Discovery QDR Series Technical Manual
2-21
2.10.3 Analog To Digital Board
The Analog to Digital (ADC) subsection of the Detector Assembly converts analog
signals received from the Integrator/Multiplexor subsection to a digital format.
Analog signals from the Integrator/Multiplexor subsection are applied to differential
amplifiers on the ADC subsection. Outputs from the differential amplifiers are combined
in a final multiplexor consisting of four analog switches. The multiplexed signals pass
through a programmable gain amplifier and summing amplifier before being applied to an
A/D converter. A one-volt fixed DC offset is inserted at the summing amplifier to insure
that no channels ever go negative. The A/D converter converts the analog signal into 16
bit parallel data for processing by a Digital Signal Processor.
The ADC subsection uses a Motorola 56000 Digital Signal processor to generate all the
control signals necessary for the Detector Assembly. This processor also provides a high-
speed serial data link to the computer.
2.10.4 Power
The 128-Channel Detector Assembly receives +/-15V and +5V from the C-Arm Interface
Board. The +/-15V is passed through this board to the Detector subsection. It is also
regulated to +/- 12V by series regulators to power operational amplifiers and analog
switches located on this board. The +/- 15V is also used to generate +/- 5V to power the
analog-to-digital converter circuit. The +7V is reduced to +5V to power the digital section
of this board.
2.10.5 Interface Connections
Figure 2-9 shows the interconnections between the 128-Channel Detector Assembly and
the C-Arm Interface Board. Table 2-13 describes the interface signals and identifies the
connectors and their pin assignments.
STD+, STD-
STCLK+, STCLK-
STFRM+, STFRM-
SRD+, SRD-
SRCLK+, SRCLK-
SRFRM+, SRFRM-
SYSRST_DAS+, SYSRST_DAS-
INTEGRATE+, INTEGRATE-
XR_ZEROX_DAS+, XR_ZEROX_DAS-
+15V
15V_RET
-15V
+7V
Detector
Assembly
C-ARM INTERFACE
BOARD
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