MIC5191BML(2004) 데이터 시트보기 (PDF) - Micrel
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MIC5191BML Datasheet PDF : 13 Pages
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MIC5191
Using the MIC5191 as a filter for a switching regulator
reduces output noise due to ripple and high frequency switch-
ing noise. It also reduces undershoot (Figure 12) and over-
shoot (Figure 13) due to load transients with decreased
capacitance.
Micrel
If a large circuit board has multiple small-geometry ASICs, it
will require the powering of multiple loads with its one power
source. Assuming that the ASICs are dispersed throughout
the board and that the core voltage requires a regulated 1V,
Figure 14 shows the long traces from the power supply to the
loads. Not only do we have to contend with the tolerance of
the supply (line regulation, load regulation, output accuracy
and temperature tolerances), but the trace lengths create
additional issues with resistance and inductance. With lower
voltages these parasitic values can easily bump the output
voltage out of a usable tolerance.
Load
Circuit Board
Load
TIME (100µs/div)
Figure 13. Transient Response
Due to the high DC gain (80dB) of the MIC5191, it also adds
increased output accuracy and extremely high load regula-
tion.
Distributed Power Supply
As technology advances and processes move to smaller and
smaller geometries, voltage requirements go down and cur-
rent requirements go up. This creates unique challenges
when trying to supply power to multiple devices on a board.
When there is one load to power, the difficulties are not quite
as complex; trying to distribute power to multiple loads from
one supply is much more problematic.
Switching
Power
Supply
Load
Long Traces
Load
Figure 14. Board Layout
But by placing multiple, small MIC5191 circuits close to each
load, the parasitic trace elements caused by distance to the
power supply are almost completely negated. By adjusting
the switching supply voltage to 1.2V, for example, the MIC5191
will provide accurate 1V output, efficently and with very little
noise.
Load
Circuit Board
MIC5191
MIC5191
Load
Load
MIC5191
Switching
Power
Supply
MIC5191
Load
Figure 15. Improved Distributed Supplies
April 2004
12
M9999-042804
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