Datasheet
27W
5kW
5kW 2kW
2kW
+5V
0.1nF
+3V
+3V
0.1 Fm
0.1 Fm
0.1 Fm
±5V
OPA2350
0.1 Fm
27W
5kW
5kW 2kW
2kW
+5V
0.1nF
±5V
OPA2350
0.1 Fm
2nd-Order
DS Modulator
FPGA
or
ASIC
CHA+
AVDD
CHA-
Output
Interface
Circuit
RC
Oscillator
20MHz
Out EN
Clock
Select
Divider
REFINA
Reference
Voltage
2.5V
REFOUT
OUTA
OUTB
CLKIN
AGNDAGNDAGNDAGND
BVDD
CLKOUT
BVDD
BGND
+5V
0.1 Fm
+5V
0.1 Fm
+5V
0.1 Fm
+5V
0.1 Fm
CLKSEL
AVDD
AVDD
AVDD
AVDD
2nd-Order
DS Modulator
CHB+
CHB-
REFINB
+5V
OPA336
ADS1209
www.ti.com
SBAS491 –FEBRUARY 2010
GENERAL DESCRIPTION
The ADS1209 is a two-channel, second-order, CMOS An application-specific integrated circuit (ASIC) or
device with two delta-sigma (ΔΣ) modulators, field-programmable gate array (FPGA) can be used
designed for medium- to high-resolution A/D signal to implement the digital filter. Alternatively, TI's
conversions from dc to 40kHz (filter response –3dB) if AMC1210 offers four programmable digital filters that
an oversampling ratio (OSR) of 64 is chosen. The can be used. Figure 20 and Figure 21 show typical
output of the converter (OUTx) provides a stream of application circuits with the ADS1209 connected to an
digital ones and zeros. The time average of this serial FPGA or ASIC.
output is proportional to the analog input voltage.
The overall performance (that is, speed and
The modulator shifts the quantization noise to high accuracy) depends on the selection of an appropriate
frequencies. A low-pass digital filter should be used OSR and filter type. A higher OSR produces greater
at the output of the ΔΣ modulator. The filter serves output accuracy while operating at a lower data rate.
two functions. First, it filters out high-frequency noise. Alternatively, a lower OSR produces lower output
Second, the filter converts the 1-bit data stream at a accuracy, but operates at a higher data rate. This
high sampling rate into a higher-bit data word at a system allows flexibility with the digital filter design
lower rate (decimation). and is capable of A/D conversion results that have a
dynamic range exceeding 86dB with an OSR = 256.
Figure 20. Single-Ended Connection Diagram for the ADS1209 ΔΣ Modulator
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Product Folder Link(s): ADS1209