May 29, 2013 – Linear Technology Korea (CEO Hong Sa-kwak) announced the release of the LTC2378-20, a 20-bit, 1 Msps, no-latency SAR (successive approximation register) analog-to-digital converter (ADC). This product provides very low Integral Non-Linearity (INL) errors of 0.5 ppm (typ) and 2 ppm (max). INL is a critical specification in precision applications such as seismic monitoring and semiconductor processing, indicating how much the ADC transmission function deviates from ideal conditions. Since linearity cannot be effectively corrected at the system level, the ADC's INL specification sets the overall system accuracy. With the best-in-class 0.5 ppm INL of the LTC2378-20, it enables a new dimension of precision systems with 20-bit precision. The proprietary architecture provides very stable 2 ppm (max) INL and -114 dB THD (max) results across the entire device operating temperature range of -40°C to 85°C.

The LTC2378-20 is a 1 Msps ADC with zero latency that achieves the industry's highest signal-to-noise ratio (SNR) of 104 dB. Its wide dynamic range and true 20-bit resolution reduce or eliminate the need for additional gain in the signal chain. This improves overall system accuracy and noise. High-speed processing speeds of 1 Msps with no latency can be achieved by using multiplexers, which can replace slow, expensive, and independent ADCs. Consequently, system costs and complexity are reduced.

The LTC2378-20 is the latest addition to the pin-compatible and software-compatible 20/18/16-bit SAR ADC family, featuring a serial SPI interface and a speed range from 250 ksps to a maximum of 2 msps. 20-bit 250 ksps (LTC2376-20) and 500 ksps (LTC2377-20) versions are scheduled for release in May. The family operates on a 2.5V power supply and provides a ±5V fully differential input range using an external 5V reference. At 1 msps, the device achieves a low power consumption of 21 mW, which measures linearity at the sample rate. Shutdown mode reduces power consumption to 2.5 μW when not in operation. The LTC2378-20 family features proprietary digital gain compression (DGC) capabilities, eliminating the need for a negative (-) ADC drive power supply while preserving the full resolution of the ADC. Therefore, the total power consumption of the signal chain can be reduced without significantly degrading SNR performance.

The DC1925A evaluation kit demonstrates the 0.5 ppm INL and 104 dB SNR performance of the LTC2378-20. The board provides flexible LT6203 ADC driver features and 5V LTC6655-5 precision, low-noise, low-power reference features to interface differential or single-ended input signals. For full low-power signal chain solutions using digital gain compression, Linear recommends the LTC6362 fully differential driver operating on a single 5V supply (1mA). This product achieves a maximum SNR of 100dB when used with the LTC2378-20 and the 4.096V LTC6655-4.096 reference.

LTC2378-20, LTC2377-20, and LTC2376-20 are available in small MSOP-16 and 4mm x 3mm DFN-16 packages and are priced at $29.50, $25.50, and $18.17 per unit, respectively, based on a quantity of 1,000. For detailed information, refer to www.linear.com/product/LTC2378-20 .

Photo Caption: 20-bit zero-latency serial SAR ADC providing 1 Msps processing speed & 0.5 ppm INL

LTC2378-20 Product Features

 1Msps processing speed
 ±0.5ppm INL (Typ), ±2ppm INL (Max)
 20-bit No Lost Code Guarantee
 Low power: 21mW at 1msps, 21μW at 1ksps
 104dB SNR at fIN = 2kHz (Typ)
–125dB THD (Typ) at fIN = 2kHz
DGC(Digital Gain Compression)
 85°C operation guaranteed
 2.5V power supply
 Differential search input range ±VREF
 VREF Input Range: 2.5V ~ 5.1V
 No pipeline delay, no cycle delay
 1.8V ~ 5V I/O voltage
 SPI-compatible continuous with daisy-chain mode capability
 Internal conversion clock
 16-pin MSOP & 4mm × 3mm DFN package