ADS1274
ADS1278
www.ti.com
SBAS367–JUNE 2007
OVERVIEW
High-Speed, High-Resolution, Low-Power, and
Low-Speed. Table 1 summarizes the performance of
each mode.
The ADS1274 (quad) and ADS1278 (octal) are 24-bit,
delta-sigma ADCs based on the single-channel
ADS1271. They offer the combination of outstanding
dc accuracy and superior ac performance. Figure 57
shows the block diagram. Note that both devices are
functionally the same, except that the ADS1274 has
four ADCs and the ADS1278 has eight ADCs. The
packages are identical, and the ADS1274 pinout is
compatible with the ADS1278, permitting true drop-in
expandability. The converters are comprised of four
(ADS1274) or eight (ADS1278) advanced, 6th-order,
chopper-stabilized, delta-sigma modulators followed
by low-ripple, linear phase FIR filters. The modulators
measure the differential input signal, VIN = (AINP –
In High-Speed mode, the maximum data rate is
128kSPS (when operating at 128kSPS, Frame-Sync
format must be used). In High-Resolution mode, the
SNR = 111dB (VREF = 3.0V); in Low-Power mode, the
power dissipation is 31mW/channel; and in
Low-Speed mode, the power dissipation is only
7mW/channel at 10.5kSPS. The digital filters can be
bypassed, enabling direct access to the modulator
output.
The ADS1274/78 is configured by simply setting the
appropriate I/O pins—there are no registers to
program. Data are retrieved over a serial interface
that supports both SPI and Frame-Sync formats. The
ADS1274/78 has a daisy-chainable output and the
ability to synchronize externally, so it can be used
conveniently in systems requiring more than eight
channels.
AINN), against the differential reference, VREF
=
(VREFP – VREFN). The digital filters receive the
modulator signal and provide a low-noise digital
output. To allow tradeoffs among speed, resolution,
and power, four operating modes are supported:
VREFP
AVDD
VREFN
DVDD
IOVDD
Mod 1
Mod 2
R
S
Modulator
Output
VCOM
VREF
R
Mod 8
VIN1
DS
AINP1
AINN1
Digital
DRDY/FSYNC
SCLK
S
S
Modulator1
SPI
and
Filter1
DOUT[4:1]/[8:1](1)
Frame-Sync
Interface
DIN
VIN2
DS
AINP2
AINN2
Digital
Filter2
Modulator2
TEST[1:0]
FORMAT[2:0]
CLK
Control
Logic
SYNC
PWDN[4:1]/[8:1](1)
AINP4/8(1)
AINN4/8(1)
VIN4/8
DS
Modulator4/8(1)
Digital
Filter4/8(1)
CLKDIV
S
MODE[1:0]
AGND
DGND
NOTE: (1) The ADS1274 has four channels; the ADS1278 has eight channels.
Figure 57. ADS1274/ADS1278 Block Diagram
Table 1. Operating Mode Performance Summary
MODE
High-Speed
High-Resolution
Low-Power
Low-Speed
MAX DATA RATE (SPS)
PASSBAND (kHz)
57,984
SNR (dB)
106
NOISE(μVRMS
)
POWER/CHANNEL (mW)
128,000
52,734
52,734
10,547
8.5
5.5
8.5
8.0
70
64
31
7
23,889
110
23,889
106
4,798
107
20
Copyright © 2007, Texas Instruments Incorporated
Submit Documentation Feedback
Product Folder Link(s): ADS1274 ADS1278
BB [ BURR-BROWN CORPORATION ]
