Data acquisition
rate, reduces noise and enables oversampling to achieve exceptionally low rms noise and detection of small amplitude signals over a wide bandwidth. In other words, a 15MSPS sample rate greatly relaxes antialiasing filter requirements and maximises bandwidth when digitising fast transients and small signal levels. Oversampling refers to sampling much faster than twice the signal bandwidth required to meet the Nyquist criterion. For instance, oversampling the ADAQ23875 by a factor of four provides one additional bit of resolution or a 6dB increase in dynamic range - in other words, the DR improvement due to this oversampling is defined
as: ΔDR = 10 × log10 (OSR) in dB. The ADAQ23875 typical dynamic range is 91dB at 15MSPS for a 4.096V reference with its inputs shorted to ground. For example, when the ADAQ23875 is oversampled by a factor of 256×, this corresponds to a signal bandwidth of 29.297kHz and a dynamic range close to 111dB for the different gain options, which can precisely
detect small amplitude µV signals. Additional oversampling can be applied to trade off between noise and bandwidth to suit the measurement being performed.
performance comparison for two signal chains when the PGIA drives the ADAQ23875 vs. when the combination of the LTC6373 and ADA945-1 drives the LTC2387-16 at 15MSPS.
Integral Nonlinearity (INL) and
Figure 13. A DNL plot for the PGIA (G = 2) driving the ADAQ23875.
Figure 11. THD signal chain performance comparison for the PGIA driving the ADAQ23875 and the LTC6373 + ADA4945-1 + LTC2387-16.
Differential Nonlinearity (DNL) When the PGIA drives the ADAQ23875, it is also important that the overall DC accuracy of the signal chain is maintained. Figure 12 and Figure 13 show the typical INL and DNL performance with a PGIA gain of 2. For all other gain settings, INL and DNL stay within typically ±0.5LSB.
CONCLUSION This article features the design aspects of a discrete wide bandwidth PGIA built using the ADA4898-1 amplifiers, the ADG1209 multiplexer, and the LT5400 precision matched resistors. It showcases the high accuracy measurements of tens of millivolts to sub-10volts single- ended/differential signals feeding into the 16-bit,
15MSPS ADAQ23875 signal chain µModule solution. A complete signal chain offers an overall better precision performance than what can be achieved using the monolithic PGIAs available in the market. This wide bandwidth signal chain is tailored for a specific set of customers building test instruments used in automated test equipment, power supply monitoring, and analysers.
Analog Devices
www.analog.com
Figure 9. SNR vs. frequency with the PGIA driving the ADAQ23875.
Distortion
Figure 10 and Figure 11 show the THD performance of the signal chain (up to 100kHz and from 100kHz up to 1MHz) when the ADAQ23875 is driven by the discrete PGIA. The THD gradually degrades as the PGIA gain and input signal frequency are increased since the bandwidth and slew rate of the ADA4898-1 start to deteriorate. Figure 11 also shows a THD
Figure 12. An INL plot for the PGIA (G = 2) driving the ADAQ23875.
ANALOG DEVICES AND AUO TEAM UP ON DISPLAYS A
Figure 10. THD vs. frequency with the PGIA driving the ADAQ23875.
44
UO will use ADI’s matrix LED display driver technology in their market- leading automotive widescreen display
portfolio. This industry-first technology enables local dimming, significantly improving power consumption by a minimum of 50 per cent and supporting functional safety requirements. “To help us maintain our leadership position in the market as one of the world’s top automotive display manufacturers catering to some of the largest OEMs, ADI’s local dimming automotive display drivers deliver the power efficiency consistent with the quality standard of the AUO brand,” says Simon Hsu, head of Automotive Business Unit at AUO. “AUO AmLED displays feature power savings, excellent sunlight readability and high
contrast ratio, which greatly upgrade driving safety and in-cabin entertainment experience. In response to the trend of smart mobility, AUO continues to advance display technology, and we look forward to further collaborations with the ADI team.” Patrick Morgan, corporate vice president of Automotive Electrification and Sustainable Energy at Analog Devices, adds: “Through this collaboration, our technology and leadership for high performance automotive power enables bringing the next wave of widescreen displays into the market with significantly improved power consumption and full functional safety capabilities.”
Analog Devices
www.analog.com November 2022 Instrumentation Monthly
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