High-Voltage Integrated Circuits

Are there disadvantages to HVICs?
Only one: HVICs do not provide galvanic isolation, whereas optocouplers and some of the other solutions do. However, galvanic isolation can be achieved in HVICs by moving the isolation barrier to the input signals.

How do I choose an HVIC for an application?
First, check whether there is an HVIC designed specifically for your application. Application-specific HVICs offer tremendous cost savings over designing a controller from scratch. If you cannot find a specific HVIC, start by determining the maximum voltage of your application. HVIC voltages can range from 100 to 1200 V. Next, decide on functionality. Do you need a simple driver or a bit more, like a half-bridge or three-phase driver?

Consider the input, output, and switching frequency. What will drive the HVIC? HVICs can accommodate 3.3-, 5-, and 15-V input logic, with most having a 20-V maximum at the inputs. Other questions include whether the HVIC will be working at 10 to 100 kHz or 300 to 500 kHz. Is input/output delay important in this application? Is delay matching of the high-side and low-side sections important? What are the output drive current requirements? Are you driving small switches or large ones? Will you be paralleling some of them?

HVIC output drives can range from few hundred milliamps to well over 4 A. Which one do you need to fulfill your timing requirements? Finally, consider which protection features your application requires. Do you need a "shut-down" pin? Do you need current sensing?

What must I watch for when designing with HVICs?
Watch out for fast dv/dts on the floating well. While most HVICs can withstand well over 50-V/ns transitions, higher transitions might cause false triggering in the high side. Keep transition dv/dts below the maximum recommended limit. Also, the high-side well needs to always be biased at or above the lowest potential in the circuit. Due to the HVIC’s internal parasitic components, damage could result if the well is pushed below the recommended level for an appreciable time. And as the natural environment for HVICs is noisy, the layout of switches and the HVIC is critical for the proper operation of the system. Keep switches and the drivers in close proximity, and use short traces to minimize inductance and avoid ringing on the gates.