LT8686S
Info : RECOMMENDED FOR NEW DESIGNS
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LT8686S

42V Quad, Gangable, Synchronous, Monolithic Step-Down Regulator

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Info : RECOMMENDED FOR NEW DESIGNS tooltip
Info : RECOMMENDED FOR NEW DESIGNS tooltip
Part Details
Part Models 4
1ku List Price Starting From $4.28
Features
  • Silent Switcher®2 Architecture
    • Ultralow EMI Emissions
    • Optional Spread Spectrum Modulation
  • Two High Voltage Synchronous Buck Regulators
    • 3V to 42V Input Voltage Range
    • Output Currents Up to 2A per Channel
    • Channels May Be Connected in Parallel Using a Single Inductor
  • Two Low Voltage Synchronous Buck Regulators
    • 3V to 8V Input Voltage Range
    • Output Currents up to 2A per Channel
    • Channels May Be Connected in Parallel Using a Single Inductor
  • 12μA IQ All Channels Active and No-Load
  • Flexible Supply Sequencing and Control
  • Adjustable and Synchronizable: 350kHz to 3MHz
  • Available in 32-Pin LQFN (5mm × 5mm)
  • AEC-Q100 Qualified for Automotive Applications
Additional Details
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The LT8686S is a highly flexible, four-channel, current mode, monolithic regulator able to power a wide range of automotive and industrial applications while occupying minimal board space.

The LT8686S combines two 42V capable 2A buck regulators with two 8V capable 2A buck regulators. The two 42V regulators may be combined to provide up to 4A of output current using a single inductor. Similarly, the two 8V regulators may be combined to provide up to 4A of output current using a single inductor. Individual channel enable, track/soft-start and power good pins provide flexible power supply sequencing and control. The LT8686S features a Silent Switcher 2 architecture, plus selectable spread spectrum mode, to provide ultralow EMI/EMC emissions while delivering high efficiency at high switching frequencies.

The LT8686S incorporates thermal shutdown and individual channel cycle-by-cycle current limit for short-circuit protection and robust operation.

APPLICATIONS

  • Automotive Systems
  • Industrial Controls and Power Supplies
Part Models 4
1ku List Price Starting From $4.28

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Documentation

Documentation

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Apr 21, 2023

- 23_0037

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Software & Part Ecosystem

Software & Part Ecosystem

Evaluation Kit

Evaluation Kits 1

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DC3126A

LT8686S | 42V Quad, Gangable, Synchronous, Monolithic Step-Down Regulator

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DC3126A

LT8686S | 42V Quad, Gangable, Synchronous, Monolithic Step-Down Regulator

LT8686S | 42V Quad, Gangable, Synchronous, Monolithic Step-Down Regulator

Product Detail

Demonstration circuit 3126A is a quad power supply featuring the LT8686S. The LT8686S is a 42V quad channel current mode monolithic synchronous step-down regulator. The LT8686S combines two 42V capable 2A buck regulators with two 8V capable 2A buck regulators. The demo board is designed for 5V, 3.3V, 1.8V, and 1.2V outputs from a nominal 12V input with switching frequency set at 2MHz. The 5V and 3.3V converters are powered from a wide range of 6V to 42V. The 1.8V and 1.2V converters are powered from the 5V output by default or from 3V to 8V supply alternatively. The current capability is 2A for all 4 outputs when running individually.

The DC3126A provides two 42V regulators that can be combined to deliver up to 4A of output current using a singular inductor. Similarly, the two 8V regulators can be combined to deliver up to 4A of output current using a singular inductor. The allowed channel combinations are given in the data sheet.

The independent track/soft-start and power good for each output simplify the complex design of quad-output power converters. Each output can be independently disabled into low quiescent current shutdown mode with its own TRK/SS pin.

A user-selectable SYNC/MODE pin on the demo board provides two primary modes of operation: pulse-skipping mode and low ripple Burst Mode® operation, plus the option of selecting frequency spread-spectrum for each to improve the EMI/EMC performance. Burst Mode delivers higher efficiency at light load than pulse-skipping mode. In pulse-skipping mode, full switching frequency is maintained to lower load currents than Burst Mode. The SYNC/MODE pin can also be used to synchronize the switching frequency to an external clock. The switching frequency for all regulators can be programmed either via an oscillator resistor or an external clock over a 350kHz to 3MHz range. At all frequencies, a 180° phase shift is maintained between channel 1 and channel 2, channel 3 and channel 4, reducing the input peak current and voltage ripple.

The demo board has an EMI filter installed on the bottom layer. The conducted and radiated EMI performance of the board is shown on Figure 4 in the user guide. The red line in Figure 4 is CISPR25 Class 5 peak limit. The figure shows that the circuit passes the test with a wide margin. To achieve EMI/EMC performance as shown in Figure 4, the input EMI filter is required, and the input voltage should be applied at VEMI turret.

The LT8686S data sheet gives a complete description of the part operation and application information. The data sheet must be read in conjunction with the quick start guide for DC3126A. The LT8686S is assembled in a 5mm × 5mm LQFN package with exposed pads for low thermal resistance. Proper board layout is essential for both low EMI operation and best thermal performance.

Tools & Simulations

Tools & Simulations 1

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.

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