Octal, simultaneous sampling, true 18-bits ADC

June 10, 2015 // By Graham Prophet
LTC2348-18 is an 18-bit, 8-channel simultaneous sampling successive approximation register (SAR) ADC combining performance and flexibility.

While converting eight channels at 200 ksamples/sec per channel throughput, each SoftSpan input can be independently configured on a conversion-by-conversion basis to accept ±10.24V, 0V to 10.24V, ±5.12V, or 0V to 5.12V signals. The differential analogue inputs operate over a 34V input common mode range, allowing the ADC to directly digitise a variety of signals to simplify the signal-chain design. The input signal flexibility, combined with ±3LSB maximum INL, no missing codes at 18 bits, and 96.7 dB SNR, suits the LTC2348-18 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 5V reference can be used to expand the analogue input range to ±12.5V. The device dissipates 140 mW when converting eight channels simultaneously at 200 ksamples/sec per channel, and features nap and power-down modes to reduce power dissipation at slower throughputs.

In addition to its analogue characteristics, 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 1.8V and 5V. In CMOS mode, applications can employ between one and eight lanes of serial output data, enabling the user to optimise bus width and data throughput. LVDS mode offers low noise, high speed communications over greater distances using differential signalling. 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 comes in a 48-lead, 7 x 7 mm LQFP package, priced starting at $23.35 (1,000).

Linear Technology; www.linear.com/product/LTC2348-18