Pseudo-differential serial SAR ADC achieves 96.5-dB SNR

November 08, 2011 // By Paul Buckley
Linear Technology has introduced the LTC2369-18, a serial 18-bit, 1.6 Msps pseudo-differential SAR analog-to-digital converter, which achieves 96.5 dB SNR and -120 dB THD while supporting a 0 V to 5 V unipolar input range. The pseudo-differential input simplifies the ADC driver requirement, enabling single-ended drive while benefiting from the reduction of unwanted signals common to both inputs.

The input reduces complexity and lowers the power requirements in the signal chain. Operating from a 2.5 V supply, the LTC2369-18 consumes 18 mW, with a low power shutdown mode that consumes 2.25 µW. When used in combination with the recommended single-ended ADC driver LT6202, the combined power dissipation is 53 mW, a 40% reduction from a fully differential drive circuit. The LTC2369-18 claims to be the industry’s highest performing 18-bit pseudo-differential SAR ADC, featuring a maximum INL of ±2.5 LSB with no missing codes and guaranteed specifications over the -40 to 125°C temperature range.

Complementing the LTC2369-18 is the pin- and software-compatible 16-bit, 2 Msps LTC2370-16. The LTC2370-16 achieves outstanding 94 dB SNR and ±0.85 LSB maximum INL. The LTC2369-18 and LTC2370-16 are the first in a family of 18-/16-bit high performance pseudo-differential SAR ADCs with speeds ranging from 250 ksps to 2 Msps. They offer a user-friendly SPI interface, explicit Busy and Chain pins, I/O voltages from 1.8 V to 5 V and an internal oscillator that simplifies digital timing and minimizes external component count. Their true no-latency operation enables accurate one-shot measurements even after lengthy idle periods with no minimum sample rate required.

The LTC2369-18 family of 18-/16-bit pseudo-differential SAR ADCs broadens the LTC2379-18 family of up to 102 dB SNR, fully differential SAR ADCs introduced earlier in 2011. Linear’s complete portfolio of high performance pseudo and fully differential 18-/16-bit SAR ADCs with high SNR, fast throughput and low power dissipation is ideal for high performance medical, industrial and automotive applications.

The LTC2369-18 and LTC2370-16 are available in small 16-lead MSOP and 4 mm x 3 mm DFN packages.

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