+
−
BANDGAP
1.2 V, 1.45 V, 2.5 V
+
−
Switch
Mux
Bandgap and buffer ready
REFMODEREQ
REFBGREQ
Bandgap
Buffer
REFBIASREQ
BIAS
OR
AND
OR
OR
REFGENREQ
From
ADCx
From COMP_Ex
REF_A
REFON
REFGENOT
Temperature
Sensor
REFVSEL
BGMODE
REFBGOT
Variable Reference
Local
Buffer
ADC
COMP
Local
Buffer/Amp
LCD
DAC
Local
Buffer/Amp
Request
Bandgap
Request
Bandgap
Request
Reference
Request
Reference
Reference ready
Buffered Bandgap Reference
OR
MODE ENABLE
ENABLE
ENABLE
REF_A Introduction
836
SLAU356I – March 2015 – Revised June 2019
Copyright © 2015–2019, Texas Instruments Incorporated
Reference Module (REF_A)
21.1 REF_A Introduction
The REF_A module generates reference voltages for use by various analog modules in a device. The
heart of the REF_A module is the bandgap from which all other reference voltages are derived by unity or
noninverting gain stages. The REFGEN subsystem inside the REF_A module consists of the bandgap, the
bandgap bias, and the noninverting buffer stage that generates the primary voltage references available in
the system: 1.2 V, 1.45 V, and 2.5 V. In addition, when enabled, a buffered bandgap voltage is available.
Features of the REF_A include:
•
Centralized factory-calibrated bandgap with excellent PSRR, temperature coefficient, and accuracy
•
1.2-V, 1.45-V, or 2.5-V user-selectable internal reference voltages
•
Buffered bandgap voltage available to rest of the system
•
Power-saving features
•
Hardware reference requests and reference ready signals for bandgap and variable reference voltages
for safe operation
shows a block diagram of the REF_A module in an example device with an ADC, a DAC, an
LCD controller, and a comparator.
Figure 21-1. REF_A Block Diagram