Triple-supply controller simplifies power system design, protects against reversed inputs
The LTC4417 controller selects the highest priority valid supply among three inputs to power 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 256 ms. 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 −42 V.
PowerPath switching is implemented by external back-to-back P-channel MOSFETs protected by integrated 6 V gate clamps. Carefully designed fast switch control blocks reverse and cross-conduction current while preventing output voltage droop. A low 28 µA operating current, sub-1 µA 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 (4 mm x 4 mm) 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.
More information about the PowerPath controllers at
www.linear.com/powerpath_controllers
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