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Analog Devices Inc. LT8391D Evaluation Board (EVAL-LT8391D-AZ)

Analog Devices Inc. LT8391D Evaluation Board (EVAL-LT8391D-AZ) is a reference design for a buck-boost LED driver circuit based on the LT8391D LED Controller. The LT8391D is a synchronous 4-switch buck-boost LED controller that regulates LED current from input voltage above, below, or equal to the output voltage. The proprietary peak-buck peak-boost current mode control scheme allows adjustable and synchronizable 150kHz to 650kHz fixed frequency operation or internal ±15% triangle spread spectrum operation for low EMI. With 4V to 60V input, 0V to 60V output, and seamless low noise transitions between operation regions, the LT8391 is ideal for LED driver and battery charger applications in automotive, industrial, and battery-powered systems.

The Analog Devices Inc. LT8391D Evaluation Board can drive a single string of LEDs at up to 1.5A and up to 50V when VIN is between 6V and 45V. The Evaluation Board runs at a 400kHz switching frequency, and efficiency can exceed 97%. The Evaluation Board offers low EMI features, including an optimized layout, spread spectrum frequency modulation (SSFM), and an input EMI filter. SSFM can be turned on or off with a simple jumper.

The LT8391D allows adjustable switching frequency between 150kHz and 650kHz. It can be PWM dimmed with an external PWM signal. When run with PWM dimming and either fixed switching frequency or SSFM, the internal oscillator aligns with the PWM signal for flicker-free operation. On EVAL-LT8391D-AZ, the PWM pin is pulled up to INTVCC through a 100k resistor. Therefore, the LED string is 100% ON when there is no external PWM signal. It can also be analog dimmed with a control voltage on its control pin (CTRL).

The LT8391D Evaluation Board features MOSFETs that complement the 5V gate drive of the LT8391D to achieve high efficiency. All MOSFETs used on the 4-switch topology are rated at 60V and are AEC-Q101 qualified. Ceramic capacitors are used on both the input and output sides due to the small size and high ripple current capability. In addition to ceramic capacitors, one aluminum electrolytic capacitor is on the input side to mitigate the effects of the input and output transients.

Features

  • LT8391D in a QFN-28 package
  • Input voltage range (VIN)
    • 6V to 45V @ 6V ≤VLED ≤50V, ILED ≤1.5A, output ≤22.5W
    • 9V to 45V @ 6V ≤VLED ≤36V, ILED ≤1.5A, output ≤45.0W
  • Switching frequency (fSW)
    • 400kHz @ R17 = 100k, SSFM = OFF
    • 340kHz to 460kHz @ R17 = 100k, SSFM = ON
  • 4.2V VIN undervoltage lockout (UVLO) falling
  • 5.0V VIN enable turn-on (EN) rising
  • 1.47A LED current (ILED)
  • 6V to 50V LED voltage range (VLED)
  • 55.5V open LED voltage (VOUT)
  • 94% efficiency, 100% PWM DC (EFF)

Supported Devices

Analog Devices Inc. LT8391 Synchronous Buck-Boost LED Controllers

60V Synchronous 4-Switch Buck-Boost LED Controllers with Spread Spectrum.

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Test Setup

Mechanical Drawing - Analog Devices Inc. LT8391D Evaluation Board (EVAL-LT8391D-AZ)
Publicado: 2022-08-29 | Actualizado: 2022-09-09