4

Distributed Bus Architecture

The LSM series DC/DC converters are an ideal solution for modern interme-

diate bus architecture (IBA) or distributed bus architecture (DBA) applications

used in telecommuncations and dedicated stand-alone systems. DBA's see

implementation whenever multiple final power voltages are required (each

using a dedicated single-voltage DC/DC converter) while retaining overall

system power isolation.

DBA's position the final DC/DC right at the load (also called Point of Load,

POL converters). This provides the best possible dynamic response, regu-

lation, and noise reduction. It also distributes the thermal load to avoid

system hotspots or concentrations of high switching currents. Since the POL

DC/DC's are non-isolated models, their physical size is reduced, making

them ideal for tape and reel automated surface mounting.

A single system-wide master high power bus converter performs the initial

power voltage conversion. A 48Vdc input is typical with 12Vdc outputs distrib-

LSM-3.3/10-D12

3.3VDC

12VDC

SYSTEM

ISOLATION

BARRIER

POINT-OF-LOAD

DC/DC CONVERTERS

48VDC

INPUT

POWER

(TYPICAL)

DATEL

SBC-12/22-L48

BUS CONVERTER

SYSTEM

LOGIC

LSM-5/10-D12

5VDC

LOCAL GROUNDS

AS APPROPRIATE

I/O PORTS

LSM-1.2/10-D12

1.2VDC

CPU

uted to several POL DC/DC's. DBA's also retain very high system efficiency,

important for battery operated and standby applications.

In the diagram below, a DATEL model SBC-12/22-L48 acts as the bus

converter from system 48 Volts to 12 Volts distributed to each POL converter.

One POL converter powers 3.3V system logic while a separate 1.2V POL

converter runs the CPU. A third 5V POL converter powers legacy I/O ports.

Notice that the 12V power leads are routed all the way back to the the bus

converter for best performance. Also observe that only one source of isolation

is required (in the bus converter) so that individual POL converters can be

lower cost non-isolated versions.

The Distributed Bus Architecture offers a lower overall system cost than using

separate bulkier isolated converters at each voltage load. And it prevents

possible crosstalk of high power digital switching signals. A final advantage

of DBA's is that the designer has a choice of where and how to interconnect

system grounds and is not restricted by a noisy system "mecca" ground.

Figure 2. Distributed Bus Architecture

LSM-EB Series

10 Amp DC/DC Power Converter Evaluation Boards

www.murata-ps.com

MDC_LSM_EB.B01 Page 4 of 5