CAEN
Electronic Instrumentation
UM3148
–
DT5730/DT5725 User Manual rev. 2
19
9
Functional Description
Analog Input Stage
Input dynamics can be 2 V
pp
(default) or 0.5 V
pp
, by software selection (basing on the Programmable Gain Amplifier in
the scheme of
Fig. 9.1
), on single ended MCX coaxial connectors (see §
8
). A 16-bit DAC allows to add a DC offset in
order to preserve the full dynamic range also in the extreme case of unipolar positive or negative input signal. The
input bandwidth ranges from DC to 250 MHz (@3dB) for DT5730, to 125 MHz (@3dB) for DT5725, by 2
nd
order linear
phase anti-aliasing low-pass filter.
+1.00
0
+2.00
-1.00
-2.00
Input Dynamic Range: 2 Vpp
Positive Unipolar
DAC = FSR
Negative Unipolar
DAC = 0
Bipolar
DAC = FSR/2
+0.25
0
-0.50
-0.25
-0.50
Input Dynamic Range: 0.5 Vpp
Positive Unipolar
DAC = FSR
Negative Unipolar
DAC = 0
Bipolar
DAC = FSR/2
MCX
OpAmp
5
0
o
h
m
DAC
Vref
14 bit
ADC
Input
FPGA
16 bit
+
-
DC Offset
PGA
G1 or G4
Fig. 9.1:
Analog Input Diagram
Setting the input range requires a write access at register address 0x1n28, while at register address 0x1n98 it is
possible to configure the DC offset level.