AD7797_15 Datasheet, PDF (1/24 Pages) Analog Devices – Low Power, 16-/24-Bit Sigma-Delta ADC

Low Power, 16-/24-Bit Sigma-Delta ADC
for Bridge Sensors
AD7796/AD7797
FEATURES
RMS noise: 65 nV
Instrumentation amp
Temperature sensor
Internal clock oscillator
Simultaneous 50 Hz/60 Hz rejection
Update rate: 4.17 Hz to 123 Hz
Current: 250 μA typ
Power-down: 1 μA
Power supply: 2.7 V to 5.25 V
–40°C to +85°C temperature range
Independent interface power supply
16-lead TSSOP
INTERFACE
3-wire serial
SPI®, QSPI™, MICROWIRE™, and DSP compatible
Schmitt trigger on SCLK
GENERAL DESCRIPTION
The AD7796/AD7797 are complete, analog front ends for high
precision, bridge sensor applications such as weigh scales. The
AD7796/AD7797 contain a Σ-Δ ADC capable of 16-/24-bit
resolution, respectively. The on-chip instrumentation amplifier
has a fixed gain of 128, allowing small amplitude signals such as
those from bridge sensors to be directly interfaced to the ADC.
Each part has one differential input and contains a temperature
sensor that is internally connected to the ADC. This sensor can
be used to perform temperature compensation of the bridge.
The devices can be operated with the internal clock or an
external clock. The output data rate from the parts is software-
programmable and can be varied from 4.17 Hz to 123 Hz.
The AD7796/AD7797 operate with a power supply from 2.7 V
to 5.25 V. Each part consumes a current of 250 μA typical and is
housed in a 16-lead TSSOP.
APPLICATIONS
Weigh scales
Strain gages
Industrial process control
Instrumentation
Portable instrumentation
AIN(+)
AIN(–)
FUNCTIONAL BLOCK DIAGRAM
GND ^AVDD
REFIN(+) REFIN(–)
AV_DD
AD7796: 16-BIT ADC
AD7797: 24-BIT ADC
MUX
×128
Σ-Δ
ADC
SERIAL
INTERFACE
AND
CONTROL
LOGIC
DOUT/RDY
DIN
SCLK
CS
GND
AD7796/
AD7797
REFERENCE
TEMP
SENSOR
INTERNAL
CLOCK
CLK
Figure 1.
DV_DD
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone]
www.analog.com
Fax: [phone]
©2006 Analog Devices, Inc. All rights reserved.