Datasheet ADR318 Datasheet (Analog Devices)

Precision Low Drift SOT-23

a

FEATURES
Initial Accuracy: ⴞ5 mV Max, ⴞ0.27% Max
Low Temperature Coefficient: 25 ppm/ⴗC Max
Load Regulation: 100 ppm/mA
Line Regulation: 25 ppm/V
Low Supply Headroom: 0.6 V
Wide Operating Range: (V
Low Power: 120 ␮A Max
Shutdown to Less than 3 ␮A Max
Output Current: 5 mA
Wide Temperature Range: 0ⴗC to 70ⴗC
Tiny 5-Lead SOT-23 Package

APPLICATIONS
Battery Powered Instrumentation
Portable Medical Instruments
Data Acquisition Systems
Industrial Process Control Systems
Fault Protection Critical Systems

GENERAL DESCRIPTION

+ 0.6 V) to 15 V

OUT

Voltage Reference with Shutdown

The ADR318 is a precision 1.8 V band gap voltage reference
featuring high accuracy, high stability, and low power consump­tion in a tiny footprint. Patented temperature drift curvature
correction techniques minimize nonlinearity of the voltage change
with temperature. The wide operating range and low power con­sumption with additional shutdown capability make the part ideal
for battery powered applications. The V

OUT (SENSE)

pin enables
greater accuracy by supporting full Kelvin operation in PCBs
employing thin or long traces.

The ADR318 is a low dropout voltage (LDV) device that provides
a stable output voltage from supplies as low as 600 mV above
the output voltage. This device is specified over the industrial
operating range of 0°C to 70°C, and is available in the tiny
5-lead SOT-23 package.

The combination of V

OUT (SENSE)

and shutdown functions also
enables a number of unique applications, combining precision
reference/regulation with fault decision and overcurrent protection.
Details are provided in the Applications section.

PIN CONFIGURATION

5-Lead SOT-23

SHDN

V

OUT (SENSE)

1

V

2

ADR318

IN

3

5

4

ADR318

GND

–V

OUT (FORCE)

*

*Protected by U.S. Patent No. 5,969,657; other patents pending.

REV. 0

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Tel: [phone] www.analog.com
Fax: [phone] © 2003 Analog Devices, Inc. All rights reserved.

ADR318–SPECIFICATIONS

ELECTRICAL CHARACTERISTICS

(TA = T

MIN

to T

,1 VIN = 5 V, unless otherwise noted.)

MAX

Parameter Symbol Conditions Min Typ Max Unit

Initial Accuracy V
Initial Accuracy Error V
Temperature Coefficient TCV
Minimum Supply Voltage Headroom V
Line Regulation ∆V

Load Regulation ∆V

Quiescent Current I

Voltage Noise e
Turn-On Settling Time t
Long Term Stability

2

Output Voltage Hysteresis V
Ripple Rejection Ratio RRR f
Short Circuit to Ground I

Shutdown Supply Current I
Shutdown Logic Input Current I
Shutdown Logic Low V
Shutdown Logic High V

NOTES

1

T

= 0°C, T

MIN

2

The long-term stability specification is noncumulative. The drift in subsequent 1,000 hour periods is significantly lower than in the first 1,000 hour period.

Specifications subject to change without notice.

MAX

= 70°C

O

OERR

IN

SY

N

R

∆V

O_HYS

SC

SHDN

LOGIC

INL

INH

O

– V

OUT

OUT

OUT

OUT

/∆V

IN

/∆I

LOADVIN

0°C to 70°C525ppm/°C

VIN = 2.5 V to 15 V 10 25 ppm/V
0°C < T

0°C < T

< 70°C

A

= 3 V, I

< 70°C

A

= 0 mA to 5 mA 100 ppm/mA

LOAD

No load 100 120 µA
0°C < T

< 70°C 140 µA

A

0.1 Hz to 10 Hz 5 µV p-p

= 60 Hz 85 dB

IN

VIN = 5.0 V 25 mA

= 15.0 V 30 mA

V

IN

1.795 1.8 1.802 V
–0.27 +0.27 %

600 mV

20 µs
50 ppm/1,000 hrs
40 ppm

3 µA
500 nA

0.8 V

2.4 V

REV. 0–2–

ADR318

ABSOLUTE MAXIMUM RATINGS

1, 2

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

Output Short-Circuit Duration

to GND . . . . . . . . . . . . . . . . . . . . . Observe Derating Curves

Storage Temperature Range

RJ Package . . . . . . . . . . . . . . . . . . . . . . . . .–65°C to +125°C

Operating Temperature Range . . . . . . . . . . . . . . . 0°C to 70°C

Junction Temperature Range

RJ Package . . . . . . . . . . . . . . . . . . . . . . . . .–65°C to +150°C

Lead Temperature Range

Soldering, 60 sec . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300°C

NOTES

1

Absolute maximum ratings apply at 25°C, unless otherwise noted.

2

Stresses above those listed under Absolute Maximum Ratings may cause perma-

nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational
sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.

ORDERING GUIDE

Temperature Package Package Branding Output Devices

Model Range Description Option Information Voltage per Reel

ADR318ARJ-REEL7 0ºC to 70ºC 5-Lead SOT-23 RJ-5 R0A 1.800 V 3,000

Package Type ␪

JA

␪

JC

Unit

5-Lead SOT-23 (RJ) 230 146 °C/W

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
ADR318 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.

REV. 0

–3–

ADR318–Typical Performance Characteristics

–

1.802

1.801

– V

1.800

OUT

V

1.799

1.798
010

20 30 40 50 60 70

TEMPERATURE – ⴗC

TPC 1. Typical Output Voltage
vs. Temperature

0

–5

–10

–15

–20

LINE REGULATION – ppm/mV

110

70ⴗC

100

25ⴗC

90

0ⴗC

80

SUPPLY CURRENT – ␮A

70

2.5 5.0 15.0

7.5 10.0 12.5

INPUT VOLTAGE – V

TPC 2. Supply Current vs.
Input Voltage

2.5

2.3

0ⴗC

– V

2.1

IN_MIN

V

1.9
70ⴗC

25ⴗC

30

–40

–50

–60

–70

LOAD REGULATION – ppm/mA

–80

010

10V

2.5V

20 30 40 50 60 70

TEMPERATURE – ⴗC

TPC 3. Load Regulation vs.
Temperature

VOLTA GE – 2mV/DIV

–25

010

20 30 40 50 60 70

TEMPERATURE – ⴗC

TPC 4. Line Regulation vs.
Temperature

VOLTA GE – 10mV/DIV

TIME – 10ms/DIV

TPC 7. Typical Output Voltage
Noise 10 Hz to 10 kHz

1.7

012

LOAD CURRENT – mA

345

TPC 5. Minimum Input Voltage
vs. Load Current

VOLTA GE – 50mV/DIV

TIME – 40␮s/DIV

TPC 8. Line Transient
Response, C

BYPASS

= 0 µF

TIME – 400ms/DIV

TPC 6. Typical Output Voltage

Noise 0.1 Hz to 10 Hz

VOLTA GE – 50mV/DIV

TIME – 40␮s/DIV

TPC 9. Line Transient
Response, C

BYPASS

= 0.1 µF

REV. 0–4–

ADR318

LOAD OFF LOAD ON

VOLTA GE – 200mV/DIV

TIME – 200␮s/DIV

TPC 10. Load Transient Response,

= 0 nF

C

L

V

IN

V

VOLTA GE – 50mV/DIV

OUT

TIME – 40␮s/DIV

TPC 13. Turn On/Turn Off

= 1.8 k

Response at 5 V, R

LOAD

Ω

LOAD OFF LOAD ON

VOLTA GE – 200mV/DIV

TIME – 200␮s/DIV

TPC 11. Load Transient Response,

= 1 nF

C

L

V

IN

VOLTA GE – 2V/DIV

V

OUT

TIME – 100␮s/DIV

TPC 14. Turn On/Turn Off Response

at 5 V, R

= 1.8 kΩ, C

LOAD

BYPASS

= 0.1 µF

LOAD OFF LOAD ON

VOLTA GE – 200mV/DIV

TIME – 200␮s/DIV

TPC 12. Load Transient Response,

= 100 nF

C

L

V

OUT

VOLTA GE – 1V/DIV

SHUTDOWN PIN

TIME – 4␮s/DIV

TPC 15. Shutdown Pin Response

REV. 0

–5–

ADR318

P

TT

D

A

=

−

J

JA

θ

PARAMETER DEFINITIONS
Temperature Coefficient

Temperature coefficient is the change of output voltage with
respect to operating temperature changes, normalized by the
output voltage at 25°C. This parameter is expressed in ppm/°C,
and can be determined with the following equation:

–

VT VT

TCV

ppm





O





C

°





() ()

21

OO

=

VCTT

°

25

()

O

–

×

()

21

6

10

×

(1)

where:

V

(25°C) = VO at 25°C

O

V

) = VO at temperature 1

O(T1

V

) = VO at temperature 2

O(T2

Long Term Stability

Long term stability is the typical shift of output voltage at 25°C
on a sample of parts subjected to a test of 1,000 hours at 25°C:

∆∆VVtVt

=

()−()

OO O

V ppm

O

01

Vt Vt

()−()

OO

01

=

[]

Vt

O

()

0

6

(2)

×

10

where:

V

) = VO at 25°C at time 0

O(t0

V

) = VO at 25°C after 1,000 hours operation at 25°C

O(t1

Thermal Hysteresis

Thermal hystereses is defined as the change of output voltage
after the device is cycled through temperature from +25°C to
–40°C to +125°C and back to +25°C. This is a typical value from a
sample of parts put through such a cycle.

VVCV

OHYS OOTC

__

V ppm

OHYS

_

25

=°

[]

−

()

°

25

VCV

()

OOTC

=

VC

O

−

_

10

25

°

()

×

6

(3)

where:

V

(25°C) = VO at 25°C

O

V

= VO at 25°C after temperature cycle at +25°C to –40°C

O_TC

to +125°C and back to +25°C

THEORY OF OPERATION

Band gap references are the high performance solution for low
supply voltage and low power voltage reference applications,
and the ADR318 is no exception. The uniqueness of this product
lies in its architecture. By observing Figure 1, the ideal zero TC
band gap voltage is referenced to the output, not to ground.
Therefore, if noise exists on the ground line, it will be greatly
attenuated on V

. The band gap cell consists of the PNP pair

OUT

Q51 and Q52, running at unequal current densities. The difference

results in a voltage with a positive TC that is amplified by

in V

BE

the ratio of 2 ⫻ R58/R54. This PTAT voltage, combined with

s of Q51 and Q52, produces the stable band gap voltage.

the V

BE

Reduction in band gap curvature is performed by the ratio of
the resistors R44 and R59, one of which is linearly temperature
dependent. Precision laser trimming and other patented circuit
techniques are used to further enhance the drift performance.

V

IN

SHDN

Q1

R59

R54

R60

Q51

R44

R49R58

R53

Q52

R48

R61

V

OUT(FORCE)

V

OUT(SENSE)

GND

Figure 1. Simplified Schematic

Device Power Dissipation Considerations

The ADR318 is capable of delivering load currents up to 5 mA
with an input voltage that ranges from 2.4 V to 15 V. When this
device is used in applications with high input voltages, care should
be taken to avoid exceeding the specified maximum power dissi­pation or junction temperature that could result in premature
device failure. The following formula should be used to calculate
the device’s maximum junction temperature or dissipation:

(4)

In Equation 4, T
ambient temperatures, P

is the device package thermal resistance.

θ

JA

and TA are, respectively, the junction and

J

is the device power dissipation, and

D

Shutdown Mode Operation

The ADR318 includes a shutdown feature that is TTL/CMOS
compatible. A logic LOW or a 0 V condition on the SHDN pin
is required to turn the device off. During shutdown, the output
of the reference becomes a high impedance state where its potential
would then be determined by external circuitry. If the shutdown
feature is not used, the SHDN pin should be connected to V

IN

(Pin 2).

REV. 0–6–

ADR318

APPLICATIONS
Basic Voltage Reference Connection

The circuit in Figure 2 illustrates the basic configuration for the
ADR318. Decoupling capacitors are not required for circuit stability.
The ADR318 is capable of driving capacitative loads from 0 µF to
10 µF. However, a 0.1 µF ceramic output capacitor is recommended
to absorb and deliver the charge as is required by a dynamic load.

SHUTDOWN

INPUT

SHDN

V

C

0.1␮F

I

IN

V

OUT(S)

ADR318

V

GND

OUT(F)

C

O

OUTPUT

0.1␮F

Figure 2. Voltage Reference Connection

Precision Negative Voltage Reference without Precision Resistors

A negative reference can be easily generated by combining the
ADR318 with an op amp. Figure 3 shows this simple negative
reference configuration. V

OUT(F)

and V

are at virtual ground

OUT(S)

and therefore the negative reference can be taken directly from
the output of the op amp. The op amp should be a dual-supply,
low offset, rail-to-rail amplifier, such as the OP1177.

General-Purpose 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, the ADR318 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 R1, which sets the output current into the
load. With this configuration, circuit precision is maintained for
load currents in the range from the reference’s supply current,
typically 90 mA to approximately 5 mA. The supply current is a
function of I

and will increase slightly at a given I

SET

+V

DD

V

GND

IN

V

V

ADR318

OUT(F)

OUT(S)

I

SY (ISET

)

0.1␮F

R1

I

SY

ADJ

I

OUT = ISET

R

L

U1

SHDN

I

SET

+ I

SET

SV (ISET

.

)

+V

DD

ADR318

V

IN

V

OUT(F)

V

SHDN

OUT(S)

GND

OP1177

–V

SS

Figure 3. Negative Reference

Figure 4. General-Purpose Current Source

–VREF

REV. 0

–7–

ADR318

High Power Performance with Current Limit

In some cases, the user may want higher output current delivered
to a load and still achieve better than 0.5% accuracy out of the
ADR318. The accuracy for a reference is normally specified on
the data sheet with no load. However, the output voltage changes
with load current.

The circuit in Figure 5 provides high current without compromis­ing the accuracy of the ADR318. The power BJT Q1 provides
the required current, up to a 1 A. The ADR318 delivers the base
drive to Q1 through the force pin. The sense pin of the ADR318
is a regulated output and is connected to the load.

The transistor Q2 protects Q1 during short circuit limit faults by
robbing its base drive. The maximum current is I

V

IN

OUT(S)

ADR318

V

IN

V

GND

OUT(F)

Q2

R1

4.7k⍀

SHDN

V

L, MAX

R

S

R

L

= 0.6 V/RS.

Q1

A similar circuit function can also be achieved using the Darlington
transistor configuration, as shown in Figure 6.

V

IN

OUT(S)

ADR318

V

IN

V

OUT(F)

GND

Q1

R

S

R

L

R1Q24.7k⍀

SHDN

V

Figure 6. High Output Current with Darlington
Drive Configuration

C03431–0–1/03(0)

Figure 5. High Power Performance with Current Limit

OUTLINE DIMENSIONS

5-Lead Plastic Surface-Mount Package [SOT-23]

Dimensions shown in millimeters

2.90 BSC

4 5

1.60 BSC

1 3

2

PIN 1

1.30

1.15

0.90

0.15 MAX

1.90

BSC

0.50

0.30

COMPLIANT TO JEDEC STANDARDS MO-178AA

(RJ-5)

2.80 BSC

0.95 BSC

1.45 MAX

SEATING
PLANE

0.22

0.08

10ⴗ

PRINTED IN U.S.A.

0ⴗ

0.60

0.45

0.30

–8–

REV. 0