Analog Devices Inc. EVAL-LT8356-1-AZ Demonstration Board
Analog Devices Inc. EVAL-LT8356-1-AZ Demonstration Board is a high-voltage LED controller featuring the LT8356-1. It is assembled as a buck-boost mode LED driver but can be altered by adjusting the FB network and LED connection to a boost LED driver. EVAL-LT8356-1-AZ drives a single string of LEDs up to 36V at 1A when the input is between 8V and 36V. The board has an undervoltage lockout (UVLO) set at 6.5V falling and 7.5V rising and features PWM dimming, analog dimming, shutdown, open/short LED fault protection, and reporting.
EVAL-LT8356-1-AZ runs at 250kHz switching frequency and features Spread Spectrum Frequency Modulation (SSFM) that modulates the switching frequency from 250kHz to 310kHz to reduce EMI emissions. Small ceramic input/output capacitors are used to save space and cost. As assembled, a high voltage 100V external power switch and a 100V catch diode are used for up to 36W buck-boost mode output. If the LED string is opened, the open LED overvoltage protection (OVP) uses the IC’s constant voltage regulation loop to limit the LED+ to LED– voltage to approximately 41V, and the VOUT, if referenced to GND, will jump to VIN + 41V.
The input and output filters on the Analog Devices EVAL-LT8356-1-AZ help further reduce the EMI. These filters contain a small ferrite bead or inductor and high-frequency ceramic capacitors. A small resistor on the gate pin of the power MOSFET reduces high-frequency EMI. Combined with a proper board layout and SSFM, these filters effectively lower EMI to comply with CISPR25 class 5 limits.
Features
- PWM dimming
- Analog dimming
- Open/short LED fault protection
- 8V to 36V input voltage range
- 250MHz to 310MHz switching frequency range
- 41V typical open LED protection (LED+ to LED-)
- 91.5% to 92% typical peak efficiency range
- 10A typical peak switch current limit
- Internally-generated PWM dimming
- 1/128% to 100% range
- 260Hz typical frequency
Applications
- High-voltage LED applications
- Automotive head/running lamps
- Accurate current-limited voltage regulators
Resources
Related Products
Analog Devices Inc. LT8356-1 DC-DC LED Controller
Offers a fixed-frequency, current-mode architecture and is designed to drive high-current LEDs.