TM4C1237H6PGE_15 Datasheet, PDF (1220/1324 Pages) Texas Instruments – Tiva Microcontroller

Analog Comparators
Table 19-2. Internal Reference Voltage and ACREFCTL Field Values (continued)
ACREFCTL Register
EN Bit Value RNG Bit Value
RNG=0
EN=1
RNG=1
Output Reference Voltage Based on VREF Field 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 19-3 on page 1220.
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 19-4 on page 1221.
Note that the values shown in Table 19-2 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 19-3 and Table 19-4. Note that these examples are only valid for V_DDA = 3.3V; values
scale up and down with V_DDA.
Table 19-3. Analog Comparator Voltage Reference Characteristics, V_DDA = 3.3V, EN= 1, and
RNG = 0
VREF Value
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xA
0xB
0xC
0xD
0xE
0xF
V_IREF Min
0.731
0.843
0.955
1.067
1.180
1.292
1.404
1.516
1.629
1.741
1.853
1.965
2.078
2.190
2.302
2.414
Ideal V_IREF
0.786
0.898
1.010
1.122
1.235
1.347
1.459
1.571
1.684
1.796
1.908
2.020
2.133
2.245
2.357
2.469
V_IREF Max
Unit
0.841
V
0.953
V
1.065
V
1.178
V
1.290
V
1.402
V
1.514
V
1.627
V
1.739
V
1.851
V
1.963
V
2.076
V
2.188
V
2.300
V
2.412
V
2.525
V
1220
Texas Instruments-Production Data
June 12, 2014