Datasheet

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LTC3129

3129fa

For more information www.linear.com/LTC3129

Typical applicaTion

FeaTures DescripTion

15V, 200mA Synchronous

Buck-Boost DC/DC Converter

with 1.3µA Quiescent Curr

ent

The LT C

3129 is a high efficiency, 200mA buck-boost

DC/DC c

onverter with a wide V

and V

OUT

range. It includes

an accurate RUN pin threshold to allow predictable regula-

tor turn

-on and a maximum power point control (MPPC)

capability

that ensures maximum power extraction from

non-ideal power sources such as photovoltaic panels.

The LTC3129 employs an ultralow noise, 1.2MHz PWM

switching architecture that minimizes solution footprint by

allowing the use of tiny, low profile inductors and ceramic

capacitors. Built-in loop compensation and soft-start

simplify the design. For high efficiency operation at light

loads, automatic Burst Mode operation can be selected,

reducing the quiescent current to just 1.3µA.

Additional features include a power good output, less than

10nA of shutdown current and thermal shutdown.

The LTC3129 is available in thermally enhanced 3mm ×

3mm QFN and 16-lead MSOP packages. For fixed output

voltage options, see the functionally equivalent LTC3129-1,

which eliminates the need for an external feedback divider.

L, LT , LT C , LT M , Linear Technology, the Linear logo and Burst Mode are registered trademarks

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

property of their respective owners.

applicaTions

Regulates V

OUT

Above, Below or Equal to V

Wide V

Range: 2.42V to 15V, 1.92V to 15V After

Start-Up (Bootstrapped)

Wide V

OUT

Range: 1.4V to 15.75V

200mA Output Current in Buck Mode

Single Inductor

1.3µA Quiescent Current

Programmable Maximum Power Point Control

1.2MHz Ultralow Noise PWM

Current Mode Control

Pin Selectable Burst Mode

Operation

Up to 95% Efficiency

Accurate RUN Pin Threshold

Power Good Indicator

10nA Shutdown Current

Thermally Enhanced 3mm × 3mm QFN and

16-Lead MSOP Packages

Industrial Wireless Sensor Nodes

Post-Regulator for Harvested Energy

Solar Panel Post-Regulator/Charger

Intrinsically Safe Power Supplies

Wireless Microphones

Avionics-Grade Wireless Headsets

BST1

OUT

SW1 SW2

LTC3129

22nF

BST2

PGOOD

GND

2.42V

TO 15V

RUN

MPPC

PWM

22nF

10µH

10µF

10µF 10pF

2.2µF

3129 TA01a

PGND

3.32M

1.02M

5V AT 200mA, V

> 5V

5V AT 100mA, V

< 5V

Efficiency and Power Loss vs Load

100

OUTPUT CURRENT (mA)

0.01

EFFICIENCY (%)

POWER LOSS (mW)

1000

100

0.1

0.01

3129 TA01b

0.1 100 1000101

= 2.5V

= 3.6V

= 5V

= 15V

EFFICIENCY

POWER LOSS

OUT

= 5V

Summary of content (30 pages)

PAGE 1
LTC3129 15V, 200mA Synchronous Buck-Boost DC/DC Converter with 1.3µA Quiescent Current Description Features n n n n n n n n n n n n n n n Regulates VOUT Above, Below or Equal to VIN Wide VIN Range: 2.42V to 15V, 1.92V to 15V After Start-Up (Bootstrapped) Wide VOUT Range: 1.4V to 15.75V 200mA Output Current in Buck Mode Single Inductor 1.3µA Quiescent Current Programmable Maximum Power Point Control 1.
PAGE 2
LTC3129 Absolute Maximum Ratings (Notes 1, 8) VIN, VOUT Voltages ..................................... –0.3V to 18V SW1 DC Voltage............................. –0.3V to (VIN + 0.3V) SW2 DC Voltage..........................–0.3V to (VOUT + 0.3V) SW1, SW2 Pulsed (<100ns) Voltage...............–1V to 19V BST1 Voltage ..................... (SW1 – 0.3V) to (SW1 + 6V) BST2 Voltage .....................(SW2 – 0.3V) to (SW2 + 6V) RUN, PGOOD Voltages................................ –0.
PAGE 3
LTC3129 Electrical Characteristics The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). Unless otherwise noted, VIN = 12V, VOUT = 5V. PARAMETER CONDITIONS VIN Start-Up Voltage MIN l Input Voltage Range VCC > 2.42V (Back-Driven) l 1.92 VIN UVLO Threshold (Rising) VCC > 2.42V (Back-Driven) TYP MAX UNITS 2.25 2.42 V 15 V l 1.8 1.9 2.
PAGE 4
LTC3129 Electrical Characteristics The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). Unless otherwise noted, VIN = 12V, VOUT = 5V. PARAMETER CONDITIONS MIN TYP VOUT UV Hysteresis MAX UNITS 150 VOUT Current – Shutdown RUN = 0V, VOUT = 15V Including Switch Leakage VOUT Current – Sleep PWM = 0V, FB = 1.25V VOUT Current – Active PWM = VCC, VOUT = 15V (Note 4), FB = 1.
PAGE 5
LTC3129 Typical Performance Characteristics Power Loss, VOUT = 3.3V 100 1000 Efficiency, VOUT = 5V 10 1 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 10V VIN = 15V BURST 1 100 10 OUTPUT CURRENT (mA) 60 50 PWM 40 30 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 10V VIN = 15V 20 10 0 0.01 1000 0.1 1 100 10 OUTPUT CURRENT (mA) Efficiency, VOUT = 12V PWM 40 30 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 10V VIN = 15V 20 10 0 0.01 0.1 1 100 10 OUTPUT CURRENT (mA) POWER LOSS (mW) EFFICIENCY (%) 60 250 0.01 0.
PAGE 6
LTC3129 Typical Performance Characteristics 1.2 70 1.1 50 40 VOUT = 2.5V VOUT = 3.3V VOUT = 4.1V VOUT = 5V VOUT = 6.9V VOUT = 8.2V VOUT = 12V VOUT = 15V 30 20 10 0 2 4 6 8 10 VIN (V) 12 14 0.9 0.8 0.7 0.6 0.4 –45 16 0 –1 –20 5 30 55 80 TEMPERATURE (°C) 105 5 30 55 80 TEMPERATURE (°C) 70 60 50 40 30 20 10 0 1.13 1.135 1.14 1.145 1.15 1.155 1.16 1.165 1.17 MPPC PIN VOLTAGE (V) –1.
PAGE 7
LTC3129 Typical Performance Characteristics Fixed Frequency Ripple on VOUT TA = 25°C, unless otherwise noted.
PAGE 8
LTC3129 Pin Functions (QFN/MSOP) BST1 (Pin 1/Pin 15): Bootstrapped Floating Supply for High Side NMOS Gate Drive. Connect to SW1 through a 22nF capacitor, as close to the part as possible. The value is not critical. Any value from 4.7nF to 47nF may be used. VIN (Pin 2/Pin 16): Input Voltage for the Converter. Connect a minimum of 4.7µF ceramic decoupling capacitor from this pin to the ground plane, as close to the pin as possible. VCC (Pin 3/Pin 1): Output voltage of the internal voltage regulator.
PAGE 9
LTC3129 Block Diagram BST1 VIN SW2 LDO START 4.1V VCC_GD DRIVER A DRIVER B VOUT START VCC 1.175V VREF VREF 0.9V + – 1.22V + – NC ISENSE C START SD DRV_C DRV_A DRV_D + – ISENSE 1.175V – + ISENSE 20mA RESET MPPC 1.175V – + UV ILIM FB 1.1V LOGIC ENABLE UVLO NC DRIVER DRV_B 500mA – + DRIVER D VREF_GD RUN VOUT VCC ISENSE VIN BST2 VCC VREF VCC SW1 IZERO THERMAL SHUTDOWN ISENSE PWM VC – + + – + – VIN 1.
PAGE 10
LTC3129 Operation Introduction Pwm Mode Operation The LTC3129 is a 1.3µA quiescent current, monolithic, current mode, buck-boost DC/DC converter that can operate over a wide input voltage range of 1.92V to 15V and provide up to 200mA to the load. Internal, low RDS(ON) N-channel power switches reduce solution complexity and maximize efficiency.
PAGE 11
LTC3129 Operation When stepping down from a high input voltage to a lower output voltage, the converter operates in buck mode and switch D remains on for the entire switching cycle except for the minimum switch low duration (typically 90ns). During the switch low duration, switch C is turned on which forces SW2 low and charges the flying capacitor, CBST2. This ensures that the switch D gate driver power supply rail on BST2 is maintained.
PAGE 12
LTC3129 Operation inductor current is approximately 275mA (typical). In Buck mode, the output current is approximately equal to the inductor current IL. IOUT(BUCK) ≈ IL • 0.89 The 90ns SW1/SW2 forced low time on each switching cycle briefly disconnects the inductor from VOUT and VIN resulting in about 11% less output current in either buck or boost mode for a given inductor current.
PAGE 13
LTC3129 Operation functions of the IC, significantly reducing the quiescent current of the LTC3129 to just 1.3µA typical. This greatly improves overall power conversion efficiency when the output load is light. Since the converter is not operating in sleep, the output voltage will slowly decay at a rate determined by the output load resistance and the output capacitor value.
PAGE 14
LTC3129 Operation VOUT Undervoltage There is also an undervoltage comparator that monitors the output voltage. Until VOUT reaches 1.15V (typical), the average current limit is reduced by a factor of two. This reduces power dissipation in the device in the event of a shorted output. In addition, N-channel switch D, which feeds VOUT, will be disabled until VOUT exceeds 1.15V.
PAGE 15
LTC3129 Operation PGOOD Comparator The LTC3129 provides an open-drain PGOOD output that pulls low if VOUT falls more than 7.5% (typical) below its programmed value. When VOUT rises to within 5% (typical) of its programmed value, the internal PGOOD pull-down will turn off and PGOOD will go high if an external pullup resistor has been provided. An internal filter prevents nuisance trips of PGOOD due to short transients on VOUT.
PAGE 16
LTC3129 Operation The MPPC pin controls the converter in a linear fashion when using sources that can provide a minimum of 5mA to 10mA of continuous input current. For operation from weaker input sources, refer to the Applications Information section to see how the programmable RUN pin can be used to control the converter in a hysteretic manner to provide an effective MPPC function for sources that can provide as little as 5µA or less.
PAGE 17
LTC3129 Applications Information A standard application circuit for the LTC3129 is shown on the front page of this data sheet. The appropriate selection of external components is dependent upon the required performance of the IC in each particular application given considerations and trade-offs such as PCB area, input and output voltage range, output voltage ripple, transient response, required efficiency, thermal considerations and cost.
PAGE 18
LTC3129 Applications Information It should be noted that the worst-case peak-to-peak inductor ripple current occurs when the duty cycle in buck mode is minimum (highest VIN) and in boost mode when the duty cycle is 50% (VOUT = 2 • VIN). As an example, if VIN (minimum) = 2.5V and VIN (maximum) = 15V, VOUT = 5V and L = 10µH, the peak-to-peak inductor ripples at the voltage extremes (15V VIN for buck and 2.
PAGE 19
LTC3129 Applications Information Burst Mode operation and improve transient response. In addition, due to the wide VIN and VOUT operating range of the LTC3129 and its fixed internal loop compensation, some applications may require the use of a feedforward capacitor to assure light-load stability (less than ~15mA) when operating in PWM mode (PWM pin pulled high).
PAGE 20
LTC3129 Applications Information When powered through long leads or from a power source with significant resistance, a larger value bulk input capacitor may be required and is generally recommended. In such applications, a 47µF to 100µF low-ESR electrolytic capacitor in parallel with a 1µF ceramic capacitor generally yields a high performance, low cost solution. Note that applications using the MPPC feature should use a minimum CIN of 22µF. Larger values can be used without limitation.
PAGE 21
LTC3129 Applications Information When using high value divider resistors (in the MΩ range) to minimize current draw on VIN, a small noise filter capacitor may be necessary across the lower divider resistor to prevent noise from erroneously tripping the RUN comparator. The capacitor value should be minimized so as not to introduce a time delay long enough for the input voltage to drop significantly below the desired VIN threshold before the converter is turned off.
PAGE 22
LTC3129 Applications Information that allows VCC to be driven above its nominal regulation level with only a very slight amount of reverse current. Please note that the bootstrapping supply (either VOUT or a separate regulator) must be limited to less than 5.7V so as not to exceed the maximum VCC voltage of 5.5V after the diode drop. By maintaining VCC above its UVLO threshold, bootstrapping, even to a 3.3V output, also allows operation down to the VIN UVLO threshold of 1.8V (typical).
PAGE 23
LTC3129 Typical Applications Hiccup Converter Powers Wireless Sensor from Indoor Lighting UVLO = 3.5V VIN 4.7µF + 4.9cm × 5.8cm BST1 SW1 4.5 22µF LTC3129 3.5 VOUT 3.6V 1M 976k MPPC NC PGOOD PGOOD VCC NC 2.37M 2M FB PWM 10pF 4.0 VOUT RUN 470µF 6.3V PULSED IOUT 25mA FOR 5ms SW2 BST2 VIN 4.42M VCC PV PANEL SANYO AM-1815 22nF 4.7µH TRANSMIT RATE (Hz) 22nF Transmit Rate vs Light Level (Fluorescent) GND 3.0 2.5 2.0 1.5 1.0 0.5 0 2.
PAGE 24
LTC3129 Typical Applications Solar Powered Converter with MPPC Charges Storage Capacitor 22nF BST1 SW1 UVLO = 4.3V VIN 22nF 4.7µH SW2 BST2 VOUT VIN 1M 4.7µF LTC3129 47µF CERAMIC VCC 1F COOPER BUSSMANN PB-5R0V105-R PGOOD PGOOD VCC NC 392k 1M FB PWM NC 8.4cm × 3.7cm 3.09M VOUT 4.8V RUN MPPC PowerFilm SP4.2-37 SOLAR MODULE + GND 2.2µF PGND 3129 TA04a Average Output Current vs Light Level (Daylight) OUTPUT CURRENT (mA) 100.0 10.0 1.0 0.
PAGE 25
LTC3129 Typical Applications Li-Ion Powered 3V Converter with 3.1V Input UVLO Reduces Low Battery IQ to 3µA 22nF BST1 SW1 UVLO = 3.1V 22nF 4.7µH SW2 BST2 10µF LTC3129 2M + VOUT 3V 200mA VOUT VIN 33pF Li-Ion 1.58M RUN 4.7µF VCC FB MPPC 1.27M 1.02M PGOOD PWM VCC NC NC 10pF GND 2.2µF PGND 3129 TA05 15V Converter Operates from Three to Eight AA or AAA Cells 22nF VIN 2.
PAGE 26
LTC3129 Typical Applications Energy Harvesting Converter Operates from a Variety of Weak Sources 22nF BAS 70-05 BST1 SW1 UVLO = 3.3V INPUT SOURCES: • RF • AC • PIEZO • COIL-MAGNET 22nF 4.7µH SW2 BST2 VOUT 5V VOUT VIN 10µF LTC3129 4.99M 3.32M 22pF RUN FB 100µF CERAMIC VCC MPPC BAS 70-06 VCC NC 3.01M 1.02M PGOOD PWM NC 10pF GND 2.2µF PGND 3129 TA07 Solar Powered Converter Extends Battery Life in Low Power 3V Primary Battery Applications TOKO DEM2812C 22nF BST1 SW1 UVLO = 3.
PAGE 27
LTC3129 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. UD Package 16-Lead Plastic QFN (3mm × 3mm) UD Package (Reference LTC DWG # 05-08-1700 Rev A) 16-Lead Plastic QFN (3mm × 3mm) (Reference LTCPad DWG # 05-08-1700 Rev A) Exposed Variation AA Exposed Pad Variation AA 0.70 ±0.05 3.50 ±0.05 1.65 ±0.05 2.10 ±0.05 (4 SIDES) PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 ±0.
PAGE 28
LTC3129 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MSE Package 16-Lead Plastic , Exposed Die Pad MSEMSOP Package (Reference LTC MSOP, DWG # 05-08-1667 Rev Pad F) 16-Lead Plastic Exposed Die (Reference LTC DWG # 05-08-1667 Rev F) BOTTOM VIEW OF EXPOSED PAD OPTION 2.845 ±0.102 (.112 ±.004) 5.10 (.201) MIN 2.845 ±0.102 (.112 ±.004) 0.889 ±0.127 (.035 ±.005) 8 1 1.651 ±0.102 (.065 ±.004) 1.651 ±0.102 3.20 – 3.45 (.065 ±.004) (.
PAGE 29
LTC3129 Revision History REV DATE DESCRIPTION A 5/14 Clarified VCC Leakage to VIN if VCC > VIN: from –7µA to –27µA PAGE NUMBER 4 3129fa 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 representaFor more information www.linear.com/LTC3129 tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
PAGE 30
LTC3129 Typical Application Dual VIN Application, Using the LTC4412 PowerPath™ Controller 22nF MBR0520 22nF 10µH 12V WALL ADAPTER INPUT FDN338 BSS314 BST1 SW1 SW2 BST2 VOUT VIN LTC3129 10µF LTC4412 + GATE VIN VCC SENSE Li-Ion CTL 10pF 3.01M FB MPPC 324k PGOOD VCC NC NC GND VOUT 12V 10µF 25V RUN PWM STAT VIN = 12V, IOUT = 200mA VIN = 3.6V, IOUT = 50mA GND PGND 2.