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LTC3105

3105fa

TYPICAL APPLICATION

FEATURES DESCRIPTION

400mA Step-Up DC/DC

Converter with Maximum Power

Point Control and 250mV Start-Up

The LTC

3105 is a high efficiency step-up DC/DC converter

that can operate from input voltages as low as 225mV. A

250mV start-up capability and integrated maximum power

point controller (MPPC) enable operation directly from low

voltage, high impedance alternative power sources such as

photovoltaic cells, TEGs (thermoelectric generators) and

fuel cells. A user programmable MPPC set point maximizes

the energy that can be extracted from any power source.

Burst Mode operation, with a proprietary self adjusting

peak current, optimizes converter efficiency and output

voltage ripple over all operating conditions.

The AUX powered 6mA LDO provides a regulated rail for

external microcontrollers and sensors while the main

output is charging. In shutdown, I

is reduced to 10µA

and integrated thermal shutdown offers protection from

overtemperature faults. The LTC3105 is offered in 10-lead

3mm × 3mm × 0.75mm DFN and 12-lead MSOP packages.

Output Current vs Input Voltage

APPLICATIONS

Low Start-Up Voltage: 250mV

Maximum Power Point Control

Wide V

Range: 225mV to 5V

Auxiliary 6mA LDO Regulator

Burst Mode

Operation: I

= 24µA

Output Disconnect and Inrush Current Limiting

> V

OUT

Operation

Antiringing Control

Soft Start

Automatic Power Adjust

Power Good Indicator

10-Lead 3mm × 3mm × 0.75mm DFN and 12-Lead

MSOP Packages

Solar Powered Battery/Supercapacitor Chargers

Energy Harvesting

Remote Industrial Sensors

Low Power Wireless Transmitters

Cell Phone, MP3, PMP and GPS Accessory Chargers

L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks

and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the

property of their respective owners.

3105 TA01a

10µF

Li-Ion

1020k

225mV TO 5V

OUT

4.1V

332k

PGOOD

LDO

FBLDO

MPPC

SHDN

AUX

OUT

4.7µF

2.2V

40.2k

1µF

LTC3105

GND

10µF

10µH

PHOTOVOLTAIC

CELL

OFF

–

Single Photovoltaic Cell Li-Ion Trickle Charger

INPUT VOLTAGE (V)

0.2

OUTPUT CURRENT (mA)

0.3

0.4

0.5 0.6 0.80.7 0.9

1.0

3105 TA01b

OUT

= 5V

OUT

= 3.3V

OUT

= 4.2V

MPPC DISABLED

Summary of content (18 pages)

PAGE 1
LTC3105 400mA Step-Up DC/DC Converter with Maximum Power Point Control and 250mV Start-Up FEATURES n n n n n n n n n n n n DESCRIPTION Low Start-Up Voltage: 250mV Maximum Power Point Control Wide VIN Range: 225mV to 5V Auxiliary 6mA LDO Regulator Burst Mode® Operation: IQ = 24µA Output Disconnect and Inrush Current Limiting VIN > VOUT Operation Antiringing Control Soft Start Automatic Power Adjust Power Good Indicator 10-Lead 3mm × 3mm × 0.
PAGE 2
LTC3105 ABSOLUTE MAXIMUM RATINGS (Note 1) SW Voltage DC............................................................. –0.3V to 6V Pulsed (<100ns)............................................–1V to 7V Voltage, All Other Pins.................................. –0.3V to 6V Operating Junction Temperature Range (Note 2)..........................................–40°C to 85°C Maximum Junction Temperature (Note 4)............. 125°C Storage Temperature..............................
PAGE 3
LTC3105 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). VAUX = VOUT = 3.3V, VLDO = 2.2V, VIN = 0.6V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Step-Up Converter Input Operating Voltage Input Start-Up Voltage l (Note 5) TJ = 0°C to 85°C (Note 5) 0.225 0.25 l Output Voltage Adjust Range l 1.5 Feedback Voltage (FB Pin) l 0.984 1.004 5 V 0.
PAGE 4
LTC3105 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, VAUX = VOUT = 3.3V, VLDO = 2.2V, VIN = 0.6V, unless otherwise noted. Minimum Input Start-Up Voltage vs Temperature Shutdown Thresholds vs Input Voltage 340 900 300 280 260 240 220 IC Enable Delay vs Input Voltage IC ENABLE 800 100 700 600 DELAY TIME (µs) THRESHOLD VOLTAGE (mV) INPUT VOLTAGE (mV) 320 200 –45 –30 –15 120 1000 IC DISABLE 500 400 300 80 60 200 100 0 15 30 45 60 TEMPERATURE (°C) 75 90 0 1.25 3105 G01 2.25 4.25 3.
PAGE 5
LTC3105 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, VAUX = VOUT = 3.3V, VLDO = 2.2V, VIN = 0.6V, unless otherwise noted. Exiting MPPC Control on Input Voltage Step IPEAK and IVALLEY Current Limit Change vs Temperature 100 IPEAK CHANGE FROM 25°C (%) 0.5 INDUCTOR CURRENT 100mA/DIV MPPC VOLTAGE 200mV/DIV 90 0 EFFICIENCY (%) VMPPC = 400mV VIN VOLTAGE 200mV/DIV Efficiency vs VIN 1.0 IVALLEY –0.5 –1.0 –1.5 –2.5 –45 –30 –15 3105 G10 0 15 30 45 60 TEMPERATURE (°C) 60 VIN = 0.6V VIN = 0.
PAGE 6
LTC3105 PIN FUNCTIONS (DFN/MSOP) FB (Pin 1/Pin 1): Step-Up Converter Feedback Input. Connect the VOUT resistor divider tap to this input. The output voltage can be adjusted between 1.5V and 5.25V. LDO (Pin 2/Pin 2): LDO Regulator Output. Connect a 4.7µF or larger capacitor between LDO and GND. FBLDO (Pin 3/Pin 3): LDO Feedback Input. Connect the LDO resistive divider tab to this input. Alternatively, connecting FBLDO directly to GND will configure the LDO output voltage to be internally set at 2.
PAGE 7
LTC3105 BLOCK DIAGRAM (Pin Numbers for DFN Package Only) L1 10µH 7 SHUTDOWN SLEEP SW OR WELL CONTROL AUX VIN LOW VOLTAGE START-UP CURRENT ADJUST CIN 10µF SHUTDOWN VCC 5 RMPPC VCC SHDN – + –g m + 1.5V TO 5.25V COUT 10µF 9 2 CLDO 4.7µF PEAK CURRENT LIMIT SHUTDOWN VALLEY CURRENT LIMIT LOGIC 2M USER SHUTDOWN SLEEP BURST CONTROL – + VIN VAUX CAUX 1µF 10µA MPPC VIN 4 – + VOUT LDO VAUX VCC FB 0.9V 11 PGOOD 1.004V FB EXPOSED PAD FBLDO 1.
PAGE 8
LTC3105 OPERATION Introduction The LTC3105 is a unique, high performance, synchronous boost converter that incorporates maximum power point control, 250mV start-up capability and an integrated LDO regulator. This part operates over a very wide range of input voltages from 225mV to 5V. Its Burst Mode architecture and low 24µA quiescent current optimize efficiency in low power applications.
PAGE 9
LTC3105 INDUCTOR CURRENT OPERATION OUTPUT VOLTAGE TIME VAUX VLDO VOUT 1.4V VOUT IN REGULATION LDO IN REGULATION START-UP MODE NORMAL OPERATION TIME VOUT = VAUX VOUT SYNCHRONOUS RECTIFIER ENABLED 3105 F01 Figure 1. Typical Converter Start-Up Sequence above VAUX , an internal switch is enabled to connect the two outputs together. If VIN is greater than the voltage on the driven output (VOUT or VAUX), or the driven output is less than 1.2V (typical), the synchronous rectifiers are disabled.
PAGE 10
LTC3105 OPERATION When the converter is placed in shutdown mode, the LDO is forced into reverse-blocking mode with reverse current limited to under 1µA. After the shutdown event has ended, the LDO remains in reverse-blocking mode until VAUX has risen above the LDO voltage. MPPC Operation The maximum power point control circuit allows the user to set the optimal input voltage operating point for a given power source.
PAGE 11
LTC3105 APPLICATIONS INFORMATION Step-Up Converter Feedback Configuration MPPC Threshold Configuration A resistor divider connected between the VOUT and FB pins programs the step-up converter output voltage, as shown in Figure 2. An optional 22pF feedforward capacitor, CFF1, can be used to reduce output ripple and improve load transient response. The equation for VOUT is: The MPPC circuit controls the inductor current to maintain VIN at the voltage on the MPPC pin.
PAGE 12
LTC3105 APPLICATIONS INFORMATION Industrial Current Loops 4mA TO 20mA CURRENT LOOP The low 250mV start-up and low voltage operation of the LTC3105 allow it to be supplied by power from a diode placed in an industrial sensor current loop, as shown in Figure 6. In this application, a large input capacitor is required due to the very low available supply current (less than 4mA). The loop diode should be selected for a minimum forward drop of 300mV.
PAGE 13
LTC3105 TYPICAL APPLICATIONS 3.3V from Multiple Stacked-Cell Photovoltaic with Source Temperature Tracking L1** 6.8µH + – + CIN 10µF – VIN SW R1 1.37M LTC3105 RMPPC 4.99k THERMALLY COUPLED FB PGOOD MPPC OFF ON D1* VOUT 3.3V VOUT LDO SHDN CMPPC 10nF AUX D2* 2.2V COUT 10µF R2 604k FBLDO GND CAUX 1µF CLDO 4.7µF 3105 TA03 * MRA4003T3 ** PANASONIC ELL-VEG6R8N Thermoelectric Generator to 2.
PAGE 14
LTC3105 TYPICAL APPLICATIONS Industrial Sensor 4mA to 20mA Current Loop Power Tap L1** 10µH VIN 4mA TO 20mA CURRENT LOOP SW VOUT R1 2M LTC3105 VFWD = 330mV FB CIN 470µF D1* PGOOD 280mV LDO MPPC RMPPC 28k OFF ON AUX * MBRS190T3 ** COILCRAFT MSS5131-103MX µP + 10µF VOUT, 3V – VDD 2.2V CLDO 4.
PAGE 15
LTC3105 PACKAGE DESCRIPTION DD Package DD (3mm Package 10-Lead Plastic DFN × 3mm) 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699 Rev C) (Reference LTC DWG # 05-08-1699 Rev C) 0.70 ±0.05 3.55 ±0.05 1.65 ±0.05 2.15 ±0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 2.38 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 ±0.10 (4 SIDES) R = 0.125 TYP 6 0.40 ± 0.10 10 1.65 ± 0.10 (2 SIDES) PIN 1 NOTCH R = 0.20 OR 0.35 × 45° CHAMFER PIN 1 TOP MARK (SEE NOTE 6) 0.
PAGE 16
LTC3105 PACKAGE DESCRIPTION MS Package 12-Lead Plastic MSOP MSDWG Package (Reference LTC # 05-08-1668 Rev Ø) 12-Lead Plastic MSOP (Reference LTC DWG # 05-08-1668 Rev Ø) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 4.039 ± 0.102 (.159 ± .004) (NOTE 3) 0.65 (.0256) BSC 0.42 ± 0.038 (.0165 ± .0015) TYP 12 11 10 9 8 7 RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) DETAIL “A” 3.00 ± 0.102 (.118 ± .004) (NOTE 4) 4.90 ± 0.152 (.193 ± .006) 0° – 6° TYP 0.406 ± 0.076 (.016 ± .
PAGE 17
LTC3105 REVISION HISTORY REV DATE DESCRIPTION PAGE NUMBER A 02/11 Added (Note 5) notation to Input Start-Up Voltage conditions 3 Added Note 5 3 Updated Start-Up Mode Operation section 8 3105fa 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.
PAGE 18
LTC3105 TYPICAL APPLICATION Single-Cell Powered Remote Wireless Sensor L1* 10µH + – VIN SW CIN 10µF R1 2.32M LTC3105 FB MPPC RMPPC 40.2k COUT 100µF R2 1.02M XMTR I/O OFF ON EN PGOOD SHDN LDO AUX 2N7000 VOUT 3.3V VOUT CAUX 1µF 2.2V FBLDO GND µC RPG 499k VDD CLDO 4.7µF * COILCRAFT MSS5131-103MX A/D SENSOR GPIO GND 3105 TA07 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3108/LTC3108-1 Ultralow Voltage Step-Up Converter and Power Manager VIN : 0.02V to 1V; VOUT = 2.2V, 2.