ADS1298R Daughter Card Hardware Details
49
SBAU181B – March 2011 – Revised Janurary 2016
Copyright © 2011–2016, Texas Instruments Incorporated
ADS1298R
Table 8. Digital Supply Configurations (DVDD/DGND)
DVDD
+3.0V
+1.8V
JP24
1-2
2-3
6.3
Clock
The ADS1298R has an on-chip oscillator circuit that generates a 2.048MHz clock (nominal). This clock
can vary by ±2% over temperature. For applications that require higher accuracy, the ADS1298R can also
accept an external clock signal. The ADS1298R provides an option to test both internal and external clock
configurations. It also provides an option to generate the external clock from either the onboard oscillator
or from an external clock source.
The onboard oscillator is powered by the DVDD supply of the ADS1298R. Care must be taken to ensure
that the external oscillator can operate either with +1.8V or +3.0V, depending on the DVDD supply
configuration.
shows the jumper settings for the three options for the ADS1298R clocks.
Table 9. CLK Jumper Options
ADS1298R Clock
Internal Clock
External OSC Clock
External Clock
JP18
Not Installed
2-3
1-2
JP23
Open or 2-3
1-2 (Disable)
Don't Care
J3 – pin 17
Don't Care
Don't Care
Clock Source
A 2.048MHz oscillator installed on the EVM for +3V DVDD operation is FXO-HC735-2.048MHz. If
operation at +1.8V DVDD is desired, the oscillator will need to be replaced. SiT8002AC-34-18E-2.048 is a
possible oscillator for +1.8V DVDD operation. The EVM is shipped with the external oscillator enabled.
6.4
Reference
The ADS1298R has an on-chip internal reference circuit that provides reference voltages to the device.
Alternatively, the internal reference can be powered down and VREFP can be applied externally. This
configuration is achieved with the external reference generators (U3 and U4) and driver buffer. The
external reference voltage can be set to either 4.096V or 2.5V, depending on the analog supply voltage.
Measure TP3 to make sure the external reference is correct. The setting for the external reference is
described in
.
Table 10. External Reference Jumper Options
Internal Reference
External Reference
ADS1298R Reference
VREF = 2.5V
VREFP = 4.096V
VREFP = 2.5V
JP25
Don't Care
2-3
1-2
JP3
Not Installed
Installed
Installed
The software uses the V
REF
value from the
Reference Voltage
control (
CONFIG3
register) in
) to calculate the input-referred voltage value for all the tests. The default value is 2.5V. If
the user is using an alternative value, the control must be updated to display the collected data to the
proper scale.
6.5
Analog Output Signals
Several output signals from the ADS1298R are provided on the J5 header.
lists the various test
signals and their location on the header. The PACEOUT pins can also be used as an auxiliary differential
input channel. Alternatively with appropriate user configuration, these pins may provide PACE detection
for use with external PACE detection circuitry (see PACE Detect Register in
