With just two resistors, a supply is configured to ramp up as a function of a "master" signal. This master signal 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 doesn’t 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.

For more information, visit www.linear.com.

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