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ADR290 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADR290
Beschreibung Low Noise Micropower Precision Voltage References
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 15 Seiten
ADR290 Datasheet, Funktion
a
Low Noise Micropower
Precision Voltage References
ADR290/ADR291/ADR292
FEATURES
Voltage Options 2.048 V, 2.500 V and 4.096 V
2.7 V to 15 V Supply Range
Supply Current 12 A max
Initial Accuracy ؎2 mV max
Temperature Coefficient 8 ppm/؇C max
Low-Noise 6 V p-p (0.1 Hz–10 Hz)
High Output Current 5 mA min
Temperature Range ؊40؇C to ؉125؇C
REF02/REF19x Pinout
APPLICATIONS
Portable Instrumentation
Precision Reference for 3 V and 5 V Systems
A/D and D/A Converter Reference
Solar Powered Applications
Loop-Current Powered Instruments
GENERAL DESCRIPTION
The ADR290, ADR291 and ADR292 are low noise, micro-
power precision voltage references that use an XFETreference
circuit. The new XFET architecture offers significant perfor-
mance improvements over traditional bandgap and Zener-based
references. Improvements include: one quarter the voltage noise
output of bandgap references operating at the same current,
very low and ultralinear temperature drift, low thermal hyster-
esis and excellent long-term stability.
The ADR29x family are series voltage references providing stable
and accurate output voltages from supplies as low as 2.7 V. Out-
put voltage options are 2.048 V, 2.5 V and 4.096 V for the
ADR290, ADR291 and ADR292 respectively. Quiescent current
is only 12 µA, making these devices ideal for battery powered in-
strumentation. Three electrical grades are available offering initial
output accuracies of ± 2 mV, ± 3 mV and ± 6 mV max for the
ADR290 and ADR291 and ± 3 mV, ± 4 mV and ± 6 mV max for
the ADR292. Temperature coefficients for the three grades are
8 ppm/°C, 15 ppm/°C and 25 ppm/°C max, respectively. Line
regulation and load regulation are typically 30 ppm/V and
30 ppm/mA, maintaining the reference’s overall high perfor-
mance. For a device with 5.0 V output, refer to the ADR293
data sheet.
The ADR290, ADR291 and ADR292 references are specified
over the extended industrial temperature range of –40°C to
+125°C. Devices are available in the 8-lead SOIC, 8-lead TSSOP
and the TO-92 package.
PIN CONFIGURATIONS
8-Lead Narrow Body SO (R Suffix)
18
VIN 2
ADR29x
TOP VIEW
7
3 (Not to Scale) 6 VOUT
GND 4
5
8-Lead TSSOP (RU Suffix)
18
VIN 2
ADR29x 7
TOP VIEW
3 (Not to Scale) 6 VOUT
GND 4
5
3-Pin TO-92 (T9 Suffix)
PIN 1 PIN 2 PIN 3
VIN GND VOUT
BOTTOM VIEW
Part Number Nominal Output Voltage (V)
ADR290
ADR291
ADR292
2.048
2.500
4.096
XFET is a trademark of Analog Devices, Inc.
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.
Tel: 617/329-4700 World Wide Web Site: http://www.analog.com
Fax: 617/326-8703
© Analog Devices, Inc., 2000






ADR290 Datasheet, Funktion
ADR290/ADR291/ADR292
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ؉18 V
Output Short-Circuit Duration . . . . . . . . . . . . . . . . . Indefinite
Storage Temperature Range
T9, R, RU Package . . . . . . . . . . . . . . . . . Ϫ65°C to ؉150°C
Operating Temperature Range
ADR290/ADR291/ADR292 . . . . . . . . . . . Ϫ40°C to ؉125°C
Junction Temperature Range
T9, R, RU Package . . . . . . . . . . . . . . . . . Ϫ65°C to ؉125°C
Lead Temperature (Soldering, 60 sec) . . . . . . . . . . . . ؉300°C
Package Type
8-Lead SOIC (R)
8-Lead TO-92 (T9)
3-Pin TSSOP (RU)
JA1 JC Units
158 43 °C/W
162 120 °C/W
240 43 °C/W
*CAUTION
1. Stresses above those listed under Absolute Maximum
Ratings may cause permanent damage to the device. This is a
stress rating only; functional operation at or above this specifi-
cation is not implied. Exposure to the above maximum rating
conditions for extended periods may affect device
reliability.
2. Remove power before inserting or removing units from their
sockets.
3. Ratings apply to both DICE and packaged parts, unless other-
wise noted
NOTE
1θJA is specified for worst case conditions, i.e. θJA is specified for device in socket
for PDIP, and θJA is specified for a device soldered in circuit board for SOIC
packages.
ORDERING GUIDE
Model
Temperature Range
Package
ADR290ER, ADR290FR, ADR290GR
ADR290ER-REEL, ADR290FR-REEL, ADR290GR-REEL
ADR290ER-REEL7, ADR290FR-REEL7, ADR290GR-REEL7
ADR290GT9
ADR290GT9-REEL
ADR290GRU-REEL
ADR290GRU-REEL7
ADR290GBC
ADR291ER, ADR291FR, ADR291GR
ADR291ER-REEL, ADR291FR-REEL, ADR291GR-REEL
ADR291ER-REEL7, ADR291FR-REEL7, ADR291GR-REEL7
ADR291GT9
ADR291GT9-REEL
ADR291GRU-REEL
ADR291GRU-REEL7
ADR291GBC
ADR292ER, ADR292FR, ADR292GR
ADR292ER-REEL, ADR292FR-REEL, ADR292GR-REEL
ADR292ER-REEL7, ADR292FR-REEL7, ADR292GR-REEL7
ADR292GT9
ADR292GT9-REEL
ADR292GRU-REEL
ADR292GRU-REEL7
ADR292GBC
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
ϩ25°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
ϩ25°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
Ϫ40°C to ؉125°C
ϩ25°C
8-Lead SOIC
8-Lead SOIC
8-Lead SOIC
3-Pin TO-92
3-Pin TO-92
8-Lead TSSOP
8-Lead TSSOP
DICE
8-Lead SOIC
8-Lead SOIC
8-Lead SOIC
3-Pin TO-92
3-Pin TO-92
8-Lead TSSOP
8-Lead TSSOP
DICE
8-Lead SOIC
8-Lead SOIC
8-Lead SOIC
3-Pin TO-92
3-Pin TO-92
8-Lead TSSOP
8-Lead TSSOP
DICE
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although
the ADR290/ADR291/ADR292 features proprietary ESD protection circuitry, permanent damage
may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
precautions are recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
–6– REV. A

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ADR290 pdf, datenblatt
ADR290/ADR291/ADR292
THEORY OF OPERATION
The ADR29x series of references uses a new reference generation
technique known as XFET (eXtra implanted junction FET). This
technique yields a reference with low noise, low supply current
and very low thermal hysteresis.
The core of the XFET reference consists of two junction field-
effect transistors, one of which has an extra channel implant to
raise its pinch-off voltage. By running the two JFETS at the
same drain current, the difference in pinch-off voltage can be
amplified and used to form a highly stable voltage reference.
The intrinsic reference voltage is around 0.5 V with a negative
temperature coefficient of about –120 ppm/K. This slope is es-
sentially locked to the dielectric constant of silicon and can be
closely compensated by adding a correction term generated in
the same fashion as the proportional-to-temperature (PTAT)
term used to compensate bandgap references. The big advan-
tage over a bandgap reference is that the intrinsic temperature
coefficient is some thirty times lower (therefore less correction is
needed) and this results in much lower noise since most of the
noise of a bandgap reference comes from the temperature com-
pensation circuitry.
The simplified schematic below shows the basic topology of the
ADR29x series. The temperature correction term is provided by
a current source with value designed to be proportional to abso-
lute temperature. The general equation is:
( )( )VOUT
=
VP

R1
+
R2
R1
+
R3

+
I PTAT
R3
where VP is the difference in pinch-off voltage between the two
FETs, and IPTAT is the positive temperature coefficient correc-
tion current. The various versions of the ADR29x family are
created by on-chip adjustment of R1 and R3 to achieve 2.048 V,
2.500 V or 4.096 V at the reference output.
The process used for the XFET reference also features vertical
NPN and PNP transistors, the latter of which are used as output
devices to provide a very low drop-out voltage.
I1 I1
VIN
*
VP
VOUT
R1
IPTAT
R2
R3
*EXTRA CHANNEL IMPLANT
VOUT ؍ R1؉R2؉R3 ؋ VP؉ IPTAT ؋R3
R1
GND
Figure 30. ADR290/ADR291/ADR292 Simplified Schematic
Device Power Dissipation Considerations
The ADR29x family of references is guaranteed to deliver load
currents to 5 mA with an input voltage that ranges from 2.7 V
to 15 V (minimum supply voltage depends on output voltage
option). When these devices are used in applications with large
input voltages, care should be exercised to avoid exceeding the
published specifications for maximum power dissipation or
junction temperature that could result in premature device fail-
ure. The following formula should be used to calculate a device’s
maximum junction temperature or dissipation:
PD
=
TJ TA
θ JA
In this equation, TJ and TA are the junction and ambient tem-
peratures, respectively, PD is the device power dissipation, and
θJA is the device package thermal resistance.
Basic Voltage Reference Connections
References, in general, require a bypass capacitor connected
from the VOUT pin to the GND pin. The circuit in Figure 31
illustrates the basic configuration for the ADR29x family of ref-
erences. Note that the decoupling capacitors are not required
for circuit stability.
+
10F
NC 1
2
NC
0.1F
3
4
ADR29x
8 NC
7 NC
OUTPUT
6
5 NC
0.1F
Figure 31. Basic Voltage Reference Configuration
Noise Performance
The noise generated by the ADR29x family of references is typi-
cally less than 12 µV p-p over the 0.1 Hz to 10 Hz band. Figure
21 shows the 0.1 Hz to 10 Hz noise of the ADR290 which is
only 6 µV p-p. The noise measurement is made with a bandpass
filter made of a 2-pole high-pass filter with a corner frequency at
0.1 Hz and a 2-pole low-pass filter with a corner frequency at
10 Hz.
Turn-On Time
Upon application of power (cold start), the time required for the
output voltage to reach its final value within a specified error
band is defined as the turn-on settling time. Two components
normally associated with this are the time for the active circuits
to settle, and the time for the thermal gradients on the chip to
stabilize. Figure 28 shows the turn-on settling time for the
ADR291.
APPLICATIONS SECTION
A Negative Precision Reference without Precision Resistors
In many current-output CMOS DAC applications, where the
output signal voltage must be of the same polarity as the refer-
ence voltage, it is often required to reconfigure a current-switch-
ing DAC into a voltage-switching DAC through the use of a
1.25 V reference, an op amp and a pair of resistors. Using a cur-
rent-switching DAC directly requires the need for an additional
operational amplifier at the output to reinvert the signal. A
negative voltage reference is then desirable from the point that
–12–
REV. A

12 Page





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