ZHCSHN9A February 2018 – April 2018 LMK05028
PRODUCTION DATA.
If some VDD core supplies are driven from different supply rails, TI recommends starting the PLL calibration after all of the core supplies have settled at 3.135 V. This can be realized by delaying the PDN low-to-high transition. The PDN input incorporates a 200-kΩ resistor to VDD_DIG and as shown in Figure 66, a capacitor from the PDN pin to GND can be used to form an R-C time constant with the internal pullup resistor. This R-C time constant can be designed to delay the low-to-high transition of PDN until all the core supplies have settled at 3.135 V. Alternatively, the PDN pin can be driven high by a system host or power management device to delay the device power-up sequence until all VDD supplies have ramped.