+
−
BANDGAP
1.2, 2.0, 2.5 V
+
−
Switch
Mux
Bandgap and buffer ready
REFMODEREQ
REFBGREQ
Bandgap
Buffer
REFBIASREQ
BIAS
OR
AND
OR
ENABLE
ENABLE
OR
REFGENREQ
From
ADCx
From COMP_Ex
ENABLE
ENABLE
MODE
REF_A
REFON
REFGENOT
REFTCOFF
REFVSEL
Devices with ADC only
BGMODE
REFBGOT
SET
SET
From
T
imer
or software
From
T
imer
or software
Variable Reference
Local
Buffer
ADC
COMP
Local
Buffer/Amp
LCD
DAC
Local
Buffer/Amp
Request Bandgap
Request Bandgap
Request Reference
(always with static mode)
Request Reference
(always with static mode)
Reference ready
REF_A Introduction
862
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
REF_A
33.1 REF_A Introduction
The reference module (REF) is responsible for generation of all critical reference voltages that can be
used by various analog peripherals in a given device. The heart of the reference system is the bandgap
from which all other references are derived by unity or noninverting gain stages. The REFGEN subsystem
consists of the bandgap, the bandgap bias, and the noninverting buffer stage, which generates the three
primary voltage reference available in the system (1.2 V, 2.0 V, and 2.5 V). In addition, when enabled, a
buffered bandgap voltage is available.
Features of the REF_A include:
•
Centralized factory-trimmed bandgap with excellent PSRR, temperature coefficient, and accuracy
•
1.2-V, 2.0-V, or 2.5-V user-selectable internal references
•
Buffered bandgap voltage available to rest of system
•
Power saving features
•
Hardware reference request and reference ready signals for bandgap and variable reference voltages
for safe operation
shows an example block diagram of the REF_A module. The example shown here is for a
device with an ADC, a DAC, an LCD, and two Comparators.
Figure 33-1. REF_A Block Diagram