Modulator Clock
1-4
Table 1−2. Selection Between Internal/External Reference
Reference Designator
Voltage Reference Selection
SW1 8−9
Internal
External
0
Not selected
Selected
1
Selected
Not selected
To use the external reference voltage, the user must apply an input voltage via
J7; the voltage supplied must be between 8 V and 40 V.
The external reference voltage is generated differentially and can be adjusted
by three potentiometers, detailed in Table 1−3.
Table 1−3. External Reference
Reference Designator
Function
RV2
Adjusts main +5 V
RV1
Adjusts REF+ voltage
RV3
Adjusts REF− voltage
Figure 1−3 shows a block diagram of the configuration.
Figure 1−3. Block Diagram
Gain = 1
Gain = 1
Gain = 1
Gain = 1
5 V
Reference
8 V − 40 V
REF+
V
MID
=
(REF+) + (REF−)
2
REF−
V
CM
To ADC
To Analog Input
1.6
Modulator Clock
The ADS1605 and ADS1606 partition the modulator clock as part of the analog
section. There are two options available. The clock may either be supplied via
the on-board 40-MHz oscillator, or externally via J5. This option is useful for
low-jitter coherent sampling during testing.
Table 1−4. Modulator Clock Options
Reference
Factory Set Condition
Reference
Designator
Description
1−2
Clock
.
40 MHz
2−3
Clock
.
J5
W7
Modulator Clock Source
Installed
Not installed
