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ADS1298ECG-FE/ADS1198ECG-FE Hardware Details
38
SBAU171D – May 2010 – Revised January 2016
Copyright © 2010–2016, Texas Instruments Incorporated
ADS1298ECG-FE/ADS1198ECG-FE
Table 7. Analog Supply Configurations (AVDD/AVSS)
Unipolar Analog Supply
Bipolar Analog Supply
AVDD/AVSS
3V
5V
±1.5V
±2.5V
JP20
1-2
1-2
2-3
2-3
JP2
2-3
2-3
1-2
1-2
U7
Don't Care
Don't Care
U9
Don't Care
Don't Care
U8
Don't Care
Don't Care
R52
Don't Care
Don't Care
21k
Ω
47.5k
Ω
R53
Don't Care
Don't Care
78.7k
Ω
43k
Ω
R56
Don't Care
Don't Care
23.3k
Ω
49.9k
Ω
R57
Don't Care
Don't Care
95.3k
Ω
46.4k
Ω
C87, C67, C62
Not Installed
Not Installed
Not Installed
Not Installed
Table 8. Digital Supply Configurations (DVDD/DGND)
DVDD
+3.0V
+1.8V
JP24
1-2
2-3
5.3
Clock
The ADS1298 has an on-chip oscillator circuit that generates a 2.048MHz clock (nominal). This clock can
vary by ±5% over temperature. For applications that require higher accuracy, the ADS1298 also accepts
an external clock signal. The ADS1298ECG-FE provides an option to test both internal and external clock
configurations. For the external signal, circuitry is available to generate the external clock from an on-
board oscillator or from an externally connected source.
The external oscillator included on the EVM is powered from DVDD, the same supply as the ADS1298.
Care must be taken to ensure that the externally supplied clock 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 ADS1298 clocks.
Table 9. CLK Jumper Options
ADS1298 Clock
Internal Clock
External OSC Clock
External Clock
JP18
Not Installed
2-3
1-2
JP19
Don't Care
1-2 (Disable)
Don't Care
2-3 (Enable)
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.
5.4
Reference
The ADS1298 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.
NOTE:
U3,
U4, and driver buffer are not installed. The externally provided 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 settings for the external reference is described in