ADS1225 View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
ADS1225 Datasheet PDF : 24 Pages
| |||
ADS1225
ADS1226
SBAS346 – MAY 2006
www.ti.com
OVERVIEW
The ADS1225 and ADS1226 are 24-bit delta-sigma
A/D converters. Figure 19 shows a conceptual
diagram of the device. The ADS1225 has a single
channel, while the ADS1226 allows for one of two
input channels to be selected through a multiplexer.
A buffer can also be selected to increase the input
impedance. The modulator measures the differential
input signal VIN = (AINP – AINN) against the
differential reference VREF = (VREFP – VREFN). The
full-scale input range is ±VREF. A 2-wire serial
interface indicates conversion completion and
provides the user with the output data. An internal
oscillator allows for free-running of the ADS1225 and
ADS1226.
Two other pins are used to control the operation of
the ADS1225 and ADS1226. The START pin initiates
conversions. The MODE pin puts the device into one
of two modes. In High-Speed mode, the device gives
data at 100 samples per second (SPS). In
High-Resolution mode, data comes out at 16SPS
with lower noise. In both modes, the device has
single-cycle settling, reducing the latency of the
output data.
ANALOG INPUTS (AINx+, AINx–)
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 is generalized as AINN. The signal is
selected though the input MUX, which is controlled
by MUX, as shown in Table 1. The ADS1225 and
ADS1226 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 (AINN) to ground
and connect the input signal to the positive input
(AINP). Note that when the ADS1225 and ADS1226
are configured this way, only half of the converter
full-scale range is used since only positive digital
output codes are produced. An input buffer can be
selected to increase the input impedance of the A/D
converter with the BUFEN pin.
Table 1. Input Channel Selection with MUX
DIGITAL PIN
MUX
0
1
SELECTED ANALOG INPUTS
POSITIVE INPUT NEGATIVE INPUT
AINP1
AINN1
AINP2
AINN2
TEMPEN
AINP1
AINN1
AINP2
AINN2
MUX
AINP
AINN
Buffer
VREFP VREFN
VIN
S
S
VREF
DS
ADC
Serial Interface
START
SCLK
DRDY/DOUT
Oscillator
MODE
MUX
ADS1226 Only
BUFEN
Figure 19. Conceptual Diagram of the ADS1225 and ADS1226
10
Submit Documentation Feedback
Share Link: 