Analog Devices LTC7803 | Tech Explainer
This Tech Explainer is part of a video series that details specific products and technologies and their applications.
Analog Devices LTC7803
It is possible to reduce the cost of electronic components by using the same designs for different applications.
This can be applied to the automotive-grade LTC7803 synchronous step-down DC-to-DC switching regulator controller to create both positive and negative output DC-to-DC converters.
A positive output buck converter can be achieved with this layout where the converter generates a stable 5 volt output voltage at 15 amps with an input voltage ranging from 5 to 38 volts. The power train includes switching MOSFETs, an inductor, and two capacitors.
The voltage and current stress on the powertrain components can be seen by these equations.
A negative output, negative buck-boost converter can be seen in this schematic where the same interconnections and controller are used as well as the same components in the powertrain.
The difference occurs in the grounding of the controller, switching MOSFETs, and input and output filters.
The capacitors CIN1 and CIN2 filter the AC between the VIN and minus VOUT rails. These expressions can be used to estimate the stresses on the power train components.
The negative buck-boost topology has a reverse voltage swing at the output filter with an amplitude that is not more than one diode voltage drop. This is caused by the controller’s operating current through the forward-biased diode to system ground.
Both the positive and negative output converters were designed with the LTC7803 advanced controller and thoroughly tested with the DC2834A evaluation board.
The efficiency of both converters with natural convective cooling can be seen here.
Designers can successfully design two entirely different converting topologies using the same fundamental qualified parts, this helps automotive manufacturers save on cost and allows for a quicker time to market.
For more information, visit Mouser.com.
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