LT8356-1

100V_IN/120V_OUT LED Controller with Exponential PWM and Scalable Dimming

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Overview

Features and Benefits
Product Details

Features and Benefits

128:1 Internal Exponential PWM Dimming
Two-Pin Multiplying Analog Dimming
Internal Spread Spectrum Frequency Modulation
20,000:1 External PWM Dimming at 100Hz
Rail-to-Rail LED Current Sensing: 0V to 120V
±2% LED Current Regulation
±2% Output Voltage Regulation
LED Short/Open Protection and Indication
Wide Input Voltage Range (5V to 100V)

PMOS Switch Driver for PWM and Output Disconnect
Constant-Voltage and Constant-Current Regulation
Adjustable Switching Frequency Up to 2MHz
Programmable V_IN UVLO with Hysteresis
Side Solderable 20-Lead 3mm × 4mm QFN Package
AEC-Q100 Qualified for Automotive Applications

Product Details

The LT8356-1 is a DC/DC controller designed to drive high current LEDs. The fixed frequency, current mode architecture results in stable operation over a wide range of supply and output voltages. A voltage feedback pin serves as the input for several LED protection features and makes it possible for the converter to operate as a constant-voltage source. The LT8356-1 can implement boost, boost-to-battery, buck-mode, SEPIC, and flyback LED drivers.

The LT8356-1 senses output current at the high or low side of the load. The product of CTRL and IADJ inputs provides analog programming of the output current. The PWM input and PWMTG high side PMOS driver provides precision time-based LED dimming capability. When driven by an external digital signal, the PWM input provides LED dimming ratios of up to 20,000:1 at 100Hz. When driven by a constant voltage, the PWM input selects from one of 128 internally generated, precision, exponentially spaced dimming ratios ranging from 0.78% up to 100%.

APPLICATIONS

High Voltage LED Applications
Automotive Head Lamps/Running Lamps
Accurate Current Limited Voltage Regulator

Product Categories

Power Management

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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)

EVAL-LT8356-1-AZ

LT8356-1 100V_IN/120V_OUT LED Controller with SSFM

EVAL-LT8356-1-AZ

View Detailed Evaluation Kit Information

Evaluation board EVAL-LT8356-1-AZ is a high voltage LED controller featuring the LT8356-1. It is assembled as a buck-boost mode LED driver but can be altered to a boost LED driver by adjusting the FB network and LED-connection. EVAL-LT8356-1-AZ drives a single string of LEDs up to 36V at 1A when the input is between 8V and 36V. It has an undervoltage lockout (UVLO) set at 6.5V falling and 7.5V rising. The evaluation board features PWM dimming, analog dimming, shutdown, open LED and short LED fault protection and reporting.

EVAL-LT8356-1-AZ runs at 250kHz switching frequency and features spread spectrum frequency modulation (SSFM) modulating its switching frequency from 250kHz to 310kHz to reduce EMI emissions. Small ceramic input and output capacitors are used to save space and cost. A high voltage 100V external power switch and 100V catch diode are used for up to 36W buck-boost mode output as assembled. The open LED overvoltage protection (OVP) uses the IC’s constant voltage regulation loop to limit the LED+ to LED– voltage to approximately 41V if the LED string is opened. The V_OUT, if referenced to GND, will jump to V_IN + 41V if the LED string is opened.

The input and output filters on EVAL-LT8356-1-AZ help further reduce its EMI. These filters consist of a small ferrite bead or inductor and high frequency ceramic capacitors. A small resistor on the gate pin of the power MOSFET is used to reduce high frequency EMI. These filters, combined with proper board layout and SSFM, are very effective in reducing EMI to comply with CISPR25 class 5 limits. Please follow the recommended layout and the four-layer PCB thickness of EVAL-LT8356-1-AZ. For best efficiency and PWM dimming performance, the EMI filters can be removed.

The LT8356-1’s integrated PWMTG high-side PMOS driver assists with PWM dimming of the connected LEDs. The LED string can be PWM-dimmed for accurate brightness control with an externally generated PWM signal for highest achievable dimming ratio. It can also utilize LT8356-1’s internally generated PWM feature for up to 128:1 exponential dimming. When running PWM dimming, the SSFM aligns itself with the PWM signal for flicker-free operation of the LED string. This applies to both internal and external PWM dimming. The LT8356-1 uses CTRL and IADJ pins for two-pin analog dimming.

The input undervoltage lockout (UVLO), LED current, output overvoltage protection (OVP), and switching frequency, can all be easy adjusted with simple resistor changes to EVAL-LT8356-1-AZ. Modifications can be made to convert the board from buck-boost mode LED driver to boost and buck mode LED Driver, and maintain low EMI, PWM dimming and fault diagnostic features. Buck mode and boost LED Driver schematics are provided in the data sheet. Please consult the data sheet or the applications team regarding how to customize EVAL-LT8356-1-AZ.

The LT8356-1 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 evaluation board EVAL-LT8356-1-AZ. The LT8356IUDCM-1 is assembled in a 20-lead side solderable plastic QFN package with a thermally enhanced exposed ground pad. Proper board layout is essential for maximum performance. See the data sheet section “Designing the Printed Circuit Board”.

Resources

Documentation & Resources

Data Sheets

LT8356-1: 100V_IN/120V_OUT LED Controller with Exponential PWM and Scalable Dimming Data Sheet (Rev. 0)
1/11/2022

PDF

1 M

User Guides

EVAL-LT8356-1-AZ - Demo Manual (Rev. A)
2/18/2022

PDF

1 M

Technical Articles

Automotive LED Driver Power Conversion Topology Guide
6/1/2022 Analog Dialogue
Can Nonsynchronous DC-to-DC Boost Converters (with a Catch Diode) Still Have Low Emissions?
3/2/2022

Tools & Simulations

LTspice

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.

LTspice downloads and documentation

LTspice Simulations

LT8356-1 Boost Topology LED Driver Example Circuit

LT8356-1 Buck-boost Mode LED Driver Example Circuit

Models for the following parts are available in LTspice:

LT8356-1

Design Resources

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.View our quality and reliability program and certifications for more information.

Part Number	Material Declaration	Reliability Data	Pin/Package Drawing	CAD Symbols, Footprints & 3D Models
LT8356IUDCM-1#WPBF	Material Declaration	Reliability Data	20-Lead Plastic Side Solderable QFN (3mm × 4mm)	Ultra Librarian SamacSys
LT8356IUDCM-1#WTRPBF	Material Declaration	Reliability Data	20-Lead Plastic Side Solderable QFN (3mm × 4mm)	Ultra Librarian SamacSys
Wafer Fabrication Data

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Support & Discussions

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Evaluation Boards

Pricing displayed is based on 1-piece.

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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.