TYPICAL PERFORMANCE CURVES
(Cont.)
At T
A
= +25°C, AV
DD
= DV
DD
= +5V, MCLK = 320kHz, REF
EN
LOW, BIAS
EN
LOW, and external +2.5V reference, unless otherwise specified.
CMRR vs V
DIN
110
105
100
95
90
85
80
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
V
DIN
(V)
GENERAL DESCRIPTION
The ADS1201 is a single channel, second-order, CMOS
analog modulator designed for high resolution conversions
from dc to 1000Hz. The output of the converter (MOUT)
provides a stream of digital ones and zeros. The time
average of this serial output is proportional to the analog
input voltage. The combination of an ADS1201 and a
processor that is programmed to implement a digital filter
results in a high resolution A/D converter system. This
system allows flexibility with the digital filter design and is
capable of A/D conversion results that have a dynamic range
that exceeds 130dB (see Figure 1).
CMRR (dB)
THEORY OF OPERATION
The differential analog input of the ADS1201 is imple-
mented with a switched capacitor circuit. This switched
capacitor circuit implements a 2nd-order modulator stage
which digitizes the input signal into a binary output stream.
The input stage of the converter can be configured to sample
an analog signal or to perform a calibration which quantifies
offset and gain errors. The sample clock (MCLK) provides
the switched capacitor network and modulator clock signal
for the A/D conversion process, as well as the output data
framing clock. Different frequencies for this clock allows
for a variety of performance solutions in resolution and
signal bandwidth. The analog input signal is continuously
sampled by the A/D converter and compared to an internal
or external voltage reference. A digital stream appears at the
output of the converter. This digital stream accurately repre-
sents the analog input voltage over time.
Analog Supply
1
2
10µF
3
0.1µF
4
200Ω
5
200Ω
6
7
47pF
47pF
8
AV
DD
REF
OUT
REF
IN
NIC
ADS1201
A
IN
P
A
IN
N
AGND
V
BIAS
REF
EN
16
MOUT 15
MCLK 14
DV
DD
13
0.1µF
DGND 12
CAL 11
GAIN/OFFSET 10
BIAS
EN
9
Digital
Supply
Processor
FIGURE 1. Connection Diagram for the ADS1201 Delta-Sigma Modulator Including External Processor.
®
5
ADS1201
TI [ TEXAS INSTRUMENTS ]
