SBAU171D May 2010 – January 2016 ADS1198 , ADS1298
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 Table 10.
Internal Reference | External Reference | ||
---|---|---|---|
ADS1298 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 VREF value from the Reference Voltage control (CONFIG3 register) in Section 3.4.2.1) 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.