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PRELIMINARY

Vicor Corp. Tel: 800-735-6200, 978-470-2900 Fax: 978-475-6715

MicroRAM

Rev. 1.1

Page 3 of 8

Electrical Characteristics (continued)

APPLICATION SCHEMATIC DRAWINGS USING VICOR CONVERTERS AND THE µRAM

DC-DC

Converter

µRAM

+Out

–Out

+In

SC

–In

+Out

+S

SC

–S

–Out

+In

PC

PR

–In

(2)

5.1

22

µF

Figure 1—Typical Configuration using Remote Sensing

DC-DC

Converter

+Out

SC

–Out

+In

PC

PR

–In

µRAM

+Out

–Out

+In

SC

–In

Functional Description

The MicroRAM has an internal passive filter that

effectively attenuates ripple in the 50kHz to 1MHz range.

An active filter provides attenuation from low frequency

up to the 1MHz range. The user must set the headroom

to optimize performance. The MicroRAM must be connected

as shown in Figures 1 or 2 depending on the load sensing

method. The transient load current performance can be

capacitance, plus optional external capacitance, during the

time it takes the converter loop to respond to the increase

in load. The MicroRAM’s active loop responds in roughly

one microsecond to output voltage perturbations. There

are limitations to the magnitude and the rate of change of

the transient current that the MicroRAM can sustain while

the converter responds. See Figures 8-16, on pp. 6 and 7,

for examples of dynamic performance. A larger headroom

voltage setting will provide increased transient performance,

ripple attenuation and power dissipation while reducing

overall efficiency (see Figures 4a, 4b, 4c and 4d on p. 5).