Datasheet ADR290, ADR292 Datasheet (ANALOG DEVICES)

查询ADR290供应商查询ADR290供应商

Low Noise Micropower

2.048 V, 2.5 V, and 4.096 V

a

FEATURES
Supply Range

2.35 V to 15 V, ADR290

2.8 V to 15 V, ADR291

4.4 V to 15 V, ADR292
Supply Current 12 A Max
Low-Noise 6 V, 8 V, 12 V p-p (0.1 Hz–10 Hz)
High Output Current 5 mA
Temperature Range 40C to 125C
Pin Compatible with REF02/REF19x

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

Precision Voltage References

ADR290/ADR291/ADR292

PIN CONFIGURATIONS

8-Lead Narrow Body SO (SO Suffix)

NC

1

ADR29x

V

2

IN

TOP VIEW

(Not to Scale)

NC

3

4

GND

NC = NO CONNECT

8-Lead TSSOP (RU Suffix)

NC

1

ADR29x

V

2

IN

TOP VIEW

(Not to Scale)

NC

3

4

GND

NC = NO CONNECT

8

NC

NC

7

V

6

OUT

NC

5

8

NC

NC

7

V

6

OUT

NC

5

GENERAL DESCRIPTION

The ADR290, ADR291 and ADR292 are low noise, micro­power precision voltage references that use an XFET
circuit. The new XFET

architecture offers significant perfor-

®

reference

mance improvements over traditional bandgap and Buried
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 hysteresis and excellent long-term stability.

The ADR29x family are series voltage references providing stable
and accurate output voltages from supplies as low as 2.35 V for the
ADR290. Output voltage options are 2.048 V, 2.5 V, and 4.096 V
for the ADR290, ADR291, and ADR292 respectively. Quiescent

ADR29x Product

Output Voltage Initial Accuracy Temperature Coefficient

Part Number (V) (%) (ppm/C) Max

ADR290 2.048 0.10, 0.15, 0.29 8, 15, 25
ADR291 2.500 0.08, 0.12, 0.24 8, 15, 25
ADR292 4.096 0.07, 0.10, 0.15 8, 15, 25
ADR293 5.000 (See ADR293 Data Sheet)

current is only 12 µA, making these devices ideal for battery-
powered instrumentation. 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 performance. 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 and 8-lead
TSSOP packages.

XFET is a registered trademark of Analog Devices, Inc.

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
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: [phone] World Wide Web Site: http://www.analog.com
Fax: [phone] © Analog Devices, Inc., 2001

ADR290/ADR291/ADR292

ADR290–SPECIFICATIONS

ELECTRICAL SPECIFICATIONS

(VS = 2.7 V, TA = +25C unless otherwise noted)

Parameter Symbol Conditions Min Typ Max Unit

E GRADE

I

Output Voltage V
Initial Accuracy V

O

OERR

= 0 mA 2.046 2.048 2.050 V

OUT

–2 +2 mV
–0.10 +0.10 %

F GRADE

I

Output Voltage V
Initial Accuracy V

O

OERR

= 0 mA 2.045 2.048 2.051 V

OUT

–3 +3 mV
–0.15 +0.15 %

G GRADE

Output Voltage V
Initial Accuracy V

O

OERR

I

= 0 mA 2.042 2.048 2.054 V

OUT

–6 +6 mV
–0.29 +0.29 %

LINE REGULATION

“E/F” Grades ∆V

O

/∆V

2.7 V to 15 V, I

IN

= 0 mA 30 100 ppm/V

OUT

“G” Grade 40 125 ppm/V

LOAD REGULATION

“E/F” Grades ∆V

/∆I

O

LOADVS

= 5.0 V, 0 mA to 5 mA 30 100 ppm/mA

“G” Grade 40 125 ppm/mA

LONG-TERM STABILITY ∆V

NOISE VOLTAGE e

WIDEBAND NOISE DENSITY e

N

N

O

After 1000 hrs of Operation @ 125°C 50 ppm

0.1 Hz to 10 Hz 6 µV p-p
@ 1 kHz 420 nV/√Hz

ELECTRICAL SPECIFICATIONS

(VS = 2.7 V, TA = –25C ≤ TA ≤ +85C unless otherwise noted)

Parameter Symbol Conditions Min Typ Max Unit

TEMPERATURE COEFFICIENT

I

“E” Grade TCV

O

= 0 mA 3 8 ppm/°C

OUT

“F” Grade 6 15 ppm/°C
“G” Grade 10 25 ppm/°C

LINE REGULATION

“E/F” Grades ∆V

O

/∆V

2.7 V to 15 V, I

IN

= 0 mA 35 125 ppm/V

OUT

“G” Grade 50 150 ppm/V

LOAD REGULATION

“E/F” Grades ∆V

/∆I

O

LOADVS

= 5.0 V, 0 mA to 5 mA 20 125 ppm/mA

“G” Grade 30 150 ppm/mA

ELECTRICAL SPECIFICATIONS

(VS = 2.7 V, TA = 40C ≤ TA ≤ +125C unless otherwise noted)

Parameter Symbol Conditions Min Typ Max Unit

TEMPERATURE COEFFICIENT

I

“E” Grade TCV

O

= 0 mA 3 10 ppm/°C

OUT

“F” Grade 5 20 ppm/°C
“G” Grade 10 30 ppm/°C

LINE REGULATION

“E/F” Grades ∆V

O

/∆V

2.7 V to 15 V, I

IN

= 0 mA 40 200 ppm/V

OUT

“G” Grade 70 250 ppm/V

LOAD REGULATION

“E/F” Grades ∆V

/∆I

O

LOADVS

= 5.0 V, 0 mA to 5 mA 20 200 ppm/mA

“G” Grade 30 300 ppm/mA

SUPPLY CURRENT I

S

TA = +25°C812µA
–40°C ≤ TA ≤ +125°C1215µA

THERMAL HYSTERESIS V

Specifications subject to change without notice.

O–HYS

SO-8, TSSOP-8 50 ppm

–2–

REV. B

ADR291–SPECIFICATIONS

ADR290/ADR291/ADR292

ELECTRICAL SPECIFICATIONS

(VS = 3.0 V, TA = +25C unless otherwise noted)

Parameter Symbol Conditions Min Typ Max Unit

E GRADE

I

Output Voltage V
Initial Accuracy V

O

OERR

= 0 mA 2.498 2.500 2.502 V

OUT

–2 +2 mV
–0.08 +0.08 %

F GRADE

Output Voltage V
Initial Accuracy V

O

OERR

I

= 0 mA 2.497 2.500 2.503 V

OUT

–3 +3 mV
–0.12 +0.12 %

G GRADE

I

Output Voltage V
Initial Accuracy V

O

OERR

= 0 mA 2.494 2.500 2.506 V

OUT

–6 +6 mV
–0.24 +0.24 %

LINE REGULATION

“E/F” Grades ∆V

O

/∆V

3.0 V to 15 V, I

IN

= 0 mA 30 100 ppm/V

OUT

“G” Grade 40 125 ppm/V

LOAD REGULATION

“E/F“ Grades ∆V

/∆I

O

LOADVS

= 5.0 V, 0 mA to 5 mA 30 100 ppm/mA

“G“ Grade 40 125 ppm/mA

LONG-TERM STABILITY ∆V

NOISE VOLTAGE e

WIDEBAND NOISE DENSITY e

N

N

O

After 1000 hrs of Operation @ 125°C 50 ppm

0.1 Hz to 10 Hz 8 µV p-p
@ 1 kHz 480 nV/√ Hz

ELECTRICAL SPECIFICATIONS

(VS = 3.0 V, TA = –25C ≤ TA ≤ +85C unless otherwise noted)

Parameter Symbol Conditions Min Typ Max Unit

TEMPERATURE COEFFICIENT

“E” Grade TCV

O

I

= 0 mA 3 8 ppm/°C

OUT

“F” Grade 5 15 ppm/°C
“G” Grade 10 25 ppm/°C

LINE REGULATION

“E/F” Grades ∆V

O

/∆V

3.0 V to 15 V, I

IN

= 0 mA 35 125 ppm/V

OUT

“G” Grade 50 150 ppm/V

LOAD REGULATION

“E/F” Grades ∆V

/∆I

O

LOADVS

= 5.0 V, 0 mA to 5 mA 20 125 ppm/mA

“G” Grade 30 150 ppm/mA

(V

ELECTRICAL SPECIFICATIONS

= 3.0 V, TA = –40C ≤ TA ≤ +125C unless otherwise noted)

S

Parameter Symbol Conditions Min Typ Max Unit

TEMPERATURE COEFFICIENT

“E” Grade TCV

O

I

= 0 mA 3 10 ppm/°C

OUT

“F” Grade 5 20 ppm/°C
“G” Grade 10 30 ppm/°C

LINE REGULATION

“E/F” Grades ∆V

O

/∆V

3.0 V to 15 V, I

IN

= 0 mA 40 200 ppm/V

OUT

“G” Grade 70 250 ppm/V

LOAD REGULATION

“E/F” Grades ∆V

/∆I

O

LOADVS

= 5.0 V, 0 mA to 5 mA 20 200 ppm/mA

“G” Grade 30 300 ppm/mA

SUPPLY CURRENT I

S

TA = +25°C912µA
–40°C ≤ TA ≤ +125°C1215µA

THERMAL HYSTERESIS V

Specifications subject to change without notice.

O–HYS

SO-8, TSSOP-8 50 ppm

REV. B

–3–

ADR290/ADR291/ADR292

ADR292–SPECIFICATIONS

ELECTRICAL SPECIFICATIONS

(VS = 5 V, TA = +25C unless otherwise noted)

Parameter Symbol Conditions Min Typ Max Unit

E GRADE

Output Voltage V
Initial Accuracy V

O

OERR

I

= 0 mA 4.093 4.096 4.099 V

OUT

–3 +3 mV
–0.07 +0.07 %

F GRADE

Output Voltage V
Initial Accuracy V

O

OERR

I

= 0 mA 4.092 4.096 4.1 V

OUT

–4 +4 mV
–0.10 +0.10 %

G GRADE

I

Output Voltage V
Initial Accuracy V

O

OERR

= 0 mA 4.090 4.096 4.102 V

OUT

–6 +6 mV
–0.15 +0.15 %

LINE REGULATION

“E/F” Grades ∆V

O

/∆V

IN

4.5 V to 15 V, I

= 0 mA 30 100 ppm/V

OUT

“G” Grade 40 125 ppm/V

LOAD REGULATION

“E/F” Grades ∆V

/∆I

O

LOADVS

= 5.0 V, 0 mA to 5 mA 30 100 ppm/mA

“G” Grade 40 125 ppm/mA

LONG-TERM STABILITY ∆V

NOISE VOLTAGE e

WIDEBAND NOISE DENSITY e

O

N

N

After 1000 hrs of Operation @ 125°C 50 ppm

0.1 Hz to 10 Hz 12 µV p-p
@ 1 kHz 640 nV/√ Hz

ELECTRICAL SPECIFICATIONS

(VS = 5 V, TA = –25C ≤ TA ≤ +85C unless otherwise noted)

Parameter Symbol Conditions Min Typ Max Unit

TEMPERATURE COEFFICIENT

“E” Grade TCV

O

I

= 0 mA 3 8 ppm/°C

OUT

“F” Grade 5 15 ppm/°C
“G” Grade 10 25 ppm/°C

LINE REGULATION

“E/F” Grades ∆V

O

/∆V

IN

4.5 V to 15 V, I

= 0 mA 35 125 ppm/V

OUT

“G” Grade 50 150 ppm/V

LOAD REGULATION

“E/F” Grades ∆V

/∆I

O

LOADVS

= 5.0 V, 0 mA to 5 mA 20 125 ppm/mA

“G” Grade 30 150 ppm/mA

(V

ELECTRICAL SPECIFICATIONS

= 5 V, TA = –40C ≤ TA ≤ +125C unless otherwise noted)

S

Parameter Symbol Conditions Min Typ Max Unit

TEMPERATURE COEFFICIENT

“E” Grade TCV

O

I

= 0 mA 3 10 ppm/°C

OUT

“F” Grade 5 20 ppm/°C
“G” Grade 10 30 ppm/°C

LINE REGULATION

“E/F” Grades ∆V

O

/∆V

IN

4.5 V to 15 V, I

= 0 mA 40 200 ppm/V

OUT

“G” Grade 70 250 ppm/V

LOAD REGULATION

“E/F” Grades ∆V

/∆I

O

LOADVS

= 5.0 V, 0 mA to 5 mA 20 200 ppm/mA

“G” Grade 30 300 ppm/mA

SUPPLY CURRENT I

S

TA = +25°C1015µA
–40°C ≤ TA ≤ +125°C1218µA

THERMAL HYSTERESIS V

Specifications subject to change without notice.

O–HYS

SO-8, TSSOP-8 50 ppm

–4–

REV. B

ADR290/ADR291/ADR292

WARNING!

ESD SENSITIVE DEVICE

ABSOLUTE MAXIMUM RATINGS

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 V

Output Short-Circuit Duration to GND . . . . . . . . . . Indefinite

Storage Temperature Range

SO, RU Package . . . . . . . . . . . . . . . . . . . ⫺65°C to 150°C

Operating Temperature Range

Package Type JA* 

8-Lead SOIC (SO) 158 43 °C/W
8-Lead TSSOP (RU) 240 43 °C/W

*θJA is specified for worst-case conditions, i.e., θ

testing. In practice, θ

is specified for a device soldered in the circuit board.

JA

ADR290/ADR291/ADR292. . . . . . . . . . . ⫺40°C to 125°C

Junction Temperature Range

SO, RU Package . . . . . . . . . . . . . . . . . . . ⫺65°C to 125°C

Lead Temperature (Soldering, 60 sec) . . . . . . . . . . . . . 300°C

NOTES

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 specification 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.

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.

JC

is specified for device in socket

JA

Unit

ORDERING GUIDE

Temperature Number of

Output Initial Coefficient Package Package Parts per

Model Voltage Accuracy (%) Max (ppm/C) Description Option Package

ADR290

ER, ER-REEL7, ER-REEL 2.048 0.10 8 SOIC SO-8 98, 1000, 2500
FR, FR-REEL7, FR-REEL 2.048 0.15 15 SOIC SO-8 98, 1000, 2500
GR, GR-REEL7, GR-REEL 2.048 0.29 25 SOIC SO-8 98, 1000, 2500
GRU-REEL7, GRU-REEL 2.048 0.29 25 TSSOP RU-8 1000, 2500

ADR291

ER, ER-REEL7, ER-REEL 2.50 0.08 8 SOIC SO-8 98, 1000, 2500
FR, FR-REEL7, FR-REEL 2.50 0.12 15 SOIC SO-8 98, 1000, 2500
GR, GR-REEL7, GR-REEL 2.50 0.24 25 SOIC SO-8 98, 1000, 2500
GRU-REEL7, GRU-REEL 2.50 0.24 25 TSSOP RU-8 1000, 2500

ADR292

ER, ER-REEL7, ER-REEL 4.096 0.07 8 SOIC SO-8 98, 1000, 2500
FR, FR-REEL7, FR-REEL 4.096 0.10 15 SOIC SO-8 98, 1000, 2500
GR, GR-REEL7, GR-REEL 4.096 0.15 25 SOIC SO-8 98, 1000, 2500
GRU-REEL7, GRU-REEL 4.096 0.15 25 TSSOP RU-8 1000, 2500

See ADR293 data sheet for ordering guide.

OTHER XFET PRODUCTS

Part Nominal Output Package
Number Voltage (V) Type

ADR420 2.048 8-Lead_µSOIC/SOIC
ADR421 2.50 8-Lead_µSOIC/SOIC

REV. B

–5–

ADR290/ADR291/ADR292

PARAMETER DEFINITION

Line Regulation

The change in output voltage due to a specified change in input
voltage. It includes the effects of self-heating. Line regulation is
expressed in either percent-per-volt, parts-per-million-per­volt, or microvolts-per-volt change in input voltage.

Load Regulation

The change in output voltage due to a specified change in load
current. It includes the effects of self-heating. Load regulation
is expressed in either microvolts-per-milliampere, parts-per­million-per-milliampere, or ohms of dc output resistance.

Long-Term Stability

Typical shift of output voltage at 25°C on a sample of parts
subjected to high-temperature operating life test of 1000
hours at 125°C.

∆∆VVtVt

=×()– ()

OO

V ppm

O

0O1

Vt Vt

()– ()

OO

[] 10

01

=

Vt

O

()

0

6

Where

V

(t0) = VO at 25°C at time 0

O

(t1) = VO at 25°C after 1000 hours operation at 125°C

V

O

Temperature Coefficient

The change of output voltage over the operating temperature
change and normalized by the output voltage at 25°C, expressed
in ppm/°C. The equation follows:

TCV ppm C

[/]

O

°=

OO

VCTT

()(– )

°×

25

O

21

6

×

10

VT VT

()– ()

21

Where

V

(25°C) = VO at 25°C

O

V

) = VO at Temperature 1

O(T1

V

) = VO at Temperature 2

O(T2

Thermal Hysteresis

Thermal hysteresis is defined as the change of output voltage af­ter the device is cycled through temperature from +25°C to
–40°C to +85°C and back to +25°C. This is a typical value from
a sample of parts put through such a cycle.

25

VVCV

V ppm

=°

O HYS O O TC

– _

O HYS

–

()–

VCV

=

[]

25

°

()–

OOTC

25

VC

()

O

_

°

6

10

×

Where

V

(25°C) = VO at 25°C

O

V

= VO at 25°C after temperature cycle at +25°C to

O–TC

–40°C to +85°C and back to +25°C

NC = No Connect
(There are in fact internal connections at NC pins which are
reserved for manufacturing purposes. Users should not connect
anything at NC pins.)

–6–

REV. B

Typical Performance Characteristic–

ADR290/ADR291/ADR292

2.054

VS = 5V

2.052

2.050

2.048

2.046

OUTPUT VOLTAGE – V

2.044

2.042
–50 125–25

TPC 1. ADR290 V

2.506

VS = 5V

2.504

2.502

2.500

2.498

OUTPUT VOLTAGE – V

2.496

3 TYPICAL PARTS

0255075100

TEMPERATURE – C

vs. Temperature

OUT

3 TYPICAL PARTS

14

12

A

10



QUIESCENT CURRENT –

8

6

4

2

0

0162

468101214

INPUT VOLTAGE – V

TA = +125C

TA = +25C

TA = –40C

TPC 4. ADR290 Quiescent Current vs. Input Voltage

14

12

A

10



8

6

4

QUIESCENT CURRENT –

2

TA = +125C

TA = +25C

TA = –40C

2.494
–50 125–25

TPC 2. ADR291 V

4.102

VS = 5V

4.100

4.098

4.096

4.094

OUTPUT VOLTAGE – V

4.092

4.090
–50 125–25

TPC 3. ADR292 V

0255075100

TEMPERATURE – C

vs. Temperature

OUT

3 TYPICAL PARTS

0255075100

TEMPERATURE – C

vs. Temperature

OUT

0

0162

468101214

INPUT VOLTAGE – V

TPC 5. ADR291 Quiescent Current vs. Input Voltage

16

14

12

A



10

QUIESCENT CURRENT –

8

6

4

2

0

0162

468101214

INPUT VOLTAGE – V

TA = +125C

TA = +25C

TA = –40C

TPC 6. ADR292 Quiescent Current vs. Input Voltage

REV. B

–7–

ADR290/ADR291/ADR292

14

VS = 5V

12

A



10

8

SUPPLY CURRENT –

6

4

–50 125–25

ADR292

0 255075100

TEMPERATURE –C

ADR291

ADR290

TPC 7. ADR290/ADR291/ADR292 Supply Current vs.
Temperature

100

ADR290: VS = 2.7V TO 15V

80

60

ADR291: V
ADR292: V

= 3.0V TO 15V

S

= 4.5V TO 15V

S

ADR292

I

OUT

= 0mA

0.7

0.6

0.5

0.4

0.3

0.2

DIFFERENTIAL VOLTAGE – V

0.1

TA = +125C

0

0 5.00.5

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
LOAD CURRENT – mA

TA = –40C

TA = +25C

TPC 10. ADR290 Minimum Input-Output Voltage
Differential vs. Load Current

0.7

0.6

0.5

0.4

TA = +125C

TA = +25C

40

LINE REGULATION – ppm/V

20

0

–50 125–25

0 255075100

TEMPERATURE –C

ADR290

ADR291

TPC 8. ADR290/ADR291/ADR292 Line Regulation vs.
Temperature

100

ADR290: VS = 2.7V TO 7.0V
ADR291: V
ADR292: V

80

60

ADR291

40

LINE REGULATION – ppm/V

20

0

–50 125–25

= 3.0V TO 7.0V

S

= 4.5V TO 9.0V

S

0 255075100

TEMPERATURE –C

I

ADR290

= 0mA

OUT

ADR292

TPC 9. ADR290/ADR291/ADR292 Line Regulation vs.
Temperature

0.3

0.2

DIFFERENTIAL VOLTAGE – V

0.1

0

0 5.00.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

LOAD CURRENT – mA

TA = –40C

TPC 11. ADR291 Minimum Input-Output Voltage
Differential vs. Load Current

0.7

0.6

0.5

0.4

0.3

0.2

DIFFERENTIAL VOLTAGE – V

0.1

0

0 5.00.5

TA = +125C

TA = +25C

TA = –40C

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
LOAD CURRENT – mA

TPC 12. ADR292 Minimum Input-Output Voltage
Differential vs. Load Current

–8–

REV. B

ADR290/ADR291/ADR292

SOURCING LOAD CURRENT – mA

0

–1250

–2000

0.1 101



V

OUT

FROM NOMINAL –



V

–1750

–1500

–500

–250

TA = +25C

TA = +125C

TA = –40C

–1000

–750

SOURCING LOAD CURRENT – mA

0

–2500

–4000

0.1 101



V

OUT

FROM NOMINAL –



V

–3500

–3000

–1000

–500

TA = +25C

TA = +125C

TA = –40C

–2000

–1500

200

VS = 5V

160

120

80

LINE REGULATION – ppm/mA

40

0

–50 125–25

0 255075100

TEMPERATURE –C

I

OUT

I

OUT

= 1mA

= 5mA

TPC 13. ADR290 Line Regulation vs. Temperature

200

VS = 5V

160

I

= 1mA

120

80

OUT

I

OUT

= 5mA

500

250

V



0

–250

FROM NOMINAL –

–500

OUT

V



–750

–1000

0.1 101

TPC 16. ADR290 ∆V

TA = +25C

TA = +125C

TA = –40C

SOURCING LOAD CURRENT – mA

from Nominal vs. Load Current

OUT

40

LOAD REGULATION – ppm/mA

0

–50 125–25

TPC 14. ADR291 Load Regulation vs. Temperature

200

VS = 5V

160

120

80

LOAD REGULATION – ppm/mA

40

0

–50 125–25

TPC 15. ADR292 Load Regulation vs. Temperature

0 255075100

TEMPERATURE –C

I

= 1mA

OUT

I

OUT

0 255075100

TEMPERATURE –C

= 5mA

TPC 17. ADR291 ∆V

TPC 18. ADR292 ∆V

from Nominal vs. Load Current

OUT

from Nominal vs. Load Current

OUT

REV. B

–9–

ADR290/ADR291/ADR292

1000

900

800

700

600

500

400

300

200

VOLTAGE NOISE DENSITY – nV/冪Hz

100

0

10 1000100

ADR292

ADR291

ADR290

FREQUENCY – Hz

TPC 19. Voltage Noise Density vs. Frequency

120

100

80

60

40

RIPPLE REJECTION – dB

20

V

IN

T

A

VS = 5V

= 15V

= 25C

50

VS = 5V
I

= 0 mA

L

40



30

20

OUTPUT IMPEDANCE –

10

0

0 10k10

100 1k

FREQUENCY – Hz

TPC 22. ADR290 Output Impedance vs. Frequency

50

VS = 5V
I

= 0 mA

L

40



30

20

OUTPUT IMPEDANCE –

10

0

10 1000100

FREQUENCY – Hz

TPC 20. ADR290/ADR291/ADR292 Ripple Rejection vs.
Frequency

1s

100

90

2V p-p

10

0%

TPC 21. ADR290 0.1 Hz to 10 Hz Noise

0

0 10k10

100 1k

FREQUENCY – Hz

TPC 23. ADR291 Output Impedance vs. Frequency

50

VS = 5V
I

= 0 mA

L

40



30

20

OUTPUT IMPEDANCE –

10

0

0 10k10

100 1k

FREQUENCY – Hz

TPC 24. ADR292 Output Impedance vs. Frequency

–10–

REV. B

ADR290/ADR291/ADR292

OFF

ON

OFF

ON

100

90

10

0%

TPC 25. ADR291 Load Transient

IL = 5mA

= 1nF

C

L

100

90

1msIL = 5mA

1V

1ms

100

90

10

0%

TPC 28. ADR291 Turn-On Time

100

90

500sIL = 5mA

1V

10msIL = 0mA

OFF

ON

10

0%

TPC 26. ADR291 Load Transient

IL = 5mA

= 100nF

C

100

90

10

0%

L

1V

5ms

1V

18

16

14

12

10

8

FREQUENCY

6

4

2

0

10

0%

TPC 29. ADR291 Turn-Off Time

0

–200

–180

–160

–140

–120

–100

–80

–60

V

OUT

204060

–40

–20

DEVIATION – ppm

1V

TEMPERATURE

–40C

+25C

85C +25C

80

100

120

140

160

180

200

MORE

REV. B

TPC 27. ADR291 Load Transient

TPC 30. Typical Hysteresis for the ADR291 Product

–11–

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 field­effect 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
essentially 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 advantage
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 com­pensation 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 abso­lute temperature. The general equation is:



RR R

++

VV

=

∆

OUT P PTAT

123



R





IR

+

()()



1



3

where ∆VP is the difference in pinch-off voltage between the two
FETs, and I

is the positive temperature coefficient correc-

PTAT

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.

V

IN

I

1I1

*

EXTRA CHANNEL IMPLANT

*

+ R2 +

R3

R1

V

OUT

=

 V

R1

V

R1

P

R2

R3

+ I

 R3

P

PTAT

I

PTAT

GND

V

OUT

Figure 1. 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 failure.
The following formula should be used to calculate a device’s maxi­mum junction temperature or dissipation:

TT

–

J

P

=

D

A

θ

J

A

In this equation, TJ and TA are the junction and ambient tem­peratures, respectively, P

θ

is the device package thermal resistance.

JA

is the device power dissipation, and

D

Basic Voltage Reference Connections

References, in general, require a bypass capacitor connected
from the V

pin to the GND pin. The circuit in Figure 2

OUT

illustrates the basic configuration for the ADR29x family of ref­erences. Note that the decoupling capacitors are not required for
circuit stability.

NC

1

ADR29x

2

NC

+

10F

0.1F

3

4

NC = NO CONNECT

8

7

6

5

NC

NC

OUTPUT

NC

0.1F

Figure 2. Basic Voltage Reference Configuration

Noise Performance

The noise generated by the ADR29x family of references is typi­cally less than 12 µV p-p over the 0.1 Hz to 10 Hz band. TPC
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. TPC 28 shows the turn-on settling time for the ADR291.

–12–

REV. B

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 reference
voltage, it is often required to reconfigure a current-switching
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 current­switching 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
an additional operational amplifier is not required for either
reinversion (current-switching mode) or amplification (voltage­switching mode) of the DAC output voltage. In general, any
positive voltage reference can be converted into a negative volt­age reference through the use of an operational amplifier and a
pair of matched resistors in an inverting configuration. The dis­advantage to that approach is that the largest single source of
error in the circuit is the relative matching of the resistors used.

The circuit illustrated in Figure 3 avoids the need for tightly
matched resistors with the use of an active integrator circuit. In
this circuit, the output of the voltage reference provides the
input drive for the integrator. The integrator, to maintain circuit
equilibrium adjusts its output to establish the proper relationship
between the reference’s V

and GND. Thus, any negative

OUT

output voltage desired can be chosen by simply substituting for
the appropriate reference IC. One caveat with this approach
should be mentioned: although rail-to-rail output amplifiers
work best in the application, these operational amplifiers require
a finite amount (mV) of headroom when required to provide
any load current. The choice for the circuit’s negative supply
should take this issue into account.

V

IN

ADR290/ADR291/ADR292

V

IN

ADR29x

V

OUT

R1

GND

Figure 4. A Precision Current Source

High Voltage Floating Current Source

The circuit of Figure 5 can be used to generate a floating
current source with minimal self heating. This particular con­figuration can operate on high supply voltages determined by
the breakdown voltage of the N-channel JFET.

V

IN

ADR29

X

GND

OP90

1F

ADJUST

R

I

L

OUT

P1

E231
SILICONIX

2N3904

2.10k

SET

I

SY

R

+V

S

ADR29x

V

OUT

GND

100k

1k

1F

A1 = 1/2 OP291,

1/2 OP295

1F

A1

+5V

–5V

100

–V

REF

Figure 3. A Negative Precision Voltage Reference Uses No
Precision Resistors

A Precision Current Source

Many times in low power applications, the need arises for a pre­cision current source that can operate on low supply voltages.
As shown in Figure 4, any one of the devices in the ADR29x
family of references can be configured as a precision current
source. The circuit configuration illustrated is a floating current
source with a grounded load. The reference’s output voltage is
bootstrapped across R

which sets the output current into the

SET,

load. With this configuration, circuit precision is maintained for
load currents in the range from the reference’s supply current,
typically 12 µA to approximately 5 mA.

–V

S

Figure 5. High Voltage Floating Current Source

Kelvin Connections

In many portable instrumentation applications, where PC board
cost and area go hand-in-hand, circuit interconnects are very often
of dimensionally minimum width. These narrow lines can cause
large voltage drops if the voltage reference is required to provide
load currents to various functions. In fact, a circuit’s interconnects
can exhibit a typical line resistance of 0.45 mΩ/square (1 oz. Cu,
for example). Force and sense connections also referred to as
Kelvin connections, offer a convenient method of eliminating the
effects of voltage drops in circuit wires. Load currents flowing
through wiring resistance produce an error (V

= R ⫻ IL ) at

ERROR

the load. However, the Kelvin connection of Figure 6, overcomes
the problem by including the wiring resistance within the forcing
loop of the op amp. Since the op amp senses the load voltage, op
amp loop control forces the output to compensate for the wiring
error and to produce the correct voltage at the load.

REV. B

–13–

ADR290/ADR291/ADR292

V

IN

R

LW

+V

OUT

V

IN

ADR29x

A1

100k

A1 = 1/2 OP295

GND

V

OUT

1F

Figure 6. Advantage of Kelvin Connection

Low Power, Low Voltage Reference For Data Converters

The ADR29x family has a number of features that makes it
ideally suited for use with A/D and D/A converters. The low
supply voltage required makes it possible to use the ADR290
and ADR291 with today’s converters that run on 3 V supplies
without having to add a higher supply voltage for the reference.
The low quiescent current (12 µA max) and low noise, tight
temperature coefficient, combined with the high accuracy of
the ADR29x makes it ideal for low power applications such
as hand-held, battery operated equipment.

One such ADC for which the ADR291 is well suited is the
AD7701. Figure 7 shows the ADR291 used as the reference for
this converter. The AD7701 is a 16-bit A/D converter with on­chip digital filtering intended for the measurement of wide
dynamic range, low frequency signals such as those representing
chemical, physical or biological processes. It contains a charge
balancing (sigma-delta) ADC, calibration microcontroller with
on-chip static RAM, a clock oscillator and a serial communica­tions port.

This entire circuit runs on ±5 V supplies. The power dissipation
of the AD7701 is typically 25 mW and, when combined with
the power dissipation of the ADR291 (60 µW), the entire circuit
still consumes about 25 mW.

SENSE

R

LW

+V

OUT

FORCE

R

L

Voltage Regulator For Portable Equipment

The ADR29x family of references is ideal for providing a stable,
low cost and low power reference voltage in portable equipment
power supplies. Figure 8 shows how the ADR290/ADR291/
ADR292 can be used in a voltage regulator that not only has
low output noise (as compared to switch mode design) and
low power, but also a very fast recovery after current surges.
Some precautions should be taken in the selection of the out­put capacitors. Too high an ESR (Effective Series Resistance)
could endanger the stability of the circuit. A solid tantalum
capacitor, 16 V or higher, and an aluminum electrolytic capacitor,
10 V or higher, are recommended for C1 and C2, respectively.
Also, the path from the ground side of C1 and C2 to the ground
side of R1 should be kept as short as possible.

CHARGER

INPUT

LEAD-ACID

BATTERY

0.1F

R3

V

IN

510k

ADR29x

6V

V

TEMP

GND

OUT

402k

1%

OP20

R1

R2

402k

1%

C1
68F
TANT

IRF9530

+

5V, 100mA

+

C2
1000F
ELECT

+

Figure 8. Voltage Regulator for Portable Equipment

+5V

ANALOG

SUPPLY

RANGES

SELECT

CALIBRATE

ANALOG

ANALOG

GROUND

ANALOG

SUPPLY

0.1F

0.1F

INPUT

–5V

0.1F

10F

V

V

OUT

ADR291

GND

0.1F

IN

10F

AV

DD

V

REF

BP/UP

CAL

A

IN

AGND

AV

SS

AD7701

DV

SLEEP

MODE

DRDY

CS

SCLK

SDATA

CLKIN

CLKOUT

SC1
SC2

DGND

DV

DD

SS

0.1F

DATA READY

READ

(TRANSMIT)

SERIAL

SERIAL

0.1F

CLOCK

CLOCK

Figure 7. Low Power, Low Voltage Supply Reference for
the AD7701

–14–

REV. B

0.0098 (0.25)

0.0075 (0.19)

0.0500 (1.27)

0.0160 (0.41)

8
0

0.0196 (0.50)

0.0099 (0.25)

 45

85

41

0.1968 (5.00)

0.1890 (4.80)

0.2440 (6.20)

0.2284 (5.80)

PIN 1

0.1574 (4.00)

0.1497 (3.80)

0.0500 (1.27)
BSC

0.0688 (1.75)

0.0532 (1.35)

SEATING

PLANE

0.0098 (0.25)

0.0040 (0.10)

0.0192 (0.49)

0.0138 (0.35)

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).

8-Lead Narrow Body SO (SO Suffix)

8-Lead TSSOP (RU Suffix)

0.122 (3.10)

0.114 (2.90)

8

5

0.177 (4.50)

0.169 (4.30)

0.256 (6.50)

0.246 (6.25)

0.0433
(1.10)
MAX

0.0079 (0.20)

0.0035 (0.090)

PIN 1

0.006 (0.15)

0.002 (0.05)

SEATING

PLANE

0.0256 (0.65)
BSC

0.0118 (0.30)

0.0075 (0.19)

41

ADR290/ADR291/ADR292

C00163–0–3/01 (B)

8
0

0.028 (0.70)

0.020 (0.50)

REV. B

PRINTED IN U.S.A.

–15–