After power-up, the internal registers must be initialized to their default values through a hardware reset by applying a high pulse on the RESET pin, as shown in Figure 9-6.
Apply AVDD and IOVDD (no specific sequence required). After AVDD is applied the internal bandgap reference will power up and settle out in ~ 2ms.
Configure REFBUF pin (pull high or low even if configured via SPI later on) and apply the sampling clock.
Apply hardware reset. After hardware reset is released, the default registers
are loaded from internal fuses and the internal power up capacitor calibration is
initiated. The calibration takes approximately 200000 clock cycles.
Begin programming using SPI interface.
Figure 9-6 Initialization of serial registers after power
Table 9-5 Power-up timing
Power-on delay: delay from power up to logic level of REFBUF pin
Delay from REFBUF pin logic level to RESET rising edge