使用频率
REF6225、REF6230、REF633、，REF6250 SBOS748 3.1集成ADC驱动器缓冲器许多ADC数据表规定了REF引脚的平均电流消耗数微安。几乎所有的电压基准都提供这几微安的平均电流；但并非所有电压基准都适用于驱动高分辨率、高通量SAR ADC。电压基准的最坏情况需求是在突发模式转换期间，即ADC空闲很长时间后，转换开始之前，并且预期转换的第一个样本是精确的。通常，在ADC的REF引脚和接地引脚之间（有时在REFP引脚和REFM引脚之间）连接一个大电容器，以平滑电流负载并减少电压基准的负担。电压基准必须能够提供对基准电容器完全充电所需的平均电流，但不会导致基准电压显著下降。大多数电压基准缺乏对基准电容器完全充电的能力，并且当二进制加权电容器被切换到REF引脚时，由于输出阻抗较大，电压基准会稳定下来。通常，电压基准在高于100 Hz的频率下具有10欧姆范围内的输出阻抗。电压基准的输出电压必须用低输出阻抗（通常为高带宽）放大器进行缓冲，以实现优异的线性和失真性能。为高精度ADC设计参考缓冲器时要考虑的关键放大器规格是：低偏移、低漂移、宽带宽和低输出阻抗。虽然可以选择一个充分满足所有这些要求的放大器，但该放大器以过度功耗为代价。例如，OPA350是一款38 MHz带宽放大器，最大偏置为0.5 mV，低偏置漂移为4µV/ºC，但消耗的静态电流为5.2mA。这是因为（从放大器设计的角度来看）偏移和漂移是直流规格，而带宽、低输出阻抗和高电容驱动能力是高频规格。因此，在一个放大器中实现所有性
Frequency of use
REF6225, REF6230, REF633, REF6250 SBOS748 3.1 Integrated ADC Driver Buffer Many ADC data sheets specify the average current consumption of the REF pin in microamps. Almost all voltage references provide the average current of these microamps; However, not all voltage references are suitable for driving high-resolution, high-throughput SAR ADC. The worst case requirement of the voltage reference is that during the burst mode conversion, that is, after the ADC is idle for a long time, before the conversion starts, and the first sample of the expected conversion is accurate. Generally, a large capacitor is connected between the REF pin and the grounding pin of the ADC (sometimes between the REFP pin and the REFM pin) to smooth the current load and reduce the burden of the voltage reference. The voltage reference must be able to provide the average current required to fully charge the reference capacitor without causing a significant drop in the reference voltage. Most voltage references lack the ability to fully charge the reference capacitor, and when the binary weighted capacitor is switched to the REF pin, the voltage reference will stabilize due to the large output impedance. Typically, a voltage reference has an output impedance in the 10 ohm range at frequencies above 100 Hz. The output voltage of the voltage reference must be buffered with a low output impedance (usually high bandwidth) amplifier to achieve excellent linearity and distortion performance. The key amplifier specifications to consider when designing reference buffers for high-precision ADC are: low offset, low drift, broadband and low output impedance. Although it is possible to select an amplifier that fully meets all these requirements, this amplifier comes at the expense of excessive power consumption. For example, the OPA350 is a 38 MHz bandwidth amplifier with a maximum offset of 0.5 mV and a low offset drift of 4 µ V/º C, but consumes a quiescent current of 5.2 mA. This is because (from the perspective of amplifier design) offset and drift are DC specifications, while bandwidth, low output impedance and high capacitance drive capability are high-frequency specifications. Therefore, all performance is achieved in one amplifier
