mcf51jf128 Freescale Semiconductor, Inc, mcf51jf128 Datasheet - Page 721

• Manufacturer Part Number: mcf51jf128
• Description: Mcf51jf128 Reference Manual
• Manufacturer: Freescale Semiconductor, Inc

32.3 Functional Description
The Voltage Reference is a bandgap buffer system. Unity gain amplifiers are used.
The VREF_OUT signal is used as an internal reference when it is used in low power
mode and is used for internal peripherals only. If it used in high power mode, a 100 nF
capacitor is required.
The following table shows all possible function configurations of the Voltage Reference.
Freescale Semiconductor, Inc.
MODE_LV
Reserved
Reserved
Reserved
VREFEN
VREFST
REGEN
Field
1–0
7
6
5
4
3
2
Internal Voltage Reference enable
This bit is used to enable the bandgap Voltage Reference module.
NOTE: After the VREF is enabled, turning off the clock to the VREF module via the corresponding clock
0
1
Regulator enable
This bit is used to enable the internal 1.75 V regulator to produce a stable voltage reference in order to
reduce the supply variation.
0
1
This read-only bit is reserved and always has the value zero.
This read-only bit is reserved and always has the value zero.
This read-only bit is reserved and always has the value zero.
Internal Voltage Reference stable
This bit indicates that the Voltage Reference module has completed its startup and stabilization.
0
1
Buffer Mode selection
These bits select the buffer modes for the Voltage Reference module.
00
01
10
11
The module is disabled.
The module is enabled.
Internal 1.75 V regulator is disabled.
Internal 1.75 V regulator is enabled.
The module is disabled or not stable.
The module is stable.
Bandgap on only, for stabilization and startup
Low-power buffer enabled
Tight-regulation buffer enabled
Reserved
gate register will not disable the VREF. VREF must be disabled via this VREFEN bit.
MCF51JF128 Reference Manual, Rev. 2, 03/2011
VREF_SC field descriptions
Preliminary
Description
Chapter 32 Voltage Reference (VREF)
721