Analog Devices Inc. DC2788A Demonstration Circuit for LT3950

Analog Devices DC2788A Demonstration Circuit for LT®3950 is a boost LED driver featuring the LT3950. This demonstration circuit powers a string of LEDs at 330mA. The step-up topology can be used to drive a string of up to 28V LEDs as assembled. The maximum output voltage capability of the LT3950 is 60V. DC2788A runs from an input voltage range of 6V to 24V as built. It also runs at 2MHz and can turn on spread spectrum frequency modulation (SSFM) for a frequency range of 2.0MHz to 2.5MHz. Dimming control can be achieved with analog dimming or PWM dimming—either from an external or internally-generated clock source. DC2788A features an undervoltage lockout (UVLO) set at 6.6V with a 1.0V hysteresis for turn-on. The UVLO voltage, LED current, output voltage range, switching frequency, brightness control, SSFM, and the topology can all be adjusted with simple modifications to the demonstration circuit.

Analog Devices LT3950 is a monolithic 1.5A peak switch current, 60V LED driver. The guaranteed peak switch current rating of the IC is 1.5A, and this is important to know when calculating the maximum output current at a given LED voltage and input voltage for a boost converter. The LT3950 features SSFM and a well-controlled SW node for low emissions. A frequency range of 200kHz to 2MHz and a high-side PWMTG PWM-dimming MOSFET make this a versatile IC for many applications. It can be used for boost, buck-boost mode, and buck mode LED driver applications. The PWMTG MOSFET not only provides high PWM dimming ratio capability but also serves as a short-circuit protection device. The FAULT flag indicates when there is either a short-circuit or open-LED fault at the output.