This document introduces LTC3878 and LTC3879, two power converters with low output voltage, low duty factor and wide control bandwidth. LTC3878 and LTC3879 are the latest No RSENSE series power converters, which can meet the requirements of digital electronics for low voltage power supplies.
The document describes the LTC3878, a pin-compatible replacement for the LTC1778 designed as a compact No Reggys—p™ controller. It utilizes constant on-time valley current mode architecture to simplify loop compensation and improve transient response in low duty factor applications.
Key features include continuously programmable current limit sensing via the bottom MOSFET Vpg voltage, fast transient response with variable switching frequency, and start-up options that allow for soft-start or input voltage tracking depending on circuit requirements.
All internal bias is activated when the RUN/SS pin voltage exceeds 0.7V.
Switching begins when the RUN/SS pin voltage exceeds 1.5V.
The typical off-time is 220ns.