AD7298

Manufacturer Part NumberAD7298
Description8-Channel, 1MSPS, 12-Bit SAR ADC with Temperature Sensor
ManufacturerAnalog Devices
AD7298 datasheet
 


Specifications of AD7298

Resolution (bits)12bit# Chan8
Sample Rate1MSPSInterfaceSPI
Analog Input TypeSE-UniAin RangeUni (Vref),Uni 1.0V,Uni 1.25,Uni 2.0V,Uni 2.5V
Adc ArchitectureSARPkg TypeCSP
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FEATURES
12-bit SAR ADC
8 single-ended inputs
Channel sequencer functionality
Fast throughput of 1 MSPS
Analog input range: 0 V to 2.5 V
12-bit temperature-to-digital converter
Temperature sensor accuracy of ±1°C
Temperature range: −40°C to +125°C
Specified for V
: 2.8 V to 3.6 V
DD
Logic voltage V
: 1.65 V to 3.6 V
DRIVE
Power-down current: <10 μA
Internal 2.5 V reference
Internal power-on reset
High speed serial interface SPI
20-lead LFCSP
GENERAL DESCRIPTION
The AD7298 is a 12-bit, high speed, low power, 8-channel,
successive approximation ADC with an internal temperature
sensor. The part operates from a single 3.3 V power supply and
features throughput rates up to 1 MSPS. The device contains a
low noise, wide bandwidth track-and-hold amplifier that can
handle input frequencies in excess of 30 MHz.
The AD7298 offers a programmable sequencer, which enables
the selection of a preprogrammable sequence of channels for
conversion. The device has an on-chip, 2.5 V reference that can
be disabled to allow the use of an external reference.
The AD7298 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 device offers a 4-wire serial
interface compatible with SPI and DSP interface standards.
The AD7298 uses advanced design techniques to achieve very
low power dissipation at high throughput rates. The part also
offers flexible power/throughput rate management options.
The part is offered in a 20-lead LFCSP package.
Rev. B
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.
8-Channel, 1 MSPS, 12-Bit SAR ADC
with Temperature Sensor
FUNCTIONAL BLOCK DIAGRAM
V
DD
V
REF
REF
V
IN0
T/H
INPUT
AD7298
V
MUX
IN7
TEMP
SENSOR
PD/RST
PRODUCT HIGHLIGHTS
1.
Ideally Suited to Monitoring System Variables in a Variety
of Systems. This includes telecommunications, and process
and industrial control.
2.
High Throughput Rate of 1 MSPS with Low Power
Consumption.
3.
Eight Single-Ended Inputs with a Channel Sequencer.
A consecutive sequence of channels can be selected on
which the ADC cycles and converts.
4.
Integrated Temperature Sensor with 0.25°C Resolution.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
©2010–2011 Analog Devices, Inc. All rights reserved.
AD7298
GND
BUF
12-BIT
SUCCESSIVE
APPROXIMATION
ADC
SEQUENCER
SCLK
DOUT
CONTROL
DIN
LOGIC
CS
V
DRIVE
T
_BUSY
SENSE
Figure 1.
www.analog.com

AD7298 Summary of contents

  • Page 1

    ... High speed serial interface SPI 20-lead LFCSP GENERAL DESCRIPTION The AD7298 is a 12-bit, high speed, low power, 8-channel, successive approximation ADC with an internal temperature sensor. The part operates from a single 3.3 V power supply and features throughput rates MSPS. The device contains a low noise, wide bandwidth track-and-hold amplifier that can handle input frequencies in excess of 30 MHz ...

  • Page 2

    ... DRIVE The Internal or External Reference.......................................... 15 Control Register.............................................................................. 16 Modes of Operation ....................................................................... 17 Traditional Multichannel Mode of Operation........................ 17 Repeat Operation ....................................................................... 18 Power-Down Modes .................................................................. 19 Powering Up the AD7298 ......................................................... 20 Reset ............................................................................................. 20 Serial Interface ................................................................................ 21 Temperature Sensor Read ......................................................... 22 Layout and Configuration............................................................. 23 Power Supply Bypassing and Grounding................................ 23 Temperature Monitoring........................................................... 23 Outline Dimensions ....................................................................... 24 Ordering Guide .......................................................................... 24 ...

  • Page 3

    ... Guaranteed no missed codes to 12 bits LSB LSB ppm/°C LSB LSB ppm/°C V μA pF When in track pF When in hold mode V ±0.3% maximum @ 25°C ppm For 1000 hours ppm V μA External reference applied to Pin V Ω ppm/°C μV rms Bandwidth = 10 MHz AD7298 REF ...

  • Page 4

    ... AD7298 Parameter LOGIC INPUTS Input High Voltage, V INH Input Low Voltage, V INL Input Current Input Capacitance LOGIC OUTPUTS Output High Voltage Output Low Voltage Floating State Leakage Current 3 Floating State Output Capacitance INTERNAL TEMPERATURE SENSOR Operating Range ...

  • Page 5

    ... BUSY falling edge to CS falling edge SENSE_ ns max Delay from CS rising edge to DOUT high impedance μs max Power-up time from partial power-down ms max Internal reference power-up time from full power-down Rev Page and timed from a voltage level DRIVE , MHz IN7 SCLK AD7298 ...

  • Page 6

    ... AD7298 ABSOLUTE MAXIMUM RATINGS Table 3. Parameter V to GND, GND1 GND, GND1 DRIVE Analog Input Voltage to GND1 Digital Input Voltage to GND Digital Output Voltage to GND V to GND1 REF GND1 to GND Input Current to Any Pin Except Supplies Operating Temperature Range Storage Temperature Range ...

  • Page 7

    ... Serial Data Output. The conversion result from the AD7298 is provided on this output as a serial data stream. The bits are clocked out on the falling edge of the SCLK input. The data stream from the AD7298 consists of four address bits indicating which channel the conversion result corresponds to, followed by the 12 bits of conversion data (MSB first) ...

  • Page 8

    ... This pin can be used to reset the device by toggling the pin low for a minimum and a maximum of 100 ns. If the maximum time is exceeded, the part enters power-down mode. When placing the AD7298 in full power-down mode, the analog inputs must return ...

  • Page 9

    ... Figure 6. INL vs. V REF 0.6 DNL MAX 0.4 0 25° DRIVE –0.2 DNL MIN –0.4 –0.6 1.00 1.25 1.50 1.75 2.00 2.25 REFERENCE VOLTAGE (V) Figure 7. DNL vs. V REF 0.5 1.0 1.5 V (V) REF Figure 8. Effective Number of Bits vs. V AD7298 2.50 2.75 2.50 2. DRIVE 2.0 2.5 REF ...

  • Page 10

    ... AD7298 3 DRIVE 2.5 2.0 1.5 1.0 0 0.5 1.0 1.5 2.0 2.5 CURRENT LOAD (mA) Figure 9. V vs. Reference Output Current Drive REF TIME (Seconds) Figure 10. Response to Thermal Shock from Room Temperature into 50°C Stirred Oil – –92 DRIVE –94 –96 –98 – ...

  • Page 11

    ... Rev Page DRIVE 100 200 300 400 500 600 700 THROUGHPUT (kSPS) 4.0 –40°C +85°C 0°C +105°C 3.5 +25°C +125°C 3.0 2.5 2.0 1.5 1.0 0.5 0 2.8 2.9 3.0 3.1 3.2 3.3 3.4 V (V) DD Temperatures AD7298 800 900 1000 = DRIVE 3.5 3.6 ...

  • Page 12

    ... The theoretical signal-to-noise and distortion ratio for an ideal N-bit converter with a sine wave input is given by Signal-to-(Noise + Distortion) = (6. 1.76) dB Thus, the SINAD for an ideal 12-bit converter. Total Harmonic Distortion (THD) The ratio of the rms sum of harmonics to the fundamental. For the AD7298 defined ...

  • Page 13

    ... IN GND1 ANALOG INPUT Figure 22 shows an equivalent circuit of the analog input struc- ture of the AD7298. The two diodes, D1 and D2, provide ESD protection for the analog inputs. Care must be taken to ensure that the analog input signal never exceeds the internally . generated LDO voltage of 2 ...

  • Page 14

    ... SENSE AVG result, a moving average temperature measurement. conversion result given by the AD7298 after the SENSE AVG bit changed, the averaging function is SENSE average conversion result is the current SENSE AVG the control register. The AD7298 defaults conversion Current _ Result SENSE AVG bit ...

  • Page 15

    ... V (see the Absolute Maximum Ratings DD section). THE INTERNAL OR EXTERNAL REFERENCE The AD7298 can operate with either the internal 2.5 V on-chip reference or an externally applied reference. The EXT_REF bit in the control register is used to determine whether the internal reference is used. If the EXT_REF bit is selected in the control ...

  • Page 16

    ... CONTROL REGISTER The control register of the AD7298 is a 16-bit, write-only register. Data is loaded from the DIN pin of the AD7298 on the falling edge of SCLK. The data is transferred on the DIN line at the same time that the conversion result is read from the part. The data transferred on the DIN line corresponds to the AD7298 configuration for the next conversion ...

  • Page 17

    ... IN0 SCLK DOUT INVALID DATA DATA WRITTEN TO CONTROL DIN REGISTER CHANNEL 1 SELECTED Figure 25. Configuring a Conversion and Read with the AD7298. One channel selected for conversion SCLK INVALID DATA DOUT DATA WRITTEN TO CONTROL DIN REGISTER CH 1 AND 2 SELECTED CS 1 ...

  • Page 18

    ... This mode of operation simplifies the operation of the device by allowing consecutive channels to be converted without having to reprogram the control register or write to the part on each serial transfer. Figure 27 illustrates how to set up the AD7298 to continuously convert on a particular sequence of channels. To exit the repeat mode of operation and revert back to the traditional mode of operation of a multichannel ADC, ensure that the REPEAT bit = 0 on the next serial write ...

  • Page 19

    ... Serial Interface section. The data presented to the AD7298 on the DIN line during the first 16 clock cycles of the data transfer are loaded into the control register (provided the WRITE bit is 1). The part remains fully powered up in normal mode at the end of the conversion as long as the PPD bit is set the write transfer during that conversion ...

  • Page 20

    ... RESET The AD7298 includes a reset feature that can be used to reset the device and the contents of all internal registers, including the control register, to their default state. ...

  • Page 21

    ... SERIAL INTERFACE Figure 30 shows the detailed timing diagram for the serial interface to the AD7298. The serial clock provides the conver- sion clock and controls the transfer of information to and from the AD7298 during each conversion. The CS signal initiates the data transfer and conversion process. ...

  • Page 22

    ... Once the previous conversion result has been read, any subsequent CS falling edges which occur while the T signal is high are internally ignored by the AD7298. If addi- tional CS falling edges are provided while T the AD7298 provides an invalid digital output of all 1s. ...

  • Page 23

    ... As much as 60% of the heat transferred from the heat source to the thermal sensor on the AD7298 die is discharged via the copper tracks and the bond pads. Of the pads on the AD7298, the GND pad transfers most of the heat. Therefore, to measure the temperature of a heat source recommended that the thermal resistance between the AD7298 GND pad and the GND of the heat source be reduced as much as possible ...

  • Page 24

    ... SEATING PLANE ORDERING GUIDE 1 Model Temperature Range AD7298BCPZ −40°C to +125°C AD7298BCPZ-RL7 −40°C to +125°C EVAL-AD7298SDZ RoHS Compliant Part. ©2010–2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 4.10 0.30 4.00 SQ 0.25 3.90 0.18 16 ...