Why wide VIN ICs for a 12V or 24V rail?


Wide VIN power management ICs are popular for telecom and some industrial applications. But a large number of applications use wide VIN devices when the nominal design scenario only involves a 12V or 24V rail.  With low nominal input voltage rails, the first instinct may be to select 18V or 24V rated parts.  But as we know from experience, nominal conditions are not always the determining factor in selecting the device voltage rating. For example, although the nominal voltages are low, both automotive and industrial applications have input voltage rails with wide variations above the nominal voltages. Automotive battery connected devices typically need 42V or higher input rating whereas the industrial 24V rails can go up to twice the nominal voltage. In addition, many systems have transient specs on power line that may require clamping circuits which may be tricky to design when the power management device rating is close to nominal operating voltages. Often, the clamping circuit can be avoided altogether or its design be simplified if a wide VIN power management IC is used.

 

35% of power management ICs (controllers and regulators) are rated above 20V.

35% of power management ICs (controllers and regulators) are rated above 20V.

(Source: 2012 Databeans Incorporated)

There are many other benefits of using a wide VIN part. A few among them are enhanced reliability, the ability to re-use the design, and the ability to create multiple or negative rails. Based on my experience on the innumerable customer design and troubleshooting efforts, I have gathered a number of test cases in a white paper on the topic “Wide Input Power Management ICs Simplify Point of Load Design."

I hope the paper helps you understand and consider the benefits of using wide VIN devices in communications, industrial and automotive applications. I invite all power supply engineers to share the challenges they have faced and the work-around they employed when designing power solutions operating from wide VIN rails.  Particularly, I'd like to hear your take on the trade-off between using an input voltage protection or clamping circuit vs. using a wide input rated switcher.