The Current DACs
The
DS1864 contains two 8-bit current-sink DACs with 1.5mA or 0.5mA selectable full-scale range. The DAC outputs must be at a voltage level between 0.7V and the DS1864's V
CC.
Current-to-Voltage Conversion
An operational amplifier in differential amplifier configuration is used to convert the 0.5mA full-scale current-mode output to 1V full-scale voltage-mode output (
Figure 1).
Figure 1. Circuit shows current-to-voltage conversion.
Compact Solution
Using a chip-scale packaged op amp and 0201 resistors will provide the most compact solution. The
MAX4233 is a two-channel op amp available in 1.5mm x 2mm 10-bump UCSP™.
Output Voltage Calculation
The output voltage is calculated in Equation 1.

Using the values shown in the Figure 1 drawing, the maximum output voltage is 1.005V when the DAC current is 0.5mA. To minimize offset and gain errors, 1% tolerance resistors should be used. Further, R1 should be selected so that the voltage at the DAC pin never falls below 0.7V.
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