Sundance SMT943 - Manual (Page 9)

User Manual SMT943 Page 9 of 54 Last Edited: 23/08/2011 17:24:00
Some green LEDs are available on the board. A group of four LEDs is driven directly
from the SLB base FPGA module and can be used to return status bits. Other
indivudual LEDs should be lit and show that local power supplies are on.
3.2.1 A/D converters
The main characteristics of the SMT943 are gathered into the following table.
Analogue Inputs
Input voltage range
0dB gain setting : 2.3Vpp - Full scale - AC
coupled
6dB gain setting : 1.15Vpp – Full Scale –
AC-coupled
Programmable input gain via register
(0…6dBs) by steps of 0.5dB (coarse gain)
and steps of 0.134dB (fine gain).
Impedance
Single-ended inputs – to be connected to a
50

source.
Bandwidth Tbd – depends on ADC internal input gain.
ADC characteristics
Output Data Width per channel 14 Bits
Data Format
2’s Compliment or offset binary
(Changeable via control register)
SFDR
75 (0-db gain) / 82dBs (6-db gain)
maximum (manufacturer)
SNR
69 (0-db gain) / 66dBs (6-db gain)
maximum (manufacturer)
ENOB 11.3 bits maximum (manufacturer)
Maximum Sampling rate
250 MSPS
(1…100MSPS low speed mode)
(100…250MSPS high speed mode)
Minimum Sampling rate 1 MSPS
ADC Analog inputs on the board are single-ended. A double RF transformer
structure is used to provide single-ended to differential conversion. Both
transformers are identical and have a ratio of 1. In order to match the 50-Ohm at
the connector, the output of the second transformer has two 25-Ohm resistors
terminated to the ADC common mode voltage.
Below are some captures. All of them are 2048 points. ADCs are sampling at
245.76MHz and have an input gain of 6dBs: