Datasheet

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OVERVIEW TEMPERATURE SENSOR (ADS1232 only)
ANALOG INPUTS (AINPx, AINNx)
A0A1
AINP
AINP1
AINN1
AINP2
AINN2
AINP3
AINN3
AINP4
AINN4
10I 1I
1X 8X
AINN
ADS1232 Only
AVDD
ADS1234 Only
ADS1232
ADS1234
SBAS350F – JUNE 2005 – REVISED FEBRUARY 2008
The ADS1232 and ADS1234 are highly integrated, On-chip diodes provide temperature-sensing
24-bit ADCs that include an input multiplexer, capability. By setting the TEMP pin high, the selected
low-noise PGA, third-order delta-sigma ( Δ Σ ) analog inputs are disconnected and the inputs to the
modulator, and fourth-order digital filter. With ADC are connected to the anodes of two diodes
input-referred RMS noise down to 17nV, the scaled to 1x and 80x in current and size, as shown in
ADS1232/4 are ideally suited for measuring the very Figure 26 . By measuring the difference in voltage of
low signals produced by bridge sensors in these diodes, temperature changes can be inferred
applications such as weigh scales, strain gauges, and from a baseline temperature. Typically, the difference
pressure sensors. in diode voltage is 111.7mV at 25 ° C with a
temperature coefficient of 379 µ V/ ° C. With PGA = 1
Clocking can be supplied by an external oscillator, an
and 2, the difference voltage output from the PGA will
external crystal, or by a precision internal oscillator.
be 111.7mV and 223.4mV, respectively. With PGA =
Data can be output at 10SPS for excellent 50Hz and
64 and 128, it is impossible to use the temperature
60Hz rejection, or at 80SPS when higher speeds are
sensor function. A similar structure is used in the
needed. The ADS1232/4 are easy to configure, and
MSC1210 for temperature measurement. For more
all digital control is accomplished through dedicated
information, see TI application report SBAA100 ,
pins; there are no registers to program. A simple
Using the MSC121x as a High-Precision Intelligent
two-wire serial interface retrieves the data.
Temperature Sensor, available for download at
www.ti.com .
The input signal to be measured is applied to the
input pins AINPx and AINNx. The positive internal
input is generalized as AINP, and the negative
internal input generalized as AINN. The signal is
selected through the input mux, which is controlled by
pins A0 and A1 (ADS1234 only), as shown in
Table 5 . For the ADS1232, the A1 pin is replaced by
the TEMP pin to activate the onboard diodes (see the
Temperature Sensor section for more details). The
ADS1232/4 accept differential input signals, but can
also measure unipolar signals. When measuring
unipolar (or single-ended signals) with respect to
ground, connect the negative input (AINNx) to ground
and connect the input signal to the positive input
(AINPx). Note that when the ADS1232/4 are
configured this way, only half of the converter
full-scale range is used, since only positive digital
output codes are produced.
Table 5. Input Channel Selection with A0 and A1
(ADS1234 only)
MUX PINS SELECTED ANALOG INPUTS
A1 A0 POSITIVE INPUT NEGATIVE INPUT
0 0 AINP1 AINN1
0 1 AINP2 AINN2
1 0 AINP3 AINN3
1 1 AINP4 AINN3
Figure 26. Measurement of the Temperature
Sensor in the Input Multiplexer
Copyright © 2005 – 2008, Texas Instruments Incorporated 13
Product Folder Link(s): ADS1232 ADS1234