The 20-bit DAC11001A is a highly accurate, low-noise, voltage-output, single-channel, digital-to-analog converters (DACs). The DAC11001 are specified monotonic by design, and offer excellent linearity of less than 4 LSB (max) across all ranges. The unbuffered voltage output offers low noise performance (7 nV/√Hz) in combination with a fast settling time (1µs), making this device an excellent choice for low-noise, fast control-loop, and waveform generation applications. When designing for these applications, its is necessary to calculate the total error contributed by the DAC and the associated circuit components. This report helps in understanding various DAC errors and how to calculate the total error in the system.
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This application report describes how to calculate the total error in a DAC11001 system from various components like reference, reference buffer, output buffer, and the DAC itself. Figure 1-1 shows an example circuit topology using DAC11001 to get a 20 bit linear output. In this example, REF6025 used as reference and OPA828 as output and reference buffer respectively.
| Parameters | Specifications |
|---|---|
| Output Voltage | ±5 V |
| Reference source | 2.5 V |
| Output Type | Buffered |
| Resolution | 20-bit |
| Operating Temperature Range | -40 to 125°C |
Static errors, errors that affect the accuracy of the converter when it is converting static (dc) signals, can be described using four terms. These terms are offset error, gain error, integral nonlinearity and differential nonlinearity. Each term can be expressed in least significant bit (LSB) units or as a percentage of the full-scale range (FSR). For example, an error of ½ LSB for an 8-bit converter corresponds to 0.2% FSR. Figure 2-1 shows DAC ideal and actual transfer function. All the error sources and calculations in this document is expressed in parts-per-million (ppm).