AD7291_11 AD [Analog Devices], AD7291_11 Datasheet

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AD7291_11

Manufacturer Part Number
AD7291_11
Description
8-Channel, I2C, 12-Bit SAR ADC with Temperature Sensor
Manufacturer
AD [Analog Devices]
Datasheet
FEATURES
12-bit SAR ADC
12-bit temperature-to-digital converter
Channel sequencer operation
Specified for V
Logic voltage V
Internal 2.5 V reference
I
Out of range indicator/alert function
Autocycle mode
Power-down current: 12 μA maximum
Temperature range: −40°C to +125°C
20-lead LFCSP package
GENERAL DESCRIPTION
The AD7291 is a 12-bit, low power, 8-channel, successive
approximation analog-to-digital converter (ADC) with an
internal temperature sensor.
The part operates from a single 3.3 V power supply and features
an I
multiplexer and a track-and-hold amplifier than can handle
frequencies up to 30 MHz. The device has an on-chip 2.5 V
reference that can be disabled to allow the use of an external
reference.
The AD7291 provides a 2-wire serial interface compatible with
I
interface modes. The AD7291 normally remains in a partial
power-down state while not converting and powers up for
conversions. The conversion process can be controlled by a
command mode where conversions occur across I
operations or an autocycle mode selected through software
control.
The AD7291 includes a high accuracy band gap temperature
sensor, which is monitored and digitized by the 12-bit ADC to
give a resolution of 0.25°C.
The AD7291 offers a programmable sequencer, which enables
the selection of a preprogrammable sequence of channels for
conversion.
Rev. 0
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.
2
2
C-compatible serial interface supports standard and
C interfaces. The I
8 single-ended analog input channels
Analog input range: 0 V to 2.5 V
Temperature sensor accuracy of ±1°C typical
fast speed modes
2
C-compatible interface. The part contains a 9-channel
DD
DRIVE
of 2.8 V to 3.6 V
2
= 1.65 V to 3.6 V
C interface supports standard and fast I
2
C write
2
C
8-Channel, I
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
On-chip limit registers can be programmed with high and low
limits for the conversion results; an out-of-range indicator
output (ALERT) becomes active when the programmed high
or low limits are violated by the conversion result. This output
can be used as an interrupt.
PRODUCT HIGHLIGHTS
1.
2.
3.
4.
5.
6.
Table 1. AD7291 and Related Products
Device
AD7291
AD7298
V
V
V
REF
IN0
IN7
Ideally suited to monitoring system variables in a variety
of systems including telecommunications, process control,
and industrial control.
I
and fast modes.
Automatic partial power-down while not converting to
maximize power efficiency.
Channel sequencer operation.
Integrated temperature sensor with 0.25°C resolution.
Out of range indicator that can be software disabled or
enabled.
2
C-compatible serial interface, which supports standard
with Temperature Sensor
Resolution
12-bit
12-bit
INPUT
FUNCTIONAL BLOCK DIAGRAM
V
MUX
PD/RST
DD
REF
SENSOR
TEMP
T/H
©2011 Analog Devices, Inc. All rights reserved.
AD7291
2
Interface
I
SPI
2
C
C, 12-Bit SAR ADC
BUF
Figure 1.
ALERT
CONTROL LOGIC
APPROXIMATION
I
2
SEQUENCER
C INTERFACE
SUCCESSIVE
Features
8-channel, I
ADC with temperature sensor
8-channel, 1 MSPS, 12-bit SAR
ADC with temperature sensor
12-BIT
ADC
GND
AD7291
2
www.analog.com
C, 12-bit SAR
SCL
SDA
AS1
AS0
V
DRIVE

Related parts for AD7291_11

AD7291_11 Summary of contents

Page 1

FEATURES 12-bit SAR ADC 8 single-ended analog input channels Analog input range 2.5 V 12-bit temperature-to-digital converter Temperature sensor accuracy of ±1°C typical Channel sequencer operation Specified for Logic ...

Page 2

AD7291 TABLE OF CONTENTS Features .............................................................................................. 1 Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Product Highlights ........................................................................... 1 Revision History ............................................................................... 2 Specifications ..................................................................................... Timing Specifications ............................................................ 5 Absolute Maximum Ratings ............................................................ 6 Thermal ...

Page 3

SPECIFICATIONS DRIVE unless otherwise noted. Table 2. Parameter DYNAMIC PERFORMANCE Signal-to-Noise Ratio (SNR) 2 Signal-to-Noise (+ Distortion) Ratio (SINAD) 2 Total Harmonic Distortion (THD) ...

Page 4

AD7291 Parameter LOGIC OUTPUTS Output High Voltage Output Low Voltage Floating State Leakage Current 3 Floating State Output Capacitance TEMPERATURE SENSOR—INTERNAL Operating Range Accuracy Resolution CONVERSION RATE Conversion Time 6 Autocycle Update Rate Throughput Rate POWER ...

Page 5

I C TIMING SPECIFICATIONS Guaranteed by initial characterization. All values were measured with the input filtering enabled. C bus line, with t and t measured between 0.3 × 2.5 V internal/external −40°C to +125°C, ...

Page 6

AD7291 ABSOLUTE MAXIMUM RATINGS Table 4. Parameter V to GND1, GND GND1, GND DRIVE Analog Input Voltage to GND1 Digital Input Voltage to GND1 Digital Output Voltage to GND1 V to GND1 REF GND to GND1 Input ...

Page 7

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS Table 6. Pin Function Descriptions Pin No. Mnemonic Description Analog Inputs. The AD7291 has eight single-ended analog inputs that are multiplexed into the on-chip track-and- IN3 IN4 18 ...

Page 8

AD7291 TYPICAL PERFORMANCE CHARACTERISTICS DRIVE f = 22.22ksps 400kHz –20 SCL f = 10kHz IN SNR = 71.209 THD = –81.66 –40 –60 –80 –100 –120 ...

Page 9

DRIVE 2.5 2.0 1.5 1.0 0 0.5 1.0 1.5 2.0 2.5 3.0 CURRENT LOAD (mA) Figure 10. V vs. Reference Output Drive REF ...

Page 10

AD7291 9 DRIVE 8 8.8 8.7 8.6 8.5 8.4 8.3 8.2 8.1 8 120 180 240 SCL FREQUENCY (kHz) Figure 16. Power vs. Throughput in Normal Mode 2.5 2.0 1.5 1.0 ...

Page 11

TERMINOLOGY Signal-to-Noise and Distortion Ratio (SINAD) The measured ratio of signal-to-noise and distortion at the output of the ADC. The signal is the rms amplitude of the fundamental. Noise is the sum of all nonfundamental signals up to half the ...

Page 12

AD7291 CIRCUIT INFORMATION The AD7291 includes an 8-channel multiplexer, an on-chip track-and-hold amplifier, an analog-to-digital converter (ADC), an on-chip oscillator, internal data registers, an internal tempera- 2 ture sensor, and an I C-compatible serial interface, all housed in a 20-lead ...

Page 13

ADC TRANSFER FUNCTION The output coding of the AD7291 is straight binary for the analog input channel conversion results and twos complement for the temperature conversion result. The designed code tran- sitions occur at successive LSB values (that is, 1 ...

Page 14

AD7291 Temperature Value Format One LSB of the ADC corresponds to 0.25°C. The temperature reading from the ADC is stored in a 12-bit twos complement format, to accommodate both positive and negative tempera- ture measurements. Sample temperature values are listed ...

Page 15

INTERNAL REGISTER STRUCTURE The AD7291 contains 34 internal registers (see Figure 23) that are used to store conversion results, high and low conversion limits, and information to configure and control the device. There are 33 data registers and one address ...

Page 16

AD7291 Table 9. AD7291 Register Addresses Hex Code 0x00 0x01 0x02 0x03 0x04 0x05 0 0 ...

Page 17

COMMAND REGISTER (0x00) The command register is a 16-bit write-only register that is used to set the operating modes of the AD7291. The bit functions are outlined in Table 10. A two-byte write is necessary when writing to the command ...

Page 18

AD7291 Table 12. Channel Selection Bits for Command Register D15 D14 D13 D12 D11 ...

Page 19

Table 17. T Conversion Result Register (First Read) SENSE MSB D15 D14 D13 D12 D11 ADD3 ADD2 ADD1 ADD0 B11 Table 18. T Result Register (Second Read) SENSE AVERAGE ...

Page 20

AD7291 HYSTERESIS REGISTER Each analog input channel and the internal temperature sensor has its own hysteresis register, which is a 16-bit read/write register. Only the 12 LSBs are used. Bit D15 to Bit D12 are not used in the register ...

Page 21

I C INTERFACE Control of the AD7291 is carried out via the I serial bus. The AD7291 is connected to this bus as a slave device under the control of a master device such as the processor. SERIAL BUS ...

Page 22

AD7291 WRITING TO THE AD7291 WRITING TWO BYTES OF DATA TO A 16-BIT REGISTER All registers on the AD7921 are 16-bit registers; therefore, two bytes of data are required to write a value to any one of these registers. Writing ...

Page 23

READING DATA FROM THE AD7291 READING TWO BYTES OF DATA FROM A 16-BIT REGISTER Reading the contents from any of the 16-bit registers is a 2-byte read operation. In this protocol, the first part of the transaction writes to the ...

Page 24

AD7291 MODES OF OPERATION When supplies are first applied to the AD7291, the ADC powers up in partial power-down mode and normally remains in this partial power-down state while not converting. Once the master addresses the AD7291, it exits partial ...

Page 25

The example in Figure 28 shows the command mode convert- ing on a sequence of channels including V 1. The master device asserts a start condition on SDA. 2. The master sends the 7-bit slave address followed by the write ...

Page 26

AD7291 AUTOCYCLE MODE The AD7291 can be configured to convert continuously on a programmable sequence of channels, making it the ideal mode of operation for system monitoring. This mode is useful for monitoring signals, such as battery voltage and temperature, ...

Page 27

OUTLINE DIMENSIONS PIN 1 INDICATOR 0.80 0.75 0.70 SEATING PLANE ORDERING GUIDE 1 Model Temperature Range AD7291BCPZ −40°C to +125°C AD7291BCPZ-RL7 −40°C to +125°C EVAL-AD7291SDZ RoHS Compliant Part. 4.10 0.30 4.00 SQ 0.25 3.90 0.18 16 0.50 ...

Page 28

AD7291 NOTES refers to a communications protocol originally developed by Philips Semiconductors (now NXP Semiconductors). ©2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D08711-0-1/11(0) Rev ...

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