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ADC Sampling Time STM32L053C8

Question asked by Andrew on Mar 27, 2015
Latest reply on Mar 4, 2018 by waclawek.jan
When I configure the ADC sampling time using SMP[2:0] of the ADC_SMPR register, the resulting conversion time (1.5 cycles + sampling time) does not match what I expect. 

RM0367, v2, section 14.13.6 lists the following possible sample time:
1.5, 7.5, 13.5, 28.5, 41.5, 55.5, 71.5, 239.5.

Respectively, my measured results for the sample time are as follows (12.5 cycle conversion time removed)
1.5, 3.5, 7.5, 12.5, 19.5, 39.5, 79.5, 165.5.

Chip is STM32L053C8

While testing the ADC was running from HSI16 with various prescaler values, all producing the same measured values for the sample time cycles.  It is interesting that the measured value matches for the minimum case of 1.5 cycles, and differs for all the others.

Could this be an error in the reference manual, or am I missing something?