Tag Archives: Buck-Boost

150VIN & VOUT Synchronous 4-Switch Buck-Boost Controller with Integrated Switching Bias Supply

Analog Devices announces the Power by Linear™ LTC3777, a 150V high efficiency (up to 99%) 4-switch synchronous buck-boost DC/DC controller, which operates from input voltages above, below or equal to the regulated output voltage. Its 4.5V to 150V input voltage range operates from a high input voltage source or from an input that has high voltage surges, eliminating the need for external surge suppression devices, ideal for transportation, industrial and medical applications.

To prevent high on-chip power dissipation in high input voltage applications, the LTC3777 integrates a low quiescent current high efficiency switching bias supply for its internal power consumption. The output voltage of the LTC3777 can be set from 1.2V to 150V at output currents up to tens of amps, depending on the choice of external components. Output power up to 500W can be delivered with a single device. Higher powers can be achieved when multiple circuits are configured in parallel. The LTC3777’s powerful 1.5Ω N-channel MOSFET gate drivers can be adjusted from 6V to 10V, enabling the use of logic-level or standard-threshold MOSFETs.

The LTC3777 employs a proprietary current mode control architecture for constant frequency in buck, boost or buck-boost modes. The operating frequency can be synchronized to an external clock from 50kHz to 600kHz, while an input/output constant current loop provides support for battery charging and overload protection. The user can select either forced continuous mode or discontinuous mode to maximize light load efficiency. Additional features include seamless transfers between operating regions, a power good output voltage monitor, adjustable soft-start and input overvoltage lockout, and output voltage disconnect during shutdown.

The LTC3777 is available in a 48-lead e-LQFP package with pin skipping for high voltage spacing. Extended and industrial versions are available from –40 to 125°C.

Summary of Features: LTC3777

  • 4-Switch Synchronous Current Mode Buck-Boost Architecture
  • Operation with Input Voltages Above, Below or Equal to the Output Voltage
  • 4.5V to 150V Input Voltage Range
  • 1.2V to 150V Output Voltage Range
  • Up to 99% Efficiency
  • Integrated Switching Bias Supply
  • Input or Output Average Current Limit
  • Adjustable 6V to 10V MOSFET Gate Drivers
  • Compatible with Logic-Level or Standard-Threshold NMOS
  • 500 Watts Output Power Capable with a Single Device
  • Fixed Synchronizable Operating Frequency from 50kHz to 600kHz
  • Output Voltage Disconnect from VIN During Shutdown
  • Adjustable Soft-Start
  • ±1% Reference Voltage Accuracy over -40°C to 125°C
  • 48-Lead e-LQFP Package with High Voltage Pin Skipping


2.7V to 38V/500 mA low noise buck-boost charge pump

Graham Prophet @ eedesignnewseurope.com discuss about Linear’s low noise buck-boost converter LTC3246, able to produce 3.3V, 5V or ADJ regulated with an input range of 2.7V to 38V :

LTC3246 is a low noise buck-boost charge pump with integrated watchdog timer capable of up to 500 mA of output current. It uses multimode switched capacitor conversion to maintain regulation over a 2.7V to 38V input voltage range and produces a regulated 3.3V, 5V, or externally adjustable (2.5V to 5V) output.

2.7V to 38V/500 mA low noise buck-boost charge pump – [Link]

2.7V-4.2V input to 3.3V output Buck-Boost Converter

This project shows a DC-DC buck boost circuit which can produce an output of 3.3V for an input of 2.7V to 4.2V , for example from a Li-on battery. The Circuit uses LTC3440 Buck boost IC which is a fixed frequency boost converter. To get high efficient results, inductor with high frequency core material should be used.


  • Input(V): 2.7V DC to 4.2V DC
  • Output(V): 3.3V DC
  • Output load: 600mA
  • PCB:23mmX15mm

2.7V-4.2V input to 3.3V output Buck-Boost Converter – [Link]

Benefits of Using A Buck-Boost Converter As A Pre-regulator For LDOs

Intersil published a new white paper titled “Preventing Subsystem Brownouts in Mobile Devices“. This white paper demonstrates the benefit of using a buck-boost converter as a pre-regulator, which leads to better overall system efficiency and enhanced battery life.


Systems powered from a battery may have voltage brownout when they are subjected to a burst current discharge, that is because of internal resistance of the battery. The internal resistance in Li-Ion battery varies according to its charging level. It can reach 200 Milli-ohm at the end of the discharge. Thus, a 4A burst current can cause an 800mV droop at the terminal, pushing the nominal 3.4V voltage to 2.6V, which is considered as a brownout voltage if the target LDO output is 2.85V. In this case boost converters prevent the momentary brownout.

Overall system efficiency is another useful aspect of using a buck-boost converter as a pre-regulator. The battery voltage is first converted to a voltage slightly higher than the highest LDO output voltage of the target LDOs, which is typically 3.3V. The buck-boost output is then set to 3.4V. So, the LDOs see a 3.4V input voltage, regardless of the battery voltage.

We can see, by numbers, the improvement of efficiency by comparing the two setups, with and without using the buck-boost converter.



The figure below shows the comparison of battery discharge with and without a pre-regulator, while running the same applications with the same battery. You can see 12% enhancement to battery life.


[White Paper]

ISL91128 – A New Buck-Boost Regulator With I2C Interface From Intersil

If your application requires a changing supply voltage, then this new IC is ideal for you. Intersil announced the ISL91128, a new buck-boost regulator. The new regulator has an I2C interface to select a broad set of features including output voltage range and slew rate. This eliminates the need of feedback resistors and allows the reuse of the same design for multiple output voltage needs.

The input voltage range is from 1.8V to 5.5V, and the output voltage range is from 1.9V to 5.5V with output current up to 2.2A. ISL91128 has 2.5MHz switching frequency. It is fully protected for short-circuit, over-temperature and undervoltage, according to the datasheet.

isl91128_applicationISL91128 is available in a small 2.15mm x 1.74mm WLCSP package.

intersil_bbIntersil provides ISL91128IIN-EVZ, an evaluation board for ISL91128. ISL91128 is part of ISL911xx family of buck-boost/boost regulators.

Key Differences in Family
Key Differences in Family

[Product Page]


Via: ElectronicsWeekly

Basic Switching Voltage Regulator Tutorial


James Lewis @ baldengineer.com discuss about switching regulator types and uses.

A switching voltage regulator is one of my favorite circuits. In school, they were the first circuits I built where I understood how transistors worked. In fact, they were the first circuit I saw an inductor being useful! Switching regulators are incredibly efficient when designed properly. Of course, this detail about design is important.

Basic Switching Voltage Regulator Tutorial – [Link]

LT8391 – 60V Synchronous 4-Switch Buck-Boost LED Controller


The LT8391 is a synchronous 4-switch buck-boost LED controller that regulates LED current from input voltage above, below, or equal to the output voltage. The proprietary peak-buck peak-boost current mode control scheme allows adjustable and synchronizable 150kHz to 650kHz fixed frequency operation, or internal ±15% triangle spread spectrum operation for low EMI. With 4V to 60V input, 0V to 60V output, and seamless low noise transitions between operation regions, the LT8391 is ideal for LED driver and battery charger applications in automotive, industrial, and battery-powered systems.

LT8391 – 60V Synchronous 4-Switch Buck-Boost LED Controller – [Link]


LTC3335 – Nanopower Buck-Boost DC/DC with Integrated Coulomb Counter


The LTC®3335 is a high efficiency, low quiescent current (680nA) buck-boost DC/DC converter with an integrated precision coulomb counter which monitors accumulated battery discharge in long life battery powered applications. The buck-boost can operate down to 1.8V on its input and provides eight pin-selectable output voltages with up to 50mA of output current.

The coulomb counter stores the accumulated battery discharge in an internal register accessible via an I2C interface. The LTC3335 features a programmable discharge alarm threshold. When the threshold is reached, an interrupt is generated at the IRQ pin.

To accommodate a wide range of battery types and sizes, the peak input current can be selected from as low as 5mA to as high as 250mA and the full-scale coulomb counter has a programmable range of 32,768:1.

LTC3335 – Nanopower Buck-Boost DC/DC with Integrated Coulomb Counter – [Link]