ANALOG DEVICES LT 1021 DCS8-10 Datasheet

FEATURES

■

Ultralow Drift: 5ppm/°C Max Slope

■

Very Low Noise: <1ppm

■

100% Noise Tested

■

Pin Compatible with Most Bandgap Reference

(0.1Hz to 10Hz)

P-P

Applications, Including Ref 01, Ref 02, LM368, MC1400 and MC1404 with Greatly Improved Stability, Noise and Drift

■

Trimmed Output Voltage

■

Operates in Series or Shunt Mode

■

Output Sinks and Sources in Series Mode

■

>100dB Ripple Rejection

■

Minimum Input/Output Differential of 1V

■

Available in 5-Lead Can, N8 and S8 Packages

U

APPLICATIO S

LT1021

Precision Reference

U

DESCRIPTIO

The LT and noise, extremely good long term stability and almost total immunity to input voltage variations. The reference output will both source and sink up to 10mA. Three voltages are available: 5V, 7V and 10V. The 7V and 10V units can be used as shunt regulators (two-terminal zeners) with the same precision characteristics as the threeterminal connection. Special care has been taken to minimize thermal regulation effects and temperature induced hysteresis.

The LT1021 references are based on a buried zener diode structure that eliminates noise and stability problems associated with surface breakdown devices. Further, a subsurface zener exhibits better temperature drift and time stability than even the best bandgap references.

®

1021 is a precision reference with ultralow drift

■

A/D and D/A Converters

■

Precision Regulators

■

Digital Voltmeters

■

Inertial Navigation Systems

■

Precision Scales

■

Portable Reference Standard

TYPICAL APPLICATIO

Basic Positive and Negative Connections

LT1021

IN

V

IN

OUT

GND

V

OUT

R1 =

NC

V

I

LOAD

U

(7 AND 10 ONLY)

IN

– (V–)

OUT

+ 1.5mA

LT1021

GND

–15V

–

(V

Unique circuit design makes the LT1021 the first IC reference to offer ultralow drift without the use of high power on-chip heaters.

The LT1021-7 uses no resistive divider to set output voltage, and therefore exhibits the best long term stability and temperature hysteresis. The LT1021-5 and LT102110 are intended for systems requiring a precise 5V or 10V reference with an initial tolerance as low as ±0.05%.

, LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.

Typical Distribution of Temperature Drift

24

21

18

OUT

–V

OUT

R1

)

1021 TA01

15

12

UNITS (%)

9

6

3

– 0

–5

–3 –1 1 52–4 –2 0 4

OUTPUT DRIFT (ppm/°C)

DISTRIBUTION OF THREE RUNS

3

1021 TA01

1021fc

1

LT1021

A

W

O

LUTEXI TIS

S

A

WUW

U

ARB

G

(Note 1)

Input Voltage .......................................................... 40V

Input/Output Voltage Differential ............................ 35V

Output-to-Ground Voltage (Shunt Mode Current Limit)

LT1021-5............................................................. 10V

LT1021-7............................................................. 10V

LT1021-10........................................................... 16V

Trim Pin-to-Ground Voltage

Positive ............................................... Equal to V

OUT

Negative ........................................................... – 20V

WU

/

PACKAGE

*CONNECTED INTERNALLY. DO NOT CONNECT EXTERNAL CIRCUITRY TO THESE PINS. **NO TRIM PIN ON LT1021-7. DO NOT CONNECT EXTERNAL CIRCUITRY TO PIN 5 ON LT1021-7

O

RDER I FOR ATIO

TOP VIEW

NC*

8

1

NC*

2

V

IN

3

NC*

GND

H PACKAGE

8-LEAD TO-5 METAL CAN

T

= 150°C, θJA = 150°C/W,θJC = 45°C/W

JMAX

NC*

7

6

V

OUT

5

TRIM

4

**

U

Output Short-Circuit Duration

VIN = 35V ......................................................... 10 sec

V

≤ 20V ................................................... Indefinite

IN

Operating Temperature Range

Commercial ............................................ 0°C to 70°C

Industrial ........................................... – 40°C to 85°C

Military ............................................ –55°C to 125°C

Storage Temperature Range ................ –65°C to 150°C

Lead Temperature (Soldering, 10 sec)................ 300°C

TOP VIEW

DNC*

1

V

2

IN

DNC*

3

GND

4

N8 PACKAGE 8-LEAD PDIP

*CONNECTED INTERNALLY. DO NOT CONNECT EXTERNAL CIRCUITRY TO THESE PINS. **NO TRIM PIN ON LT1021-7. DO NOT CONNECT EXTERNAL CIRCUITRY TO PIN 5 ON LT1021-7

T

= 130°C, θJA = 130°C/W (N)

JMAX

T

= 130°C, θJA = 150°C/W (S)

JMAX

8-LEAD PLASTIC SO

DNC*

8

DNC*

7

V

6

TRIM**

5

S8 PACKAGE

0UT

ORDER PART NUMBER

LT1021BCH-5 LT1021BMH-5 LT1021CCH-5 LT1021CMH-5 LT1021BMH-10

LT1021DCH-5 LT1021DMH-5 LT1021BCH-7 LT1021BMH-7 LT1021DCH-7 LT1021DMH-7 LT1021BCH-10 LT1021CMH-10 LT1021DCH-10 LT1021DMH-10

OBSOLETE

Order Options Tape and Reel: Add #TR

Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/

Consult LTC Marketing for parts specified with wider operating temperature ranges.

N8 ORDER PART NUMBER

LT1021BCN8-5 LT1021CCN8-5 LT1021CIN8-5 LT1021DCN8-5 LT1021DIN8-5 LT1021BCN8-7 LT1021DCN8-7 LT1021BCN8-10 LT1021CCN8-10 LT1021CIN8-10 LT1021DCN8-10 LT1021DIN8-10

S8 ORDER PART NUMBER

LT1021DCS8-5 LT1021DCS8-7 LT1021DCS8-10

S8 PART MARKING

2105 2107 2110

1021fc

2

LT1021

LECTRICAL C CHARA TERIST

E

range, otherwise specifications are T

PARAMETER CONDITIONS MIN TYP MAX UNITS

Output Voltage (Note 2) LT1021C-5 4.9975 5.000 5.0025 V

Output Voltage Temperature Coefficient (Note 3) T

Line Regulation (Note 4) 7.2V ≤ VIN ≤ 10V 4 12 ppm/V

Load Regulation (Sourcing Current) 0 ≤ I

Load Regulation (Sinking Current) 0 ≤ I

Supply Current 0.8 1.2 mA

Output Voltage Noise (Note 6) 0.1Hz ≤ f ≤ 10Hz 3.0 µV

Long Term Stability of Output Voltage (Note 7) ∆t = 1000Hrs Noncumulative 15 ppm Temperature Hysteresis of Output ∆T = ± 25°C 10 ppm

= 25°C. VIN = 10V, I

A

ICS

LT1021B-5/LT1021D-5 4.9500 5.000 5.0500 V

≤ TJ ≤ T

MIN

LT1021B-5 LT1021C-5/LT1021D-5

10V ≤ V

OUT

(Note 4)

OUT

(Note 4)

10Hz ≤ f ≤ 1kHz 2.2 3.5 µV

The ● denotes specifications that apply over the full operating temperature

= 0, unless otherwise noted.

OUT

LT1021-5

MAX

≤ 40V 2 6 ppm/V

IN

≤ 10mA 10 20 ppm/mA

≤ 10mA 60 100 ppm/mA

●

2 5 ppm/°C 3 20 ppm/°C

20 ppm/V

10 ppm/V

35 ppm/mA

150 ppm/mA

1.5 mA

P-P

RMS

The

●

denotes specifications that apply over the full operating temperature range, otherwise specifications are TA = 25°C.

VIN = 12V, I

PARAMETER CONDITIONS MIN TYP MAX UNITS

Output Voltage (Note 2) 6.95 7.00 7.05 V

Output Voltage Temperature Coefficient (Note 3) T

Line Regulation (Note 4) 8.5V ≤ VIN ≤ 12V 1.0 4 ppm/V

Load Regulation (Sourcing Current) 0 ≤ I

Load Regulation (Shunt Mode) 1.2mA ≤ I

Supply Current (Series Mode) 0.75 1.2 mA

Minimum Current (Shunt Mode) VIN is Open 0.7 1.0 mA

Output Voltage Noise (Note 6) 0.1Hz ≤ f ≤ 10Hz 4.0 µV

Long Term Stability of Output Voltage (Note 7) ∆t = 1000Hrs Noncumulative 7 ppm Temperature Hysteresis of Output ∆T = ± 25°C 3 ppm

= 0, unless otherwise noted.

OUT

LT1021-7

≤ TJ ≤ T

MIN

LT1021B-7 LT1021D-7

12V ≤ V

(Note 4)

(Notes 4, 5)

10Hz ≤ f ≤ 1kHz 2.5 4.0 µV

MAX

≤ 40V 0.5 2 ppm/V

IN

≤ 10mA 12 25 ppm/mA

OUT

≤ 10mA 50 100 ppm/mA

SHUNT

●

2 5 ppm/°C 3 20 ppm/°C

2.0 8 ppm/V

1.0 4 ppm/V

40 ppm/mA

150 ppm/mA

1.5 mA

1.2 mA

P-P

RMS

1021fc

3

LT1021

LECTRICAL C CHARA TERIST

E

range, otherwise specifications are T

PARAMETER CONDITIONS MIN TYP MAX UNITS

Output Voltage (Note 2) LT1021C-10 9.995 10.00 10.005 V

Output Voltage Temperature Coefficient (Note 3) T

Line Regulation (Note 4) 11.5V ≤ VIN ≤ 14.5V 1.0 4 ppm/V

Load Regulation (Sourcing Current) 0 ≤ I

Load Regulation (Shunt Mode) 1.7mA ≤ I

Supply Current (Series Mode) 1.2 1.7 mA

Minimum Current (Shunt Mode) VIN is Open 1.1 1.5 mA

Output Voltage Noise (Note 6) 0.1Hz ≤ f ≤ 10Hz 6.0 µV

Long Term Stability of Output Voltage (Note 7) ∆t = 1000Hrs Noncumulative 15 ppm Temperature Hysteresis of Output ∆T = ± 25°C 5 ppm

= 25°C. VIN = 15V, I

A

ICS

LT1021B-10/LT1021D-10 9.950 10.00 10.050 V

≤ TJ ≤ T

MIN

LT1021B-10 LT1021C-10/LT1021D-10

14.5V ≤ V

OUT

(Note 4)

(Notes 4, 5)

10Hz ≤ f ≤ 1kHz 3.5 6 µV

The ● denotes specifications that apply over the full operating temperature

= 0, unless otherwise noted.

OUT

LT1021-10

MAX

≤ 40V 0.5 2 ppm/V

IN

≤ 10mA 12 25 ppm/mA

≤ 10mA 50 100 ppm/mA

SHUNT

●

2 5 ppm/°C 5 20 ppm/°C

6 ppm/V

4 ppm/V

40 ppm/mA

150 ppm/mA

2.0 mA

1.7 mA

P-P

RMS

Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.

Note 2: Output voltage is measured immediately after turn-on. Changes due to chip warm-up are typically less than 0.005%.

Note 3: Temperature coefficient is measured by dividing the change in output voltage over the temperature range by the change in temperature. Separate tests are done for hot and cold; T

Incremental slope is also measured at 25°C. Note 4: Line and load regulation are measured on a pulse basis. Output

changes due to die temperature change must be taken into account separately. Package thermal resistance is 150°C/W for TO-5 (H), 130°C/W for N and 150°C/W for the SO-8.

to 25°C and 25°C to T

MIN

MAX

.

Note 5: Shunt mode regulation is measured with the input open. With the input connected, shunt mode current can be reduced to 0mA. Load regulation will remain the same.

Note 6: RMS noise is measured with a 2-pole highpass filter at 10Hz and a 2-pole lowpass filter at 1kHz. The resulting output is full-wave rectified and then integrated for a fixed period, making the final reading an average as opposed to RMS. Correction factors are used to convert from average to RMS and correct for the non-ideal bandpass of the filters.

Peak-to-peak noise is measured with a single highpass filter at 0.1Hz and a 2-pole lowpass filter at 10Hz. The unit is enclosed in a still-air environment to eliminate thermocouple effects on the leads. Test time is 10 seconds.

Note 7: Consult factory for units with long term stability data.

4

1021fc

LPER

OUTPUT CURRENT (mA)

0

INPUT/OUTPUT VOLTAGE (V)

1.2

1.6

16

1021 G03

0.8

0.4

0

4

8

12

20

1.0

1.4

0.6

0.2

14

2

6

10

18

TJ = 125 °C

TJ = –55 °C

TJ = 25 °C

FREQUENCY (Hz)

100

NOISE VOLTAGE (nV/√Hz)

200

250

350

400

10 1k 10k

LT1021 G06

0

100

300

150

50

LT1021-10

LT1021-5

LT1021-7

)

Ripple Rejection

115

f = 150Hz

110

105

100

REJECTION (dB)

95

90

85

0

515

10 20

INPUT VOLTAGE (V)

Start-Up (Series Mode)

13

VIN = 0V TO 12V

12

11

10

9

8

7

6

OUTPUT VOLTAGE (V)

5

4

3

04

2

F

LT1021-10

LT1021-7

LT1021-5

6

TIME (µs)

R

O

LT1021-7

LT1021-10

LT1021-5

25

8

LT1021

UW

ATYPICA

30

35

LT1021 G01

12

10

LT1021 G04

CCHARA TERIST

E

C

Ripple Rejection

130

VIN = 15V C

OUT

120

110

100

90

80

REJECTION (dB)

70

60

50

40

10

Start-Up (Shunt Mode) LT1021-7, LT1021-10

11

10

9

8

7

OUTPUT VOLTAGE (V)

6

14

5

ICS

= 0

LT1021-7

LT1021-5

100 1k 10k

FREQUENCY (Hz)

LT1021-10

+ 2V

V

OUT

0V

NC

LT1021-7

61012

02

48

TIME (µs)

LT1021-10

1k

OUT

IN

GND

LT1021 G02

V

OUT

LT1021 G05

Minimum Input/Output Differential LT1021-7, LT1021-10

Output Voltage Noise Spectrum

Output Voltage Noise

16

C

= 0

OUT

FILTER = 1 POLE

14

= 0.1Hz

f

LOW

12

10

8

6

RMS NOISE (µV)

4

2

0

10

LT1021-10

100 1k 10k

BANDWIDTH (Hz)

LT1021-7

LT1021-5

LT1021 G07

Output Voltage Temperature Drift LT1021-5

5.006

5.004

5.002

5.000

4.998

OUTPUT VOLTAGE (V)

4.996

4.994 –50

0

–25

TEMPERATURE (°C)

50

25

Load Regulation LT1021-5

5

VIN = 8V

4

3

2

1

0

–1

–2

OUTPUT CHANGE (mV)

–3

–4

100

LT1021 G08

125

75

–5

–6–8 –4 0 4 8

–10

–2

SOURCING SINKING

OUTPUT CURRENT (mA

2

6

10

LT1021 G09

1021fc

5

LT1021

)

LPER

Quiescent Current LT1021-5

1.8

1.6

1.4

1.2

1.0

0.8

0.6

INPUT CURRENT (mA)

0.4

0.2

= 0

I

OUT

TJ = – 55°C

TJ = 25°C

TJ = 125°C

0

5 10152025 40

0

INPUT VOLTAGE (V)

UW

R

F

O

ATYPICA

3530

LT1021 G10

CCHARA TERIST

E

C

Sink Mode* Current Limit LT1021-5

60

VIN = 8V

50

40

30

20

CURRENT INTO OUTPUT (mA)

10

0

26

0

4

*NOTE THAT AN INPUT VOLTAGE IS REQUIRED

FOR 5V UNITS.

ICS

10 18

12

8

OUTPUT VOLTAGE (V)

14

16

LT1021 G11

Thermal Regulation LT1021-5

VIN = 25V ∆POWER = 200mW

0

– 0.5

–1.0

OUTPUT CHANGE (mV)

LOAD REGULATION

I

LOAD

0

20

= 10mA

40

TIME (ms)

60

THERMAL REGULATION

80

100

120

LT1021 G12

140

Load Transient Response LT1021-5, C

I

SOURCE

I

SOURCE

I

SOURCE

OUTPUT CHANGE (50mV/DIV)

∆I

SOURCE

LOAD

= 0

50mV 50mV

= 0.5mA

= 2-10mA

= 100µA

P-P

102413

3

TIME (µs)

Output Voltage Temperature Drift LT1021-7

7.003

7.002

7.001

7.000

6.999

OUTPUT VOLTAGE (V)

6.998

6.997 –50

–25

25

0

TEMPERATURE (°C)

= 0

Output Noise 0.1Hz to 10Hz LT1021-5

FILTERING = 1 ZERO AT 0.1Hz

OUTPUT VOLTAGE NOISE (5µV/DIV)

035

2 POLES AT 10Hz

5µV (1ppm)

12

TIME (MINUTES)

46

LT1021 G15

∆I

I

SINK

0

I

SINK

I

= 0

= 0.2mA

SINK

= 2-10mA

= 100µA

2

P-P

LT1021 G13

Load Transient Response LT1021-5, C

I

= 0

SOURCE

20mV 20mV

I

SOURCE

I

= 2-10mA

SOURCE

OUTPUT CHANGE (20mV/DIV)

∆I

= 100µA

SOURCE

4

501020515

LOAD

= 0.2mA

P-P

15

TIME (µs)

= 1000pF

I

= 0

SINK

I

SINK

I

SINK

∆I

SINK

0

= 0.2mA

= 2-10mA

= 100µA

10

LT1021 G14

P-P

20

Load Regulation LT1021-7, LT1021-10

5

VIN = 12V

4

3

2

1

0

–1

–2

OUTPUT CHANGE (mV)

–3

–4

50

75

100

LT1021 G16

125

–5

–6–8 –4 0 4 8

–10

SOURCING SINKING

–2

OUTPUT CURRENT (mA

2

6

10

LT1021 G17

Quiescent Current LT1021-7

1.8

1.6

1.4

1.2

1.0

0.8

0.6

INPUT CURRENT (mA)

0.4

0.2

= 0

I

OUT

TJ = – 55°C

TJ = 25°C

TJ = 125°C

0

5 10152025 40

0

INPUT VOLTAGE (V)

3530

LT1021 G18

1021fc

6

LPER

)

INPUT VOLTAGE (V)

0

INPUT CURRENT (mA)

0.2

0.6

0.8

1.0

3530

1.8

1021 G27

0.4

5 10152025 40

1.2

1.4

1.6

TJ = – 55°C

TJ = 25°C

TJ = 125°C

I

OUT

= 0

F

O

Shunt Characteristics LT1021-7

1.2 INPUT PIN OPEN

1.0

0.8

0.6

0.4

CURRENT INTO OUTPUT (mA)

0.2

TJ = 25°C

TJ = –55°C

T

= 125°C

J

R

ATYPICA

UW

CCHARA TERIST

E

C

Shunt Mode Current Limit LT1021-7

60

INPUT PIN OPEN

50

40

30

20

CURRENT INTO OUTPUT (mA)

10

ICS

Thermal Regulation LT1021-7

VIN = 27V ∆POWER = 200mW

0

–0.5

–1.0

–1.5

OUTPUT CHANGE (mV)

LOAD

REGULATION

I

= 10mA

LOAD

LT1021

THERMAL REGULATION*

0

10.006

10.004

10.002

10.000

9.998

OUTPUT VOLTAGE (V)

9.996

9.994

13

2

0

OUTPUT TO GROUND VOLTAGE (V)

59

6

4

Load Transient Response LT1021-7, C

I

= 0

SOURCE

5mV

I

SOURCE

OUTPUT VOLTAGE CHANGE

I

SOURCE

∆I

= 100µA

SOURCE

102413

NOTE VERTICAL SCALE CHANGE BETWEEN SOURCING AND SINKING

LOAD

= 0.5mA

= 2-10mA

P-P

3

TIME (µs)

= 0

∆I

0

I

SINK

I

SINK

I

SINK

I

Output Voltage Temperature Drift LT1021-10

50

–50

–25

25

0

TEMPERATURE (°C)

7

= 0.8mA

= 1.2mA

50mV

= 1.4mA

SINK

= 2-10mA

= 100µA

2

75

8

1021 G19

P-P

LT1021 G22

100

LT1021 G25

4

125

0

26

0

4

8

OUTPUT VOLTAGE (V)

Load Transient Response LT1021-7, C

I

SOURCE

OUTPUT VOLTAGE CHANGE

∆I

SOURCE

NOTE VERTICAL SCALE CHANGE BETWEEN SOURCING AND SINKING

LOAD

= 0

5mV

I

= 0.5mA

SOURCE

I

= 2-10mA

SOURCE

= 100µA

P-P

501020515

15

5µs/DIV

Load Regulation LT1021-7, LT1021-10

5

VIN = 12V

4

3

2

1

0

–1

–2

OUTPUT CHANGE (mV)

–3

–4

–5

–6–8 –4 0 4 8

–10

SOURCING SINKING

–2

OUTPUT CURRENT (mA

14

10 18

16

12

LT1021 G20

= 1000pF

I

= 0.6mA

SINK

20mV

I

= 0.8mA

SINK

= 1mA

I

SINK

I

= 2-10mA

SINK

= 100µA

∆I

SINK

0

10

LT1021 G23

2

6

P-P

1021 G26

80

0

20

*INDEPENDENT OF TEMPERATURE COEFFICIENT

60

40

TIME (ms)

100

120

LT1021 G21

140

Output Noise 0.1Hz to 10Hz LT1021-7

FILTERING = 1 ZERO AT 0.1Hz

OUTPUT VOLTAGE NOISE (5µV/DIV)

20

035

2 POLES AT 10Hz

5µV (0.7ppm)

12

TIME (MINUTES)

46

LT1021 G24

Input Supply Current LT1021-10

10

1021fc

7

LT1021

TIME (ms)

OUTPUT CHANGE (mV)

–1.0

–0.5

0

140

1021 G30

–1.5

20

60

100

0

40

80

120

LOAD

REGULATION

THERMAL REGULATION*

I

LOAD

= 10mA

*INDEPENDENT OF TEMPERATURE COEFFICIENT

VIN = 30V ∆POWER = 200mW

LPER

Shunt Characteristics LT1021-10

1.8 INPUT PIN OPEN

1.6

1.4

1.2

1.0

0.8

0.6

0.4

CURRENT INTO OUTPUT (mA)

0.2

0

TJ = – 55°C

0

OUTPUT TO GROUND VOLTAGE (V)

F

O

TJ = 125°C

42 6 10 12

8

R

ATYPICA

TJ = 25°C

1021 G28

UW

CCHARA TERIST

E

C

Shunt Mode Current Limit LT1021-10

60

INPUT PIN OPEN

50

40

30

20

CURRENT INTO OUTPUT (mA)

10

0

26

0

4

ICS

10 18

12

8

OUTPUT VOLTAGE (V)

Thermal Regulation LT1021-10

14

16

1021 G29

Load Transient Response LT1021-10, C

I

= 0

SOURCE

10mV

I

= 0.2mA

SOURCE

OUTPUT VOLTAGE CHANGE

I

SOURCE

∆I

= 100µA

SOURCE

102413

NOTE VERTICAL SCALE CHANGE

BETWEEN SOURCING AND SINKING

LOAD

= 2-10mA

P-P

3

TIME (µs)

= 0

I

∆I

0

SINK

I

SINK

= 0.6mA

50mV

I

SINK

I

SINK

= 100µA

= 0.8mA

= 1mA

= 2-10mA

2

1021 G31

P-P

Load Transient Response LT1021-10, C

I

= 0

SOURCE

5mV

I

= 0.5mA

SOURCE

OUTPUT VOLTAGE CHANGE

I

SOURCE

∆I

= 100µA

SOURCE

4

102413

NOTE VERTICAL SCALE CHANGE

BETWEEN SOURCING AND SINKING

LOAD

I

SINK

= 2-10mA

P-P

3

TIME (µs)

= 1000pF

I

SINK

20mV

= 1.2mA

I

SINK

∆I

SINK

0

= 0.8mA

= 1.4mA

SINK

= 2-10mA

= 100µA

2

P-P

4

1021 G32

Output Noise 0.1Hz to 10Hz LT1021-10

FILTERING = 1 ZERO AT 0.1Hz

OUTPUT VOLTAGE NOISE (10µV/DIV)

035

2 POLES AT 10Hz

10µV (1ppm)

12

TIME (MINUTES)

46

1021 G33

8

1021fc

LT1021

U

WUU

APPLICATIONS INFORMATION

Effect of Reference Drift on System Accuracy

A large portion of the temperature drift error budget in many systems is the system reference voltage. This graph indicates the maximum temperature coefficient allowable if the reference is to contribute no more than 0.5LSB error to the overall system performance. The example shown is a 12-bit system designed to operate over a temperature range from 25°C to 65°C. Assuming the system calibration is performed at 25°C, the temperature span is 40°C. It can be seen from the graph that the temperature coefficient of the reference must be no worse than 3ppm/°C if it is to contribute less than 0.5LSB error. For this reason, the LT1021 family has been optimized for low drift.

Maximum Allowable Reference Drift

100

8-BIT

The LT1021-10 “C” version is pre-trimmed to ± 5mV and therefore can utilize a restricted trim range. A 75k resistor in series with a 20kΩ potentiometer will give ±10mV trim range. Effect on the output TC will be only 1ppm/°C for the ± 5mV trim needed to set the “C” device to 10.000V.

LT1021-5

The LT1021-5 does have an output voltage trim pin, but the TC of the nominal 4V open-circuit voltage at this pin is about –1.7mV/°C. For the voltage trimming not to affect reference output TC, the external trim voltage must track the voltage on the trim pin. Input impedance of the trim pin is about 100kΩ and attenuation to the output is 13:1. The technique shown below is suggested for trimming the output of the LT1021-5 while maintaining minimum shift in output temperature coefficient. The R1/R2 ratio is chosen to minimize interaction of trimming and TC shifts, so the exact values shown should be used.

10-BIT

10

0.5LSB ERROR (ppm/°C)

MAXIMUM TEMPERATURE COEFFICIENT FOR

1.0 100

12-BIT

14-BIT

20 100

40

50

30

TEMPERATURE SPAN (°C)

807060

90

LT1021 AI01

Trimming Output Voltage

LT1021-10

The LT1021-10 has a trim pin for adjusting output voltage. The impedance of the trim pin is about 12kΩ with a nominal open-circuit voltage of 5V. It is designed to be driven from a source impedance of 3kΩ or less to minimize changes in the LT1021 TC with output trimming. Attenuation between the trim pin and the output is 70:1. This allows ± 70mV trim range when the trim pin is tied to the wiper of a potentiometer connected between the output and ground. A 10kΩ potentiometer is recommended, preferably a 20 turn cermet type with stable characteristics over time and temperature.

LT1021-5

IN

GND

OUT

TRIM

R1 27k

1N4148

V

R2 50k

1021 AI02

OUT

LT1021-7

The 7V version of the LT1021 has no trim pin because the internal architecture does not have a point which could be driven conveniently from the output. Trimming must therefore be done externally, as is the case with ordinary reference diodes. Unlike these diodes, however, the output of the LT1021 can be loaded with a trim potentiometer. The following trim techniques are suggested; one for voltage output and one for current output. The voltage output is trimmed for 6.95V. Current output is 1mA, as shown, into a summing junction, but all resistors may be scaled for currents up to 10mA.

Both of these circuits use the trimmers in a true potentiometric mode to reduce the effects of trimmer TC. The voltage output has a 200Ω impedance, so loading must be

1021fc

9

LT1021

U

WUU

APPLICATIONS INFORMATION

minimized. In the current output circuit, R1 determines output current. It should have a TC commensurate with the LT1021 or track closely with the feedback resistor around the op amp.

LT1021-7

IN

LT1021-7

IN

GND

OUT

GND

50k

OUT

R3

10k

TC TRACKING TO 50ppm/°C

R2**

182k

R2*

14k

1%

R1*

7.15k

1.000mA

R1* 200Ω 1%

V

OUT

6.950V

1021 AI03

Kelvin Connections

Although the LT1021 does not have true force/sense capability at its outputs, significant improvements in ground loop and line loss problems can be achieved with proper hook-up. In series mode operation, the ground pin of the LT1021 carries only ≈1mA and can be used as a sense line, greatly reducing ground loop and loss problems on the low side of the reference. The high side supplies load current so line resistance must be kept low. Twelve feet of #22 gauge hook-up wire or 1 foot of 0.025 inch printed circuit trace will create 2mV loss at 10mA output current. This is equivalent to 1LSB in a 10V, 12-bit system.

The following circuits show proper hook-up to minimize errors due to ground loops and line losses. Losses in the output lead can be greatly reduced by adding a PNP boost transistor if load currents are 5mA or higher. R2 can be added to further reduce current in the output sense lead.

Standard Series Mode

–

OP AMP

+

1021 AI04

RESISTOR TC DETERMINES I

*

TC ≤ (10 • R1) TC. R2 AND R3 SCALE

**

WITH R1 FOR DIFFERENT OUTPUT CURRENTS

OUT

TC

Capacitive Loading and Transient Response

The LT1021 is stable with all capacitive loads, but for optimum settling with load transients, output capacitance should be under 1000pF. The output stage of the reference is class AB with a fairly low idling current. This makes transient response worst-case at light load currents. Because of internal current drain on the output, actual worstcase occurs at I –0.8mA (sinking) on LT1021-7 and I

= 0 on LT1021-5, I

LOAD

=

LOAD

= 1.4mA (sinking) on LT1021-10. Significantly better load transient response is obtained by moving slightly away from these points. See Load Transient Response curves for details. In general, best transient response is obtained when the output is sourcing current. In critical applications, a 10µF solid tantalum capacitor with several ohms in series provides optimum output bypass.

INPUT

GROUND

RETURN

LT1021

IN

GND

KEEP THIS LINE RESISTANCE LOW

OUT

Series Mode with Boost Transistor

INPUT

R1 220Ω

2N3906

IN

LT1021

OUT

GND

GROUND

RETURN

*OPTIONAL—REDUCES CURRENT IN OUTPUT SENSE LEAD R2 = 2.4k (LT1021-5), 3k (LT1021-7), 5.6k (LT1021-10)

R2*

1021 AI06

+

LOAD

1021 AI05

LOAD

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10

LT1021

U

WUU

APPLICATIONS INFORMATION

Effects of Air Movement on Low Frequency Noise

The LT1021 has very low noise because of the buried zener used in its design. In the 0.1Hz to 10Hz band, peak-to-peak noise is about 0.5ppm of the DC output. To achieve this low noise, however, care must be taken to shield the reference from ambient air turbulence. Air movement can create noise because of thermoelectric differences between IC package leads (especially kovar lead TO-5) and printed circuit board materials and/or sockets. Power dissipation in the reference, even though it rarely exceeds 20mW, is enough to cause small temperature gradients in the package leads. Variations in thermal resistance, caused by uneven air flow, create differential lead temperatures, thereby causing thermoelectric voltage noise at the output of the reference. The following XY plotter trace dramatically illustrates this effect. The first half of the plot was done with the LT1021 shielded from ambient air with a small foam cup. The cup was then removed for the second half of the trace. Ambient in both cases was a lab environment with no excessive air turbulence from air conditioners, opening/closing doors, etc. Removing the foam cup increases the output noise by almost an order of magnitude in the 0.01Hz to 1Hz band! The kovar leads of the TO-5 (H) package are the primary culprit. Alloy 42 and

copper lead frames used on dual-in-line packages are not nearly as sensitive to thermally generated noise because they are intrinsically matched.

There is nothing magical about foam cups—any enclosure which blocks air flow from the reference will do. Smaller enclosures are better since they do not allow the build-up of internally generated air movement. Naturally, heat generating components external to the reference itself should not be included inside the enclosure.

Noise Induced By Air Turbulence (TO-5 Package)

LT1021-7 (TO-5 PACKAGE) f = 0.01Hz TO 10Hz

20µV

OUTPUT VOLTAGE NOISE (20µV/DIV)

0610

24

TIME (MINUTES)

FOAM CUP REMOVED

812

1021 AI07

U

TYPICAL APPLICATIONS

Restricted Trim Range for Improved

Resolution, 10V, “C” Version Only

LT1021C-10

IN 10.000V

IN

OUT V

GND TRIM

TRIM RANGE ≈ ±10mV

R1

75k

R2 50k

1021 TA11

LT1021-10 Full Trim Range (± 0.7%)

LT1021-10

V

IN

GND

OUT

TRIM

IN

*CAN BE RAISED TO 20k FOR LESS CRITICAL APPLICATIONS

R1* 10k

1021 TA03

V

OUT

–15V

Negative Series Reference

15V

R2

4.7k

Q1

2N2905

R1

4.7k

D1 15V

LT1021-10

IN

GND

LT1021 TA04

OUT

–10V AT 50mA

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11

LT1021

LT1021-10

OUT

IN

TRIM

GND

4.32k

V

OUT

= 10.24V

V

IN

5k

V

–

= –15V*

*MUST BE WELL REGULATED

dV

OUT

dV

–

=

15mV

V

1021 TA12

U

TYPICAL APPLICATIONS

Boosted Output Current

with No Current Limit

V+ ≥ (V

OUT

+ 1.8V)

LT1021

2-Pole Lowpass Filtered Reference

LT1021

IN

V

IN

OUT

GND

IN

GND

R1 220Ω

OUT

R1

36k

+

f = 10Hz

2N2905

10V AT 100mA

2µF SOLID TANT

1021 TA05

1µF

MYLAR

R2

36k

+

≥ V

V

–

LT1001

+

0.5µF MYLAR

Boosted Output Current

with Current Limit

+ 2.8V

OUT

D1* LED

LT1021

*GLOWS IN CURRENT LIMIT, DO NOT OMIT

V

IN

V

REF

TOTAL NOISE ≤2µV

RMS

1Hz ≤ f ≤ 10kHz

IN

GND

Ultraprecise Current Source

R1 220Ω

OUT

+

8.2Ω

2N2905

10V AT 100mA

2µF SOLID TANT

1021 TA06

15V

LT1021-7

IN

OUT

GND

6

Operating 5V Reference from 5V Supply

C1*

5µF

+

1N914

+

CMOS LOGIC GATE**

≥ 2kHz*

f

IN

FOR HIGHER FREQUENCIES C1 AND C2 MAY BE DECREASED

*

PARALLEL GATES FOR HIGHER REFERENCE CURRENT LOADING

**

TRIM

100Ω

≈8.5V

C2* 5µF

17.4k 1%

15V

7

–

2

LT1001

–15V

3

+

4

REGULATION < 1ppm/V

COMPLIANCE = –13V TO 7V

LT1021-5

IN

OUT

GND

I

OUT

6.98k*

0.1%

*LOW TC

= 1mA

5V LOGIC SUPPLY

5V REFERENCE

1021 TA07

1021 TA16

LT1021-10

12

OUT

GND

–15V

TRIM

1.2k

–V

REF

1021 TA13

CMOS DAC with Low Drift Full-Scale Trimming**

4.02K

R1

4.99k 1%

R2

40.2Ω 1%

TC LESS THAN 200ppm/°C

*

NO ZERO ADJUST REQUIRED

**

WITH LT1007 (V

REF

7520, ETC

CMOS

DAC

0S

FB

≤ 60µV)

I

OUT

30pF

–

LT1007C

+

R3

1%

Trimming 10V Units to 10.24V

R4* 100Ω FULL-SCALE ADJUST

10V F.S.

LT1236 TA15

1021fc

U

LT1021-10

OUT

GND

IN

1021 TA08

R

L

30mA

15V

R1* 169Ω

V

OUT

10V

TYPICAL LOAD CURRENT = 30mA

SELECT R1 TO DELIVER TYPICAL LOAD CURRENT. LT1021 WILL THEN SOURCE OR SINK AS NECESSARY TO MAINTAIN PROPER OUTPUT. DO NOT REMOVE LOAD AS OUTPUT WILL BE DRIVEN UNREGULATED HIGH. LINE REGULATION IS DEGRADED IN THIS APPLICATION

*

TYPICAL APPLICATIONS

LT1021

Strain Gauge Conditioner for 350Ω Bridge

R1

357Ω

1/2W

LM301A

1

100pF

OF AMPLIFIER

IN

28mA

+

†

–

8

28.5mA

3

2

LT1021-10

15V

*

THIS RESISTOR PROVIDES POSITIVE FEEDBACK TO THE BRIDGE TO ELIMINATE LOADING EFFECT OF THE AMPLIFIER. EFFECTIVE Z STAGE IS ≥1MΩ. IF R2 TO R5 ARE CHANGED, SET R6 = R3

IN

OUT

GND

6 6

5V

350Ω STRAIN GAUGE BRIDGE**

R2

20k

R4

20k

R5 2M

–5V

357Ω 1/2W

–15V

BRIDGE IS ULTRALINEAR WHEN ALL LEGS ARE

**

ACTIVE, TWO IN COMPRESSION AND TWO IN TENSION, OR WHEN ONE SIDE IS ACTIVE WITH ONE COMPRESSED AND ONE TENSIONED LEG

†

OFFSET AND DRIFT OF LM301A ARE VIRTUALLY ELIMINATED BY DIFFERENTIAL CONNECTION OF LT1012C

2

3

–

LT1012C

+

R6*

2M

R3

2M

1021 TA09

Negative Shunt Reference Driven

by Current Source

LT1021-10

OUT

GND

V

OUT

× 100

LM334

–11V TO – 40V

2.5mA

–10V (I

LOAD

27Ω

≤ 1mA)

1021 TA14

Precision DAC Reference with System TC Trim

LT1021-10

15V

IN

OUT

GND

TRIMS 1mA REFERENCE CURRENT

*

TC BY ± 40ppm/°C. THIS TRIM SCHEME HAS VERY LITTLE EFFECT ON ROOM TEMPERATURE CURRENT TO MINIMIZE ITERATIVE TRIMMING

8.87k 1%

1.24k 1%

D1 1N457

50k

TC TRIM*

10k 1%

D2 1N457

50k

50k ROOM TEMP TRIM

200k 1%

10.36k 1%

1mA

Handling Higher Load Currents

8.45k

DAC

1021 TA17

1021fc

13

LT1021

U

TYPICAL APPLICATIONS

Ultralinear Platinum Temperature Sensor*

LT1021-10

IN

OUT

20V

100k

R2* 5k

R1** 253k

R8

R9

10M

–15V

R3** 5k

R7 392k 1%

†

R

S

100Ω AT 0°C

R10

182k

1%

4.75k

R4

1%

GND

R14 5k

R11

6.65M 1%

2

R5 200k 1%

3

R6

†

619k

STANDARD INDUSTRIAL 100Ω PLATINUM 4-WIRE SENSOR,

1%

ROSEMOUNT 78S OR EQUIVALENT. α = 0.00385 TRIM R9 FOR V

TRIM R12 FOR V TRIM R14 FOR V USE TRIM SEQUENCE AS SHOWN. TRIMS ARE NONINTERACTIVE SO THAT ONLY ONE TRIM SEQUENCE IS NORMALLY REQUIRED.

*

FEEDBACK LINEARIZES OUTPUT TO ±0.005°C FROM –50°C TO 150°C

**

WIREWOUND RESISTORS WITH LOW TC

–

LT1001

+

R

654k

20V

–15V

**

F

7

4

6

= 0V AT 0°C

OUT

= 10V AT 100°C

OUT

= 5V AT 50°C

OUT

R15 10k

R13

24.3k

R12 1k

=100mV/°C

V

OUT

–50°C ≤ T ≤ 150°C

1021 TA10

U

W

EQUIVALE T SCHE ATIC

D4

6.3V

INPUT

Q3

D1

D2

OUTPUT

D3

R1

Q1

+

–

A1

Q2

R2

LT1021 ES

GND

1021fc

14

PACKAGE DESCRIPTION

SEATING

PLANE

45°

U

H Package

8-Lead TO-5 Metal Can (.200 Inch PCD)

(Reference LTC DWG # 05-08-1320)

.335 – .370

(8.509 – 9.398)

DIA

.305 – .335

(7.747 – 8.509)

.016 – .021**

(0.406 – 0.533)

.050

(1.270)

MAX

.027 – .045

(0.686 – 1.143)

PIN 1

GAUGE PLANE

(5.080)

.010 – .045*

(0.254 – 1.143)

.028 – .034

(0.711 – 0.864)

.040

(1.016)

MAX

(12.700 – 19.050)

.200

TYP

.165 – .185

(4.191 – 4.699)

.500 – .750

REFERENCE PLANE

LT1021

.110 – .160

(2.794 – 4.064)

INSULATING

STANDOFF

*

LEAD DIAMETER IS UNCONTROLLED BETWEEN THE REFERENCE PLANE AND THE SEATING PLANE

**

FOR SOLDER DIP LEAD FINISH, LEAD DIAMETER IS

N8 Package

8-Lead PDIP (Narrow .300 Inch)

(Reference LTC DWG # 05-08-1510)

87 6

.255 ± .015*

(6.477 ± 0.381)

1234

.300 – .325

(7.620 – 8.255)

.065

(1.651)

.008 – .015

(0.203 – 0.381)

+.035

.325

–.015 +0.889

8.255

()

–0.381

NOTE:

1. DIMENSIONS ARE

*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)

INCHES

MILLIMETERS

TYP

.045 – .065

(1.143 – 1.651)

.100

(2.54)

BSC

.016 – .024

(0.406 – 0.610)

.400*

(10.160)

MAX

H8(TO-5) 0.200 PCD 0204

5

.130 ± .005

(3.302 ± 0.127)

(3.048)

.018 ± .003

(0.457 ± 0.076)

.120

MIN

.020

(0.508)

MIN

N8 1002

1021fc

Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

15

LT1021

PACKAGE DESCRIPTION

8-Lead Plastic Small Outline (Narrow .150 Inch)

.050 BSC

U

S8 Package

(Reference LTC DWG # 05-08-1610)

.045 ±.005

.189 – .197

(4.801 – 5.004)

8

NOTE 3

7

5

6

.245 MIN

.030 ±.005

TYP

RECOMMENDED SOLDER PAD LAYOUT

.010 – .020

(0.254 – 0.508)

.008 – .010

(0.203 – 0.254)

NOTE:

1. DIMENSIONS IN

2. DRAWING NOT TO SCALE

3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)

× 45°

.016 – .050

(0.406 – 1.270)

INCHES

(MILLIMETERS)

.160 ±.005

0°– 8° TYP

.228 – .244

(5.791 – 6.197)

.053 – .069

(1.346 – 1.752)

.014 – .019

(0.355 – 0.483)

TYP

.150 – .157

(3.810 – 3.988)

1

3

2

4

(0.101 – 0.254)

.050

(1.270)

BSC

RELATED PARTS

PART NUMBER DESCRIPTION COMMENTS

LT1019 Precision Bandgap Reference 0.05%, 5ppm/°C

LT1027 Precision 5V Reference 0.02%, 2ppm/°C

LT1236 Precision Reference SO-8, 5V and 10V, 0.05%, 5ppm/°C

LTC®1258 Micropower Reference 200mV Dropout, MSOP

LT1389 Nanopower Shunt Reference 800nA Operating Current

LT1460 Micropower Reference SOT-23, 2.5V, 5V, 10V

LT1634 Micropower Shunt Reference 0.05%, 10ppm/°C, MSOP

NOTE 3

.004 – .010

SO8 0303

16

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507

●

www.linear.com

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LT 1005 REV C • PRINTED IN USA