SBAS813 June 2018 ADS8688AT
PRODUCTION DATA.
The device supports a hardware and software power-down mode (PWR_DN) in which all internal circuitry is powered down, including the internal reference and buffer. A minimum time of 15 ms is required for the device to power up and convert the selected analog input channel after exiting PWR_DN mode, if the device is operating in the internal reference mode (REFSEL = 0). The hardware power-down mode for the device is explained in the RST/PD (Input) section. The primary difference between the hardware and software power-down modes is that the program registers are reset to default values when the devices wake up from hardware power-down, but the previous settings of the program registers are retained when the devices wake up from software power-down.
To enter PWR_DN mode using software, execute a valid write operation as depicted in Figure 94 on the command register with a software PWR_DN command of 8300h. The command is executed and the device enters PWR_DN mode on the next CS rising edge following this write operation. The device remains in PWR_DN mode if no valid conversion command (AUTO_RST or MAN_Ch_n) is executed and SDI remains low (see the Continued Operation in the Selected Mode (NO_OP) section) during the subsequent data frames. When the device operates in PWR_DN mode, the program register settings can be updated (as explained in the Program Register Read/Write Operation section) using 16 SCLK cycles. However, if 32 complete SCLK cycles are provided, then the device returns invalid data on the SDO line because there is no ongoing conversion in PWR_DN mode. The program register read operation can take place normally during this mode.
In order to exit from PWR_DN mode, as shown in Figure 95, a valid 16-bit write command must be executed. The device comes out of PWR_DN mode on the next CS rising edge. For operation in internal reference mode (REFSEL = 0), 15 ms are required for the device to power-up the reference and other internal circuits and settle to the required accuracy before valid conversion data are output for the selected input channel.