Linear Technology Corp. (LTC, Milpitas, CA) introduced the LTC2923, a simple and flexible power supply tracking controller in the 10-lead MSOP package for systems with specific supply tracking or sequencing requirements. The LTC2923 controls power supply startup and shutdown by introducing currents into the feedback nodes. With just two resistors, a supply is configured to ramp up as a function of a "master" signal, which can be a third supply, a capacitor charging up or a signal generated externally.
By properly selecting the resistors, the supplies can be configured to ramp-up and ramp-down together, with options for fixed-voltage offsets, time delays or different ramp rates. The LTC2923 allows an additional supply to be controlled with a series FET for systems that require tracking of a third supply, or when a supply does not allow direct access to its feedback resistors.
The LTC2923 causes the two power supply outputs to track or to follow a sequence without inserting any pass element losses. The LTC2923 does not affect the transient response or stability of the supplies, since the currents are controlled in an open-loop manner. Furthermore, the device presents a high impedance when power-up is complete, effectively removing it from the dc/dc circuit.
Offered in the MSOP-10 package, pricing for the LTC2923 starts at $2.95 each for 1,000-piece quantities.
