LM3S3W26 Datasheet, PDF (792/877 Pages) Texas Instruments – Stellaris® LM3S3W26 Microcontroller

Analog Comparators
In the high-range mode, the V_IREF threshold voltages start at the ideal high-range starting voltage
of V_DDA/3.875 and increase in ideal constant voltage steps of V_DDA/31.
In the low-range mode, the V_IREF threshold voltages start at:0V and increase in ideal constant voltage
steps of V_DDA/23. The ideal V_IREF step voltages for each mode and their dependence on the RNG
and VREF fields are summarized in Table 17-2 on page 792.
Table 17-2. Internal Reference Voltage and ACREFCTL Field Values
ACREFCTL Register
EN Bit
Value
RNG Bit Value ^{Output Reference Voltage Based on VREF Field Value}
EN=0
RNG=X
0 V (GND) for any value of VREF. It is recommended that RNG=1 and VREF=0 to minimize noise
on the reference ground.
RNG=0 Total resistance in ladder is 31 R.
VIREF = VDDA × ^RVREF
EN=1
RNG=1
TTohte^VVVVV_VVVV^VV_VVVV^VV_VVVVV^VVVVV_alr^I_I^I_I^I_IIII^IIII_III^II_IIII^IIIIIar^RRR_RRRRRRRRR^RRRRRR_RRRR^RRRRR_enEEE^EEE_EEEEEEs^EEEEEE_EEEE^EEEEEgi^FFF_FFFFFFFFF^FFFFFFFFFFF_FFFFsetaonf⁼⁼⁼⁼⁼₌⁼⁼₌₌₌₌⁼⁼⁼⁼⁼_=======⁼⁼_=cinete^VV_VVVV^VVVVV_VVVVVV^VVVVV000_000000inrn^DDDDDD_D^D_D^D_D^D_D^D_DD^DD_DDDD^..._{......laaDDDDD}^DDDDD_D^DD_DDDD^DDDDD888₈₈₈₁₁₁ld_AAAAA^AAAAA_A^AAAAAAA_AAAArd₄₄₄⁵⁵⁵₅₅₅eef^{×××××}_{××××××}^××_{××××}^{×××××}e_333r r⁺⁺⁺_+++ise^V_VVVV^RRR_RRR^RRRRR(((((_{(×××}n2^VVVVV_Vc⁰⁰⁰₀₀₀^R_RRRR3^VVVVVVVV_VVV^RRRRRRRRRR₂₂₂₂e^RRRRR_RVVV^RRRRRRRR_RRR^..._...R^E_EEEE^TTTTTTTTTTTT₃₃₃₃i^EEEEEEEE_EEE^EEEEE_En_RRR.¹¹¹₁₁₁^F_FFFF^FFFFFFFF_FFF³³³³₃₃^FFFFF_Ft_EEEh⁰⁰⁰₀₀₀¹¹¹¹₁₁i_FFFs⁶⁶⁶₆₆₆⁺⁺⁺⁺⁺₊mo^×××_×××⁸⁸⁸⁸⁸₈de^VVV_VVV⁾⁾⁾⁾⁾₎is^RRR_RRR0^EEE_EEE.8^FFF_FFF5-2.448 V.
VIREF = V0D.D1A4×3 ^V×^R2V^E3R^FEF
VIREF = 0.143 ײV³REF
VIREF = 0.143 × VREF
17.4
The range of internal reference for this mode is 0-2.152 V.
Initialization and Configuration
The following example shows how to configure an analog comparator to read back its output value
from an internal register.
1. Enable the analog comparator clock by writing a value of 0x0010.0000 to the RCGC1 register
in the System Control module (see page 249).
792
January 21, 2012
Texas Instruments-Production Data