New Content (1)
Features and Benefits
- ±1.5% LED Current Regulation
- ±2% Output Voltage Regulation
- 5000:1 PWM Dimming at 100Hz
- 128:1 Internal PWM Dimming
- Spread-Spectrum Frequency Modulation
- Silent Switcher® Architecture for Low EMI
- 3.6V to 60V Input Voltage Range
- 0V to 60V LED String Voltage
- 3A, 60V Internal Switches
- 200kHz to 2MHz with SYNC Function
- 99.9% Maximum Duty Cycle
- 20:1 Analog or Duty Cycle LED Current Control
- Open/Short LED Protection and Fault Indication
- Accurate LED Current Sense with Monitor Output
- Programmable UVLO
- Thermally Enhanced 28-Lead (4mm × 5mm) LQFN
The LT8376 is a monolithic, synchronous, step-down DC/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 the duty cycle of pulses at the CTRL pin. An output voltage limit can be set with a resistor divider to the FB pin.
The switching frequency is programmable from 200kHz to 2MHz by an external resistor at the RT pin or by an external clock at the SYNC/SPRD pin. With the optional spread spectrum frequency modulation enabled, the frequency varies from 100% to 125% to reduce EMI. The LT8376 also includes a driver for an external, high side PMOS for PWM dimming and an internal PWM signal generator for analog control of PWM dimming when an external signal is not available.
Additional features include an LED current monitor, an accurate EN/UVLO pin threshold, open-drain fault reporting for open-circuit and short-circuit load conditions, and thermal shutdown. The LT8376 utilizes the proprietary Silent Switcher technology for very low EMI.
- Automotive Lighting
- Industrial and General Purpose Lighting
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)
Evaluation board EVAL-LT8376-AZ is a 60V, 2A synchronous Buck LED driver featuring the LT8376. EVAL-LT8376-AZ drives a single string of LEDs up to 36V at 1.5A when VIN is between 43V and 57V. EVAL-LT8376-AZ has an undervoltage lockout (UVLO) set at 40V with 2V hysteresis for turn-on. EVAL-LT8376-AZ runs at 350kHz switching frequency and features optional spread spectrum modulation (SSFM). With SSFM enabled, LT8376 modulates its switching frequency from fSW to fSW + 25% to reduce EMI emissions.
The LT8376 has an input voltage range of 3.6V to 60V. LT8376 has internal, synchronous 60V switches for high efficiency and small size. LT8376 has an adjustable switching frequency between 200kHz and 2MHz. The LT8376 can be synchronized with an external clock source or configured with SSFM enabled for low EMI. EVAL-LT8376-AZ includes a SYNC/SSFM jumper to configure the LT8376 for either external frequency synchronization, SSFM enabled for low EMI, or set to normal operation with SSFM disabled.
The LT8376’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 or an internally-generated PWM signal. EVAL-LT8376-AZ has jumpers that can be set to switch between internally-generated PWM signal, externally generated PWM signal, and 100% on with no PWM signal. The LT8376 can also be analog dimmed by placing a controllable DC voltage on the CTRL pin. When running PWM dimming with SSFM enabled, 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.
Small ceramic input and output capacitors are used to save space and cost. The input and output filters on EVAL-LT8376-AZ reduce its EMI. The filters consist of a small ferrite bead or inductor and high frequency ceramic capacitors. 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-LT8376-AZ. For best efficiency and PWM dimming performance, the EMI filters at the input and output can be removed.
The open LED overvoltage protection (OVP) uses the IC’s constant voltage regulation loop to regulate the output to approximately 41V if the LED string is opened. The output current can be monitored through the ISMON pin. Also, the FAULT pin can be used for open and short detection.
The input undervoltage lockout (UVLO), LED current, output overvoltage protection (OVP), and switching frequency, can all be easy adjusted with simple modifications to EVAL-LT8376-AZ.
The LT8376 data sheet gives a complete description of the device, operation, and applications information. The data sheet must be read in conjunction with this demo manual for evaluation board EVAL-LT8376-AZ. The LT8376RV is assembled in a 28-lead plastic LQFN 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”.
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