Multi-Channels 24-bit ADCs for Industrial Signal Acquisition Applications - TI’s ADS1274 and ADS1278

Posted in Texas Instruments, Industrial Control, Data Acquisition
On Sunday, July 22, 2007

Texas Instruments has released the ADS1274 and ADS1278 24-bit industrial delta-sigma ADCs (Analog-to-Digital Converters). The quad ADS1274 and octal ADS1278 ADCs are are based on the single-channel ADS1271. These multi channels ADCs are targeted for multi-channels signal acquisition applications, such as medical monitoring, vibration analysis and energy metering equipment. TI’s new multi-channels ADCs feature up to 111dB SNR, 62kHz bandwidth, and 0.8uV/C offset drift. Four operating modes allow for optimization of resolution, speed, and power dissipation.

Traditionally, industrial delta-sigma ADCs offering good drift performance use digital filters with large passband droop, resulting in limited signal bandwidth and mostly suited for DC measurements. High-resolution ADCs for audio applications offer larger usable bandwidths, but the offset and drift specifications are significantly worse than their industrial counterparts. The new ADS1274 and ADS1278 ADCs allow high-precision industrial measurements with excellent DC and AC specifications by combining these two types of converters.

Key features of ADS1274 and ADS1278 multi-channels ADCs:

Simultaneously Measure Four Channels (ADS1274 ) / Eight Channels (ADS1278)
Up to 128kSPS Data Rate
DC Accuracy:
- 0.8µV/°C Offset Drift
- 1.3ppm/°C Gain Drift
AC Performance:
- 111dB SNR (High-Resolution Mode)
- 62kHz Bandwidth
- -108dB THD
Selectable Operating Modes:
- High-Speed: 128kSPS, 106dB SNR
- High-Resolution: 52kSPS, 111dB SNR
- Low-Power: 52kSPS, 31mW/ch
- Low-Speed: 10kSPS, 7mW/ch
Linear Phase Digital Filter
Low Sampling Aperture Error
SPI™ or Frame-Sync Serial Interface
Modulator Output Option (digital filter bypass)
Analog Supply: 5V
Digital Core: 1.8V
I/O Supply: 1.8V to 3.3V
APPLICATIONS
- Multi-Channel Data Acquisition
- Vibration/Modal Analysis
- Pressure Sensors
- Acoustics/Dynamic Strain Gauges

The high-order, chopper-stabilized modulator achieves very low drift and low noise over the signal bandwidth of DC up to the Nyquist frequency. The onboard decimation filter suppresses modulator and out-of-band noise, providing a usable signal bandwidth up to 90 percent of the Nyquist rate with less than 0.005dB of ripple.

A selectable frame-sync or SPI serial interface provides for convenient interfacing to DSPs, FPGAs and microcontrollers. Either interface supports daisy chaining to simplify readback of multiple ADS1274s or ADS1278s in high channel count systems. The ADCs are fully specified over the extended industrial range (-40C to +125C for ADS1274 and -40C to +105C for ADS1278).

Comparison of TI’s ADS1271, ADS1274 and ADS1278 multi-channels ADCs:

	ADS1271	ADS1274	ADS1278
Resolution(Bits)	24	24	24
Sample Rate (max)	105kSPS	128kSPS	128kSPS
Architecture	Delta-Sigma	Delta-Sigma	Delta-Sigma
# Input Ch (Diff)	1	4	8
Power Consumption(Typ)(mW)	92	285	530
Bipolar Input Type	Pseudo	Pseudo	Pseudo
SNR(dB)	109	111	111
SFDR(dB)	-108	-109	-109
INL (+/- %)(Max)	0.0015	0.0012	0.0012
No Missing Codes(Bits)	24	24	24
Analog Voltage AV/DD(Min)(V)	4.75	4.75	4.75
Analog Voltage AV/DD(Max)(V)	5.25	5.25	5.25
Logic Voltage DV/DD(Min)(V)	1.65	1.65	1.65
Logic Voltage DV/DD(Max)(V)	3.6	1.95	1.95
Input Type	Voltage	Voltage	Voltage
Analog Input BW(MHz)	0.05	0.062	0.062
Input Configuration Range	+/-2.5V	+/-2.5V	+/-2.5V
No. of Supplies	2	3	3
Pin/Package	16TSSOP	64HTQFP	64HTQFP

The ADS1274 and ADS1278 are optimized to work with TI's TMS320 DSP platforms. TI also has a range of amplifiers, such as the OPA1632 and OPA350, which are well suited to work with these ADCs to achieve highest performance.

The ADS1274 and ADS1278 multi-channels ADCs are available in HTQFP-64 packages with suggested resale price:

ADS1274 starts at $13.95 (1K unit qty)
ADS1278 starts at $23.95 (1K unit qty)

More info: TI’s Multi-Channels 24-bit Industrial ADCs

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