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Maxim > Design Support > Technical Documents > Application Notes > Communications Circuits > APP 4055
Maxim > Design Support > Technical Documents > Application Notes > Power-Supply Circuits > APP 4055
Keywords: DC/DC Converter, resistive feedback divider network, current DAC, full-scale current, source
current, sink current, output voltage margin
APPLICATION NOTE 4055
Using the DS4402/DS4404 to Margin the Output
Voltage of a DC-DC Converter
Jun 18, 2007
Abstract: A DS4402 or DS4404 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 in a DC-DC
converter's feedback divider network when a DS4402 or DS4404 is employed in the design.
The Adjustable Power Supply
The DS4402/DS4404 DACs contain two/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. (See Figure 1.)
Figure 1. DC-DC converter circuit with adjustable-current DACs used to margin the converter's output
voltage.
The DS4402/DS4404 sink and source current from their OUT pins. Valid full-scale current values range
from 0.5mA to 2.0mA. The value of the full-scale current, I
FS
, is determined by the size of the resistor
connected to the DAC's FS pin of the corresponding OUT pin. The source/sink current generated by the
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