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Maxim > Design Support > Technical Documents > Application Notes > Digital Potentiometers > APP 4280
Keywords: DC-DC converter, resistive feedback divider network, current DAC, full-scale current, source
current, sink current, output voltage margin, power supply, test margining, DC-DC converter feedback
margining
APPLICATION NOTE 4280
Using the DS4424 to Margin the Output Voltage of
a DC-DC Converter
Sep 22, 2008
Abstract: A DS4424 adjustable-current DAC is used to adjust the margin of a DC-DC converter's output
voltage. This article describes how to properly select the resistor values of a DC-DC converter's feedback
divider network when the DS4424 is employed in the design.
Introduction
The DS4424 adjustable-current DAC is similar to the DS4404 adjustable-current DAC with two major
differences. First, the DS4424 has 127 settings each for sink and source mode, while the DS4404 has
31 settings. Second, the DS4424's default I²C address is set to 20h, whereas the DS4404's default I²C
address is 90h. Both devices' addresses are determined by the states of the A0 and A1 address pins.
This article focuses on the DS4424, which can be used to adjust the margin of a DC-DC converter's
output voltage. The article explains how to properly select resistor values of the DC-DC converter's
feedback divider network when the DS4424 is employed in the design.
The Adjustable Power Supply
The DS4424 contains four I²C adjustable current sources capable of sinking and sourcing current. A
typical application for these DACs is margining the output voltage of a DC-DC converter (Figure 1).
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