Octal simultaneous sampling ADC achieves true 18-bit performance
Linear Technology has introduced the LTC2348-18, an 18-bit, 8-channel simultaneous sampling successive-approximation-register (SAR) ADC. While converting eight channels at 200 kS/s per channel throughput, each SoftSpan input can be independently configured on a conversion-by-conversion basis to accept ±10.24-V, 0- to 10.24-V, ±5.12-V, or 0- to 5.12-V signals. The differential analog inputs operate over a 34-V input common-mode range, allowing the ADC to directly digitize a variety of signals to simplify the signal-chain design. The input signal flexibility, combined with ±3-LSB maximum INL, no missing codes at 18 bits, and 96.7-dB SNR, makes the LTC2348-18 suitable for high-performance industrial-process-control, test-and-measurement, power-line-monitoring, instrumentation, and automatic-test-equipment applications.
The LTC2348-18 features a precision internal reference with 20-ppm/°C maximum temperature coefficient and an integrated reference buffer capable of accurate one-shot measurements, providing space savings in densely packed circuit boards. Optionally, an external 5-V reference can be used to expand the analog input range to ±12.5 V. The device dissipates 140mW when converting eight channels simultaneously at 200 kS/s per channel, and features nap and power-down modes to reduce power dissipation at slower throughputs.
In addition to its analog characteristics, the LTC2348-18 offers digital flexibility, featuring pin-selectable SPI CMOS and LVDS serial interfaces. The wide digital output supply range allows the device to communicate with any CMOS logic between 1.8 V and 5 V. In CMOS mode, applications can employ between one and eight lanes of serial output data, enabling the user to optimize bus width and data throughput. LVDS mode offers low-noise, high-speed communications over greater distances using differential signaling. Together, these I/O interface options allow the LTC2348-18 to communicate equally well with legacy microcontrollers and modern FPGAs.
The LTC2348-18 is the first in a family of multichannel 18-/16-bit simultaneous sampling SAR ADCs. All specifications are guaranteed over the extended -40°C to 125°C temperature range. The LTC2348-18 is available now in a 48-lead, 7-mm x 7-mm LQFP package, priced starting at $23.35 each in 1,000-piece quantities. Samples and demo boards may be requested.
About the Author
Rick Nelson
Contributing Editor
Rick is currently Contributing Technical Editor. He was Executive Editor for EE in 2011-2018. Previously he served on several publications, including EDN and Vision Systems Design, and has received awards for signed editorials from the American Society of Business Publication Editors. He began as a design engineer at General Electric and Litton Industries and earned a BSEE degree from Penn State.