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Maxim > Design Support > Technical Documents > Application Notes > A/D and D/A Conversion/Sampling Circuits > APP 4149
Maxim > Design Support > Technical Documents > Application Notes > Power-Supply Circuits > APP 4149
Keywords: DS4404, DS4402, power supply, power supplies, margining, power supply margining, power
supply tolerance, tolerance, feedback, resistive, divider, vfb, feedback node, vref, reference voltage,
DC/DC, DC-DC, converter, current, source, sink
APPLICATION NOTE 4149
How to Add Margining Capability to a DC-DC
Converter
By: Brian Vasquez
Nov 03, 2008
Abstract: This application note explains how easy it is to add margining capability to a DC-DC converter
by connecting it to a DS4404 4-channel adjustable current DAC (or the DS4402, 2-channel version).
This application note shows how to connect the DS4404, a 4-channel adjustable current DAC (or the
DS4402, a 2-channel version of the DS4404), to a DC-DC converter circuit to add margining capability.
The circuit in Figure 1 illustrates how simple it is to integrate the DS4404 into an existing design. The
DS4404 is added to the feedback node (see the dashed line) so that the V
OUT
of the DC-DC converter
can be adjusted. On power up, the DS4404 outputs a current of 0A (appears as high impedance),
essentially making the DS4404 transparent until it is written to through I²C.
Figure 1. Connecting a DS4404 to a DC-DC converter feedback circuit.
Assume the following for our example (which are independent of the DS4404):
V
IN
= 3V to 5.5V
V
OUT
= 1.8V (desired nominal output voltage)
V
FB
= 0.6V (not to be confused with V
REF
of the DS4404)
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