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Linear Technology Corp.
40V, 2A Buck-Boost Converter
Tony ArmstrongDirector of Product Marketing, Power Products
© 2011 Linear Technology
2
Why the Need for the LTC3115-1?1) Regulated Output with Input Above, Below or Equal to VOUT
Enables Continual Operation Even with Wide Input Fluctuations: Example: Automotive Application with Input Ranging from 3.3V in Cold-Crank to 36V Transient During Load-Dump Scenario, when Output Must Be a Continuous 5V
2) Operation from 2.7V to 40V is Ideal for Wide Range of Input Power Sources: From Single/dual/triple-Cell Li-Ion, to USB, FireWire, Wall Adapter or Automotive Inputs
3) When Well-Regulated Output is Required with a Discharging Energy Storage Device, i.e. Battery or SuperCapacitor
4) For 5V Output, LTC3115 can Deliver up to 2A when VIN>6V, and 1A when VIN>3.6
5) Up to 95% Efficiency Maximizes Battery Run-Time and Minimizes Thermal Constraints
6) Very Low IQ (< 50uA) Preserves Battery Life During Standby/Light Load Operation
7) Very Simple, Compact Footprint
© 2011 Linear Technology
3
• 2A Monolithic Synchronous Buck-Boost DC/DC Converter
• Regulated Output with Input Voltage Above, Below
or Equal to the Output Voltage
• Wide VIN Range: 2.7V to 40V
• Wide VOUT Range: 2.7V to 40V
• Low Noise Buck-Boost Architecture (<5mVPK-PK in PWM Mode)
LTC3115-1: What Is It?
© 2011 Linear Technology
4
LTC3115-1: Key Features
• Wide VIN Range: 2.7V to 40V
• Wide VOUT Range: 2.7V to 40V
• 1A Output Current for VIN ≥ 3.6V, VOUT = 5V
• 2A Output Current in Step-Down Operation for VIN ≥ 6V
• Programmable Frequency: 100kHz to 2MHz
• Supports Synchronization with an External Clock
• Up to 95% Efficiency
• 50μA Burst ModeR Quiescent Current
• Ultralow Noise Buck-Boost PWM
• Internal Soft-Start
• 3μA Supply Current in Shutdown
• Programmable Input Undervoltage Lockout
• Small 4mm × 5mm × 0.75mm DFN Package or Thermally Enhanced 20-Lead TSSOP Package
© 2011 Linear Technology
8
How the LTC3115-1 Fits with Our Other Synchronous Buck-Boost DC/DC Converters
Supplier Linear Tech Linear Tech Linear Tech
Part # LTC3115-1 LTC3112 LTC3789
TopologyMonolithic
Synch Buck/Boost
Monolithic Synch
Buck/Boost
Synch Buck/Boost Controller
VIN Range 2.7V to 40V 2.7V to 15V 4V to 38V
V OUT Range 2.7V to 40V 2.5V to 14V 0.8V to 38V
Efficiency (VIN=12V,
VOUT=5V@1A) 91% 91% 92%
Output Current (VIN>6V, VOUT=5V)
2A 2.5A5A- 4 N-Channel External FETs
Output Current (VIN=3.6V, VOUT=5V)
1A 1.5A 5A
Output Current (VIN=4V, VOUT=12V)
500mA 1A 5A
Frequency (MHz) 100kHz to 2MHz 750kHz 200kHz to 600kHz
Synchronizable Yes Yes Yes
Max Duty Cycle 100% 100% 100%
Quiescent Current (µA) 50μA 50μA 3mA
Output RipplePK-PK
(12VIN to 5VOUT @ 1A)5mVPK-PK 10mVPK-PK 5mVPK-PK
Output RipplePK-PK In BurstMode
50mVPK-PK 70mVPK-PK n/a
Auto BurstMode Yes Yes n/a
Output Current Monitor/Control
No Yes Control on I/O
BurstMode Defeat Yes Yes n/a
Inductor Value 10µH 4.7µH 4.7µHCOUT Type 22µF-Cer 47µF-Cer 330µF-Tant
Package 4 x 5 DFN-16 TSSOP-20E
4 x 5 DFN-16 TSSOP-20E
4x5 QFN-28, SSOP-28
Pricing (1K) $5.35 $4.00/$4.15 $4.65