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BCM™ Bus Converter

B048F096T24

Rev. 4.9

Page 10 of 12

Parallel Operation

The BCM™ bus converter will inherently current share when operated

in an array. Arrays may be used for higher power or redundancy in an

application.

Current sharing accuracy is maximized when the source and load

impedance presented to each bus converter within an array are equal.

The recommended method to achieve matched impedances is to

dedicate common copper planes within the PCB to deliver and return

the current to the array, rather than rely upon traces of varying lengths.

In typical applications the current being delivered to the load is larger

than that sourced from the input, allowing traces to be utilized on the

input side if necessary. The use of dedicated power planes is, however,

preferable.

The bus converter power train and control architecture allow bi-

directional power transfer, including reverse power processing from the

module output to its input. Reverse power transfer is enabled if the

module input is within its operating range and the module is otherwise

enabled. The bus converter’s ability to process power in reverse

improves the module’s transient response to an output load dump.

Thermal Considerations

distribution varies greatly for each part number as well as with the

input /output conditions, thermal management and environmental

conditions. Maintaining the top of the B048F096T24 case to less than

100°C will keep all junctions within the module below 125°C for most

applications. The percent of total heat dissipated through the top

surface versus through the J-lead is entirely dependent on the particular

mechanical and thermal environment. The heat dissipated through the

top surface is typically 60%. The heat dissipated through the J-lead

onto the PCB board surface is typically 40%. Use 100% top surface

dissipation when designing for a conservative cooling solution.

It is not recommended to use a module for an extended period of time

at full load without proper heat sinking.

Input Impedance Recommendations

To take full advantage of the BCM™ bus converter capabilities, the

impedance presented to its input terminals must be low from DC to

approximately 5 MHz. The source should exhibit low inductance and

should have a critically damped response. If the interconnect inductance

is excessive, the module input pins should be bypassed with an RC

damper (e.g., 47 µF in series with 0.3 ohm) to retain low source

impedance and proper operation. Given the wide bandwidth of the

module, the source response is generally the limiting factor in the

overall system response.

Anomalies in the response of the source will appear at the output of

the module multiplied by its K factor. The DC resistance of the source

should be kept as low as possible to minimize voltage deviations. This is

especially important if the module is operated near low or high line as

the overvoltage /undervoltage detection circuitry could be activated.

Input Fuse Recommendations

in configuring power systems. However, input line fusing of the

modules must always be incorporated within the power system. A fast

acting fuse should be placed in series with the +In port.

Application Notes

For application notes on soldering, thermal management, board layout,

and system design click on the link below:

http://www.vicorpower.com/technical_library/application_information/chips/

Application Note