ASL3417SHNY

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1. Describe

The ASL3417SHN has a hysteretic step-down DC-DC topology. With input voltages from 10 V to 80 V, it provides maximum flexibility in output voltage per channel, supporting applications up to 20 LEDs. It also provides output currents up to 1.5 A per channel and beyond. 1 Additionally, two output channels can be connected together to provide higher currents. It drives an external high-side N-channel MOSFET from an internally regulated adjustable power supply. The ASL3417SHN buck driver provides a flexible system design that can be used to drive three LED strings with the same architecture. The ASL3417SHN provides an SPI interface for extensive control and diagnostic communication with an external microcontroller. Additionally, the ASL3417SHN integrates a customer programmable limp mode. It allows configurable operation in limp mode if SPI communication with the microcontroller fails. The ASL3417SHN provides adjustable hysteresis to optimize external components and minimize LED current ripple. Additionally, the ASL3417SHN provides output voltages up to 70 V. It has measurement functions that can be used to identify open or shorted LED conditions. A microcontroller can read this voltage and use it to detect open or short circuit conditions. There are other diagnostic functions, such as the currently reached state. Additional features include input undervoltage lockout and thermal shutdown when the junction temperature of the ASL3417SHN exceeds +175°C. It is packaged in an ultra-small HVQFN32-pin package with exposed thermal pad and is designed to meet the stringent requirements of automotive applications. It is fully AEC Q100 Class 1 compliant. It operates in the automotive ambient temperature range of -40 °C to +125 °C.

2. Features

    1. The ASL3417SHN is an AEC-Q100 Grade 1 qualified automotive grade product.

    2. Ambient operating temperature range from -40 °C to +125 °C

    3. Wide operating input voltage range of +10 V to +80 V

    4. Capable of driving up to 20 LEDs, wide operating LED voltage range regulated from 2.5 V to 70 V

    5. Output currents up to 1.5 A and beyond with high LED current accuracy of ±5 % over the entire operating temperature range

    6. Output current can be programmed via SPI interface

    7. Read back programming current via SPI

    8. Customer programmable limp home mode.

    9. Two output current ranges, programmable with 5 % accuracy via SPI interface

  10. Hysteretic converter

  11. High-efficiency fast gate drive

  12. Programmable internal gate drive voltage regulator

  13. Support logic level and standard level FET

  14. Integrated bootstrap diode

  15. PWM input for individual dimming of each channel

  16. Low Electromagnetic Emissions (EME) and High Electromagnetic Immunity (EMI)

  17. Input voltage monitoring and input under-voltage protection

  18. Output voltage monitoring

  19. Enable the control signal of the device

  20. Junction temperature monitoring via SPI

  21. Small package outline HVQFN32

  22. Low quiescent current < 5 µA at 25 °C when EN = 0

  23. Short circuit and open circuit output protection

3. Application

    1. Automotive LED lighting

        - Daytime running lights

        - Location or parking lights

        - Low beam

        - High beam

        - Turn indicator

        - Fog lights

        - Turn signal

        - Advanced headlamps

4. Pin configuration

5. Buck converter

The ASL3417SHN is a buck converter IC delivering constant current to the LEDs. It is a hysteretic controller that regulates the inductor current. It switches off the external FET when the inductor current rises above the upper threshold current. It switches on when the current falls below the lower threshold. The width of the hysteresis window can be programmed via SPI to keep the switching frequency between bounds. The anode of the LED string is connected to the driver, while the cathode of the LED string is connected to ground. This arrangement helps to reduce the total number of connections to the LEDs.

6. Function control register

To monitor the status of the SPI interface, use the function control register. It allows a reset of the fail silent mode and offers the control of the PWM inputs. After enabling the device, the SPI_status bit should be set. When a query returns that the bit is set, the SPI interface is operational and the device can be configured. Configuration of the device is not permitted before this bit is set. When the device enters fail silent mode due to an error condition, bit Clr_error can be set to bring the device back into operation mode. Once the error bits are cleared, the device clears the Clr_error bit automatically. If the Clr_error bit is set, when no error is present, the Clr_error bit remains set, until an error occurs. This error is cleared automatically.