(chop oscillator start up time). You must wait this time (Tchop_osc_stup) after the
internal bandgap has been enabled to ensure the VREF internal reference voltage has
stabilized.
When the Voltage Reference is already enabled and stabilized, changing SC[MODE_LV]
will not clear SC[VREFST] but there will be some startup time before the output voltage
at the VREF_OUT pin has settled. This is the buffer start up delay (Tstup) and the value
is specified in the appropriate device data sheet. Also, there will be some settling time
when a step change of the load current is applied to the VREF_OUT pin. When the 1.75V
VREF regulator is disabled, the VREF_OUT voltage will be more sensitive to supply
voltage variation. It is recommended to use this regulator to achieve optimum
VREF_OUT performance.
The TRM[CHOPEN], SC[REGEN] and SC[ICOMPEN] bits must be written to 1 to
achieve the performance stated in the device data sheet.
Chapter 26 Voltage Reference (VREFV1)
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Freescale Semiconductor, Inc.
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