Analog Devices LT3964 | Demoboard DC2424A

Beschreibung

The DC2424A is a 36V synchronous dual LED driver withI2C featuring the LT®3964. It drives two separate LEDs(or channels of LEDs) at 1A when VIN is between 5Vand 36V. DC2424A runs at 2MHz switching frequency.Its two channels can drive separate LED strings whichcan have different currents, voltages, or dimming ratios.It can be controlled with I2C communications or it canbe run in non-I2C mode with proper ADDR pin settings.It is protected against both open and short LED conditionsand reports the faults. In I2C mode, faults can beenabled or disabled. Up to 9 different DC2424As can beplaced on the same I2C bus with unique addresses. Agraphical user interface (GUI) is available through QuikEval™when connected to a DC2026C Linduino® Onedemo circuit.The LT3964 has an input voltage range from 4V to 36V. Ithas two independent 1.6A, 40V bucks with internal, synchronous40V switches for high efficiency and small size.It has adjustable switching frequency between 200kHzand 2MHz. It can be synchronized to an external sourceor programmed with a clock output (CLKOUT) from theserial interface. The PWMTG high side PWM MOSFETdrivers assist with short-circuit protection and versatility.Although the demo circuit is optimized for just one LEDper channel, it can be altered to be buck regulators withas high as 33V of LEDs if VIN is high enough and circuitcomponents are changed appropriately.In non-I2C mode, each channel can separately be PWMandanalog-dimmed by placing a PWM signal or CTRLvoltage on the provided turrets. In I2C mode, each channelcan be dimmed to up to 8192:1 and analog dimmed to ahigh ratio using serial communications.Small ceramic input and output capacitors are used tosave space and cost. The open LED overvoltage protectionuses the IC’s constant voltage regulation loop to regulatethe output to approximately 4.2V if the LED stringis opened. There is a protection diode from each LED+to GND to prevent negative ringing during a short-circuitcondition.Undervoltage lockout can be adjusted on the circuit with afew simple resistor choices. The output voltage (overvoltageprotection) can be adjusted by changing the feedbackresistors for higher string voltages. Other componentsmay need to be changed to accommodate higher voltagesalso.The LT3964 data sheet gives a complete description ofthe device, operation and applications information. Thedata sheet must be read in conjunction with this demomanual for DC2424A. The LT3964EUHE is assembled in a36-lead plastic 5mm × 6mm QFN package with a thermallyenhanced ground pad. Proper board layout is essentialfor maximum thermal performance. See the data sheetLayout Considerations section.

Weiterführende Informationen

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