SBAS745B December 2015 – January 2023 ADS54J66
PRODUCTION DATA
The ADS54J66 provides a fast overrange indication (FOVR) that can be presented in the digital output data stream via SPI configuration. When the FOVR indication is embedded in the output data stream, it replaces the LSB (normal 0) of the 16 bit going to the 8b/10b encoder as shown in Figure 7-18.
The fast OVR is triggered if the input voltage exceeds the programmable overrange threshold and it gets presented after just 44 input clock cycles enabling a quicker reaction to an overrange event.
The input voltage level at which the overload is detected is referred to as the threshold. It is programmable using the FOVR THRESHOLD bits.
These register bits set the OVR threshold for all channels.
The input voltage level that fast OVR is triggered is:
Full-scale × [the decimal value of the FOVR threshold bits] / 255)
The default threshold is E3h (227), corresponding to a threshold of –1 dBFS.
In terms of full-scale input, the fast OVR threshold can be calculated as shown in Equation 1:
Table 7-8 is an example register write to set the FOVR threshold for all four channels.
ADDRESS | DATA | COMMENT |
---|---|---|
11h | 80h | Go to master page |
59h | 20h | Set the ALWAYS WRITE 1 bit. This bit configures the OVR signal as fast OVR. |
11h | 0Fh | Go to ADC page |
5Fh | FFh | Set FOVR threshold for all channels to 255 |
4004h | 68h | Go to main digital page of the JESD bank |
4003h | 00h | |
60ABh | 01h | Enable bit D0 overwrite |
70ABh | 01h | |
60ADh | 03h | Select FOVR to replace bit D0 |
70ADh | 03h | |
6000h | 01h | Pulse the IL RESET register bit. Register writes in main digital page take effect when the IL RESET register bit is pulsed. |
7000h | 01h | |
6000h | 00h | |
7000h | 00h |