

VIN = 10V VOUT = 1.8V CFF = 12pF COUT = 100µF COUT = 68µF COUT = 47µF INPUT VOLTAGE (V) 100 5 7

3104 G26

MAXIMUM DUTY CYCLE (%) IOUT = 1mA IOUT = 300mA INPUT VOLTAGE (V) BURST THRESHOLD (ILOAD, mA) 100 140 4 8 10

3104 G27

VOUT = 1.2V VOUT = 1.8V VOUT = 2.5V VOUT = 3.3V VOUT = 5V

PIN FUNCTIONS (DFN/MSOP) MODE (Pin 1/Pin 2): Logic-Controlled Input to Select Mode of Operation. Forcing this pin high commands high efficiency automatic Burst Mode operation where the buck will automatically transition from PWM operation at heavy load to Burst Mode operation at light loads. Forcing this pin low commands low noise, fixed frequency, forced continuous operation. V IN (Pin 2/Pin 3): Main Supply Pin. Decouple with a 10µF or larger ceramic capacitor . The capacitor should be as close to the part as possible. SW (Pin 3/Pin 4): Switch Pin Connects to the Inductor . This pin connects to the drains of the internal main and synchronous power MOSFET switches. BST (Pin 4/Pin 5): Bootstrapped Floating Supply for High Side Gate Drive. Connect to SW through a 22nF (minimum) capacitor . The capacitor must be connected between BST and SW and be located as close as possible to the part as possible. GND (Pin 5/Pin 6): Power Ground. RUNLDO (Pin 6/Pin 7): Logic-Controlled LDO Enable Pin. This pin may be tied to V IN to enable the LDO. PGOOD (Pin 7/Pin 8): Open-drain output that is pulled to ground when the feedback voltage falls 10% (typical) below the regulation point, during a thermal shutdown event or if the converter is disabled. The PGOOD output is valid 1ms after the buck converter is enabled. NC (Pin 8/Pins 1, 9, 16): No Connect Pin(s) Must Be Tied to GND. V CC (Pin 9/Pin 10): Internally Regulated Supply Rail. Internal power rail regulated off of V IN to power control circuitry. Decouple with a 1µF or larger ceramic capacitor placed as close to the part as possible. RUN (Pin 10/Pin 11): Run Pin Comparator Input. A voltage greater than 0.84V will enable the IC. Tie this pin to VIN to enable the IC or connect to an external resistor divider from V IN to provide an accurate undervoltage lockout threshold. 60mV of hysteresis is provided internally. FB (Pin 11/Pin 12): Feedback Input to Error Amplifier . The resistor divider connected to this pin sets the buck converter output voltage. FBLDO (Pin 12/Pin 13): Feedback Input to the LDO Error Amplifier . The resistor divider on this pin sets the LDO output voltage. VLDO (Pin 13/Pin 14): LDO Regulator Output. Decouple with a 4.7µF or larger ceramic capacitor placed as close to the part as possible. VINLDO (Pin 14/Pin 15): LDO Supply Pin (15V Maximum). Decouple with a 10µF or larger ceramic capacitor . GND (Exposed Pad Pin 15/Exposed Pad Pin 17): Back- pad Ground Common. This pad must be soldered to the PC board and connected to the ground plane for optimal thermal performance. TYPICAL PERFORMANCE CHARACTERISTICSTA = 25°C unless otherwise noted LDO Output Voltage Load Step LDO Ripple Rejection (Automatic Burst Mode Operation) VLDO 20mV/DIV AC-COUPLED ILOAD 10mA/DIV 20ms/DIV

3104 G31

ILOAD = LOAD STEP , NO LOAD TO 10mA VLDO = 1.8V VIN(LDO) = VIN = 10V CIN = 10µF COUT = 10µF VLDO 20mV/DIV AC-COUPLED VOUT 50mV/DIV AC-COUPLED IL 200mA/DIV 50µs/DIV

3104 G32

ILOAD = 10mA ILDO = 1mA VLDO = 1.8V , VIN = 10V VIN(LDO) = VOUT = 2.5V CIN = 10µF , COUT = 22µF CLDO = 4.7µF , L = 10µH

IPEAK(REF) TOP_ON BOT_ON VREF_GOOD SHUTDOWN CONTROL LOGIC ANTICROSS CONDUCTBURST ENABLE TSD RUNLDO VREF UVLO VCC OSC IBIAS BOOSTVCC VCC PRE-REG 0.8V RUN 0.6V 0.8V SD LOGIC RUNLDO LOGIC UVLO TSD SHUTDOWN LDOENABLE BST VIN CBST VOUT VCC MODE THERMAL SHUTDOWN PWM COMP SLEEP COMP SLEEP REF GND 0.6V – 10% PWM IPEAK COMP IZERO COMP SLOPE COMP 0.6V gm SS SW FB 3104 BD PGOOD VINLDO VLDO FBLDO R4 C5 VLDO LDO VCC LDOENABLE 0.6V OPERATION The L TC3104 step-down DC/DC converter is capable of supplying 300mA to the load. The output voltage is adjust- able over a broad range and can be set as low as 0.6V . Both the power and the synchronous rectifier switches are internal N-channel MOSFETs. The converter uses a constant-frequency, current mode architecture and may be configured using automatic Burst Mode operation for highly efficient light load operation or for low noise forced continuous conduction operation where the converter is optimized to operate over a broad range of step-down ratios without pulse skipping. With the automatic Burst Mode feature and the LDO enabled, the typical DC supply current drops to only 2.6µA with no load. The L TC3104 also includes an independent, 10mA LDO regulator with a V IN range of 2.5V to 15V . Main Control Loop During normal operation, the internal top power MOSFET is turned on at the beginning of each cycle and turned off when the PWM current comparator trips. The peak

inductor current where the comparator trips is controlled by the voltage on the output of the error amplifier . The FB pin allows the internally compensated error amplifier to receive an output feedback voltage from an external resis- tive divider from V OUT . When the load current increases, the output begins to fall causing a slight decrease in the feedback voltage relative to the 0.6V reference, this in turn, causes the control voltage to increase until the average inductor current matches the new load current. While the top MOSFET is off, the bottom MOSFET is turned on until either the inductor current starts to reverse as indicated by the current reversal comparator , I ZERO, or the beginning of the next clock cycle. I ZERO is set to 40mA (typical) in automatic Burst Mode operation and –110mA (typical) in forced continuous mode. Forced Continuous Mode Grounding MODE enables forced continuous operation and disables Burst Mode operation. At light loads, forced continuous mode minimizes output voltage ripple and noise but is less efficient than Burst Mode operation. Forced continuous operation may be desirable for use in applications that are sensitive to the Burst Mode output voltage ripple or its harmonics. The L TC3104 offers a broad range of possible step down ratios without pulse skipping but for very small step-down ratios, the minimum on-time of the main switch will be reached and the converter will begin turning off for multiple cycles in order to maintain regulation. Burst Mode Operation Holding the MODE pin above 1.2V will enable automatic Burst Mode operation and disable forced continuous op- eration. As the load current increases, the converter will automatically transition between Burst Mode and PWM operation. Conversely the converter will automatically transition from PWM operation to Burst Mode operation as the load decreases. Between bursts the converter is not active (i.e., both switches are off) and most of the internal circuitry is disabled to reduce the quiescent current to 2.6µA. Burst Mode entry and exit is determined by the peak inductor current and therefore the load current at which Burst Mode operation will be entered or exited depends on the input voltage, the output voltage and the inductor value. Typical curves for Burst Mode entry threshold are provided in the Typical Performance Characteristics sec- tion of this data sheet. Soft-Start The converter has an internal closed-loop soft-start circuit with a nominal duration of 1.4ms. The converter remains in regulation during soft-start and will therefore respond to output load transients that occur during this time. In addition, the output voltage rise time has minimal depen- dency on the size of the output capacitor or load current. Thermal Shutdown If the die temperature exceeds 150°C (typical) the con - verter and LDO will be disabled. All power devices will be turned off and the switch node will be forced into a high impedance state. The soft-start circuit is reset during thermal shutdown to provide a smooth recovery once the overtemperature condition is eliminated. If enabled, the converter and the LDO will restart when the die temperature drops to approximately 130°C. Power Good Status Output The PGOOD pin is an open-drain output which indicates the output voltage status of the step-down converter . If the output voltage falls 10% below the regulation voltage, the PGOOD open-drain output will pull low. A built-in deglitch- ing delay prevents false trips due to voltage transients on load steps. The output voltage must rise 2% above the falling threshold before the pull-down will turn off. The PGOOD output will also pull low during overtemperature shutdown and undervoltage lockout to indicate these fault conditions. The PGOOD output is valid 1ms after the buck converter is enabled. When the converter is disabled the open-drain device is forced on into a low impedance state. The PGOOD pull-up voltage must be below the 6V absolute maximum voltage rating of the pin. Current Limit The peak inductor current limit comparator shuts off the buck switch once the internal limit threshold is reached. Peak switch current is no less than 400mA.

Current mode control requires the use of slope com - pensation to prevent sub-harmonic oscillations in the inductor current waveform at high duty cycle operation. In some current mode ICs, current limiting is performed by clamping the error amplifier voltage to a fixed maximum which leads to a reduced output current capability at low step-down ratios. Slope compensation is accomplished on the L TC3104 internally through the addition of a com- pensating ramp to the current sense signal. The current limiting function is completed prior to the addition of the compensation ramp and therefore achieves a peak inductor current limit that is independent of duty cycle. Short-Circuit Protection When the output is shorted to ground, the error amplifier will saturate high and the high side switch will turn on at the start of each cycle and remain on until the current limit trips. During this minimum on-time, the inductor current will increase rapidly and will decrease very slowly during the remainder of the period due to the very small reverse voltage produced by a hard output short. To eliminate the possibility of inductor current runaway in this situation, the switching frequency is reduced to approximately 300kHz when the voltage on FB falls below 0.3V . BST Pin Function The input switch driver operates from the voltage gener- ated on the BST pin. An external capacitor between the SW and BST pins and an internal synchronous PMOS boost switch are used to generate a voltage that is higher than the input voltage. When the synchronous rectifier is on (SW is low) the internal boost switch connects one side of the capacitor to V CC replenishing its charge. When the synchronous rectifier is turned off the input switch is turned on forcing SW high and the BST pin is at a potential equal to V CC + SW , relative to ground. A comparator ensures there is sufficient voltage across the boost capacitor to guarantee start-up after long sleep periods or if starting up into a pre-biased output. Undervoltage Lockout The L TC3104 has an internal UVLO which disables the converter if the supply voltage decreases below 2.1V (typi- cal). The soft-start for the converter will be reset during undervoltage lockout to provide a smooth restart once the input voltage increases above the undervoltage lockout threshold. The RUN pin can alternatively be configured as a precise undervoltage lockout (UVLO) on the V IN supply with a resistive divider connected to the RUN pin. VLDO OUTPUT The VLDO output utilizes an internal PMOS pass device that is guaranteed to support a 10mA load with a typi - cal dropout voltage of 150mV . The LDO is powered by the V INLDO input which can be tied to an independent power source or to the VOUT of the step-down converter . VINLDO can be tied to V IN only if VIN is guaranteed to be within the absolute maximum ratings of the V INLDO pin. The quiescent current will increase by about 0.3µA when V INLDO is tied to VIN. The VLDO output is only active when VIN is greater than the UVLO threshold and the RUNLDO pin is high but can be disabled independently by bringing RUNLDO below 0.5V . The LDO is specifically designed to be stable with a small 4.7µF capacitor , but to also maintain stable operation with arbitrarily large capacitance values without requiring a series resistor . The LDO output is current-limit protected to 20mA (typ). During an undervoltage or overtemperature fault, the LDO is disabled until the fault condition clears.

Typical Application on the front page of this data sheet. for the design process are provided in this section. by lowering the peak current to be closer to the average.

• 1– VOUT VIN  µH( ) A reasonable choice for ripple current is ∆I L = 120mA which represents 40% of the maximum 300mA load current. The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current in order to prevent core saturation and loss of efficiency during operation. To optimize efficiency the inductor should have a low series resistance. In particularly space restricted applications it may be advantageous to use a much smaller value inductor at the expense of larger ripple current. In such cases, the converter will operate in discontinuous conduction for a wider range of output loads and efficiency will be reduced. In addition, there is a minimum inductor value required to maintain stability of the current loop (given the fixed internal slope compensation). Specifically, if the buck converter is going to be utilized at duty cycles greater than 40%, the inductance value must be at least L MIN as given by the following equation: LMIN ≥ 2.5 • VOUT (µH) Table 1 depicts the minimum required inductance for several common output voltages using standard induc- tor values.

Table 1. Minimum Inductance that are well suited to the L TC3104 converter applications. current generally decreases with increased inductance.

capacitors assuming a feedforward capacitor is used. upper resistor divider resistor . Mode operation to continuous mode operation. of having the necessary capacitance in your application. Table 3. Recommended Output Capacitor Limits Table 2. Representative Inductor Selection

stages of the buck converter and the LDO, respectively. set of application parameters. Figure 1. Setting the Output Voltage

3104 F01

of time in which the buck switch can be in its “on” state. This time is limited by similar factors and is typically 70ns. may not be of critical importance in some cases. active when the pin is higher than the RUN pin threshold. the part in shutdown independent of the RUN pin state.

values of ~1M a 12pF ceramic capacitor will suffice. Figure 2. Setting the Undervoltage Lockout Threshold

3104 F02

3104 F03

Figure 3. Setting the LDO Output Voltage

1 VINLDO

3104 F04

Figure 4. PCB Layout Recommendations with a 1µF or larger ceramic capacitor . BST , to the voltage on VCC.

Dual Lithium-Ion to 2.5V/300mA Regulator with 1.8V /10mA LDO VIN CBST 22nF CFF 12pF BST5V TO 9V ON OFF RUN SW RUNLDO MODE VCC PGOOD FBLDO VINLDO VLDO FB L TC3104 GND R3 412k L1: TDK VLCF4018T 6.8µH 2.5V 300mA 1.8V 10mA 931k3104 TA02a COUT 47µF CLDO 4.7µFC1 1µF CIN 10µF 825k 294k ON OFF Efficiency vs Output Current 12V to 3.3V/300mA Regulator with Accurate 5V UVLO, Forced Continuous Operation and Independently Powered LDO Start-Up with Ramped Input Power into 100mA Load on VOUT VIN CBST 22nF BSTVIN 12V RUN SW RUNLDO MODE VCC PGOOD PGOOD FBLDO VINLDO VLDO FB L TC3104 GND R3 665k L1: WÜRTH 744031100 10µH 3.3V 300mA 2.2V 10mA V INLDO 2.5V TO 12V

3104 TA03a

10µF CLDO 4.7µF 10µF 1µF CIN 10µF 1.78M 442k 1.47M 280k ON OFF CFF 10pF LOAD CURRENT (A) EFFICIENCY (%) 100 0.0001 0.01 0.1 1

3104 TA02b

0.001 VIN = 5V VIN = 9V VLDO 3V/DIV VOUT 2V/DIV VIN 20V/DIV IL 100mA/DIV 1ms/DIV

3104 TA03b

Solar-Powered 2.2V Supply and 1.8V LDO with Li Battery Backup and Run Threshold Set to Battery Minimum Voltage VIN CBST 22nF BST RUN 3.2V RUN THRESHOLD SW RUNLDO MODE VCC PGOOD FBLDO VINLDO VLDO FB L TC3104 GND R3 412k L1: COILCRAFT LPS4018 15µH 2.2V 1.8V 1.78M CFF1 12pF

3104 TA04a

47µF CLDO 4.7µFC1 1µF CIN 10µF 825k 1.78M 665k 3.09M SDM20E40C 715kCBULK 100µF 3.6V TADIRAN AA LITHIUM BATTERY 4.8V , 0.6W SOLAR PANEL MPT4.8-150 (6.5VOC)

14-Lead Plastic DFN (4mm × 3mm) (Reference L TC DWG # 05-08-1708 Rev B) 3.00 ±0.10 (2 SIDES) 4.00 ±0.10 (2 SIDES) NOTE: 1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WGED-3) 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 0.40 ± 0.10 BOTTOM VIEW—EXPOSED PAD 1.70 ± 0.10 0.75 ±0.05 R = 0.115 TYP R = 0.05 TYP

3.00 REF

1.70 ± 0.05 148 PIN 1 TOP MARK (SEE NOTE 6)

0.200 REF

0.00 – 0.05 (DE14) DFN 0806 REV B PIN 1 NOTCH R = 0.20 OR 0.35 × 45° CHAMFER RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 2.20 ±0.05 0.70 ±0.05 3.60 ±0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.25 ± 0.05

0.50 BSC

3.30 ±0.05 3.30 ±0.10 Please refer to http://www.linear .com/designtools/packaging/ for the most recent package drawings.

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 representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. PACKAGE DESCRIPTION Please refer to http://www.linear .com/designtools/packaging/ for the most recent package drawings. MSOP (MSE16) 0911 REV E 0.53 ± 0.152 (.021 ± .006) SEATING PLANE 0.18 (.007) 1.10 (.043) MAX 0.17 –/uni00A00.27 (.007 – .011) TYP 0.86 (.034) REF 0.50 (.0197) BSC 16151413121110 1 2 3 4 5 6 7 8 1 8 NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD SHALL NOT EXCEED 0.254mm (.010") PER SIDE. 0.254 (.010) 0° – 6° TYP DETAIL “A” DETAIL “A” GAUGE PLANE 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 0.889 ± 0.127 (.035 ± .005) RECOMMENDED SOLDER PAD LAYOUT 0.305 ± 0.038 (.0120 ± .0015) TYP 0.50 (.0197) BSC BOTTOM VIEW OF EXPOSED PAD OPTION 2.845 ± 0.102 (.112 ± .004) 2.845 ± 0.102 (.112 ± .004) 4.039 ± 0.102 (.159 ± .004) (NOTE 3) 1.651 ± 0.102 (.065 ± .004) 1.651 ± 0.102 (.065 ± .004) 0.1016 ± 0.0508 (.004 ± .002) 3.00 ± 0.102 (.118 ± .004) (NOTE 4) 0.280 ± 0.076 (.011 ± .003) REF 4.90 ± 0.152 (.193 ± .006) DETAIL “B” DETAIL “B” CORNER TAIL IS PART OF THE LEADFRAME FEATURE. FOR REFERENCE ONL Y NO MEASUREMENT PURPOSE

0.12 REF

0.35 REF 16-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1667 Rev E)

Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear .com  LINEAR TECHNOLOGY CORPORATION 2011 LT 1011 • PRINTED IN USA RELATED PARTS TYPICAL APPLICATION 12V to 5V/300mA Regulator with High Efficiency, Ultralow IQ (2.8µA with VOUT in Regulation, No Load) and 1.8V/10mA LDO VIN CBST 22nF BST12V RUN SW RUNLDO MODE VCC PGOOD FBLDO VINLDO VLDO FB L TC3104 GND R3 1.05M L1: SUMIDA CDRH4D16FB/NP-100M 10µH 5V 300mA 1.8V 10mA 1.87M

3104 TA05

47µF CLDO 4.7µFC1 1µF CIN 10µF 2.1M 255k CFF 10pF PART NUMBER DESCRIPTION COMMENTS L TC3103 15V , 300mA Synchronous Step-Down DC/DC Converter with Ultralow Quiescent Current VIN: 2.5V to 15V , VOUT(MIN) = 0.6V , IQ = 1.8µA, ISD = 1µA, 3mm × 3mm DFN-10, MSOP-10 L TC3642 45V (T ransient to 60V) 50mA Synchronous Step-Down DC/DC Converter V IN: 4.5V to 45V , VOUT(MIN) = 0.8V , IQ = 12µA, ISD < 1µA, 3mm × 3mm DFN-8, MSOP-8 L TC3631 45V (T ransient to 60V) 100mA Synchronous Step-Down DC/DC Converter V IN: 4.5V to 45V , VOUT(MIN) = 0.8V , IQ = 12µA, ISD < 1µA, 3mm × 3mm DFN-8, MSOP-8 L TC3632 50V (T ransient to 60V) 20mA Synchronous Step-Down DC/DC Converter V IN: 4.5V to 50V , VOUT(MIN) = 0.8V , IQ = 12µA, ISD < 1µA, 3mm × 3mm DFN-8, MSOP-8 L TC3388-1/L TC3388-3 20V , 50mA High Efficiency Nano Power Step-Down Regulators V IN: 2.7V to 20V , VOUT(MIN) Fixed 1.1V to 5.5V , IQ = 720nA, ISD = 400nA, 3mm × 3mm DFN-10, MSOP-10 L TC3108/L TC3108-1 Ultralow Voltage Step-Up Converter and Power Managers VIN: 0.02V to 1V , VOUT(MIN) Fixed 2.35V to 5V , IQ = 6µA, ISD < 1µA, 3mm × 4mm DFN-12, SSOP-16 L TC3109 Auto-Polarity, Ultralow Voltage Step-Up Converter and Power Manager V IN: 0.03V to 1V , VOUT(MIN) Fixed 2.35V to 5V , IQ = 7µA, ISD < 1µA, 4mm × 4mm QFN-20, SSOP-20 L TC4071 Li-Ion/Polymer Shunt Battery Charger System with Low Battery Disconnect Charger Plus Pack Protection in One IC Low Operating Current (550nA), 50mA Internal Shunt Current, Pin Selectable Float Voltages (4.0V , 4.1V , 4.2V), 8-Lead, 2mm × 3mm, DFN and MSOP Packages L TC4070 Li-Ion/Polymer Low Current Shunt Battery Charger System Selectable V FLOAT = 4.0V , 4.1V , 4.2V , Max Shunt Current = 50mA, ICCQ = 450nA to 1.04mA, ICCQLB = 300nA, 2mm × 3mm DFN-8, MSOP-8 L TC1877 10V , 600mA High Efficiency Synchronous Step-Down DC/DC Converter V IN: 2.65V to 10V , VOUT(MIN) = 0.8V , IQ = 10µA, ISD < 1µA, MSOP-8 L TC3105 5V , 400mA, MPPC Step-Down Converter with 250mV Start-Up V IN: 0.225V to 5V , VOUT(MAX) = 5.25V , IQ = 24µA, ISD = 10µA, 3mm × 3mm DFN-10, MSOP-12