Schottky diodes are commonly used to add polarity protection and power supply ORing in scenarios where failures are unacceptable. With the ideal diode family, Nexperia now provides a more efficient component.

Designers seeking to reduce diode-borne losses often switch to PMOS-based circuitry: these do have significantly lower forward losses, but they require extensive control logic. Furthermore, many topologies are not capable of performing efficient power supply Oring.

Ideal Diodes Combine MOSFET and Control Logic

Nexperia's excellent whitepaper, found at https://www.nexperia.com/products/analog-logic-ics/power-management/power-protection/ideal-diodes, provides the construction diagram shown in the figure below.

It shows that the ideal diode consists of a FET flanked by control logic. Its job is to ensure the transistor is powered on when it should be; monitoring detects fault states and makes them visible via a fault-detection output.

The voltage drop across ideal diodes, then, is by and large constant. In the whitepaper, Nexperia claims an approximate loss of 30 mV. At 1A of current, this yields a power loss of 0.03W. Comparing this to, say, a classic 1N4007 diode with its 0.7V drop (which leads to 0.7 watts) shows a significant improvement.

NID5100 - Ideal for Reverse-Polarity Protection

Nexperia provides a selection of ideal diodes that differ in both maximum blocking voltage and current capability. The NID5100 is well-suited to situations where a barrel power supply needs to be secured in a fashion similar to the circuit shown below. In such cases, fault detection is not useful: its omission yields a lower component price.

The ideal diode's reverse-voltage protection VIN is up to -6 V absolute, while the load is permitted to draw up to 1.5 A. The EN input can be used to switch parts of the circuit on and off -- this can be useful when a single-board computer must be switched on and off by a power management controller or similar element.

Comparing NID1100 and NID5100

As mentioned above, the NID5100GW-Q100 and its TSSOP housing are but one member of the family. If a system can make do with only 1A of continuous load current, the NID1100 can be an attractive alternative. As shown in the table below, this version adds a variety of protection features.

In general, significant amounts of PCB space savings are observed when ideal diodes are deployed. As an example, Nexperia provides the comparison below, which duplicates the power supply topology of an Arduino board while using ideal diodes instead of their conventional counterparts.

Conclusion

Ideal diodes enable a significant reduction in conduction losses, thereby ensuring higher circuit efficiency. If a system fits the power/voltage profile of parts such as the NID5100, their deployment is a no-brainer.