DCMs: Spot the Difference

June 7, 2016
By

The DC-DC Converter Module (DCM) is a flexible power component that provides an isolated, regulated output from an input that accepts a wide voltage range. These components, which are available in both ChiP and VIA packaging, are considered by many engineers to be the “utility knives” of DC power system design. Despite their popularity, however, power system developers often do not fully understand the difference between DCMs in each of the different packaging platforms.

Physical and Thermal

Vicor ChiP DCMsThe most obvious differences relate to the packages themselves. The VIA package adds a heatsink, making cooling easier, while the DCM in a ChiP package typically requires external thermal management with cooling on both sides for higher-power applications, but it offers far higher power density. The larger size of the VIA package means that DCMs in this package can deliver up to 308 W/in3 (19 W/cm3), while the ChiP version will deliver over four times this power density.

DCM in VIA packaging technologyThe different packages specify operating temperatures slightly differently, with ChiP components defining a maximum junction temperature of 125°C whereas the VIA devices have a limit on case temperature of 100°C. In practice, however,they are the same as a VIA case temperature of 100°C represents a junction temperature of 125°C.

The different physical packages also mean that there are different mounting options. ChiP packaging offers through-hole (PCB mounting); the VIA packaging platform is available as through-hole or chassis mount.

Electrical

Although the core functionality and performance remains the same, the differences extend well beyond the physical characteristics of the packaging platform. The ChiP packaged version is very much a “pure” DCM, whereas the VIA versions integrate additional functionality to make these power components easier to use and reduce the additional circuitry required.

With the same DCM technology at the core of the products, both versions of the component offer similar efficiencies. The VIA packages, however, incorporate additional circuitry that improves voltage regulation to ±0.5%. This is an order of magnitude better than the inherent regulation of the ChiP DCM, although this can be improved to ±1% with additional remote sense circuitry (see application note AN35, Achieving High Accuracy Voltage (or Current) Regulation with the DCM).

The VIA package allows the integration of EMI and transient filtering that meets the needs of many common applications, whereas DCMs in the ChiP package, however, have no filtering, meaning that external components are required. Although this allows for complete flexibility in filter design, it does mean that more work needs to be done when using the ChiP package.

Other Functionality

DCMs in the ChiP package are easy to parallel, enabling higher current power systems to be designed quickly. Currently, paralleling is not supported for DCMs in the VIA package, although later this year an external digital supervisor component will be launched, which will enable paralleling of up to four DCMs in the VIA package.

The VIA package allows the incorporation of some additional functionality, including integrated output voltage sense. Both platforms provide analog communications, but the VIA packaging also allows for digital PM Bus communications to be added to the family in the future.

Summary of Differences

The table below summarizes the differences between the two versions of the DCM:

Parameter ChiP DCM DCM in a VIA package
Efficiency Comparable efficiencies since ChiP DCM is used in VIA DCM
Power Density Up to 1,244 W/in3 (76 W/cm3) Up to 308 W/in3 (19 W/cm3)
Output Voltage Regulation Accuracy Up to ±5%, ±1% can be achieved through the use of app note AN35 ±0.5%
Internal Filtering None – all filtering will need to be done externally Integrated EMI and transient filter, MIL-STD-461 compliance with external filter
Thermal Management External thermal management may be required Integrated heatsink
Operating Temperature Range1 T grade: -40 to +125°C

M grade: -55 to +125°C

C grade: -20 to +100°C

T grade: -40 to +100°C

M grade: -55 to +100°C (Available Q3)

Paralleling Up to 8 ChiP DCMs can be paralleled together Up to 4 VIA DCMs can be paralleled together using external digital supervisor (Available Q3)
Mounting Options Thru hole (PCB mount) Thru hole (PCB mount) or chassis mount
Integrated Output Voltage Sense None – see AN35 for guidance Integrated sense pin
Trim Up to -40/+10% of nominal output voltage
Communication Analog only Analog or digital (PMBus – available Q3)

1ChiP temperature measured at the junction, VIA temperature measured at the case

Conclusion

The DCM is a flexible power component that deserves a place in every power system designer’s toolbox. But the ChiP and VIA options are not simply different packages: they have been designed to meet the needs of different situations. DCMs in a ChiP package provide the core converter function, leaving the engineer the opportunity to optimize everything from heatsinking to filtering for their application. The DCMs in the VIA platform are optimized for ease of use, integrating additional functionality in a platform that simplifies thermal design to reduce time to market. This flexibility allows power engineers to select the “best” DCM for each application.

 

Tags: , , , ,

Comments are closed.

Find out more about our Cool-Power Buck Regulators DCMs - A better Brick subscribe to vicor newsletter Contact Us

Get Connected