EVAL-AD7780EBZ Analog Devices Inc, EVAL-AD7780EBZ Datasheet

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EVAL-AD7780EBZ

Manufacturer Part Number
EVAL-AD7780EBZ
Description
ADC Converter Evaluation Board
Manufacturer
Analog Devices Inc
Datasheet

Specifications of EVAL-AD7780EBZ

Silicon Manufacturer
Analog Devices
Application Sub Type
ADC
Kit Application Type
Data Converter
Silicon Core Number
AD7780
Kit Contents
Board And Literature
Number Of Adc's
1
Number Of Bits
24
Sampling Rate (per Second)
16.7
Data Interface
SPI™
Inputs Per Adc
1 Differential
Input Range
±5 V
Voltage Supply Source
Single Supply
Operating Temperature
-40°C ~ 105°C
Utilized Ic / Part
AD7780
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
FEATURES
Pin-programmable filter response
Pin-programmable in-amp gain
Pin-programmable power-down and reset
Status function
Internal clock oscillator
Internal bridge power-down switch
Current
Simultaneous 50 Hz/60 Hz rejection
Power supply: 2.7 V to 5.25 V
−40°C to +105°C temperature range
Independent interface power supply
Packages
2-wire serial interface (read-only device)
APPLICATIONS
Weigh scales
Pressure measurement
Industrial process control
Portable instrumentation
GENERAL DESCRIPTION
The AD7780 is a complete low power front-end solution for
bridge sensor products, including weigh scales, strain gages, and
pressure sensors. It contains a precision, low power, 24-bit sigma-
delta (Σ-Δ) ADC; an on-chip, low noise programmable gain
amplifier (PGA); and an on-chip oscillator.
Consuming only 330 μA, the AD7780 is particularly suitable for
portable or battery-operated products where very low power is
required. The AD7780 also has a power-down mode that allows
the user to switch off the power to the bridge sensor and power
down the AD7780 when not converting, thus increasing the
battery life of the product.
For ease of use, all the features of the AD7780 are controlled by
dedicated pins. Each time a data read occurs, eight status bits
are appended to the 24-bit conversion. These status bits contain
a pattern sequence that can be used to confirm the validity of
the serial transfer.
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.
Update rate: 10 Hz or 16.7 Hz
115 μA typical (gain = 1)
330 μA typical (gain = 128)
14-lead, narrow body SOIC
16-lead TSSOP
SPI compatible
Schmitt trigger on SCLK
Ultralow Power Sigma-Delta ADC
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
Table 1.
Parameter
Output Data Rate
RMS Noise
P-P Resolution
Settling Time
The on-chip PGA has a gain of 1 or 128, supporting a full-scale
differential input of ±5 V or ±39 mV. The device has two filter
response options. The filter response at the 16.7 Hz update rate
provides superior dynamic performance. The settling time is
120 ms at this update rate. At the 10 Hz update rate, the filter
response provides greater than −45 dB of stop-band attenuation.
In load cell applications, this stop-band rejection is useful to reject
low frequency mechanical vibrations of the load cell. The settling
time is 300 ms at this update rate. Simultaneous 50 Hz/60 Hz
rejection occurs at both the 10 Hz and 16.7 Hz update rates.
The AD7780 operates with a power supply from 2.7 V to 5.25 V.
It is available in a narrow body, 14-lead SOIC package and a 16-lead
TSSOP package.
BPDSW
24-Bit, Pin-Programmable,
AIN(+)
AIN(–)
FUNCTIONAL BLOCK DIAGRAM
GND AV
AD7780
DD
10 Hz
44 nV
17.6
300 ms
OR 128
GAIN
G = 1
©2009 Analog Devices, Inc. All rights reserved.
Gain = 128
Figure 1.
INTERNAL
REFIN(+)
CLOCK
16.7 Hz
65 nV
17.1
120 ms
24-BIT Σ-Δ
ADC
REFIN(–)
10 Hz
2.4 μV
18.8
300 ms
AD7780
www.analog.com
DOUT/RDY
SCLK
DV
FILTER
PDRST
DD
Gain = 1
16.7 Hz
2.7 μV
18.7
120 ms

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EVAL-AD7780EBZ Summary of contents

Page 1

FEATURES Pin-programmable filter response Update rate 16.7 Hz Pin-programmable in-amp gain Pin-programmable power-down and reset Status function Internal clock oscillator Internal bridge power-down switch Current 115 μA typical (gain = 1) 330 μA typical (gain = 128) ...

Page 2

AD7780 TABLE OF CONTENTS Features .............................................................................................. 1 Applications ....................................................................................... 1 Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Specifications ..................................................................................... 3 Timing Characteristics ................................................................ 5 Absolute Maximum Ratings ............................................................ 6 Thermal Resistance ...................................................................... 6 ESD ...

Page 3

SPECIFICATIONS REF DD Table 2. Parameter ADC CHANNEL Output Update Rate (f ) ADC 2 No Missing Codes Resolution Peak-to-Peak RMS Noise Integral Nonlinearity Offset Error Offset ...

Page 4

AD7780 Parameter LOGIC INPUTS 2 SCLK, FILTER, GAIN, PDRST Input Low Voltage, V INL Input High Voltage, V INH SCLK (Schmitt-Triggered Input) Hysteresis Input Currents Input Capacitance LOGIC OUTPUT (DOUT/RDY) 2 Output High Voltage Output Low Voltage, ...

Page 5

TIMING CHARACTERISTICS 5.25 V, GND = 0 V, Input Logic Input Logic Table 3. 1 Parameter Limit at T ...

Page 6

AD7780 ABSOLUTE MAXIMUM RATINGS T = 25°C, unless otherwise noted. A Table 4. Parameter AV to GND GND DD Analog Input Voltage to GND Reference Input Voltage to GND Digital Input Voltage to GND Digital Output Voltage ...

Page 7

PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS SCLK 1 DOUT/RDY 2 AD7780 NC 3 GAIN TOP VIEW 4 (Not to Scale) AIN(+) 5 AIN(–) 6 REFIN(+) CONNECT Figure 6. SOIC Pin Configuration Table 6. Pin Function Descriptions Pin ...

Page 8

AD7780 TYPICAL PERFORMANCE CHARACTERISTICS 8,388,670 8,388,660 8,388,650 8,388,640 8,388,630 8,388,620 8,388,610 8,388,600 8,388,590 8,388,580 8,388,570 0 200 400 600 SAMPLE Figure 8. Noise ( Update Rate = 16.7 Hz, Gain = 128) REF ...

Page 9

SAMPLE Figure 14. Noise ( Update Rate = 10 Hz, Gain = 1) REF DD 100 8,388,385 8,388,391 8,388,397 8,388,403 8,388,409 ...

Page 10

AD7780 OUTPUT NOISE AND RESOLUTION Table 7 and Table 8 show the rms noise of the AD7780 for the two output data rates and gain settings when 3 V and 5 V references are used. These numbers are typical and ...

Page 11

... These functions are controlled using dedicated pins, which makes the interface easy to configure. A 2-wire interface simplifies data retrieval from the AD7780. FILTER, DATA RATE, AND SETTLING TIME The AD7780 has two filter options. When the FILTER pin is low, the 16.7 Hz filter is selected ...

Page 12

AD7780 GAIN The AD7780 has two gain options: gain = 1 and gain = 128. When the GAIN pin is low, the gain is set to 128; when the GAIN pin is high, the gain is set to 1. The ...

Page 13

BRIDGE POWER-DOWN SWITCH The bridge power-down switch (BPDSW) is useful in battery- powered applications where the optimization of system power consumption is essential. A 350 Ω load cell typically consumes 15 mA when excited with power supply. ...

Page 14

AD7780 APPLICATIONS INFORMATION The AD7780 provides a low cost, high resolution analog-to-digital function. Because the analog-to-digital function is provided by a Σ-Δ architecture, the parts are more immune to noisy environ- ments, making them ideal for use in sensor measurement ...

Page 15

GROUNDING AND LAYOUT Because the analog input and reference input of the ADC are differential, most of the voltages in the analog modulator are common-mode voltages. The excellent common-mode reject- tion of the part removes common-mode noise on these inputs. ...

Page 16

AD7780 OUTLINE DIMENSIONS 4.00 (0.1575) 3.80 (0.1496) 0.25 (0.0098) 0.10 (0.0039) COPLANARITY 0.10 0.15 0.05 ORDERING GUIDE Model Temperature Range 1 AD7780BRZ –40°C to +105°C 1 AD7780BRZ-REEL –40°C to +105°C 1 AD7780BRUZ –40°C to +105°C AD7780BRUZ-REEL 1 –40°C to +105°C ...

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