TXMC638 User Manual Issue 1.0.2
Page 47 of 86
Serial ADC Interface
7.9
7.9.1 Overview
The 24 analog inputs of the TXMC638 are realized with 12 LTC2323-16 ADC devices. Each of these SAR-
ADCs has two ADC channels. Thus, a total of 24 ADC channels are available on the TXMC638.
A coarse overview over the analog input section of the TXMC638 is shown by the following figure:
Figure 7-6 : Analog Input Section
The key-features of the LTC2323-16 are:
x
Dual Channel - SAR-ADC
x
16 bit resolution
x
5Msps Throughput Rate for each Channel
x
LVDS SPI-Compatible Serial Interface to User FPGA (Kintex-7)
In order to adapt the LTC2323-16 to a ±2.5V input voltage on each input-pin (±5V differential voltage range)
and also the wide common mode voltage range of ±7.5 V two stage input operational amplifiers for input
impedance conversion and gain adaption are needed in addition to the ADC.
The following figure shows the structure and principle of two ADC inputs. Both are connected via impedance
converter and level adjustment to the LTC2313-16 dual ADC.
Figure 7-7 : Analog Input Block Diagram
Fr
ont I/O
Fr
ont I/O
24 x ADC
Input
24 x ADC
Input
FPGA
Kintex-7
FPGA
Kintex-7
2.5V LVDS
Diff.analog
Fr
ont I/O
Front I/O
Impedance
Converter
Impedance
Converter
Impedance
Converter
Impedance
Converter
Divider
and
Filter
Divider
and
Filter
Divider
and
Filter
Divider
and
Filter
Differential
ADC
LTC2323-16
Differential
ADC
LTC2323-16
FPGA
Kintex-7
FPGA
Kintex-7
2.5V LVDS
Channel 1
Channel 2
