WFD20 - 20 bit / 2 Msps Waveform digitizer

WFD20

  • 2 MHz max sample speed
  • 20 bit resolution
  • Fully differential input
  • 8 input ranges
  • Selectable filters to reduce out-of-band noise
  • -119dB THD typical (f-in=1kHz)
  • 96dB SNR typical (DC-800kHz)
  • Programmable DC-offset voltage
  • For ATX series hardware platform

The WFD20 is a 20 bit Waveform Digitizer for medium-speed / high resolution waveform capturing and analyzing. The module combines an excellent dynamic performance with a very high DC accuracy.

The module features a fully differential input path to reduce common-mode level disturbances. If the internal DC-offset voltage source is used, the negative input can still be used as a GND Sense input, so the DC performance won’t be compromised due to ground currents.

The module has 8 input ranges from 0.544Vpp to 8.16Vpp, which allows easy adaptation to a wide range of Unit Under Test output voltages.

A filter-bank with 3 Low Pass filters (40kHz, 250kHz and 800kHz) provide excellent signal conditioning to obtain the best result in dynamic performance: low noise and anti-aliasing.

The special combination of four 18 bit ADCs to a 20 bit converter gives an excellent SNR and linearity and a resolution down to 0.52µV. With 4M-word (12M-byte) of memory a large number of samples can be captured.

All these features ensure a very accurate result when performing analog measurements. The unit is very suitable for testing DAC linearity and dynamic performance.

fft_1kHz_wfd20

DC to 20kHz spectrum, 1KHz carrier, 800kHz filter-on

WFD20_Block_diagram

conditions: after 1 hour warm-up, TA=25ºC, filter bypass unless otherwise mentioned

General

Resolution 20 bit
Sample rate 1.5kHz - 2MHz in warp mode, 0 - 1.5MHz in normal mode
Pattern depth 4M words

Input characteristics

Input impedance 100MOhm
Input ranges 0.544Vpp, 0.816Vpp, 1.36Vpp, 2.04Vpp, 2.72Vpp, 4.08Vpp, 5.44Vpp, 8.16Vpp
Input filters Bypass, 40kHz (4-pole Butterw.), 250kHz (5-pole Butterworth), 800kHz (7-pole elliptic)
Bandwidth -3dB (typical) 2MHz (8.16Vpp range)
0.1dB flatness (typical) 400kHz (8.16Vpp range)
Input configuration Differential / Single Ended (-Input to Gnd, Gnd-sense or DC offset)
Input Common mode range +/- 10V

Accuracy (DC-offset off, filter bypass)

Absolute accuracy ±(40µV + 10ppm of range)
Non Linearity error ±8ppm of range (3ppm typical)
Temperature drift (typical) ±(1ppm of range + 2ppm of reading)/ºC

DC-offset source

Resolution 19-bit (20µV)
Voltage range -5V to +5V
DC-offset accuracy ±(50µV + 12ppm of value)
Non Linearity ±10ppm of range

Dynamic characteristics

(conditions: 1.67Msps, 800kHz filter on)

SNR (5Vpp, 1kHz input) 93dB
SNR (5Vpp, 10kHz input) 92dB
SNR (5Vpp, 100kHz input) 91dB
SNR (1kHz input, A-weighted) 105dB (BW 20Hz - 20kHz)
THD (2Vpp, 1kHz input) -110dB
THD (2Vpp, 10kHz input) -106dB
THD (2Vpp, 100kHz input) -92dB
SFDR (2Vpp, 1kHz input) 108 dB

Clock & Trigger inputs

Input impedance > 1MOhm
Threshold level 3.3V CMOS/TTL (5V tolerant)