Features and Benefits
- 2% LED Current Regulation
- 2.5% Output Voltage Regulation
- 50,000:1 PWM Dimming at 100Hz
- 512:1 Internal PWM Dimming
- Spread Spectrum Frequency Modulation
- Silent Switcher Architecture for Ultralow EMI
- Operates in Boost, Buck Mode and Buck-Boost Mode
- 4V to 56V Input Voltage Range
- Up to 52V LED String Voltage
- Adaptive Peak Switch Current Limit Up to 5A for Low VIN
- 200kHz to 2MHz with SYNC Function
- Analog or Duty Cycle LED Current Control
- Open/Short LED Protection and Fault Indication
- Small 28-Lead 4mm × 5mm LQFN Package
- AEC-Q100 Qualified for Automotive Applications
The LT8386 is a monolithic, synchronous, step-up DC-to-DC converter that utilizes fixed frequency, peak current control and provides PWM dimming for a string of LEDs. The LED current is programmed by an analog voltage or digital pulses at the CTRL pin. The LT8386 will maintain 2% current regulation through an external sense resistor over a wide range of output voltages.
The LT8386 features Silent Switcher® technology designed to minimize EMI/EMC emissions with high efficiency. The switching frequency is programmable from 200kHz to 2MHz by an external resistor at the RT pin or by an external clock applied at the SYNC/SPRD pin. With the optional spread spectrum frequency modulation enabled, the frequency varies from 100% to 125% to reduce EMI.
The LT8386 includes a driver for an external high side PMOS for PWM dimming. The 60V rated LT8386 is pin-to-pin compatible with the LT3922 and LT3922-1.
- Automotive and Industrial Lighting
- Heads Up Display (HUD)/Machine Vision
Product Lifecycle Recommended for New Designs
This product has been released to the market. The data sheet contains all final specifications and operating conditions. For new designs, ADI recommends utilization of these products.
Evaluation Kits (1)
Demonstration circuit DC3008A is a 60V 3A Silent Switcher synchronous step-up LED driver featuring the LT8386. It drives a single string of LEDs at 500mA up to 45V when VIN is between 4V and 40V. It runs down to VIN with reduced ILED and can withstand VIN as high as 50V, but has overvoltage lockout (OVLO) set for 45V for this application. DC3008A runs at 340kHz switching frequency. Spread spectrum frequency modulation (SSFM) can be turned on with a simple jumper, reducing EMI. DC3008A comes with low EMI features including optimized layout, SSFM and input EMI filter.
It is protected against both open and short LED conditions and reports the faults. The LT8386 boost converter has an input voltage range from 4V to 56V. Its internal synchronous 3.3A 60V switches allow up to 52V of LEDs (with adjusted FB resistors) on the output with room for over voltage protection and overshoot during an open LED event. It has adjustable switching frequency between 200kHz and 2MHz. It can be synchronized to an external source or programmed with SSFM for low EMI. The PWMTG high-side PWM MOSFET driver assists with short-circuit protection and versatility. LT8386 can be configured as a boost, boost-buck, or buck mode LED driver and maintain all of its low EMI, PWM dimming, and fault diagnostic features.
The LT8386 can be PWM dimmed with an external PWM signal or an internally-generated PWM signal. DC3008A has a jumper that can be set to switch between internally-generated PWM signal, externally-generated PWM signal, and no PWM signal (100% ON). It can be analog dimmed with a control voltage on its control pin (CTRL).
When run with both PWM dimming and SSFM, the SSFM aligns itself with the PWM signal for flicker-free operation.
Small ceramic input and output capacitors are used to save space and cost. The board is designed with small, high frequency capacitors on both sides of the VOUT pins for a reduction in emissions. The open LED overvoltage protection uses the IC’s constant voltage regulation loop to regulate the output to approximately 57V if the LED string is opened. The output current can be monitored through the ISMON test point.
Undervoltage and overvoltage lockout can be adjusted on the circuit with a few simple resistor choices. There is an EMI filter on the input of DC3008A. Please follow the recommend layout and four-layer thickness of DC3008A for low EMI applications.
The LT8386 data sheet gives a complete description of the part, operation and applications information. The data sheet must be read in conjunction with the demo manual for demonstration circuit DC3008A. The LT8386JV is assembled in a 28-lead plastic 4mm × 5mm LQFN package with a thermally-enhanced GND pad. Proper board layout is essential for maximum thermal performance. See the data sheet section Layout Considerations.
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:
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
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.