Datasheet

Table 25-2. Internal Reference Voltage and ACREFCTL Field Values (continued)
Output Reference Voltage Based on VREF Field Value
ACREFCTL Register
RNG Bit ValueEN Bit Value
V
IREF
High Range: 16 voltage threshold values indexed by VREF = 0x0 .. 0xF
Ideal starting voltage (VREF=0): V
DDA
/ 4.2
Ideal step size: V
DDA
/ 29.4
Ideal V
IREF
threshold values: V
IREF
(VREF) = V
DDA
/ 4.2 + VREF * (V
DDA
/ 29.4), for
VREF = 0x0 .. 0xF
For minimum and maximum V
IREF
threshold values, see Table 25-3 on page 1781.
RNG=0
EN=1
V
IREF
Low Range: 16 voltage threshold values indexed by VREF = 0x0 .. 0xF
Ideal starting voltage (VREF=0): 0 V
Ideal step size: V
DDA
/ 22.12
Ideal V
IREF
threshold values: V
IREF
(VREF) = VREF * (V
DDA
/ 22.12), for VREF = 0x0 ..
0xF
For minimum and maximum V
IREF
threshold values, see Table 25-4 on page 1782.
RNG=1
Note that the values shown in Table 25-2 are the ideal values of the V
IREF
thresholds. These values
actually vary between minimum and maximum values for each threshold step, depending on process
and temperature. The minimum and maximum values for each step are given by:
■ V
IREF
(VREF) [Min] = Ideal V
IREF
(VREF) – (Ideal Step size – 2 mV) / 2
■ V
IREF
(VREF) [Max] = Ideal V
IREF
(VREF) + (Ideal Step size – 2 mV) / 2
Examples of minimum and maximum V
IREF
values for V
DDA
= 3.3V for high and low ranges, are
shown inTable 25-3 and Table 25-4. Note that these examples are only valid for V
DDA
= 3.3V; values
scale up and down with V
DDA
.
Table 25-3. Analog Comparator Voltage Reference Characteristics, V
DDA
= 3.3V, EN= 1, and
RNG = 0
UnitV
IREF
MaxIdeal V
IREF
V
IREF
MinVREF Value
V0.8410.7860.7310x0
V0.9530.8980.8430x1
V1.0651.0100.9550x2
V1.1781.1221.0670x3
V1.2901.2351.1800x4
V1.4021.3471.2920x5
V1.5141.4591.4040x6
V1.6271.5711.5160x7
V1.7391.6841.6290x8
V1.8511.7961.7410x9
V1.9631.9081.8530xA
V2.0762.0201.9650xB
V2.1882.1332.0780xC
V2.3002.2452.1900xD
V2.4122.3572.3020xE
V2.5252.4692.4140xF
1781June 18, 2014
Texas Instruments-Production Data
Tiva
™
TM4C129ENCPDT Microcontroller