Synchronous Step-Down DC/DC Converter with a 300mA VLDO Regulator

All versions of the LTC3541 can be programmed via an external pin to have the synchronous buck power up independently or simultaneously with the VLDO. Additionally, when both the synchronous switcher and the VLDO are enabled, an automatic start-up sequencing feature brings up either the switcher or the VLDO in a specific order. The LTC3541 and LTC3541-2 have an automatic start-up feature that brings the buck output into regulation prior to enabling the VLDO regulator. Alternatively, the LTC3541-1 and LTC3541-3 bring the VLDO into regulation prior to enabling the switching regulator.

The VLDO can either be operated directly from the output of the switching regulator, for maximum efficiency, or from a separate input from 0.9V to 4.1V. An automatic Burst Mode® feature reduces quiescent current in the switcher to only 85uA, thereby maximizing battery run-time. For applications that are particularly noise sensitive, the Burst Mode feature can be disabled and replaced with either a pulse skipping or continuous switching operation. Other features include a power-good output and over-temperature protection.

All versions of the LTC3541 are available from stock in a 10-Lead 3mm x 3mm DFN package. Pricing starts at $1.95 each in 1,000-piece quantities.