SNIU028D February 2016 – September 2020 UCD3138 , UCD3138064 , UCD3138064A , UCD3138128 , UCD3138A , UCD3138A64
For all programs, the HFO_LN_Filter_EN bit needs to be cleared.
For the best clock accuracy over temperature, the HFO_LN_FILTER_EN bit in the CLKTRIM register should be cleared.
The data sheet specification for clock performance is characterized with this bit cleared. It is necessary for the customer program to clear this bit, since the default value is for this bit to be set.
The other bits in the CLKTRIM register are trim values which will vary from device to device, so they should not be changed.
This Caution only applies to the UCD3138. All other devices in the UCD3138 family do not need to have this bit cleared. The UCD3138A is backward compatible, so that a program which clears this bit will still run correctly.
The suggested code for clearing the bit without affecting the other trim bits is:
MiscAnalogRegs.CLKTRIM.bit.HFO_LN_FILTER_EN = 0;