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Linear Technology LTC3118 Datasheet

18v, 2a buck-boost dc/dc converter with low loss dual input powerpath
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FeaTures
Integrated High Efficiency Dual Input PowerPath™
n
Plus Buck-Boost DC/DC Converter
Ideal Diode or Priority V
n
V
and V
Range: 2.2V to 18V
n
IN1
IN2
V
Range: 2V to 18V
n
OUT
Either V
Can Be Above, Below or Equal to V
n
IN
Generates 5V at 2A for V
n
1.2MHz Low Noise Fixed Frequency Operation
n
Current Mode Control
n
All Internal N-Channel MOSFETs
n
Pin-Selectable PWM or Burst Mode
n
Accurate, Independent RUN Pin Thresholds
n
Up to 94% Efficiency
n
V
and V
Power Good Indicators
n
IN
OUT
I
of 50µA in Sleep, 2µA in Shutdown
n
Q
4mm × 5mm 24-Lead QFN or 28-Lead TSSOP Packages
n
applicaTions
Systems with Multiple Input Sources
n
Back Up Power Systems
n
Wall Adapter or Li-Ion(s) Input to 5V
n
Battery or Super Capacitor Input for Reserve Power
n
Replace Diode-OR Designs with Higher Efficiency,
n
Flexibility and Performance
Typical applicaTion
0.1µF
V
IN1
V
BST1
IN1
47nF
22µF
CM1
CP1
10nF
CN1
CN2
10nF
CP2
V
V
IN2
IN2
22µF
CM2
47nF
Select Modes
IN
OUT
> 6V
IN
Operation
®
OUT
3.3µH
0.1µF
SW1
SW2
BST2
V
OUT
FB
40.2k
LTC3118
VC
V1GD
V2GD
PGD
MODE
SEL
RUN1
PGND V
GND
RUN2
CC
4.7µF
3118 TA01a
For more information
18V, 2A Buck-Boost DC/DC
Converter with Low Loss
Dual Input PowerPath
DescripTion
The
LTC
3118
®
chronous buck-boost DC/DC converter with an intelligent,
integrated, low loss PowerPath control. The unique power
switch architecture provides efficient operation from either
input source to a programmable output voltage above,
below or equal to the input. Voltage capability of up to 18V
provides flexibility and voltage margin for a wide variety
of applications and power sources.
The LTC3118 uses a low noise, current mode architecture
with a fixed 1.2MHz PWM mode frequency that minimizes
the solution footprint. For high efficiency at light loads,
automatic Burst Mode operation can be selected consum-
ing only 50µA of quiescent current in sleep.
System level features include ideal diode or V
modes, V
and V
IN
comparators to program independent UVLO thresholds,
and output disconnect in shutdown. Other features include
2µA shutdown current, short-circuit protection, soft-start,
current limit and thermal overload protection.
The LTC3118 is offered in thermally enhanced 24-lead
4mm × 5mm QFN and 28-lead TSSOP packages.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners. Protected by U.S. Patents, including 7709976.
V
OUT
5V
400k
100µF
AC-COUPLED
22pF
100k
1.8nF
INDICATORS
CONTROL
SIGNALS
www.linear.com/LTC3118
LTC3118
is a dual-input, wide voltage range syn-
power good indicators, accurate RUN
OUT
Input Switchover Response
V
= 5V, V
= 12V, V
IN1
IN2
OUT
5V
OUT
500mV/DIV
SW1
10V/DIV
SEL
SELECT V
SELECT V
5V/DIV
IN2
100µs/DIV
priority
IN
= 5V AT 1A
IN1
3118 TA01b
3118fa
1

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Summary of Contents for Linear Technology LTC3118

  • Page 1 Battery or Super Capacitor Input for Reserve Power Replace Diode-OR Designs with Higher Efficiency, L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks and PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks Flexibility and Performance are the property of their respective owners.

  • Page 2: Absolute Maximum Ratings

    LTC3118 absoluTe MaxiMuM raTings (Note 1) Voltage ........–0.3V to 20V CP1 Voltage ......(V – 0.3V) to (V + 6V) Voltage ..........–0.3V to 20V CP2 Voltage ......(V – 0.3V) to (V + 6V) SW1 DC Voltage (Note 4) ....–0.3V to (V + 0.3V)

  • Page 3: Electrical Characteristics

    LTC3118 elecTrical characTerisTics denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at T ≈ T = 25°C (Note 2). Unless otherwise noted, V or V = 5V, V = 5V. PARAMETER CONDITIONS UNITS...
  • Page 4 ) where θ reliability and lifetime. is the thermal impedance of the package. Note 2: The LTC3118 is tested under pulsed load conditions such that T ≈ Note 3: This IC includes overtemperature protection that is intended . The LTC3112E is guaranteed to meet specifications from 0°C to 85°C to protect the device during momentary overload conditions.
  • Page 5 LTC3118 Typical perForMance characTerisTics = 25°C, unless otherwise noted. Efficiency vs V or V = 12V, Efficiency and Power = 12V, Efficiency and Power Voltage with 500mA and 1A Load Loss vs Load Current from V Loss vs Load Current from V...
  • Page 6 Die Temperature Rise vs Load Die Temperature Rise vs Load Current, V = 5V, 4-Layer Current, V = 12V, 4-Layer Current, V = 3.3V, 4-Layer LTC3118 Demo Board LTC3118 Demo Board LTC3118 Demo Board = 5V = 3.6V = 2.7V = 12V = 5V...
  • Page 7 LTC3118 Typical perForMance characTerisTics FB Program Voltage vs Supply Current (V > 5V) vs Temperature vs Active V Showing Current Limit 1.025 1.020 1.015 1.010 1.005 1.000 0.995 0.990 0.985 0.980 0.975 –50 TEMPERATURE (°C) ACTIVE V VOLTAGE (V) SUPPLY CURRENT (mA)
  • Page 8 LTC3118 Typical perForMance characTerisTics to 5V Switchover Switch and V Waveforms Waveforms, V = 12V 500mA SW1, SW2 Minimum Low Time (12V , 12V Load vs V RIPPLE AC-COUPLED 100mV/DIV 500mV/DIV 1A/DIV 1A/DIV 5V/DIV 5V/DIV 10V/DIV 5V/DIV 3118 G30 3118 G29 500µs/DIV...
  • Page 9 LTC3118 Typical perForMance characTerisTics Short-Circuit Waveforms Short-Circuit Waveforms Soft-Start Waveforms with 500mA Response and Recovery Response and Recovery Load (12V , 12V (12V , 12V (12V , 12V , 500mA Load) = 24 10V/DIV 5V/DIV 5V/DIV 1A/DIV 1A/DIV 2A/DIV SHORT...
  • Page 10 LTC3118 pin FuncTions (QFN/TSSOP) SEL (Pin 1/Pin 4): Input Select Pin. MODE (Pin 6/Pin 9): PWM or Auto Burst Mode Select Pin. SEL = Logic Low (ground): V priority mode, the con- MODE = Logic Low (ground): Enables automatic Burst...
  • Page 11 LTC3118 pin FuncTions (QFN/TSSOP) BST1 (Pin 16/Pin 22): Bootstrapped floating supply for CN2 (Pin 20/Pin 27): Negative pin for the V high side N-channel MOSFET gate drive for V or V N-channel MOSFET charge-pump capacitor. This pin is Connect to SW1 through a 0.1µF capacitor, as close to...

  • Page 12: Block Diagram

    LTC3118 block DiagraM 2.2V TO 18V 2V TO 18V 2.2V TO 18V BST1 BST2 SENSE AVERAGE CURRENT AMPLIFIER A FETs AND DRIVERS SOFT-START 1.2MHz RAMPS/ RAMP OSCILLATOR COMPARATOR DDRV 3.8V REGULATOR CP1 CP2 1.22V REFERENCE UP TO 18V BDRV CDRV –...
  • Page 13 2.2V to 18V. The output voltage when Burst Mode operation is selected. can be programmed between 2V to 18V and deliver more than 2A of load current. The LTC3118 operates from either For 5V V applications, the input quiescent currents in or V depending on the state of the SEL pin.
  • Page 14 PWM mode operation, Input Select Logic and V Power Good Indicators the LTC3118 operates at a fixed 1.2MHz frequency us- A simplified schematic diagram of the LTC3118’s input ing a current mode control loop. PWM mode minimizes select circuitry is shown in Figure 2.
  • Page 15 V is asserted, keeping V powered. IN2(GOOD) Power Good Indicator If SEL is a logic high, the LTC3118 operates in ideal diode The V power good indicator is an open-drain output mode, where V is powered from the highest input pin similar to the V1GD and V2GD pins shown in Figure 2.
  • Page 16 ) through an internal COMP frequency compensation network comprised of R The LTC3118 utilizes average current mode control for the . The average current amplifier’s output provides the pulse width modulator, as shown in Figure 3. Current mode cycle-by-cycle duty cycle command into the buck-boost control, both average and the better known peak method, PWM circuitry.
  • Page 17 I will revert very closely to its previ- COMP As part of the current control loop, the LTC3118 has cur- ous level into the PWM, and force the correct duty cycle rent sense circuitry that measures the inductor current to maintain voltage regulation at this new higher inductor of the buck-boost converter, as shown in Figure 3.
  • Page 18 If the load is very light, the LTC3118 maximum current capability of the current loop will be may only need to switch for a few cycles to restore V reduced by 40% to reduce power dissipation.
  • Page 19 Depending on the particular application, any of these rail powers the internal control circuitry and power UVLO thresholds could be the limiting factor affecting device gate drivers of the LTC3118, including the BST pin the minimum input voltage required for operation. The capacitors. The V...
  • Page 20 V and V supplies LTC3118 in a low current shutdown state. When the volt- through a high value resistor greater than 200k to prevent age on either pin is brought above a 0.65V logic threshold, a potential latch condition at the pin.
  • Page 21 Figure 7. comparators to disable switching from a particular input Ideal Diode Mode (SEL=1) is 1.05V. Ideal Diode mode operation is available on the LTC3118 for   systems with low ESR sources or where the programmed = 1.05V 1+ ...
  • Page 22 IC in order to provide a means to remove temperature cools by approximately 10°C, at which time heat from the IC and ensure that the LTC3118 is able a soft-start is initiated to provide a smooth recovery.
  • Page 23 LTC3118 applicaTions inForMaTion Top Layer 2nd Layer 3rd Layer Bottom Layer (Top View) Figure 5. Typical 4-Layer PC Board Layout 3118fa For more information www.linear.com/LTC3118...
  • Page 24 A tight of inductor current as the LTC3118 operates in PWM mode board layout near the V /CM1 and V /CM2 pins to from an active 12V input and 12V output.
  • Page 25 LTC3118 applicaTions inForMaTion A standard application circuit for the LTC3118 is shown on PWM operation, which is supplied by V . A significant the front page of this data sheet. The appropriate selection performance advantage can be attained in applications...
  • Page 26 100mΩ. The minimum low time in µs. The switch pin minimum low only exceptions are applications that have a maximum time is typically 0.1µs. output current much less than what the LTC3118 is ca- ∆I L(P-P)BUCK pable of delivering.
  • Page 27 Examining the previous equations reveals that the output voltage ripple increases with load current and is gener- In most LTC3118 applications, an output capacitor between ally higher in boost mode than in buck mode. Note that 47µF and 100µF will work well.
  • Page 28 The capacitors used to filter the input and output of the not a concern. Some capacitors exhibit a high DC leak- LTC3118 must have low ESR and must be rated to handle age current which may preclude their consideration for...
  • Page 29 LTC3118 to simplify the loop design and provide 50% of its rated capacitance when operated near its the highest possible bandwidth over a wide operating range.
  • Page 30 This can ultimately limit (application dependent) the maximum converter bandwidth that can be achieved with the LTC3118. The RHPZ is not present when operat- The voltage amplifier’s frequency response is designed ing in buck mode.
  • Page 31 RHPZ frequency may be necessary. In this example of the LTC3118, the results from the following compensa- design, we’ll plan to achieve a loop bandwidth (f ) of tion design should always be verified with time domain 20kHz, well below the RHPZ frequency.
  • Page 32 LTC3118 applicaTions inForMaTion / VC BUCK MODE BOOST MODE –6 –60 –12 –18 –120 –24 GAIN –30 –180 PHASE –36 10Hz 100Hz 1kHz 10kHz 100kHz 1MHz FREQUENCY –VC/ V OUTA –20 –40 –60 –6 –80 –12 –18 –24 –100 GAIN –30...
  • Page 33 LTC3118 applicaTions inForMaTion this pole is close to DC, R = Voltage Error Amp output As shown, a 40kΩ value for R will provide –4db of gain resistance, which is approximately 5MΩ. This pole is at crossover. With R selected, C ’s value is determined...

  • Page 34: Typical Applications

    LTC3118 Typical applicaTions System Power (Priority) or 3-Cell Li-Ion to 5V V Regulator with Automatic Burst Mode Operation 3.3µH 0.1µF 0.1µF 4V TO 5.5V 5V UP TO 1.5A, BST1 BST2 > 4.5V 232k 402k 100µF SYSTEM RUN1 POWER 22µF PGND...
  • Page 35 LTC3118 Typical applicaTions 12V Wall Adapter (When Present) or 2-Cell Li-Ion to 12V V Regulator with Automatic Burst Mode Operation 6.8µH 0.1µF 0.1µF 6V TO 8.2V 12V AT 800mA BST1 BST2 402k 1100k 100µF Li-Ion RUN1 22µF PGND 100k 100k...
  • Page 36 LTC3118 Typical applicaTions Dual Battery System to 3.3V V , Runs from Lead Acid (Priority) When Present Automatic Burst Mode Operation 3.3µH 0.1µF 0.1µF 10.5V TO 14.5V BST1 BST2 3.3V UP TO 2.5A, V > 4.5V 232k 100µF 768k LEAD ACID 22µF...
  • Page 37 LTC3118 package DescripTion Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. UFD Package 24-Lead Plastic QFN (4mm × 5mm) (Reference LTC DWG # 05-08-1696 Rev A) 0.70 ±0.05 4.50 ±0.05 3.10 ±0.05 2.65 ±0.05 2.00 REF 3.65 ±0.05 PACKAGE OUTLINE 0.25 ±0.05...
  • Page 38 LTC3118 package DescripTion Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. FE Package 28-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663 Rev K) Exposed Pad Variation EB 9.60 – 9.80* 4.75 (.378 – .386) (.187) 4.75 (.187)

  • Page 39: Revision History

    34, 35 3118fa 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- For more information www.linear.com/LTC3118 tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
  • Page 40 < 1µA, QFN and SSOP Packages 3118fa Linear Technology Corporation LT 0915 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 For more information www.linear.com/LTC3118 (408) 432-1900 FAX: (408) 434-0507 www.linear.com/LTC3118  LINEAR TECHNOLOGY CORPORATION 2015 ● ●...