Datasheet
ADS1246
ADS1247
ADS1248
SBAS426G –AUGUST 2008–REVISED OCTOBER 2011
www.ti.com
ADS1247 and ADS1248 DETAILED REGISTER DEFINITIONS (continued)
MUX1—Multiplexer Control Register 1
MUX1 - ADDRESS 02h RESET VALUE = 00h
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
CLKSTAT VREFCON1 VREFCON0 REFSELT1 REFSELT0 MUXCAL2 MUXCAL1 MUXCAL0
Bit 7 CLKSTAT
This bit is read-only and indicates whether the internal or external oscillator is being used.
0 = Internal oscillator in use
1 = External oscillator in use
Bits 6:5 VREFCON1:0
These bits control the internal voltage reference. These bits allow the reference to be turned on or
off completely, or allow the reference state to follow the state of the device. Note that the internal
reference is required for operation of the IDAC functions.
00 = Internal reference is always off (default)
01 = Internal reference is always on
10 or 11 = Internal reference is on when a conversion is in progress and shuts down when the
device receives a shutdown opcode or the START pin is taken low
Bits 4:3 REFSELT1:0
These bits select the reference input for the ADC.
00 = REF0 input pair selected (default)
01 = REF1 input pair selected (ADS1248 only)
10 = Onboard reference selected
11 = Onboard reference selected and internally connected to REF0 input pair
Bits 2:0 MUXCAL2:0
These bits are used to select a system monitor. The MUXCAL selection supercedes selections
from registers MUX0 and MUX1 (MUX_SP, MUX_SN, and VBIAS).
000 = Normal operation (default)
001 = Offset measurement
010 = Gain measurement
011 = Temperature diode
100 = External REF1 measurement (ADS1248 only)
101 = External REF0 measurement
110 = AVDD measurement
111 = DVDD measurement
Table 21 provides the ADC input connection and PGA settings for each MUXCAL setting. The PGA setting
reverts to the original SYS0 register setting when MUXCAL is taken back to normal operation or offset
measurement.
Table 21. MUXCAL Settings
MUXCAL[2:0] PGA GAIN SETTING ADC INPUT
000 Set by SYS0 register Normal operation
001 Set by SYS0 register Inputs shorted to midsupply (AVDD + AVSS)/2
010 Forced to 1 V
REFP
– V
REFN
(full-scale)
011 Forced to 1 Temperature measurement diode
100 Forced to 1 (V
REFP1
– V
REFN1
)/4
101 Forced to 1 (V
REFP0
– V
REFN0
)/4
110 Forced to 1 (AVDD – AVSS)/4
111 Forced to 1 (DVDD – DVSS)/4
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