POWER AND LINEAR IC SOLUTIONS

Ultra-Tiny 16-Bit ADCs Improve Resolution and Performance in Embedded Applications

Analogue/Digital Converters (ADCs) play a vital role in determining system performance in portable and space-constrained designs. However, the ADCs that are embedded into microcontrollers can present designers with a problem: key DC specifications such as linearity, offset error and noise are often not guaranteed, not tested, or not even listed, making it extremely difficult to assess how good real system performance will be.

Once in the lab, getting good ADC performance can be equally tough. A 16-bit embedded ADC may behave much more like a 10-bit or 12-bit ADC, not least because the ground and negative reference supplies for the converter typically come from the same noisy substrate used for the rest of the microcontroller. As these microcontrollers are not optimised for analogue functions, being built using digitally optimised processes, the ADC is often an afterthought. Within the microcontroller, there is no optimal routing for good ADC performance. Unfortunately, the ADC and the rest of the circuitry share a common silicon substrate.

A new ADC family from Linear Technology solves many of these problems. The 16-bit LTC2450 is available in a 2mm x 2mm DFN package, making it possible to replace a microcontroller’s embedded ADC with very little board space penalty. The device is engineered for excellent DC performance, so designers no longer have to choose between small space, high performance and low cost. Its linearity, offset error and gain error are all tested and guaranteed over the full industrial temperature range.



In the illustration, the map pin points to the LTC2450 ADC on the 2.8cm square demonstration board.

The LTC2450’s 4mm² size makes it possible to take an accurate ADC measurement for values such as temperature, current, voltage, or airflow without displacing surrounding circuitry. This facility is particularly useful in high-density applications such as optical networking cards, data acquisition units and servers. Its delta sigma core offers 16-bit no missing codes performance. Integral NonLinearity error (INL) is typically 2 LSBs (maximum of 10 LSBs) and gain error a maximum of 0.02%. Both specifications are guaranteed over the full industrial (-40°C to +85°C) temperature range.

At just 2.8cm x 2.8cm, the DC1067A demo board also includes an LT6660 reference/power supply. Subject to certain eligibility criteria, Linear Technology Corporation and Arrow Northern Europe can provide complimentary LTC2450 demonstration boards to Arrow Innovation readers who enquire via the link below.

Features

• 16-bit delta-sigma ADC
• Ultra-tiny 2mm x 2mm DFN package
• Single-ended rail-to-rail input
• 0.02 LSB RMS noise
• 2 LSB INL with no missing codes
• 2 LSB offset error
• 4 LSB full-scale error
• Single conversion settling time for multiplexed applications
• Single cycle operation with auto shutdown
• Low power: 350µA supply, 50nA sleep current
• 30 conversions per second
• Internal oscillator
• Single supply operation
• SPI interface

Applications

• Optical networking cards
• Data acquisition units
• Servers
• Space-constrained designs

For further information, including a copy of the LTC2450 Quick Start Guide, or to enquire about obtaining a Demo Board, please click here