Basics of eFuses

 eFuses are integrated power path protection devices that are used to limit circuit currents, voltages to safe levels during fault conditions. eFuses offer many benefits to the system and can include protection features that are often difficult to implement with discrete components. Discrete solutions are bulky, inefficient, do not incorporate thermal protection, need more components and occupy more board space. More components also raise concerns on protection-circuit robustness and reliability.

Different types of eFuses are available in the market. Here is one of my favorite eFuses, TPS259271 from TI.

This chip is a robust defence against overloads, shorts circuits, voltage surges, excessive inrush current, and reverse current. It also offers Controlled Power Down, Over Temperature Protection, Health Monitoring and Reporting.

Electronic Load Fundamentals

 

What is an electronic load?

An electronic load is a test instrument designed to sink current and absorb power out of a power source. If a power supply is used to power a device, an electronic load is used to test the power supply by emulating the device under test (DUT).

An electronic load is a programmable instrument that offers the user various modes of control such as constant voltage (CV), constant current (CC), constant power (CP) or constant resistance (CR).

Who uses electronic loads?

Device manufacturers and design engineers use electronic loads to test numerous power devices such as power supplies, DC-DC converters, chargers, adapters, batteries, solar panels, fuel-cells, and more.

Why do engineers use electronic loads instead of a fixed value power resistor?

In situations where you need a purely resistive load and no closed loop control is required, it is sufficient to use a fixed value power resistor. A fixed value resistor presents many limitations. It is not adequate for loading and testing power sources that have complex testing requirements. Such tasks require sophisticated electronic load features to validate the various states of operation.

Constant current operation mode

Constant current (CC) is the most frequent mode in which an electronic load is used. In constant current mode, the load will sink the programmed current independently from the output voltage which is typically forced by the voltage source connected to it (for example a battery).

Constant voltage operation mode

In constant voltage (CV) mode the electronic load sets a fixed programmable voltage across its terminals independently from the input current. In CV mode, the current is set by the current source connected to it – for example, a current charging circuit or a LED current driver. The load adjusts its resistance dynamically to attain the programmed voltage at any current established by the current source under test.

Constant resistance operation

In constant resistance (CR) mode, the load acts as a fixed programmable power resistor. An electronic load’s CR mode is well-suited for loading a power source that is either a voltage or current source. When the load connects to a voltage source it sinks a current equal to the source potential divided by the programmed resistance value.