ISL78268 55V Buck Controller and Eval Board

Added on August 01, 2014
Learn how to set up and use the ISL78268 55V synchronous buck controller and evaluation board.

Related Resources

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Video Transcript

Hi, I'm Ed Kohler, Marketing Manager for Intersil's Automotive Power Management Products. Today I'd like to introduce you to the ISL78268, a 55 volt synchronized buck controller. Then I'd like to demonstrate how easy it is to order and use the evaluation board.

The ISL78268 is a fully synchronous buck controller. What stands out about the ISL78268 is its versatility. It integrates a unique set of features I think you'll find very valuable. Some of those features are: a 5 to 55-volt input range, integrated 3A drivers with adaptive dead-time control, optional constant current regulation, a selection for light load operation between forced PWM mode for low noise or Diode Emulation mode for improved efficiency. And it also has a comprehensive set of protection features that includes the ability to select between latch-off or hiccup fault response.

The ISL78268's evaluation board is a great way to try out any of these features. It’s easy to order and to use. To get one, you just need to visit the 78268's page on Just click over to the order tab and then scroll down to find the evaluation board's part number. That's ISL78268EVAL1Z.

When the board arrives, this is what you should get. Inside, you'll find the ISL78268 evaluation board along with documentation. There will be a user guide for the evaluation board and a data sheet for the 78268. To get started, all we need is a power supply, a load and some cables. So, I'm using a dual 30-volt supply that I've set to operate in series mode so I can deliver up to 60 volts to the input because I want to check out the 78268's wide input voltage range. And I've preset my load to 5 amps so that should do it. Let's get started.

Okay, let me show you what I've done here. First, I installed jumpers at J28 and J10. This allows the part to automatically be enabled when the input supply comes up. Then I connected my upper meter to the input voltage monitoring test point and I connected my lower meter to the output voltage monitoring test point. Then I connected my supply to the input voltage and my load to the Vout terminals. Now, if I enable the can see I've set it up for 48 volts so I'm regulating 48 volts at the input to 12 volts at the output. Now, if I enable the load, we see that we maintain the 12-volt regulation, as you'd expect.

Now, I also have put an oscilloscope probe on the phase node so that we can see the switching action. If we look at the oscilloscope, we see that we're switching at 300 kilohertz which is default and the phase node is going between ground and being at 48 volts, as we'd expect. Here I can demonstrate the overvoltage response at the input.

So if I increase the input voltage to over 55 volts, at typically around 58 volts the overvoltage protection will kick in and stop the part from switching. And there we have it, stop switching. Now, if we allow the voltage to come back down below the overvoltage threshold, we see that the switching starts again and we're regulating again at 12 volts. The evaluation board lets you check out all the features of the ISL78268, and don't worry, the documentation will walk you through how to do all of that.

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