VREF_SC field descriptions (continued)
Field Description
0 Disabled
1 Enabled
4
Reserved
This field is reserved.
This read-only field is reserved and always has the value 0.
3
Reserved
This field is reserved.
This read-only field is reserved and always has the value 0.
2
VREFST
Internal Voltage Reference stable
This bit indicates that the bandgap reference within the Voltage Reference module has completed its
startup and stabilization.
NOTE:
This bit is valid only when the chop oscillator is not being used.
0 The module is disabled or not stable.
1 The module is stable.
MODE_LV Buffer Mode selection
These bits select the buffer modes for the Voltage Reference module.
00 Bandgap on only, for stabilization and startup
01 High power buffer mode enabled
10 Low-power buffer mode enabled
11 Reserved
37.3 Functional Description
The Voltage Reference is a bandgap buffer system. Unity gain amplifiers are used.
The VREF_OUT signal can be used by both internal and external peripherals in low and
high power buffer mode. A 100 nF capacitor must always be connected between
VREF_OUT and VSSA if the VREF is being used.
The following table shows all possible function configurations of the Voltage Reference.
Table 37-2. Voltage Reference function configurations
SC[VREFEN] SC[MODE_LV] Configuration Functionality
0 X Voltage Reference disabled Off
1 00 Voltage Reference enabled,
bandgap on only
Startup and standby
1 01 Voltage Reference enabled,
high-power buffer on
VREF_OUT available for
internal and external use. 100
nF capacitor is required.
1 10 Voltage Reference enabled,
low power buffer on
VREF_OUT available for
internal and external use. 100
nF capacitor is required.
1 11 Reserved Reserved
Functional Description
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
862 NXP Semiconductors
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