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V•I Chip Bus Converter Module

B048K160T24

Rev. 1.0

Page 11 of 15

V•I Chip Bus Converter Module

PRELIMINARY

Parallel Operation

The BCM 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 BCM 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 BCM power train and control architecture allow bi-directional power

transfer, including reverse power processing from the BCM output to its

input. Reverse power transfer is enabled if the BCM input is within its

operating range and the BCM is otherwise enabled. The BCM’s ability to

process power in reverse improves the BCM transient response to an

output load dump.

Thermal Management

The high efficiency of the V•I Chip results in relatively low power

dissipation and correspondingly low generation of heat. The heat

generated within internal semiconductor junctions is coupled with low

Ball Grid Array allowing thermal management flexibility to adapt to

specific application requirements (Figure 22).

CASE 1 Convection via heatsink to air.

mounted V•I Chip with a 0.25" heatsink is 4.8 °C/W in 300 LFM air flow

(Figure 24). At full rated output power of 240 W, the heat generated by

the BCM is approximately 11 W (Figure 6). Therefore, the junction

temperature rise to ambient is approximately 53°C. Given a maximum

junction temperature of 125°C, a temperature rise of 53°C allows the

V•I Chip to operate at rated output power at up to 72°C ambient

temperature. At 100 W of output power, operating ambient

temperature extends to 105°C.

CASE 2—Conduction to the PCB

to exchange heat from the V•I Chip, including convection from the PCB

to the ambient or conduction to a cold plate.

For example, with a V•I Chip surface mounted on a 2" x 2" area of a

multi-layer PCB, with an aggregate 8 oz of effective copper weight, the

LFM air flow (see Thermal section, Page 6). Given a maximum junction

temperature of 125°C and 11 W dissipation at 240 W of output power,

a temperature rise of 72°C allows the V•I Chip to operate at rated

output power at up to 53°C ambient temperature.

Figure 24—Junction-to-ambient thermal resistance of BCM with

0.25"

Heatsink

BCM with 0.25'' Heatsink

3

4

5

6

7

8

9

10

0

100

200

300

400

500

600

Airflow (LFM)

-40

-20

0

20

40

60

80

100

120

140

Operating Junction Temperature (°C)

0

Figure 23— Thermal derating curve

Application Note

Figure 22—Thermal resistance

240