In addition to high precision, low temperature drift, low noise, and low power consumption are also essential features for voltage reference sources to meet the increasingly stringent requirements of various electronic devices.
This issue will focus on how to select a voltage reference source chip, and take the NSREF3130 voltage reference source chip from Nanochip Microelectronics as an example to analyze in detail how voltage reference source errors will affect the ADC acquisition system.
Nanochip's NSREF30/31xx series voltage reference sources , with their superior performance and stability, not only meet the ever-growing performance requirements of electronic devices, but also help customers expand into a wider range of applications.
How to select a voltage reference source chip?
When selecting a voltage reference source chip as a reference voltage, the following factors need to be considered from the perspective of system architecture: power supply voltage, power consumption budget, load capacity, temperature range, and package size .
After meeting the basic system requirements, it is necessary to further consider whether the performance parameters of the reference source chip can meet the requirements. High precision and low noise are the basic performance requirements of a voltage reference source. The reference source must also remain stable under different external environmental changes, such as temperature changes, environmental stress changes, and time changes. These external factors will affect the performance of the voltage reference source; therefore, different performance parameters are used to calibrate the performance of the reference source, such as initial accuracy, temperature drift, noise, thermal hysteresis, long-term drift, voltage regulation, load regulation, and input-output voltage difference .
Factors for selecting a voltage reference source
Product advantages of NSREF30/31xx series
Nanochip's NSREF30/31xx voltage reference sources feature high precision, low temperature drift, low noise, and low power consumption . This series comprises two sub-series: NSREF30xx and NSREF31xx , each with six different models corresponding to six output voltage options. Each product is available in automotive and industrial grade versions, with the automotive-grade models meeting AEC-Q100 Grade 1 reliability requirements and capable of operating in harsh environments ranging from -40°C to 125°C .
Temperature drift is one of the most important parameters of a voltage reference source . It is caused by circuit defects and nonlinearity, and is often nonlinear. The nanochip micro voltage reference source uses the box method to measure and calibrate temperature drift.
In fact, temperature drift calculations only measure the maximum and minimum voltage values at a limited number of temperature measurement points, without considering which temperature points these extreme values occur at. Therefore, for a non-linear temperature drift device, its temperature drift specification cannot be used to indicate that the device's temperature drift specification is better than calibrated over a narrower temperature range.
The NSREF30xx series has a typical temperature drift of 10 ppm/℃ and a maximum of 35 ppm/℃. The NSREF31xx series offers even higher performance, with a typical temperature drift of 5 ppm/℃ and a maximum of 15 ppm/℃ , ensuring high-precision ADC sampling across the entire temperature range. Both series of reference sources also demonstrate excellent performance in other aspects.
Temperature drift performance of NSREF30xx and NSREF31xx
Low noise is another feature of the NSREF30/31xx series. Voltage reference source output voltage noise typically manifests as low-frequency 1/f noise and broadband white noise. In practical applications, broadband noise can be suppressed by compressing the bandwidth; however, low-frequency 1/f noise is difficult to eliminate and is one of the main errors in high-precision measurements.
The NSREF30/31xx employs advanced technology and a dedicated low-noise design, achieving a typical 1/f noise level of only 20μVpp (peak-to-peak) at a 2.5V output voltage, with a relatively convergent noise distribution. Its 1 sigma value is less than 2μVpp, significantly reducing the impact of low-frequency noise on ADC sampling errors. While maintaining low noise, the NSREF30/31xx consumes only 140μA (typical) of current, making it suitable for applications such as industrial field transmitters, power systems, and portable measuring equipment.
The comparison shows that, with similar static power consumption and temperature drift performance, the low-frequency 1/f noise of the NSREF30/31xx series products is far lower than that of mainstream products on the market .
Low-frequency noise performance of NSREF30xx and NSREF31xx
Thanks to its well-designed loop, the NSREF30/31xx can output its operating voltage normally when the input voltage is only 1mV higher than the output voltage (typical value). (NSSREF3012/3112 requires a minimum operating voltage of 1.8V). This makes it very suitable for applications where the power supply (such as battery power) voltage may be reduced.
In addition, the NSREF30/31xx has source current and sink current capabilities (typical ±10mA), and can stabilize the output voltage without connecting an output capacitor. It will not cause the device to malfunction due to the failure or failure of the connected capacitor, and can support a wide range of loop stabilization capacitor values, thus adapting to different application circuits and scenarios and expanding its application range.
In practical applications, periodic calibration is typically required to reduce the impact of long-term voltage reference drift on system accuracy. However, this can lead to reduced productivity and other issues. Therefore, incorporating long-term drift performance metrics is particularly important for the design of precision systems.
Long-term drift refers to the amount of voltage drift of a voltage reference source output voltage over time. Long-term drift of the reference source is mainly caused by mechanical stress and aging. Early drift is primarily introduced by mechanical stress, which typically causes a significant drift in the reference source voltage. Over time, as the packaging, soldering, and chip materials become more stable, the drift amount decreases. It is important to note that the long-term drift specified in the product datasheet refers to the drift of the reference source output voltage in the first 1000 hours, not the drift every 1000 hours.
The NSREF30/31xx series drifts at 35°C for the first 1000 hours (typical) and for the first 2000 hours (typical). For estimating drift over longer periods, the formula LTD(h), which is the square root of the drift normalized to 1000 hours, can be used.
Long-term drift performance of the reference source
Analysis of the impact of reference source performance on ADC acquisition system
Based on the performance metrics described above, taking the NSREF3130 as an example, we analyze the impact of its performance on the ADC acquisition system. System errors are typically calculated using the square root (RSS) method of statistical tolerance analysis. The table summarizes the error terms and magnitudes of the NSREF3130, and the equations show the total error calculated using the square root method, converting the total reference source error to LSBs. This example omits errors such as linear regulation and load regulation. The equations show that for a 12-bit ADC, the NSREF3130 contributes 13 LSBs to the error.
Impact of NSREF3130 on ADC Sampling Accuracy
System calibration eliminates errors introduced by initial accuracy, while improving temperature drift and long-term drift by 80% . Calculations show that the total error introduced by the NSREF3130 in the calibrated system is only 2 LSB .
The impact of NSREF3130 on ADC sampling accuracy after system calibration
Further expand application boundaries
The NSREF30/31xx series of micro voltage reference sources from Naxin Microelectronics has won high recognition and praise from customers for its many advantages, such as high precision, low temperature drift, low noise, and low power consumption.
Thanks to advanced manufacturing processes and unique design concepts, this product series not only achieves high initial accuracy but also surpasses similar products on the market in terms of low temperature drift characteristics , ensuring excellent sampling accuracy across the entire temperature range .
The NSREF30/31xx series voltage reference sources have broad application prospects and can be used in various fields such as photovoltaics, industrial automation, digital power supplies, and charging piles . They provide customers with stable and reliable performance output, helping to achieve more efficient and accurate data acquisition and processing, thereby helping customers further expand their application boundaries and explore more possibilities.
