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PowerPath Prioritizer Eases Power System Design

Linear Technology Corporation introduces the LTC4417, a triple-supply prioritized PowerPath™ controller for 2.5V to 36V systems. The controller selects the highest priority valid supply among three inputs topower the load. Priority is defined by pin assignment, while a supply is considered valid after it has been inside a voltage window set by 1.5% accurate undervoltage and overvoltage thresholds for 256ms. The LTC4417 greatly simplifies designs, deriving power from multiple, disparate voltage sources common in handheld and high availability electronics. In such systems, a prioritizer is a better solution than a simple diode-OR, especially when the preferred power source is not the highest voltage. The LTC4417 controller also protects the load from reversed inputs to ~42V.

PowerPath switching is implemented by external back-to-back P-channel MOSFETs protected by integrated 6V gate clamps. Carefully designed fast switch control blocks reverse and cross-conduction current while preventing output voltage droop. A low 28µA operating current, sub-1µA draw from the lower standby supplies, and a shutdown mode make the controller ideal for battery backup systems. The LTC4417's wide operating range accommodates a wide range of power sources such as wall adapters, USB, Firewire, supercapacitors, and batteries such as lead-acid,

Li-Ion and stacked NiCd. Built-in cascading support extends the LTC4417 prioritization beyond three supplies. To minimize start-up inrush current, the first connection is soft-started. Open-drain outputs indicate the supplies that are within their valid voltage window. Undervoltage and overvoltage hysteresis is adjustable with a single resistor. Specified over the full commercial, industrial and automotive temperature ranges, the LTC4417 is offered in 24-pin QFN (4mm x 4mm) and 24-lead narrow SSOP packages.

Pricing begins at $3.05 each for 1,000-piece quantities and the device is available today in production quantities. Evaluation circuit boards are available.

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