LTC3105 Datasheet

8/8/2019 LTC3105 Datasheet

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LTC3105

1

3105p

TYPICAL APPLICATION

FEATURES DESCRIPTION

400mA Step-Up DC/DCConverter with Maximum Power

Point Control and 250mV Start-Up

The LTC3105 is a high efficiency step-up DC/DC converterthat can operate from input voltages as low as 200mV. A250mV start-up capability and integrated maximum powerpoint controller (MPPC) enable operation directly from lowvoltage, high impedance alternative power sources such asphotovoltaic cells, TEGs (thermoelectric generators) andfuel cells. A user programmable MPPC set point maximizesthe energy that can be extracted from any power source.Burst Mode operation, with a proprietary self adjustingpeak current, optimizes converter efficiency and outputvoltage ripple over all operating conditions.

The AUX powered 6mA LDO provides a regulated rail forexternal microcontrollers and sensors while the mainoutput is charging. In shutdown, IQ is reduced to 4Aand integrated thermal shutdown offers protection fromovertemperature faults. The LTC3105 is offered in 10-lead3mm 3mm 0.75mm DFN and 12-lead MSOP packages.

Output Current vs Input Voltage

APPLICATIONS

n Low Start-Up Voltage: 250mVn Maximum Power Point Controln Wide VIN Range: 0.2V to 5Vn Auxiliary 6mA LDO Regulatorn Burst Mode Operation: IQ = 22An Output Disconnect and Inrush Current Limitingn VIN > VOUT Operationn Antiringing Controln Soft Startn Automatic Power Adjustn Power Good Indicatorn 10-Lead 3mm 3mm 0.75mm DFN and 12-Lead

MSOP Packages

n Solar Powered Battery/Supercapacitor Chargersn Energy Harvestingn Remote Industrial Sensorsn Low Power Wireless Transmittersn

Cell Phone, MP3, PMP and GPS Accessory Chargers

L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are r egistered trademarksand ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are theproperty of their respective owners.

3105 TA01a

10F

Li-Ion4.2V

1020k

0.2V TO 5V

VOUT4.1V

332k

FB

PGOOD

LDO

FBLDO

MPPC

VIN

SHDN

AUX

SW

VOUT

4.7F

2.2V

40.2k

1F

LTC3105

GND

10F

10H

PHOTOVOLTAICCELL

ONOFF

+

Single Photovoltaic Cell Li-Ion Trickle Charger

INPUT VOLTAGE (V)

0.20

OUTPUTCURRENT(mA)

20

40

60

0.3 0.4 0.5 0.6 0.80.7 0.9

80

10

30

50

70

1.0

3105 TA01b

VOUT = 5V

VOUT = 3.3V

VOUT = 4.2V

MPPC DISABLED

Electrical Specifications Subject to Change


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ABSOLUTE MAXIMUM RATINGS

SW VoltageDC ............................................................ 0.3V to 6VPulsed (


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ELECTRICAL CHARACTERISTICS

Note 1: Stresses beyond those listed under Absolute Maximum Ratingsmay cause permanent damage to the device. Exposure to any AbsoluteMaximum Rating condition for extended periods may affect devicereliability and lifetime.

Note 2: The LTC3105 is guaranteed to meet performance specifications

from 0C to 85C. Specifications over the 40C to 85C operatingtemperature range are ensured by design, characterization and correlationwith statistical process controls.

The l denotes the specifications which apply over the full operatingtemperature range, otherwise specifications are at TJ = 25C. VAUX = VOUT = 3.3V, VLDO = 2.2V, VIN = 0.6V, unless otherwise noted.

PARAMETER CONDITIONS MIN TYP MAX UNITS

Step-Up Converter

Input Voltage l 5 VInput Start-Up Voltage

TA = 0C to 85Cl 0.25 0.4

0.36VV

Output Voltage Adjust Range l 1.5 5.25 V

Feedback Voltage (FB Pin) l 0.988 1.008 1.028 V

VOUT IQ in Operation VFB = 1.10V 22 A

VOUT IQ in Shutdown SHDN = 0V 6 A

VIN Current in Shutdown VSHDN = VOUT = VAUX = 0V 4 A

MPPC Pin Output Current VMPPC = 0.6V 9.72 10 10.28 A

SHDN Input Logic High Voltage VOUT > 1.4V l 1.1 V

SHDN Input Logic Low Voltage VOUT > 1.4V l 0.3 V

N-Channel SW Pin Leakage Current VIN = VSW = 5V, VSHDN = 0V 1 10 A

P-Channel SW Pin Leakage Current VIN = VSW = 0V, VOUT = VAUX = 5.25V 1 10 A

N-Channel On-Resistance: SW to GND 0.5

P-Channel On-Resistance: SW to VOUT 0.5

Peak Input Current Limit VFB = 0.90V, VMPPC = 0.4V (Note 3) 0.4 0.45 A

Valley Current Limit VFB = 0.90V, VMPPC = 0.4V (Note 3) 0.3 0.35 A

PGOOD Threshold (% of Feedback Voltage) VOUT Falling 85 90 95 %

LDO Regulator

LDO Output Voltage External Resistive Divider, VOUT = 5.25VVFBLDO = 0V

l

l

1.42.16

2.2

52.24

VV

Feedback Voltage (FBLDO Pin) Using External Resistive Divider l 0.988 1.008 1.028 VLoad Regulation ILDO = 1mA to 6mA 0.40 %

Line Regulation VAUX = 2.5V to 5V 0.15 %

Dropout Voltage ILDO = 6mA, VOUT = VAUX = 2.2V 78 mV

LDO Current Limit VLDO 0.5V Below Regulation Voltage l 6 12 mA

LDO Reverse-Blocking Leakage Current VIN = VAUX = VOUT = 0V, VSHDN = 0V 1 A

Note 3: Current measurements are performed when the LTC3105 is notswitching. The current limit values measured in operation will be somewhathigher due to the propagation delay of the comparators.

Note 4: This IC includes over temperature protection that is intendedto protect the device during momentary overload conditions. Junction

temperature will exceed 125C when overtemperature protection is active.Continuous operation above the specified maximum operating junctiontemperature may impair device reliability


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VOUT Reverse IQ vs TemperatureDuring Shutdown

VOUT Reverse IQ vs TemperatureDuring Input UVLO

UVLO Threshold vs TemperatureMPPC Current Variationvs Temperature

LDO Soft-Start Durationvs LDO Load

Minimum Input Start-Up Voltagevs Temperature

Shutdown Thresholdsvs Input Voltage IC Enable Delay vs Input Voltage

TYPICAL PERFORMANCE CHARACTERISTICS TA = 25C, VAUX = VOUT = 3.3V, VLDO = 2.2V,VIN = 0.6V, unless otherwise noted.

TEMPERATURE (C)

45

INPUTVOLTAGE(mV)

280

15 15 45

240

260

340

220

200

320

300

30 0 75 9030 60

3105 G01

TEMPERATURE (C)

45

CHANGEFROM2

5C(%)

5

20

25

15 15 45

15

10

10

15

20

25

5

0

30 0 75 9030 60

3105 G04TEMPERATURE (C)

45

CHANGEFROM2

5C(%)

0.5

15 15 45

0.5

2.0

0

2.5

1.0

1.5

1.5

1.0

30 0 75 9030 60

3105 G05LDO LOAD CURRENT (mA)

11.20

SOFT-S

TARTTIME(ms)

1.30

1.40

2 3 4 5

1.50

1.25

1.35

1.45

6

3105 G06

TEMPERATURE (C)

45

IQ(

A)

8

18

15 15 45

4

14

6

16

2

0

12

10

30 0 75 9030 60

3105 G07

SHDN = 0V

TEMPERATURE (C)

45

IQ(

A)

8

15 15 45

4

14

6

16

2

0

12

10

30 0 75 9030 60

3105 G08

VIN = 0V

SUPPLY VOLTAGE, VIN OR VAUX (V)

00

THRESHOLDVOLTAGE(mV)

200

400

600

1 2 3 4

800

1000

100

300

500

700

900

5

3105 G02

IC DISABLE

IC ENABLE

DELAYTIME(s)

1000

3105 G03

10

100

1 54320

SUPPLY VOLTAGE, VIN OR VAUX (V)

OUTPUT VOLTAGE (V)

1.50

MAXIMUMI

NPUTVO

LTAGE(V)

1.0

2.0

3.0

2.0 3.0 4.02.5 3.5 4.5 5.0

4.0

5.0

0.5

1.5

2.5

3.5

4.5

5.5

3105 G09

NONSYNCHRONOUSOPERATION

SYNCHRONOUSOPERATION

VIN to Ensure SynchronousOperation


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Exiting MPPC Control onInput Voltage Step

IPEAK and IVALLEY Changevs Temperature

Input and Output Burst RippleEfficiency vs Output Current andPower Loss, VOUT = 3.3V

Efficiency vs Output Current andPower Loss, VOUT = 5V

No-Load Input Currentvs Input Voltage

TYPICAL PERFORMANCE CHARACTERISTICS TA = 25C, VAUX = VOUT = 3.3V, VLDO = 2.2V,VIN = 0.6V, unless otherwise noted.

INPUT VOLTAGE (V)

0.20

INPUT

CURRENT

(A)

200

400

600

0.4 0.6 0.8 1.0

800

100

300

500

700

1.2

3105 G16

VOUT = 3.3V

OUTPUT CURRENT (mA)

0.01

EFFICIENCY(%)

POWERLOSS(mW)

60

70

80

50

40

10.1 10 100

10

0

30

90

20

10

0.1

100

1

3105 G14

VIN = 0.6VVIN = 0.8VVIN = 1V

EFFICIENCY

POWER LOSS

OUTPUT CURRENT (mA)

0.01

EFFICIENCY(%)

POW

ERLOSS(mW)

60

70

80

50

40

10.1 10 100

30

100

90

20

100

0.1

1000

10

1

3105 G15

VIN = 3VVIN = 2VVIN = 1.5V

EFFICIENCY

POWER LOSS

TEMPERATURE (C)

45

CHANGEFROM2

5C(%)

0.5

15 15 45

1.5

1.0

1.0

2.0

2.5

0.5

0

30 0 75 9030 60

3105 G11

IVALLEY

IPEAK

TIME (s)

0 15 30 45 60 75

3105 G10

VIN VOLTAGE200mV/DIV

INDUCTORCURRENT100mA/DIV

MPPC VOLTAGE200mV/DIV

VMPPC = 400mV

INPUT VOLTAGE (V)

0.2540

EFFICIENCY(%)

60

80

1.25 2.25 3.25 4.25

100

50

70

90

5.25

3105 G12

VOUT = 3VILOAD = 10mALDO = 2.2V

TIME (s)

0 50 100 150 200 250 300

3105 G13

OUTPUTVOLTAGE

50mV/DIV

INPUTVOLTAGE5mV/DIV

SW CURRENT200mA/DIV

VIN = 0.6VCIN = 470F

VOUT = 3.3VIOUT = 15mACOUT = 10F

Efficiency vs VIN


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PIN FUNCTIONS

FB (Pin 1/Pin 1): Step-Up Converter Feedback Input. Con-nect the VOUT resistor divider tap to this input. The outputvoltage can be adjusted between 1.5V and 5.25V.

LDO (Pin 2/Pin 2): LDO Regulator Output. Connect a 4.7For larger capacitor between LDO and GND.

FBLDO (Pin 3/Pin 3): LDO Feedback Input. Connect theLDO resistive divider tab to this input. Alternatively, con-necting FBLDO directly to GND will configure the LDOoutput voltage to be internally set at 2.2V (nominal).

SHDN (Pin 4/Pin 4): Logic Controlled Shutdown Input.With SHDN open, the converter is enabled by an internal2M pull-up resistor. The threshold voltage for this pin

adjusts based on the input and output voltages to allowshutdown at all voltages. See the curves in the TypicalPerformance Characteristics section of this data sheetfor details.

SHDN = Low: IC Disabled

SHDN = High: IC Enabled

MPPC (Pin 5/Pin 5): Set Point Input for MaximumPower Point Control. Connect a resistor from MPPC toGND to program the activation point for the MPPC loop.To disable the MPPC circuit, connect MPPC directly

to GND.VIN (Pin 6/Pin 8): Input Supply. Connect a decouplingcapacitor between this pin and GND. The PCB trace lengthfrom the VIN pin to the decoupling capacitor should be asshort and wide as possible. When used with high imped-ance sources such as photovoltaic cells, this pin shouldhave a 10F or larger decoupling capacitor.

GND (Exposed Pad Pin 11/Pins 6, 7) : Small Signal andPower Ground for the IC. The GND connections should besoldered to the PCB ground using the lowest impedance

path possible.

SW (Pin 7/Pin 9): Switch Pin. Connect an inductor betweenSW and VIN. PCB trace lengths should be as short as pos-sible to reduce EMI. While the converter is sleeping or isin shutdown, the internal antiringing switch connects theSW pin to the VIN pin in order to minimize EMI.

PGOOD (Pin 8/Pin 10): Power Good Indicator. This is anopen-drain output. The pull-down is disabled when VOUThas achieved the voltage defined by the feedback divideron the FB pin. The pull-down is also disabled while the IC

is in shutdown mode.

VOUT (Pin 9/Pin 11): Step-Up Converter Output. This is thedrain connection of the main output internal synchronousrectifier. A 10F or larger capacitor must be connectedbetween this pin and GND. The PCB trace length from theVOUT pin to the output filter capacitor should be as shortand wide as possible.

AUX (Pin 10/Pin 12): Auxiliary Voltage. Connect a 1Fcapacitor between this pin and GND. This pin is used bythe start-up circuitry to generate a voltage rail to power

internal circuitry until the main output reaches regulation.AUX and VOUTare internally connected together once VOUTexceeds VAUX.

(DFN/MSOP)


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2MSHDN FBLDO

1.5V TO5.25V

VOUT

AUX

LDO

CIN10F

RMPPC

90mV

L1

10H

Exposed Pad

INPUT UVLO

USER SHUTDOWN

SHUTDOWN

VALLEY CURRENT LIMIT

PEAK CURRENTLIMIT

VIN6

4

7

11

9

+

LOGIC

+

+

SLEEPR3

R4

SHUTDOWN

CLDO4.7F

1.008V

1.008V

SLEEPSHUTDOWN

VIN

VCC

VAUX

++

+

VIN

10AMPPC

SW

5

LOW VOLTAGESTART-UP CURRENT

ADJUST

BURSTCONTROL

0.2VTO 5V

+

3

PGOOD

FB1

10

2

R1

R2

COUT10F

CAUX1F

0.9V

FB

8

3105 BD

SHORTCONTROL

WELLCONTROL

OR

VCC

SLEEP

VCCVAUX

VIN

gm

+

BLOCK DIAGRAM (Pin Numbers for DFN Package Only)


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Introduction

The LTC3105 is a unique, high performance, synchronous

boost converter that incorporates maximum power pointcontrol, 250mV start-up capability and an integrated LDOregulator. This part operates over a very wide range ofinput voltages from 0.2V to 5V. Its Burst Mode architectureand low 22A quiescent current optimize efficiency in lowpower applications.

An integrated maximum power point controller allows foroperation directly from high impedance sources such asphotovoltaic cells by preventing the input power source volt-age from collapsing below the user programmable MPPCthreshold. Peak current limits are automatically adjusted

with proprietary techniques to maintain operation at levelsthat maximize power extraction from the source.

The 250mV start-up voltage and 200mV minimum operat-ing voltage enable direct operation from a single photovol-taic cell and other very low voltage, high series impedancepower sources such as TEGs and fuel cells.

Synchronous rectification provides high efficiency opera-tion while eliminating the need for external Schottky diodes.The LTC3105 provides output disconnect which preventslarge inrush currents during start-up. This is particularly

important for high internal resistance power sources likephotovoltaic cells and thermoelectric generators whichcan become overloaded if inrush current is not limitedduring start-up of the power converter. In addition, outputdisconnect isolates VOUT from VIN while in shutdown.

VIN > VOUT Operation

The LTC3105 includes the ability to seamlessly maintainregulation if VIN becomes equal to or greater than VOUT.With VIN greater than or equal to VOUT, the synchro-nous rectifiers are disabled which may result in reduced

efficiency.

Shutdown Control

The SHDN pin is an active low input that places the ICinto low current shutdown mode. This pin incorporates aninternal 2M pull-up resistor which enables the converterif the SHDN pin is not controlled by an external circuit.The thresholds for the SHDN pin change dynamically withthe maximum of VIN and VAUX. At low system voltages

OPERATION

(VIN and VAUX), the shutdown pin thresholds are as lowas 50mV from the voltage rails. See the curves in theTypical Performance Characteristics section of this data

sheet for more information on SHDN threshold variationswith system voltages. In shutdown, the internal switchconnecting AUX and VOUT is enabled.

When the SHDN pin is released, the LTC3105 is enabledand begins switching after a short delay. When either VINorVAUX is above 1.4V, this delay will typically range between20s and 100s. At lower voltages, this delay can be upto several milliseconds. Refer to the Typical PerformanceCharacteristics section for more details.

Start-Up Mode Operation

The LTC3105 provides the capability to start with voltagesas low as 250mV. During start-up the AUX output initiallyis charged with the synchronous rectifiers disabled. OnceVAUXhas reached approximately 1.4V, the converter leavesstart-up mode and enters normal operation. Maximumpower point control is not enabled during start-up, however,the currents are internally limited to sufficiently low levelsto allow start-up from weak input sources.

While the converter is in start-up mode, the internal switchbetween AUX and VOUT remains disabled and the LDO

is disabled. Refer to Figure 1 for an example of a typicalstart-up sequence.

Normal Operation

When either VIN or VAUX is greater than 1.4V typical, theconverter will enter normal operation.

The converter continues charging the AUX output untilthe LDO output enters regulation. Once the LDO outputis in regulation, the converter begins charging the VOUTpin. VAUX is maintained at a level sufficient to ensure the

LDO remains in regulation. If VAUX becomes higher thanrequired to maintain LDO regulation, charge is transferredfrom the AUX output to the VOUT output. If VAUX falls toolow, current is redirected to the AUX output instead ofbeing used to charge the VOUT output. Once VOUT risesabove VAUX, an internal switch is enabled to connect thetwo outputs together.

If VIN is greater than the voltage on the driven output (VOUTor VAUX), or the driven output is less than 1.2V (typical),


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3105 F01

OUTPUT

VOLTAGE

INDUCTOR

CURRENT

TIME

TIME

NORMAL OPERATION

LDO IN

REGULATION

1.4V

VOUT SYNCHRONOUS

RECTIFIER ENABLED

VAUX VOUT

VOUT IN

REGULATION

VOUT = VAUX

START-UP MODE

VLDO

the synchronous rectifiers are disabled. With the synchro-nous rectifiers disabled, the converter operates in criticalconduction mode. In this mode, the N-channel MOSFETbetween SW and GND is enabled and remains on until theinductor current reaches the peak current limit. It is thendisabled and the inductor current discharges completelybefore the cycle is repeated.

When the output voltage is greater than the input voltageand greater than 1.2V, the synchronous rectifier is enabled.In this mode, the N-channel MOSFET between SW andGND is enabled until the inductor current reaches the peak

current limit. Once current limit is reached, the N-channelMOSFET turns off and the P-channel MOSFET between SWand the driven output is enabled. This switch remains onuntil the inductor current drops below the valley currentlimit and the cycle is repeated.

When VOUT reaches the regulation point, the N- and P-channel MOSFETs connected to the SW pin are disabledand the converter enters sleep.

Figure 1. Typical Converter Start-Up Sequence

Auxiliary LDO

The integrated LDO provides a regulated 6mA rail topower microcontrollers and external sensors. The LDO ispowered from the AUX output allowing the LDO to attainregulation while the main output is still charging. The LDOhas a 12mA current limit and an internal 1ms soft-startto eliminate inrush currents. The LDO output voltage isset by the FBLDO pin. If a resistor divider is connectedto this pin, the ratio of the resistors determines the LDOoutput voltage. If the FBLDO pin is connected directly toGND, the LDO will use a 2M internal divider network to

program a 2.2V nominal output voltage. The LDO shouldbe programmed for an output voltage less than the pro-grammed VOUT.

When the converter is placed in shutdown mode (dueto undervoltage lockout or via the SHDN pin) the LDO isforced into reverse-blocking mode with reverse currentlimited to under 1A. After the shutdown event has ended,the LDO remains in reverse-blocking mode until VAUX hasrisen above the LDO voltage.

OPERATION


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MPPC Operation

The maximum power point control circuit allows the user

to set the optimal input voltage operating point for a givenpower source. The MPPC circuit dynamically regulatesthe average inductor current to prevent the input voltagefrom dropping below the MPPC threshold. When VIN isgreater than the MPPC voltage, the inductor current isincreased until VIN is pulled down to the MPPC set point.If VIN is less than the MPPC voltage, the inductor currentis reduced until VIN rises to the MPPC set point.

Automatic Power Adjust

The LTC3105 incorporates a feature that maximizes ef-

ficiency at light load while providing increased powercapability at heavy load by adjusting the peak and valleyof the inductor current as a function of load. Lowering thepeak inductor current to 100mA at light load optimizesefficiency by reducing conduction losses. As the loadincreases, the peak inductor current is automatically in-creased to a maximum of 400mA. At intermediate loads,the peak inductor current can vary between 100mA to400mA. This function is overridden by the MPPC functionand will only be observed when the power source candeliver more power than the load requires.

PGOOD Operation

The power good output is used to indicate that VOUT is

in regulation. PGOOD is an open-drain output, and isdisabled in shutdown and undervoltage lockout. PGOODwill indicate that power is good at the beginning of thefirst sleep event after the output voltage has risen above90% of its regulation value. PGOOD remains asserted untilVOUT drops below 90% of its regulation value at whichpoint PGOOD will pull low.

Input Undervoltage Lockout

In applications such as photovoltaic conversion, the inputpower source may be absent for long periods of time.

To minimize discharge of the outputs in such cases, theLTC3105 incorporates an undervoltage lockout (UVLO)which forces the converter into shutdown mode if theinput voltage falls below 90mV (typical). In shutdown,the switch connecting AUX and VOUT is enabled andthe LDO is placed into reverse-blocking mode and thecurrent into VOUT is reduced to 4A typical. Reverse cur-rent through the LDO is limited to 1A in shutdown tominimize discharging of the output. Refer to the TypicalPerformance Characteristics curves for details on thereverse current into VOUT.

OPERATION

Component Selection

Low DCR power inductors with values between 4.7Hand 30H are suitable for use with the LTC3105. Formost applications, a 10H inductor is recommended. Inapplications where the input voltage is very low, a largervalue inductor can provide higher efficiency and a lower

start-up voltage. In applications where the input voltageis relatively high (VIN > 0.8V), smaller inductors may beused to provide a smaller overall footprint. In all cases,the inductor must have low DCR and sufficient saturationcurrent rating. If the DC resistance of the inductor is toohigh, efficiency will be reduced and the minimum operatingvoltage will increase.

Input capacitor selection is highly important in low voltage,high source resistance systems. For general applications,

APPLICATIONS INFORMATION

a 10F ceramic capacitor is recommended between VINand GND. For high impedance sources, the input capacitorshould be large enough to allow the converter to completestart-up mode using the energy stored in the input ca-pacitor. When using bulk input capacitors that have highESR, a small valued parallel ceramic capacitor should be

placed between VIN and GND as close to the converterpins as possible.

A 1F ceramic capacitor should be connected betweenAUX and GND. Larger capacitors should be avoided tominimize start-up time. A low ESR output capacitor shouldbe connected between VOUT and GND. The main outputcapacitor should be 10F or larger. The main output canalso be used to charge energy storage devices includingtantalum capacitors, supercapacitors and batteries. When


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APPLICATIONS INFORMATIONusing output bulk storage devices with high ESR, a smallvalued ceramic capacitor should be placed in parallel andlocated as close to the converter pins as possible.

Step-Up Converter Feedback Configuration

A resistor divider connected between the VOUT and FB pinsprograms the step-up converter output voltage, as shownin Figure 2. An optional 22pF feedforward capacitor, CFF1,can be used to reduce output ripple and improve loadtransient response. The equation for VOUT is:

VOUT = 1.008V

R1

R2+ 1

LDO Regulator Feedback Configuration

Two methods can be used to program the LDO outputvoltage, as shown in Figure 3. A resistor divider connectedbetween the LDO and FBLDO pins can be used to programthe LDO output voltage. The equation for the LDO outputvoltage is:

VLDO = 1.008V

R3

R4+ 1

Figure 2. FB Configuration

3105 F02

LTC3105CFF1 R1

R2

FB

VOUT

Figure 3. FBLDO Configuration

3105 F03

LDO

LTC3105R3

2.2V

R4

LDO

FBLDO FBLDO

LTC3105

Alternatively, the FBLDO pin can be connected directly toGND. In this configuration, the LDO is internally set to anominal 2.2V output.

MPPC Threshold Configuration

The MPPC circuit controls the inductor current to main-tain VIN at the voltage on the MPPC pin. The MPPC pinvoltage is set by connecting a resistor between the MPPCpin and GND, as shown in Figure 4. The MPPC voltage isdetermined by the equation:

VMPPC = 10A RMPPC

In photovoltaic cell applications, a diode can be used toset the MPPC threshold so that it tracks the cell voltageover temperature, as shown in Figure 5. The diode shouldbe thermally coupled to the photovoltaic cell to ensureproper tracking. A resistor placed in series with the diodecan be used to adjust the DC set point to better matchthe maximum power point of a particular source if theselected diode forward voltage is too low. If the diode islocated far from the converter inputs, a capacitor may berequired to filter noise that may couple onto the MPPCpin, as shown in Figure 5. This method can be extendedto stacked cell sources through use of multiple series

connected diodes.

Figure 4. MPPC Configuration

Figure 5. MPPC Configuration with Temperature Adjustment

3105 F04

MPPC

LTC3105RMPPC

10A

3105 F05

MPPC

LTC3105

C610nF

VFWD

RMPPC

10A

+


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TEMPERATURE (C)

45

MPPCVOLTAGE(V)

0.4

15 15 45

0.2

0.3

0.7

0.1

0

0.6

0.5

30 0 75 9030 60

3105 TA02aTIME (s)

0 25 50 75 100 125 150

3105 TA02b

INPUT CURRENT25mA/DIV

OUTPUT CURRENT5mA/DIV

INPUT VOLTAGE50mV/DIV

VOUT = 2.8VVMPPC = 0.4VVFB = 0.94V

APPLICATIONS INFORMATION

Industrial Current Loops

The low 250mV start-up and low voltage operation of the

LTC3105 allow it to be supplied by power from a diodeplaced in an industrial sensor current loop, as shownin Figure 6. In this application, a large input capacitoris required due to the very low available supply current(less than 4mA). The loop diode should be selected for aminimum forward drop of 300mV. The MPPC pin voltageshould be set for a value approximately 50mV below theminimum diode forward voltage.

Figure 6. Current Loop Power Tap

3105 F06

GND

MPPC

VIN

LTC3105

CINVFWD

RMPPC

4mA TO 20mA

CURRENT LOOP+

3.3V from a Single-Cell Photovoltaic Source with Temperature Tracking

VMPPC vs Temperature Input Current Step Response

3105 TA02

COUT10F

R12.26M

VOUT3.3V

R21M

FB

PGOOD

LDO

FBLDO

MPPC

SHDN

AUX

SW

CLDO4.7F

2.2VRMPPC9.09k

CAUX1F

* MRA4003T3** COILCRAFT MSS5131-103MX

LTC3105

CMPPC10nF GND

CIN10F

L1**10H

+

ONOFF

VIN

VOUT

D1*

THERMALLYCOUPLED

TYPICAL APPLICATIONS


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LTC3105

13

3105p


3.3V from Multiple Stacked-Cell Photovoltaic with Source Temperature Tracking

Thermoelectric Generator to 2.4V Super Capacitor Charger

3105 TA03

COUT10F

R11.37M

VOUT3.3V

R2604k

FB

PGOOD

LDO

FBLDO

MPPC

SHDN

AUX

SW

CLDO4.7F

2.2V

CAUX1F

RMPPC4.99k

CIN10F

* MRA4003TE** PANASONIC ELL-VEG6R8N

L1**6.8H

LTC3105

CMPPC10nF

GND

+

+

ONOFF

VIN

VOUT

D1*

D2*

THERMALLYCOUPLED

3105 TA04

CBULK1F2.5V

R11.10M

VOUT2.4V

R2787k

FB

PGOOD

LDO

FBLDO

MPPC

VIN

SHDN

AUX

SW

VOUT

CLDO4.7F

2.2V

CFF22pF

RMPPC30.1k

* MICROPELT MPG-D751** COILCRAFT MSS5131-103MX

TEG*

T 10C

CAUX1F

CIN100F

L1**10H

LTC3105

GND

COUT1F

ONOFF

+

+


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LTC3105

14

3105p

TIME (ms)

0 6 12 18 24 30 36 42 48

3105 TA05a


LDO VOLTAGE50mV/DIV

LOAD CURRENT2mA/DIV

VOUT VOLTAGE500mV/DIV

TIME (ms)

0 50 100 150 200 250 300

3105 TA05b


LDO VOLTAGE500mV/DIV

VOUT VOLTAGE500mV/DIV


Industrial Sensor 4mA to 20mA Current Loop Power Tap

VOUT, VIN, LDO and IOUT Burst Load Start-Up VIN, VOUT, VLDO

3105 TA05

R12M

VOUT, 3V

R21M

FB

ENPGOOD

LDO

FBLDO

MPPC

SHDN

AUX

SW

P

CAUX1F

RMPPC28k

280mV

2.2V

CIN470F

4mA TO 20mACURRENT LOOP

D1*

L1**10H

LTC3105

GND

10F

VFWD = 330mV

RPG499k

* MBRS190T3** COILCRAFT MSS5131-103MX

+

ONOFF

VIN

VDD

VOUT

CLDO4.7F

Single-Cell Photovoltaic NiMH Trickle Charger

3105 TA06

NiMH 2

R11.02M

VOUT3.2V

R2470k

FB

PGOOD

LDO

FBLDO

MPPC

SHDN

AUX

SW

CLDO4.7F

1.8V

RMPPC40.2k

CAUX1F

CIN10F

L1, 10H

LTC3105

GND

COUT10F

R31M

R41.27M

+

+

+

ONOFF

VIN

VOUT


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15

3105p

PACKAGE DESCRIPTION

DD Package10-Lead Plastic DFN (3mm 3mm)

(Reference LTC DWG # 05-08-1699 Rev B)

3.00 0.10(4 SIDES)

NOTE:1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION

OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENTSTATUS OF VARIATION ASSIGNMENT

2. DRAWING NOT TO SCALE3. 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 SIDE5. EXPOSED PAD SHALL BE SOLDER PLATED6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE

TOP AND BOTTOM OF PACKAGE

0.40 0.10

BOTTOM VIEWEXPOSED PAD

1.65 0.10(2 SIDES)

0.75 0.05

R = 0.125TYP

2.38 0.10(2 SIDES)

15

106

PIN 1TOP MARK

(SEE NOTE 6)

0.200 REF

0.00 0.05

(DD)DFN REV B 0309

0.25 0.05

2.38 0.05(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

1.65 0.05(2 SIDES)2.15 0.05

0.50BSC

0.70 0.05

3.55 0.05PACKAGEOUTLINE

0.25 0.050.50 BSC

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.

MSOP (MS12) 1107 REV

0.53 0.152

(.021

.006)

SEATINGPLANE

0.18

(.007)

1.10(.043)MAX

0.22 0.38

(.009 .015)TYP

0.86(.034)REF

0.650

(.0256)BSC

12 11 10 9 8 7

NOTE:1. DIMENSIONS IN MILLIMETER/(INCH)2. DRAWING NOT TO SCALE3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.

MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.

INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE5. LEAD COPLANARITY (BOTTOM OF LEADS AF TER FORMING) SHALL BE 0.102mm (.004") MAX

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

0.42 0.038(.0165 .0015)

TYP

0.65(.0256)

BSC

4.039 0.102

(.159 .004)(NOTE 3)

0.1016 0.0508

(.004 .002)

1 2 3 4 5 6

3.00 0.102

(.118 .004)(NOTE 4)

0.406 0.076

(.016 .003)REF

4.90 0.152

(.193 .006)

MS Package12-Lead Plastic MSOP

(Reference LTC DWG # 05-08-1668 Rev )


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LTC3105

3105p

Linear Technology CorporationLT 1010 PRINTED IN USA

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LTC3105 Datasheet

Documents

Transcript of LTC3105 Datasheet