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LTC3129-1

31291fa

For more information www.linear.com/LTC3129-1

Typical applicaTion

FeaTures DescripTion

15V, 200mA Synchronous

Buck-Boost DC/DC Converter

with 1.3µA Quiescent Curr

ent

The LT C

3129-1 is a high efficiency, 200mA buck-boost

DC/DC converter

with a wide V

and V

OUT

range. It

includes an accurate RUN pin threshold to allow predict-

able

regulator 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 LTC3129-1 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. To further

reduce part count and improve light load efficiency, the

LTC3129-1 includes an internal voltage divider to provide

eight selectable fixed output voltages.

Additional features include a power good output, less than

10nA of shutdown current and thermal shutdown.

The LTC3129-1 is available in thermally enhanced

3mm×3mm QFN and 16-lead MSOP packages. For an

adjustable output voltage, see the functionally equivalent

LTC3129.

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

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)

Fixed Output Voltage with Eight User-Selectable

Settings from 2.5V to 15V

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

5V AT

100mA V

< V

OUT

200mA V

> V

OUT

SW1 SW2

LTC3129-1

22nF

BST2

PGOOD

GND

2.42V TO 15V

RUN

MPPC

PWM

VS1

VS2

VS3

22nF

10µH

10µF

2.2µF

31291 TA01a

PGND

AA OR AAA

BATTERIES

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
LTC3129-1 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) Fixed Output Voltage with Eight User-Selectable Settings from 2.5V to 15V 200mA Output Current in Buck Mode Single Inductor 1.3µA Quiescent Current Programmable Maximum Power Point Control 1.
PAGE 2
LTC3129-1 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 Voltage.................................. –0.
PAGE 3
LTC3129-1 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 TYP MAX UNITS 2.25 2.42 V 15 V Input Voltage Range VCC > 2.42V (Back-Driven) l 1.92 VIN UVLO Threshold (Rising) VCC > 2.42V (Back-Driven) l 1.8 1.9 2.0 V l 80 100 130 mV l l l l l l l l 2.425 3.
PAGE 4
LTC3129-1 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 VCC UVLO Threshold (Rising) l MIN TYP MAX UNITS 2.1 2.25 2.42 V VCC UVLO Hysteresis VCC Current Limit 60 VCC = 0V l VCC Back-Drive Voltage (Maximum) 4 VCC Input Current (Back-Driven) VCC = 5.
PAGE 5
LTC3129-1 Typical Performance Characteristics Power Loss, VOUT = 2.5V Efficiency, VOUT = 2.5V 90 100 60 PWM 40 30 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 10V VIN = 15V 20 10 0.1 1 100 10 OUTPUT CURRENT (mA) 10 1 0.1 0.01 0.01 1000 0.1 31291 G01 Power Loss, VOUT = 3.3V 1 0.1 VIN = 2.5V VIN = 3.6V VIN = 5V VIN = 10V VIN = 15V 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) VIN = 2.
PAGE 6
LTC3129-1 Typical Performance Characteristics Power Loss, VOUT = 6.9V Efficiency, VOUT = 8.2V 1000 100 0.1 0.01 0.01 0.1 1 100 10 OUTPUT CURRENT (mA) 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) 31291 G06b 100 Efficiency, VOUT = 12V EFFICIENCY (%) 60 50 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) 1000 POWER LOSS (mW) VIN = 2.5V VIN = 3.
PAGE 7
LTC3129-1 Typical Performance Characteristics 1.3 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 2 4 6 8 10 VIN (V) 12 14 RDS(ON) (Ω) LOAD (mA) 1.0 50 0 0.9 0.8 0.7 0.4 –45 –1 –20 5 30 55 80 TEMPERATURE (°C) 5 30 55 80 TEMPERATURE (°C) 105 90 80 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.
PAGE 8
LTC3129-1 Typical Performance Characteristics TA = 25°C, unless otherwise noted.
PAGE 9
LTC3129-1 Pin Functions (QFN/MSOP) BST1 (Pin 1/Pin 15): Boot-Strapped 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 10
LTC3129-1 Pin Functions (QFN/MSOP) PGND (Pin 15/Pin 13, Exposed Pad Pin 17/Pin 17): Power Ground. Provide a short direct PCB path between PGND and the ground plane. The exposed pad must also be soldered to the PCB ground plane. It serves as a power ground connection, and as a means of conducting heat away from the die. Table 1. VOUT Program Settings VS3 PIN SW1 (Pin 16/Pin 14): Switch Pin. Connect to one side of the inductor. Keep PCB trace lengths as short and wide as possible to reduce EMI.
PAGE 11
LTC3129-1 Operation Introduction The LTC3129-1 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. Eight fixed, user-programmable output voltages can be selected using the three digital programming pins. Internal, low RDS(ON) N-channel power switches reduce solution complexity and maximize efficiency.
PAGE 12
LTC3129-1 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 13
LTC3129-1 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 14
LTC3129-1 Operation LTC3129-1 will go into a standby or sleep state when the output voltage achieves its nominal regulation level. The sleep state halts PWM switching and powers down all nonessential functions of the IC, significantly reducing the quiescent current of the LTC3129-1 to just 1.3µA typical. This greatly improves overall power conversion efficiency when the output load is light.
PAGE 15
LTC3129-1 Operation VOUT Undervoltage LTC3129-1 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. VIN 1.22V R3 – + ACCURATE THRESHOLD ENABLE SWITCHING RUN R4 0.
PAGE 16
LTC3129-1 Operation Note that PGOOD can be pulled up to any voltage, as long as the absolute maximum rating of 18V is not exceeded, and as long as the maximum sink current rating is not exceeded when PGOOD is low. Note that PGOOD will also be driven low if VCC is below its UVLO threshold or if the part is in shutdown (RUN below its logic threshold) while VCC is being held up (or back-driven). PGOOD is not affected by VIN UVLO or the accurate RUN threshold.
PAGE 17
LTC3129-1 Operation high resistance values that would not be practical due to the effects of noise and board leakages that would cause VOUT regulation errors. The tap point on this divider is digitally selected by using the VS1, VS2 and VS3 pins to program one of eight fixed output voltages. The VS pins should be grounded or connected to VCC to select the desired output voltage, according to the following table.
PAGE 18
LTC3129-1 Applications Information A standard application circuit for the LTC3129-1 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 19
LTC3129-1 Applications Information at large step-up ratios, the output current capability can also be limited by the total resistive losses in the power stage. These losses include, switch resistances, inductor DC resistance and PCB trace resistance. Avoid inductors with a high DC resistance (DCR) as they can degrade the maximum output current capability from what is shown in the Typical Performance Characteristics section and from the Typical Application circuits.
PAGE 20
LTC3129-1 Applications Information formula, where f is the frequency in MHz (1.2MHz), COUT is the capacitance in µF, tLOW is the switch pin minimum low time in µs (0.09µs typical) and ILOAD is the output current in amperes. ΔVP−P(BUCK) = ILOAD t LOW COUT ΔVP−P(BOOST) = V ILOAD ⎛ VOUT – VIN + tLOW fVIN ⎞ ⎜ ⎟V fCOUT ⎝ VOUT ⎠ Examining the previous equations reveals that the output voltage ripple increases with load current and is generally higher in boost mode than in buck mode.
PAGE 21
LTC3129-1 Applications Information a rather high ESR, therefore a 4.7µF (minimum) ceramic capacitor is recommended in parallel, close to the IC pins. Ceramic capacitors are often utilized in switching converter applications due to their small size, low ESR and low leakage currents. However, many ceramic capacitors intended for power applications experience a significant loss in capacitance from their rated value as the DC bias voltage on the capacitor increases.
PAGE 22
LTC3129-1 Applications Information For weak input sources with very high resistance (hundreds of Ohms or more), the LTC3129-1 may still draw more current than the source can provide, causing VIN to drop below the UVLO threshold. For these applications, it is recommended that the programmable RUN feature be used, as described in the previous section. MPPC Compensation and Gain When using MPPC, there are a number of variables that affect the gain and phase of the input voltage control loop.
PAGE 23
LTC3129-1 Typical Applications Low Noise, Fixed Frequency, Wide VIN Range 12V Converter 22nF BST1 SW1 VIN 2.42V TO 15V 22nF 6.8µH VIN < 12V, IOUT = 30mA VIN > 12V, IOUT = 200mA SW2 BST2 VOUT VIN VOUT 12V 10µF 16V LTC3129-1 1M RUN 4.7µF VCC PGOOD PGOOD MPPC PWM VS1 VCC VS2 VS3 GND 2.2µF PGND 31291 TA02 3.3V Converter Provides Extremely Long Run Time in Low Drain Applications Using Lithium Thionyl Chloride Battery 22nF BST1 SW1 VIN 22nF 4.
PAGE 24
LTC3129-1 Typical Applications 15V Converter Powered from Flexible Solar Panel 22nF BST1 SW1 VMPPC = 6V 100 IOUT = 32mA IN FULL SUN SW2 BST2 VOUT VIN 1M 10µF LTC3129-1 VOUT 15V IOUT (mA) VIN IOUT vs Light Level (Daylight) 22nF 10µH RUN 47µF MPPC PowerFilm MPT6-150 SOLAR MODULE 10 PGOOD PWM VCC 11.4cm × 15cm VS1 VCC VS2 243k VS3 1 10000 2.
PAGE 25
LTC3129-1 Typical Applications 5V Converter Operates from Two to Eight AA or AAA Cells Using Bootstrap Diode to Increase Efficiency at High VIN and Extend Operation at Low VIN 22nF 22nF 8.2µH BST1 SW1 VIN 1.92V TO 15V VIN < 5V, IOUT = 100mA VIN > 5V, IOUT = 200mA SW2 BST2 22µF LTC3129-1 AFTER STARTUP VOUT 5V VOUT VIN RUN BAT54 VCC TWO TO EIGHT AA OR AAA BATTERIES PGOOD MPPC PWM VCC VS1 10µF VS2 VS3 2.2µF PGND GND 31291 TA06 3.
PAGE 26
LTC3129-1 Typical Applications Solar Powered Converter Extends Battery Life in Low Power 3V Primary Battery Applications 22nF UVLO = 3.7V VIN 4.7µF 22nF 3.3µH BST1 SW1 FDC6312P DUAL PMOS SW2 BST2 VOUT VIN LTC3129-1 4.99M D1 3.30V 22µF S1 2.43M G1 RUN PV PANEL SANYO AM-1815 OR PowerFilm SP4.2-37 + 470µF VCC 6.3V 10pF D2 G2 VOUT MPPC PWM 2.43M VOUT 3V TO 3.3V S2 2.2µF CR2032 3V COIN CELL PGOOD VS1 BAT54 VS2 VCC VS3 GND PGND 74LVC2G04 2.
PAGE 27
LTC3129-1 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
LTC3129-1 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MSE Package 16-Lead Plastic MSOP, Exposed Die Pad MSE Package (Reference LTC DWG # 05-08-1667 Rev F) 16-Lead Plastic MSOP, Exposed Die Pad (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 ±.
PAGE 29
LTC3129-1 Revision History REV DATE DESCRIPTION A 5/14 Clarified VCC Leakage to VIN if VCC > VIN: from –7µA to –27µA PAGE NUMBER 4 31291fa 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 itsinformation circuits as described herein will not infringe on existing patent rights. For more www.linear.
PAGE 30
LTC3129-1 Typical Application TEG Powered Converter Operates from a 10°C Temperature Differential and Provides 3.3V at 25mA for 50ms Every 15 Seconds for a Wireless Sensor COILCRAFT LPR6235-123QML 33nF 1:50 + 220µF • • C1A 1nF VSTORE C1B + 470µF 6.3V C2A MARLOW NL1025T TEG MOUNTED TO A HEAT SINK WITH LESS THAN 15°C/W THERMAL RESISTANCE 330k VOUT2 C2B LTC3109 SWA VOUT2_EN SWB VINA VINB VOUT VS2 PGOOD VS1 VLDO VAUX VAUX VAUX 1µF 22nF 22nF 4.7µH BST1 SW1 SW2 BST2 VOUT 3.