LT1021BCN8-5_技术文档

LT1021

Pre c isio n Re fe re nc e

U

DESCRIPTIO

EATURE

S

F

The LT^®1021 is a precision reference with ultralow drift

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 canbeusedas shuntregulators (two-terminalzeners)

with the same precision characteristics as the three-

terminal connection. Special care has been taken to mini-

mize thermal regulation effects and temperature

induced hysteresis.

■

Pin Compatible with Most Bandgap Reference

Applications, Including Ref 01, Ref 02, LM368,

MC1400 and MC1404 with Greatly Improved

Stability, Noise and Drift

Ultralow Drift: 5ppm/°C Max Slope

Trimmed Output Voltage

Operates in Series or Shunt Mode

Output Sinks and Sources in Series Mode

Very Low Noise: <1ppm _P-P(0.1Hz to 10Hz)

>100dB Ripple Rejection

Minimum Input/Output Differential of 1V

100% Noise Tested

■

TheLT1021references arebasedonaburiedzenerdiode

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.

O U

PPLICATI

A/D and D/A Converters

Precision Regulators

Digital Voltmeters

Inertial Navigation Systems

Precision Scales

Portable Reference Standard

S

A

■

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,andthereforeexhibits thebestlongtermstability

and temperature hysteresis. The LT1021-5 and LT1021-

10areintendedforsystems requiringaprecise5Vor10V

reference with an initial tolerance as low as ±0.05%.

, LTC and LT are registered trademarks of Linear Technology Corporation.

U

O

TYPICAL APPLICATI

Typical Distribution of Temperature Drift

24

Basic Positive and Negative Connections

DISTRIBUTION

OF THREE RUNS

21

18

15

12

9

LT1021

(7 AND 10 ONLY)

LT1021

GND

V

IN

V

OUT

IN

OUT

NC

OUT

GND

–V

OUT

–

V

– (V )

OUT

6

R1 =

R1

I

+ 1.5mA

LOAD

3

–15V

(V )

–

1021 TA01

– 0

–5 –4 –3 –2 –1

0

1

2

3

4

5

OUTPUT DRIFT (ppm/°C)

1021 TA01

1

LT1021

ABSOLUTE AXI U RATI GS ^{(Note 1)}

W W W

U

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

Output Short-Circuit Duration

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

IN

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

Positive ............................................... Equal to V_OUT

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

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PACKAGE RDER I FOR ATIO

ORDER PART

NUMBER

ORDER PART

NUMBER

LT1021BCH-5

LT1021BMH-5

LT1021CCH-5

LT1021CMH-5

LT1021BCN8-5

LT1021CCN8-5

LT1021CIN8-5

TOP VIEW

NC*

DNC*

1

2

3

4

DNC*

8

7

6

5

LT1021DCN8-5

LT1021DIN8-5

LT1021DCS8-5

LT1021BCN8-7

LT1021DCN8-7

LT1021DCS8-7

LT1021BCN8-10

LT1021CCN8-10

LT1021CIN8-10

LT1021DCN8-10

LT1021DCS8-10

LT1021DIN8-10

8

1

3

NC*

7

5

V

IN

LT1021DCH-5

LT1021DMH-5

LT1021BCH-7

LT1021BMH-7

LT1021DCH-7

LT1021DMH-7

LT1021BCH-10

LT1021BMH-10

LT1021CCH-10

LT1021CMH-10

LT1021DCH-10

LT1021DMH-10

DNC*

GND

V

0UT

6

V

2

V

OUT

IN

TRIM**

TRIM

**

NC*

4

N8 PACKAGE

8-LEAD PDIP

S8 PACKAGE

8-LEAD PLASTIC SO

GND

H PACKAGE

8-LEAD TO-5 METAL CAN

*CONNECTED INTERNALLY.

D0 NOT CONNECT EXTERNAL

CIRCUITRY TO THESE PINS

**NO TRIM PIN ON LT1021-7.

DO NOT CONNECT EXTERNAL

CIRCUITRY TO PIN 5 ON LT1021-7

*CONNECTED INTERNALLY.

D0 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

_JMAX= 130°C, θ_JA= 130°C/W (N)

_JMAX= 130°C, θ_JA= 150°C/W (S)

T_JMAX= 150°C, θ_JA= 150°C/W,θ_JC= 45°C/W

S8 PART MARKING

021DC5

021DC7

021DC1

2

LT1021

ELECTRICAL CHARACTERISTICS ^The● denotes specifications that apply over the full operating temperature

range, otherwise specifications are T_A= 25°C. V = 10V, I_OUT= 0, unless otherwise noted.

IN

LT1021-5

TYP

PARAMETER

CONDITIONS

MIN

MAX

UNITS

Output Voltage (Note 2)

LT1021C-5

LT1021B-5/LT1021D-5

4.9975

4.9500

5.000

5.0025

5.0500

V

Output Voltage Temperature Coefficient (Note 3)

Line Regulation (Note 4)

T

≤ T ≤ T

LT1021B-5

LT1021C-5/LT1021D-5

MIN J MAX

●

2

3

5

20

ppm/°C

7.2V ≤ V ≤ 10V

4

12

20

6

ppm/V

IN

●

10V ≤ V ≤ 40V

2

IN

10

Load Regulation (Sourcing Current)

Load Regulation (Sinking Current)

Supply Current

0 ≤ I

(Note 4)

≤ 10mA

10

60

20

35

ppm/mA

OUT

●

0 ≤ I

100

150

ppm/mA

OUT

(Note 4)

0.8

1.2

1.5

mA

Output Voltage Noise (Note 6)

0.1Hz ≤ f ≤ 10Hz

10Hz ≤ f ≤ 1kHz

3.0

2.2

µV

P-P

µV

RMS

3.5

Long Term Stability of Output Voltage (Note 7)

Temperature Hysteresis of Output

∆t = 1000Hrs Noncumulative

∆T = ±25°C

15

10

ppm

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

V = 12V, I_OUT= 0, unless otherwise noted.

IN

LT1021-7

TYP

PARAMETER

CONDITIONS

MIN

MAX

UNITS

Output Voltage (Note 2)

6.95

7.00

7.05

V

Output Voltage Temperature Coefficient (Note 3)

T

≤ T ≤ T

MIN J MAX

LT1021B-7

LT1021D-7

●

2

3

5

20

ppm/°C

Line Regulation (Note 4)

8.5V ≤ V ≤ 12V

1.0

2.0

0.5

1.0

4

8

2

4

ppm/V

IN

●

12V ≤ V ≤ 40V

IN

Load Regulation (Sourcing Current)

Load Regulation (Shunt Mode)

Supply Current (Series Mode)

Minimum Current (Shunt Mode)

Output Voltage Noise (Note 6)

0 ≤ I

(Note 4)

≤ 10mA

12

25

40

ppm/mA

OUT

●

1.2mA ≤ I

(Notes 4, 5)

≤ 10mA

50

100

150

ppm/mA

SHUNT

0.75

0.7

1.2

1.5

mA

V is Open

IN

1.0

1.2

mA

0.1Hz ≤ f ≤ 10Hz

10Hz ≤ f ≤ 1kHz

4.0

2.5

µV

P-P

µV

RMS

4.0

Long Term Stability of Output Voltage (Note 7)

Temperature Hysteresis of Output

∆t = 1000Hrs Noncumulative

∆T = ±25°C

7

3

ppm

3

LT1021

ELECTRICAL CHARACTERISTICS ^The● denotes specifications that apply over the full operating temperature

range, otherwise specifications are T_A= 25°C. V = 15V, I_OUT= 0, unless otherwise noted.

IN

LT1021-10

TYP

PARAMETER

CONDITIONS

MIN

MAX

UNITS

Output Voltage (Note 2)

LT1021C-10

LT1021B-10/LT1021D-10

9.995

9.950

10.00

10.005

10.050

V

Output Voltage Temperature Coefficient (Note 3)

Line Regulation (Note 4)

T

≤ T ≤ T

LT1021B-10

LT1021C-10/LT1021D-10

MIN J MAX

●

2

5

20

ppm/°C

11.5V ≤ V ≤ 14.5V

1.0

4

6

2

4

ppm/V

IN

●

14.5V ≤ V ≤ 40V

0.5

IN

Load Regulation (Sourcing Current)

Load Regulation (Shunt Mode)

Supply Current (Series Mode)

Minimum Current (Shunt Mode)

Output Voltage Noise (Note 6)

0 ≤ I

(Note 4)

≤ 10mA

12

50

25

40

ppm/mA

OUT

●

1.7mA ≤ I

(Notes 4, 5)

≤ 10mA

100

150

ppm/mA

SHUNT

1.2

1.1

1.7

2.0

mA

V is Open

IN

1.5

1.7

mA

0.1Hz ≤ f ≤ 10Hz

10Hz ≤ f ≤ 1kHz

6.0

3.5

µV

P-P

µV

RMS

6

Long Term Stability of Output Voltage (Note 7)

Temperature Hysteresis of Output

∆t = 1000Hrs Noncumulative

∆T = ±25°C

15

5

ppm

Note 1: Absolute Maximum Ratings are those values beyond which the life

of a device may be impaired.

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 2: Output voltage is measured immediately after turn-on. Changes

due to chip warm-up are typically less than 0.005%.

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.

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 to 25°C and 25°C to T

.

MIN

MAX

Incremental slope is also measured at 25°C.

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 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.

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

4

LT1021

U W

TYPICALPERFOR A CE CHARACTERISTICS

Minimum Input/Output Differential

LT1021-7, LT1021-10

Ripple Rejection

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

130

115

110

105

100

95

V

C

OUT

= 15V

= 0

f = 150Hz

T = 125 °C

LT1021-7

IN

J

120

110

100

90

LT1021-7

T = –55 °C

J

LT1021-10

T = 25 °C

J

LT1021-10

LT1021-5

80

70

90

60

50

85

0

2

4

6

8

10 12 14 16 18 20

25 30

INPUT VOLTAGE (V)

0

5

10 15 20

35 40

10

100

1k

10k

OUTPUT CURRENT (mA)

FREQUENCY (Hz)

LT1021 G02

1021 G03

LT1021 G01

Start-Up (Shunt Mode)

LT1021-7, LT1021-10

Start-Up (Series Mode)

Output Voltage Noise Spectrum

13

12

11

10

9

11

10

9

400

350

300

250

200

150

100

50

V

IN

= 0V TO 12V

LT1021-10

1k

V

+ 2V

OUT

LT1021-10

V

OUT

0V

OUT

IN

GND

NC

8

LT1021-7

LT1021-5

7

LT1021-10

LT1021-7

7

6

5

6

LT1021-7

5

LT1021-5

4

0

3

6

10

12

10

100

FREQUENCY (Hz)

1k

10k

12

0

2

4

8

0

2

4

6

8

10

14

TIME (µs)

LT1021 G06

LT1021 G05

LT1021 G04

Output Voltage Temperature Drift

LT1021-5

Output Voltage Noise

Load Regulation LT1021-5

5.006

5.004

5.002

5.000

4.998

4.996

4.994

16

14

12

10

8

5

4

C

= 0

V

IN

= 8V

OUT

FILTER = 1 POLE

= 0.1Hz

f

LOW

3

2

1

0

LT1021-7

–1

– 2

– 3

– 4

– 5

6

LT1021-10

4

LT1021-5

2

0

10

100

1k

10k

–50 –25

0

25

50

75 100 125

–10 –8 – 6 – 4 – 2

0

2

4

6

8

10

TEMPERATURE (°C)

BANDWIDTH (Hz)

SOURCING

SINKING

LT1021 G07

LT1021 G08

OUTPUT CURRENT (mA)

LT1021 G09

5

LT1021

U W

TYPICALPERFOR A CE CHARACTERISTICS

Sink Mode* Current Limit

LT1021-5

Quiescent Current LT1021-5

Thermal Regulation LT1021-5

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

60

50

I

= 0

V

IN

= 8V

V

= 25V

OUT

IN

∆POWER = 200mW

LOAD

REGULATION

0

– 0.5

–1.0

40

T = – 55°C

J

THERMAL

REGULATION

30

20

T = 25°C

J

T = 125°C

J

I

= 10mA

LOAD

10

0

60 80

TIME (ms)

0

20 40

100 120 140

0

5

10 15 20 25

INPUT VOLTAGE (V)

40

0

2

4

6

8

10 12 14 16 18

30 35

OUTPUT VOLTAGE (V)

LT1021 G12

LT1021 G10

*NOTE THAT AN INPUT VOLTAGE IS REQUIRED

FOR 5V UNITS.

LT1021 G11

Output Noise 0.1Hz to 10Hz

LT1021-5

Load Transient Response

LT1021-5, C_LOAD= 1000pF

Load Transient Response

LT1021-5, C_LOAD= 0

FILTERING = 1 ZERO AT 0.1Hz

2 POLES AT 10Hz

I

= 0

I

= 0

SINK

SOURCE

I

= 0

I

= 0

SOURCE

SINK

5µV (1ppm)

50mV

20mV

I

= 0.2mA

I

= 0.2mA

SINK

I

= 0.2mA

SINK

I = 2-10mA

SINK

SOURCE

I

= 0.5mA

SOURCE

I

= 2-10mA

SOURCE

I

= 2-10mA

I

= 2-10mA

SINK

SOURCE

∆I

SOURCE

= 100µA

∆I

SOURCE

= 100µA

P-P

∆I

SINK

= 100µA

∆I

SINK

= 100µA

P-P

4

6

0

1

2

3

4

0

1

2

3

4

0

5

10 15 20

0

5

10 15 20

0

1

2

3

5

TIME (µs)

TIME (MINUTES)

LT1021 G13

LT1021 G14

LT1021 G15

Output Voltage Temperature

Drift LT1021-7

Load Regulation

LT1021-7, LT1021-10

Quiescent Current LT1021-7

7.003

7.002

7.001

7.000

6.999

6.998

6.997

5

4

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

V

IN

= 12V

I

= 0

OUT

3

2

1

T = – 55°C

J

0

T = 25°C

J

–1

– 2

– 3

– 4

– 5

T = 125°C

J

0

–10 –8 – 6 – 4 – 2

0

2

4

6

8

10

–50

0

25

50

75 100 125

–25

0

5

10 15 20 25

INPUT VOLTAGE (V)

40

30 35

TEMPERATURE (°C)

SOURCING

SINKING

OUTPUT CURRENT (mA)

LT1021 G16

LT1021 G17

LT1021 G18

6

LT1021

U W

TYPICALPERFOR A CE CHARACTERISTICS

Shunt Mode Current Limit

LT1021-7

Shunt Characteristics LT1021-7

Thermal Regulation LT1021-7

1.2

1.0

60

50

INPUT PIN OPEN

V = 27V

IN

∆POWER = 200mW

INPUT PIN OPEN

LOAD

0

–0.5

–1.0

–1.5

REGULATION

0.8

40

T = –55°C

J

T = 25°C

J

THERMAL

REGULATION*

0.6

0.4

30

20

T = 125°C

J

I

= 10mA

LOAD

0.2

0

10

0

60 80

20 40

TIME (ms)

0

100 120 140

0

1

2

3

4

5

6

7

8

9

0

2

4

6

8

10 12 14 16 18

OUTPUT VOLTAGE (V)

OUTPUT TO GROUND VOLTAGE (V)

LT1021 G20

1021 G19

*INDEPENDENT OF TEMPERATURE COEFFICIENT

LT1021 G21

Load Transient Response

LT1021-7, C_LOAD= 0

Load Transient Response

LT1021-7, C_LOAD= 1000pF

Output Noise 0.1Hz to 10Hz

LT1021-7

I

= 0

FILTERING = 1 ZERO AT 0.1Hz

2 POLES AT 10Hz

SOURCE

I

= 0.8mA

I

= 0.6mA

SINK

I

= 0

SOURCE

5mV

20mV

I

= 1.2mA

SINK

5µV (0.7ppm)

5mV

50mV

I

= 0.8mA

SINK

I

= 0.5mA

I

= 0.5mA

SOURCE

I

= 1.4mA

I

= 1mA

SINK

I

= 2-10mA

I

= 2-10mA

I

= 2-10mA

I

= 2-10mA

SINK

SOURCE

∆I

= 100µA

∆I

= 100µA

∆I

= 100µA

∆I

= 100µA

SOURCE

P-P

SOURCE P-P

SINK

1

P-P

SINK P-P

4

6

0

1

2

3

5

0

1

2

3

4

0

2

3

4

0

5

10 15 20

0

5

10 15 20

TIME (µs)

5µs/DIV

TIME (MINUTES)

NOTE VERTICAL SCALE CHANGE

LT1021 G24

BETWEEN SOURCING AND SINKING

LT1021 G22

LT1021 G23

Output Voltage Temperature

Drift LT1021-10

Load Regulation

LT1021-7, LT1021-10

Input Supply Current LT1021-10

10.006

10.004

10.002

10.000

9.998

5

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

V

IN

= 12V

I

= 0

OUT

T = – 55°C

J

4

3

T = 25°C

J

2

T = 125°C

J

1

0

–1

– 2

– 3

– 4

– 5

9.996

9.994

0

–50

0

25

50

75 100 125

–25

–10 –8 – 6 – 4 – 2

0

2

4

6

8

10

0

5

10 15 20 25

INPUT VOLTAGE (V)

40

30 35

TEMPERATURE (°C)

SOURCING

SINKING

LT1021 G25

OUTPUT CURRENT (mA)

1021 G26

1021 G27

7

LT1021

U W

TYPICALPERFOR A CE CHARACTERISTICS

Shunt Mode Current Limit

LT1021-10

Shunt Characteristics LT1021-10

Thermal Regulation LT1021-10

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

60

50

INPUT PIN OPEN

V = 30V

IN

∆POWER = 200mW

LOAD

0

–0.5

–1.0

–1.5

REGULATION

40

T = – 55°C

J

30

20

THERMAL

REGULATION*

T = 25°C

J

T = 125°C

J

I

= 10mA

LOAD

10

0

60 80

TIME (ms)

0

20 40

100 120 140

0

2

4

6

10

12

0

2

4

6

10

14 16 18

8

12

OUTPUT TO GROUND VOLTAGE (V)

OUTPUT VOLTAGE (V)

1021 G29

1021 G28

*INDEPENDENT OF TEMPERATURE COEFFICIENT

1021 G30

Load Transient Response

LT1021-10, C_LOAD= 0

Load Transient Response

LT1021-10, C_LOAD= 1000pF

Output Noise 0.1Hz to 10Hz

LT1021-10

FILTERING = 1 ZERO AT 0.1Hz

2 POLES AT 10Hz

I

= 0.6mA

I

= 0.8mA

SINK

I

= 0

I

= 0

SOURCE

20mV

50mV

10µV (1ppm)

10mV

5mV

I

= 1.2mA

SINK

I

= 0.8mA

SINK

I

= 0.2mA

SOURCE

I

= 0.5mA

SOURCE

I

= 1.4mA

I

= 1mA

SINK

I

= 2-10mA

I

= 2-10mA

I

= 2-10mA

SOURCE

SINK

SOURCE

I

= 2-10mA

SINK

= 100µA

P-P

∆I

= 100µA

∆I

SOURCE

= 100µA

P-P

∆I

= 100µA

∆I

SINK

SOURCE

P-P

SINK

P-P

0

1

2

3

4

0

1

2

3

4

0

1

2

3

4

0

1

2

3

4

0

1

2

3

4

5

6

TIME (µs)

TIME (MINUTES)

NOTE VERTICAL SCALE CHANGE

1021 G33

BETWEEN SOURCING AND SINKING

1021 G31

1021 G32

8

LT1021

U

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APPLICATIONS INFORMATION

Effect of Reference Drift on System Accuracy

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.

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 calibra-

tion is performed at 25°C, the temperature span is 40°C.

It can be seen from the graph that the temperature coeffi-

cient 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.

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

thevoltageonthetrimpin. Inputimpedanceofthetrimpin

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.

Maximum Allowable Reference Drift

100

8-BIT

10-BIT

LT1021-5

10

V

OUT

IN

GND TRIM

OUT

12-BIT

14-BIT

R1

27k

R2

50k

1N4148

1.0

0

10 20

40

60 70 80

100

90

30

50

1021 AI02

TEMPERATURE SPAN (°C)

LT1021 AI01

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 out-

putoftheLT1021canbeloadedwithatrimpotentiometer.

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.

Trimming Output Voltage

LT1021-10

TheLT1021-10has atrimpinforadjustingoutputvoltage.

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 mini-

mize 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 recom-

mended, preferably a 20 turn cermet type with stable

characteristics over time and temperature.

Both of these circuits use the trimmers in a true potentio-

metric mode to reduce the effects of trimmer TC. The

voltageoutputhas a200Ω impedance, soloadingmustbe

9

LT1021

U

W U U

APPLICATIONS INFORMATION

Kelvin Connections

minimized. In the current output circuit, R1 determines

outputcurrent.ItshouldhaveaTCcommensuratewiththe

LT1021 or track closely with the feedback resistor around

the op amp.

Although the LT1021 does not have true force/sense

capabilityatits outputs,significantimprovements inground

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.

LT1021-7

IN

OUT

R1*

200Ω

1%

R2*

14k

1%

GND

R3

V

OUT

10k

6.950V

TC TRACKING TO 50ppm/°C

1021 AI03

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.

LT1021-7

IN

OUT

R1*

7.15k

GND

R2**

182k

R3

50k

1.000mA

Standard Series Mode

–

OP AMP

LT1021

KEEP THIS LINE RESISTANCE LOW

+

INPUT

IN

OUT

1021 AI04

+

GND

LOAD

*RESISTOR TC DETERMINES I

TC

OUT

**TC ≤ (10 • R1) TC. R2 AND R3 SCALE

WITH R1 FOR DIFFERENT OUTPUT CURRENTS

GROUND

RETURN

1021 AI05

Capacitive Loading and Transient Response

The LT1021 is stable with all capacitive loads, but for

optimum settling with load transients, output capacitance

shouldbeunder1000pF. Theoutputstageofthereference

is class AB with a fairly low idling current. This makes

transient response worst-case at light load currents. Be-

cause of internal current drain on the output, actual worst-

Series Mode with Boost Transistor

INPUT

R1

220Ω

2N3906

case occurs at I_LOAD= 0 on LT1021-5, I_LOAD

=

IN

–0.8mA (sinking) on LT1021-7 and I_LOAD= 1.4mA (sink-

ing) on LT1021-10. Significantly better load transient

response is obtained by moving slightly away from these

points. SeeLoadTransientResponsecurves fordetails. 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.

LT1021

OUT

LOAD

GND

R2*

GROUND

RETURN

1021 AI06

*OPTIONAL—REDUCES CURRENT IN OUTPUT SENSE LEAD

R2 = 2.4k (LT1021-5), 3k (LT1021-7), 5.6k (LT1021-10)

10

LT1021

U

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APPLICATIONS INFORMATION

Effects of Air Movement on Low Frequency Noise

copper lead frames used on dual-in-line packages are not

nearly as sensitive to thermally generated noise because

they are intrinsically matched.

TheLT1021has verylownoisebecauseoftheburiedzener

usedinits design.Inthe0.1Hzto10Hzband,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

betweenICpackageleads (especiallykovarleadTO-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

thepackageleads.Variations inthermalresistance,caused

by uneven air flow, create differential lead temperatures,

therebycausingthermoelectricvoltagenoiseattheoutput

of the reference. The following XY plotter trace dramati-

cally 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 environ-

ment with no excessive air turbulence from air condition-

ers, opening/closing doors, etc. Removing the foam cup

increases the output noise by almost an order of magni-

tude in the 0.01Hz to 1Hz band! The kovar leads of the

TO-5 (H) package are the primary culprit. Alloy 42 and

There is nothing magical about foam cups—any enclo-

sure 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

FOAM CUP

REMOVED

8

12

0

2

4

6

10

TIME (MINUTES)

1021 AI07

U

TYPICAL APPLICATIONS

Restricted Trim Range for Improved

Resolution, 10V, “C” Version Only

LT1021-10 Full Trim Range (±0.7%)

Negative Series Reference

15V

R1

LT1021-10

IN

LT1021C-10

V

IN

V

OUT

IN

10.000V

V

IN

OUT

LT1021-10

4.7k

IN

OUT

GND TRIM

R1

75k

D1

15V

GND

R1*

10k

R2

4.7k

R2

50k

–10V AT 50mA

–15V

1021 TA03

1021 TA11

Q1

2N2905

LT1021 TA04

TRIM RANGE ≈ ±10mV

*CAN BE RAISED TO 20k FOR

LESS CRITICAL APPLICATIONS

11

LT1021

U

TYPICAL APPLICATIONS

Boosted Output Current

with No Current Limit

Boosted Output Current

with Current Limit

Ultraprecise Current Source

+

V ≥ (V

+ 1.8V)

V ≥ V

OUT

+ 2.8V

OUT

D1*

LED

R1

220Ω

R1

220Ω

LT1021-7

OUT

8.2Ω

15V

IN

2N2905

17.4k

1%

GND

2N2905

IN

LT1021

OUT

TRIM

100Ω

IN

LT1021

OUT

10V AT

100mA

6.98k*

0.1%

10V AT

100mA

GND

15V

+

2µF

SOLID

TANT

GND

7

+

2µF

SOLID

TANT

–

2

3

*LOW TC

6

LT1001

+

1021 TA05

1021 TA06

4

*GLOWS IN CURRENT LIMIT,

DO NOT OMIT

–15V

I

= 1mA

OUT

REGULATION < 1ppm/V

COMPLIANCE = –13V TO 7V

1021 TA07

Operating 5V Reference from 5V Supply

2-Pole Lowpass Filtered Reference

5V LOGIC

SUPPLY

1µF

MYLAR

1N914

V

IN

CMOS LOGIC GATE**

LT1021-5

+

1N914

≈8.5V

5V

–

f

≥ 2kHz*

IN

OUT

IN

REFERENCE

V

REF

LT1021

LT1001

+

C1*

5µF

C2*

5µF

GND

IN

OUT

+

V

IN

R1

R2

36k

GND

TOTAL NOISE

0.5µF

MYLAR

*FOR HIGHER FREQUENCIES C1 AND C2 MAY BE DECREASED

**PARALLEL GATES FOR HIGHER REFERENCE CURRENT LOADING

≤2µV

f = 10Hz

RMS

1021 TA16

1Hz ≤ f ≤ 10kHz

–V

REF

1021 TA13

Trimming 10V Units to 10.24V

CMOS DAC with Low Drift Full-Scale Trimming**

LT1021-10

V

IN

OUT

V

OUT

= 10.24V

R3

OUT

LT1021-10

TRIM

GND

4.02K

1%

TRIM GND

R4*

100Ω

FULL-SCALE

ADJUST

FB

I

R1

4.99k

1%

30pF

CMOS

DAC

7520, ETC

4.32k

5k

OUT

–

10V

F.S.

REF

LT1007C

R2

40.2Ω

1%

+

V^–= –15V*

*MUST BE WELL REGULATED

1.2k

–15V

*TC LESS THAN 200ppm/°C

**NO ZERO ADJUST REQUIRED

WITH LT1007 (V ≤ 60µV)

dV

OUT

15mV

V

=

dV^–

LT1236 TA15

1021 TA12

0S

12

LT1021

U

TYPICAL APPLICATIONS

Negative Shunt Reference Driven

Strain Gauge Conditioner for 350Ω Bridge

by Current Source

R1

357Ω

1/2W

LT1021-10

OUT

GND

28mA

LT1021-10

28.5mA

15V

IN

OUT

5V

–10V (I

≤ 1mA)

LOAD

350Ω STRAIN

GAUGE BRIDGE**

R3

2M

GND

2.5mA

R2

20k

2

3

+

3

–

LM334

6

V

×100

†

R4

20k

OUT

LT1012C

LM301A

– ²

1

+

27Ω

R5

2M

100pF

8

R6*

2M

–11V TO –40V

1021 TA14

–5V

1021 TA09

357Ω

1/2W

–15V

**BRIDGE IS ULTRALINEAR WHEN ALL LEGS ARE

*THIS RESISTOR PROVIDES POSITIVE FEEDBACK TO

THE BRIDGE TO ELIMINATE LOADING EFFECT OF

ACTIVE, TWO IN COMPRESSION AND TWO IN TENSION,

OR WHEN ONE SIDE IS ACTIVE WITH ONE COMPRESSED

AND ONE TENSIONED LEG

THE AMPLIFIER. EFFECTIVE Z OF AMPLIFIER

IN

STAGE IS ≥1MΩ. IF R2 TO R5 ARE CHANGED,

SET R6 = R3

^†OFFSET AND DRIFT OF LM301A ARE VIRTUALLY

ELIMINATED BY DIFFERENTIAL CONNECTION OF LT1012C

Precision DAC Reference with System TC Trim

Handling Higher Load Currents

15V

30mA

LT1021-10

IN

15V

OUT

R1*

169Ω

IN

8.87k

1%

GND

LT1021-10

V

10V

OUT

50k

ROOM TEMP

TRIM

D1

1N457

GND

10k

1%

TYPICAL LOAD

CURRENT = 30mA

10.36k

1%

R

L

50k

TC TRIM*

1.24k

1%

1021 TA08

200k

1%

D2

1N457

10k

1%

*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

50k

8.45k

1mA

DAC

*TRIMS 1mA REFERENCE CURRENT

TC BY ±40ppm/°C. THIS TRIM SCHEME HAS

VERY LITTLE EFFECT ON ROOM TEMPERATURE

CURRENT TO MINIMIZE ITERATIVE TRIMMING

1021 TA17

13

LT1021

TYPICAL APPLICATIONS

U

Ultralinear Platinum Temperature Sensor*

LT1021-10

IN

20V

OUT

GND

R2*

5k

R10

182k

1%

R14

5k

R1**

253k

R11

6.65M

1%

R15

10k

R8

10M

R **

F

654k

R9

100k

R12

1k

R13

24.3k

20V

7

2

R5

200k

1%

–

R4

4.75k

1%

R3**

5k

6

V

=100mV/°C

OUT

LT1001

–50°C ≤ T ≤ 150°C

3

+

4

†

R

S

100Ω AT

0°C

–15V

R6

619k

1%

^†STANDARD INDUSTRIAL 100Ω PLATINUM 4-WIRE SENSOR,

ROSEMOUNT 78S OR EQUIVALENT. α = 0.00385

R7

392k

1%

TRIM R9 FOR V

OUT

= 0V AT 0°C

= 10V AT 100°C

= 5V AT 50°C

TRIM R12 FOR V

OUT

TRIM R14 FOR V

OUT

USE TRIM SEQUENCE AS SHOWN. TRIMS ARE NONINTERACTIVE

SO THAT ONLY ONE TRIM SEQUENCE IS NORMALLY REQUIRED.

–15V

^*FEEDBACK LINEARIZES OUTPUT TO ±0.005°C FROM

–50°C TO 150°C

^**WIREWOUND RESISTORS WITH LOW TC

1021 TA10

U

W

EQUIVALE T SCHE ATIC

INPUT

Q3

D1

D2

OUTPUT

R1

D3

Q1

+

–

A1

R2

D4

6.3V

Q2

GND

LT1021 ES

14

LT1021

U

Dimensions in inches (millimeters) unless otherwise noted.

PACKAGE DESCRIPTION

H Package

8-Lead TO-5 Metal Can (0.200 PCD)

(LTC DWG # 05-08-1320)

0.335 – 0.370

(8.509 – 9.398)

DIA

0.305 – 0.335

(7.747 – 8.509)

0.040

(1.016)

MAX

0.050

(1.270)

MAX

0.165 – 0.185

(4.191 – 4.699)

REFERENCE

PLANE

SEATING

PLANE

GAUGE

PLANE

0.500 – 0.750

(12.700 – 19.050)

0.010 – 0.045*

(0.254 – 1.143)

0.016 – 0.021**

(0.406 – 0.533)

0.027 – 0.045

(0.686 – 1.143)

45°TYP

PIN 1

0.028 – 0.034

(0.711 – 0.864)

0.200

(5.080)

TYP

0.110 – 0.160

*LEAD DIAMETER IS UNCONTROLLED BETWEEN THE REFERENCE PLANE

AND 0.045" BELOW THE REFERENCE PLANE

0.016 – 0.024

**FOR SOLDER DIP LEAD FINISH, LEAD DIAMETER IS

(0.406 – 0.610)

(2.794 – 4.064)

INSULATING

STANDOFF

H8(TO-5) 0.200 PCD 1197

N8 Package

8-Lead PDIP (Narrow 0.300)

(LTC DWG # 05-08-1510)

0.400*

(10.160)

MAX

8

7

6

5

0.255 ± 0.015*

(6.477 ± 0.381)

1

2

4

3

0.130 ± 0.005

0.300 – 0.325

0.045 – 0.065

(3.302 ± 0.127)

(1.143 – 1.651)

(7.620 – 8.255)

0.065

(1.651)

TYP

0.009 – 0.015

0.125

(0.229 – 0.381)

0.020

(3.175)

MIN

+0.035

–0.015

(0.508)

MIN

0.325

0.018 ± 0.003

0.100

(2.54)

BSC

+0.889

–0.381

(0.457 ± 0.076)

8.255

(

)

N8 1098

*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.

MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)

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 represen-

tationthattheinterconnectionofits circuits as describedhereinwillnotinfringeonexistingpatentrights.

15

LT1021

U

Dimensions in inches (millimeters) unless otherwise noted.

PACKAGE DESCRIPTION

S8 Package

8-Lead Plastic Small Outline (Narrow 0.150)

(LTC DWG # 05-08-1610)

0.189 – 0.197*

(4.801 – 5.004)

7

5

8

6

0.150 – 0.157**

(3.810 – 3.988)

0.228 – 0.244

(5.791 – 6.197)

1

3

4

2

0.010 – 0.020

(0.254 – 0.508)

× 45°

0.053 – 0.069

(1.346 – 1.752)

0.004 – 0.010

(0.101 – 0.254)

0.008 – 0.010

(0.203 – 0.254)

0°– 8° TYP

0.016 – 0.050

0.406 – 1.270

0.050

(1.270)

TYP

0.014 – 0.019

(0.355 – 0.483)

*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH

SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD

FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

SO8 0996

RELATED PARTS

PART NUMBER

DESCRIPTION

COMMENTS

LT1019

Precision Bandgap Reference

Precision 5V Reference

Precision Reference

0.05%, 5ppm/°C

0.02%, 2ppm/°C

LT1027

LT1236

LTC^®1258

SO-8, 5V and 10V, 0.05%, 5ppm/°C

200mV Dropout, MSOP

Micropower Reference

LT1389

Nanopower Shunt Reference

Micropower Reference

800nA Operating Current

SOT-23, 2.5V, 5V, 10V

LT1460

LT1634

Micropower Shunt Reference

0.05%, 10ppm/°C, MSOP

1021fa LT/GP 0399 2K REV A • PRINTED IN USA

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

16

●

(408)432-1900 FAX:(408)434-0507 www.linear-tech.com

LINEAR TECHNOLOGY CORPORATION 1995


型号：	LT1021BCN8-5
厂家：	Linear
描述：	Precision Reference 精密基准
文件：	总16页 (文件大小：228K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LT1021BCN8-5 [Linear]

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