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#123: Voltage Reference Selection Basics
 Overview: Voltage references are a key building block in data conversion systems, and understanding their specifications and how they contribute to error is necessary for selecting the right reference for the application. Figure 1 shows the application of a voltage reference in a simple analog-to-digital converter (ADC) and digital-to-analog converter (DAC). In each case, the reference voltage (VREF) acts as a very precise analog 'meter stick' against which the incoming analog signal is compared (as in an ADC) or the outgoing analog signal is generated (DAC). As such, a stable system reference is required for accurate and repeatable data conversion; and as the number of bits increases, less reference error can be tolerated. Monolithic voltage references produce an output voltage which is substantially immune to variations in ambient temperature as well as loading, input supply, and time. While many ADCs and DACs incorporate an internal reference, beyond 8 to10 bits it is rare to find one with sufficient precision as high-density CMOS technologies commonly used for data converters typically produce low-quality references. In most cases, the internal reference can be overdriven by an external one to improve performance. Terms such as "high precision" and "ultra-high precision" are common in reference datasheets but do little to help designers in their selection. This article seeks to provide an explanation of common reference specifications, rank their relative importance and show how a designer can use them in some simple calculations to narrow his or her search.
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Power Designer
Published every other month, Power Designer's feature articles cover power design techniques.
| Publication |
PDF |
| #123: Voltage Reference Selection Basics |
297KB |
| #122: Optimizing Power Controller Designs through Effective Utilization of Performance Features |
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| #121: Power Supply Design Considerations for Modern FPGAs |
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| #120: Calculating Losses and Junction Temperature for High-Power-Density Switching Converters |
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| #119: Color-Management LED Drivers Have a Bright Future |
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| #118: Saving Energy via Smart Power Management |
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| #117: Overcoming Challenges in Designing Step-Down Regulator Applications with ≥40V Input Voltage |
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| #114: Best Layout Practices for Switching Power Supplies |
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| #113: Optimizing Efficiency in White LED Backlight Applications |
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| #112: Synchronous Rectification in High–Performance Power Converter Design |
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| #111: Buck Regulator Topologies for Wide Input/Output Voltage Differentials |
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| #110: Optimizing RF Power Amplifier System Efficiency Using DC-DC Converters |
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| #109: Advanced Topics in Powering FPGAs |
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| #108: Operation and Benefits of Active-Clamp Forward Power Converters |
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| #107: Analyzing Power Modules |
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| #106: Inside Current-Mode Control |
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| #105: Power Management Design for Applications Processors |
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| #104: Power Supply Design for Power-over-Ethernet Applications |
1.8MB |
| #103: Understanding Portable Applications Requirements |
429KB |
| #102: Power Management Considerations for FPGAs and ASICs |
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| #101: Feedback Techniques for Crossing the Isolation Boundary |
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Also see Signal Path Designer for expert tips, tricks, and techniques for designers of signal-path applications.
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