Demonstration circuit 3054A-B features the LTC3308B 5V, 4A synchronous step-down Silent Switcher® operating as a 6.6MHz, 3.3V to 1.8V 4A buck regulator. The LTC3308B supports adjustable output voltages from 0.5V to VIN, and operating frequencies from 3MHz up to 10MHz. The LTC3308B is a compact, ultralow emission, high efficiency, and high speed synchronous monolithic step-down switching regulator. A minimum on-time of 22ns enables high VIN to low VOUT conversion ratios at high switching frequencies.
The DC3054A-B operating mode may be selected as Burst Mode® operation, skip or forced continuous (FC) mode. Setting JP1 to the FC/SYNC position will allow the LTC3308B to sync to a clock frequency from 3MHz to 10MHz. The LTC3308B operates in forced continuous mode when syncing to an external clock. The DC3054A-B is set to a fixed 6.6MHz.
The DC3054A-B is set to a fixed 6.6MHz frequency by connecting RT to VIN through a 0Ω resistor, R9. The frequency can be easily changed by removing R9 and setting an appropriate resistor in the R4 location to obtain the desired frequency. Refer to the LTC3308B data sheet for the proper RT value for a desired switching frequency.
The LTC3308B data sheet gives a complete description of the device, operation and application information. The data sheet must be read in conjunction with the demo manual. The LTC3308B is assembled in a 2mm × 2mm LQFN package with exposed pads for low thermal resistance. The layout recommendations for low EMI operation and maximum thermal performance are available in the data sheet section Low EMI PCB Layout.
