42V, 3A Synchronous Step-Down Regulator with 2.5µA Quiescent Current
Features and Benefits
- Wide Input Voltage Range: 3.0V to 42V
- Ultralow Quiescent Current Burst Mode® Operation:
- <2.5μA IQ Regulating 12VIN to 3.3VOUT
- Output Ripple <10mVP-P
- High Efficiency 2MHz Synchronous Operation:
- >92% Efficiency at 0.5A, 5VOUT from 12VIN
- 1.5A Continuous Output Current
The LT8608 is a compact, high efficiency, high speed synchronous monolithic step-down switching regulator that consumes only 1.7µA of quiescent current. The LT8608 can deliver 1.5A of continuous current. Low ripple Burst Mode operation enables high efficiency down to very low output currents while keeping the output ripple below 10mV. Internal compensation with peak current mode topology allows the use of small inductors and results in fast transient response and good loop stability. The EN/ UV pin has an accurate 1V threshold and can be used to program VIN undervoltage lockout or to shut down the LT8608. The PG flag signals when VOUT is within ±8.5% of the programmed output voltage as well as fault conditions.
The MSOP package includes a SYNC pin to synchronize to an external clock, or to select Burst Mode operation or pulse-skipping with or without spread-spectrum; the TR/SS pin programs soft-start or tracking. The DFN package omits these pins and can be purchased in pulse-skipping or Burst Mode operation varieties.
- General Purpose Step Down
- Low EMI Step Down
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (2)
Demonstration circuit 2458A is a 42V, 1.5A micropower synchronous step-down regulator featuring the LT8608. The demo board is designed for 5V output from a 5.5V to 42V input. The wide input range allows a variety of input sources, such as automotive batteries and industrial supplies. The LT8608 is a compact, high efficiency, high speed synchronous monolithic step-down switching regulator that consumes only 2.5μA of quiescent current when output is regulated at 5V. Top and bottom power switches, compensation components and other necessary circuits are inside of the LT8608 to minimize external components and simplify design.
Demonstration circuit 2521A is a 42V, 1.5A micropower synchronous step-down regulator featuring the LT8608/ LT8608B. There are two assembly versions. DC2521A-A is for the LT8608 and DC2521A-B is for the LT8608B.
The LT8608/LT8608B is a compact, high efficiency, high speed synchronous monolithic step-down switching regulator. Top and bottom power switches, compensation components and other necessary circuits are inside of the 2mm × 2mm DFN package to minimize external components and simplify design. The difference LT8608 and LT8608B is the LT8608 works under low ripple Burst Mode® operation at light load condition, while the LT8608B has pulse-skipping mode for light load. Due to the Burst Mode operation, LT8608 consumes only 1.7μA of quiescent current when output is regulated at 5V. LT8608B has higher quiescent current because of its pulse-skipping mode operation.
The demo board is designed for 5V output from a 5.5V to 42V input. The wide input range allows a variety of input sources, such as automotive batteries and industrial supplies.
The demo board has an EMI filter installed. To use the EMI filter, the input should be tied to VEMI, not VIN. An inductor L2, which is a 0Ω jumper on the board by default now, can be added in the EMI filter to further reduce the conducted emission.
The LT8608 data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with this demo manual for DC2521A.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
To launch ready-to-run LTspice demonstration circuits for this part:
Step 1: Download and install LTspice on your computer.
Step 2: Click on the link in the section below to download a demonstration circuit.
Step 3: If LTspice does not automatically open after clicking the link below, you can instead run the simulation by right clicking on the link and selecting “Save Target As.” After saving the file to your computer, start LTspice and open the demonstration circuit by selecting ‘Open’ from the ‘File’ menu.
Models for the following parts are available in LTspice:
LTpowerCAD® is a power supply design program which selects power stage components, provides detailed power efficiency, shows quick loop Bode plot stability and load transient analysis, and can export to LTspice for simulation.
To open the project file for this circuit:
Step 1: Download and install LTpowerCAD on your computer.
Step 2: Click on the link(s) in the section below to download part-specific project files.
Step 3: If the project file doesn't run, right-click the link and select "Save Target As." Then start the LTpowerCAD tool and open the project file by selecing "Open Project" from the "File" menu.
LTpowerCAD Project Files
Design tools for the following parts are available in LTpowerCAD:
LT8608 Companion Parts
Recommended Related Parts
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Sample & Buy
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.