LT1021DCS8-10#PBF [Linear]
LT1021 - Precision Reference; Package: SO; Pins: 8; Temperature Range: 0°C to 70°C;
| 型号： | LT1021DCS8-10#PBF |
| 厂家： | 
Linear |
| 描述： | LT1021 - Precision Reference; Package: SO; Pins: 8; Temperature Range: 0°C to 70°C 光电二极管 |
| 文件： | 总16页 (文件大小：216K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1021
Precision Reference
U
DESCRIPTIO
FEATURES
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
unitscanbeusedasshuntregulators(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.
■
Ultralow Drift: 5ppm/°C Max Slope
■
Very Low Noise: <1ppm P-P (0.1Hz to 10Hz)
100% Noise Tested
■
■
Pin Compatible with Most Bandgap Reference
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
TheLT1021referencesarebasedonaburiedzenerdiode
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.
Minimum Input/Output Differential of 1V
Available in 5-Lead Can, N8 and S8 Packages
U
APPLICATIO S
Unique circuit design makes the LT1021 the first IC
reference to offer ultralow drift without the use of high
power on-chip heaters.
■
A/D and D/A Converters
■
Precision Regulators
■
Digital Voltmeters
■
Inertial Navigation Systems
The LT1021-7 uses no resistive divider to set output
voltage,andthereforeexhibitsthebestlongtermstability
and temperature hysteresis. The LT1021-5 and LT1021-
10areintendedforsystemsrequiringaprecise5Vor10V
reference with an initial tolerance as low as ±0.05%.
■
Precision Scales
■
Portable Reference Standard
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
U
TYPICAL APPLICATIO
Typical Distribution of Temperature Drift
24
Basic Positive and Negative Connections
DISTRIBUTION
OF THREE RUNS
21
18
15
12
9
LT1021
LT1021
GND
(7 AND 10 ONLY)
V
IN
IN
V
OUT
IN
OUT
NC
OUT
GND
–V
OUT
–
V
OUT
– (V )
R1 =
6
R1
–15V
I
+ 1.5mA
LOAD
3
–
(V
)
1021 TA01
– 0
–5 –4 –3 –2 –1
0
1
2
3
4
5
OUTPUT DRIFT (ppm/°C)
1021 TA01
1021fc
1
LT1021
ABSOLUTE AXI U RATI GS
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
W W W
U
(Note 1)
Output Short-Circuit Duration
VIN = 35V......................................................... 10 sec
VIN ≤ 20V ................................................... Indefinite
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 VOUT
Negative ........................................................... – 20V
W U
/O
PACKAGE RDER I FOR ATIO
TOP VIEW
TOP VIEW
NC*
8
DNC*
1
2
3
4
DNC*
DNC*
8
7
6
5
1
3
NC*
NC*
7
5
V
IN
6
V
2
V
OUT
DNC*
GND
V
0UT
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. 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
*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
TJMAX = 130°C, θJA = 130°C/W (N)
JMAX = 130°C, θJA = 150°C/W (S)
T
TJMAX = 150°C, θJA = 150°C/W,θJC = 45°C/W
ORDER PART NUMBER
N8 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
LT1021BCN8-5
LT1021CCN8-5
LT1021CIN8-5
LT1021DCN8-5
LT1021DIN8-5
LT1021BCN8-7
LT1021DCN8-7
LT1021BCN8-10
LT1021CCN8-10
LT1021CIN8-10
LT1021DCN8-10
LT1021DIN8-10
OBSOLETE
S8 PART MARKING
S8 ORDER PART NUMBER
LT1021DCS8-5
LT1021DCS8-7
LT1021DCS8-10
2105
2107
2110
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.
1021fc
2
LT1021
The
●
denotes specifications that apply over the full operating temperature
ELECTRICAL CHARACTERISTICS
range, otherwise specifications are T = 25°C. V = 10V, I = 0, unless otherwise noted.
OUT
A
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
5.000
5.0025
5.0500
V
V
Output Voltage Temperature Coefficient (Note 3)
Line Regulation (Note 4)
T
MIN
≤ T ≤ T
J
MAX
LT1021B-5
LT1021C-5/LT1021D-5
7.2V ≤ V ≤ 10V
●
●
2
3
5
20
ppm/°C
ppm/°C
4
12
20
6
ppm/V
ppm/V
ppm/V
ppm/V
IN
●
●
10V ≤ V ≤ 40V
2
IN
10
Load Regulation (Sourcing Current)
Load Regulation (Sinking Current)
Supply Current
0 ≤ I
≤ 10mA
≤ 10mA
10
60
20
35
ppm/mA
ppm/mA
OUT
(Note 4)
●
●
●
0 ≤ I
100
150
ppm/mA
ppm/mA
OUT
(Note 4)
0.8
1.2
1.5
mA
mA
Output Voltage Noise (Note 6)
0.1Hz ≤ f ≤ 10Hz
10Hz ≤ f ≤ 1kHz
3.0
2.2
µV
P-P
RMS
3.5
µV
Long Term Stability of Output Voltage (Note 7)
Temperature Hysteresis of Output
∆t = 1000Hrs Noncumulative
∆T = ± 25°C
15
10
ppm
ppm
The
IN
●
denotes specifications that apply over the full operating temperature range, otherwise specifications are T = 25°C.
A
V
= 12V, I
= 0, unless otherwise noted.
OUT
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
ppm/°C
Line Regulation (Note 4)
8.5V ≤ V ≤ 12V
1.0
2.0
0.5
1.0
4
8
2
4
ppm/V
ppm/V
ppm/V
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
≤ 10mA
12
25
40
ppm/mA
ppm/mA
OUT
(Note 4)
●
●
●
●
1.2mA ≤ I
(Notes 4, 5)
≤ 10mA
50
100
150
ppm/mA
ppm/mA
SHUNT
0.75
0.7
1.2
1.5
mA
mA
V
is Open
1.0
1.2
mA
mA
IN
0.1Hz ≤ f ≤ 10Hz
10Hz ≤ f ≤ 1kHz
4.0
2.5
µV
P-P
4.0
µV
RMS
Long Term Stability of Output Voltage (Note 7)
Temperature Hysteresis of Output
∆t = 1000Hrs Noncumulative
∆T = ± 25°C
7
3
ppm
ppm
1021fc
3
LT1021
The
●
denotes specifications that apply over the full operating temperature
ELECTRICAL CHARACTERISTICS
range, otherwise specifications are T = 25°C. V = 15V, I = 0, unless otherwise noted.
OUT
A
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
10.00
10.005
10.050
V
V
Output Voltage Temperature Coefficient (Note 3)
Line Regulation (Note 4)
T
≤ T ≤ T
MIN J MAX
LT1021B-10
●
●
2
5
5
20
ppm/°C
ppm/°C
LT1021C-10/LT1021D-10
11.5V ≤ V ≤ 14.5V
1.0
4
6
2
4
ppm/V
ppm/V
ppm/V
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
≤ 10mA
12
50
25
40
ppm/mA
ppm/mA
OUT
(Note 4)
●
●
●
●
1.7mA ≤ I
(Notes 4, 5)
≤ 10mA
100
150
ppm/mA
ppm/mA
SHUNT
1.2
1.1
1.7
2.0
mA
mA
V
is Open
1.5
1.7
mA
mA
IN
0.1Hz ≤ f ≤ 10Hz
10Hz ≤ f ≤ 1kHz
6.0
3.5
µV
P-P
6
µV
RMS
Long Term Stability of Output Voltage (Note 7)
Temperature Hysteresis of Output
∆t = 1000Hrs Noncumulative
∆T = ± 25°C
15
5
ppm
ppm
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
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.
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.
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.
Separate tests are done for hot and cold; T
Incremental slope is also measured at 25°C.
to 25°C and 25°C to T
.
MIN
MAX
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.
1021fc
4
LT1021
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Minimum Input/Output Differential
LT1021-7, LT1021-10
Ripple Rejection
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
= 15V
OUT
f = 150Hz
T
= 125 °C
IN
LT1021-7
J
= 0
120
110
100
90
LT1021-7
T
= –55 °C
J
LT1021-10
T
= 25 °C
J
LT1021-10
LT1021-5
LT1021-5
80
70
90
60
50
85
2
4
6
8
10 12 14
16
18 20
25 30
10 15 20
INPUT VOLTAGE (V)
10
100
1k
10k
0
0
5
35 40
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
400
350
300
250
200
150
100
50
11
10
9
V
= 0V TO 12V
IN
LT1021-10
1k
V
OUT
0V
+ 2V
LT1021-10
V
OUT
OUT
IN
GND
NC
8
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
1k
10k
12
0
2
4
8
0
2
4
6
8
10
14
FREQUENCY (Hz)
TIME (µs)
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
5
4
16
14
12
10
8
C
= 0
V
= 8V
OUT
FILTER = 1 POLE
= 0.1Hz
IN
f
LOW
3
2
1
0
LT1021-7
–1
– 2
– 3
– 4
– 5
6
LT1021-10
4
LT1021-5
2
0
–50 –25
0
25
50
75 100 125
–10 –8 – 6 – 4 – 2
SOURCING
0
2
4
6
8
10
10
100
1k
10k
TEMPERATURE (°C)
SINKING
BANDWIDTH (Hz)
LT1021 G07
LT1021 G08
OUTPUT CURRENT (mA)
LT1021 G09
1021fc
5
LT1021
U W
TYPICAL PERFOR 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
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
OUTPUT VOLTAGE (V)
14 16
18
30 35
LT1021 G12
LT1021 G10
*NOTE THAT AN INPUT VOLTAGE IS REQUIRED
FOR 5V UNITS.
LT1021 G11
Load Transient Response
Output Noise 0.1Hz to 10Hz
LT1021-5
Load Transient Response
LT1021-5, C = 0
LT1021-5, C
= 1000pF
LOAD
LOAD
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
50mV
20mV
20mV
I
= 0.2mA
I
= 0.2mA
SINK
I
= 0.2mA
SINK
SOURCE
I
= 0.5mA
SOURCE
I
= 2-10mA
I
= 2-10mA
SINK
SOURCE
I
= 2-10mA
I
= 2-10mA
SINK
SOURCE
∆I
= 100µA
∆I
= 100µA
SOURCE P-P
∆I
= 100µA
∆I
= 100µA
P-P
SOURCE
P-P
SINK
P-P
SINK
5
4
6
0
1
2
3
4
0
1
2
3
4
0
5
10 15 20
0
10 15 20
0
1
2
3
5
TIME (µs)
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
SOURCING
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)
SINKING
OUTPUT CURRENT (mA)
LT1021 G16
LT1021 G17
LT1021 G18
1021fc
6
LT1021
U W
TYPICAL PERFOR 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
INPUT PIN OPEN
IN
∆POWER = 200mW
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
10
14 16 18
8
12
OUTPUT TO GROUND VOLTAGE (V)
OUTPUT VOLTAGE (V)
LT1021 G20
1021 G19
*INDEPENDENT OF TEMPERATURE COEFFICIENT
LT1021 G21
Load Transient Response
LT1021-7, C = 0
Load Transient Response
Output Noise 0.1Hz to 10Hz
LT1021-7
LT1021-7, C
= 1000pF
LOAD
LOAD
I
= 0
FILTERING = 1 ZERO AT 0.1Hz
2 POLES AT 10Hz
SOURCE
I
= 0.8mA
I
= 0.6mA
SINK
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
SOURCE
I
= 1.4mA
I
= 1mA
SINK
SINK
I
= 2-10mA
I
= 2-10mA
SINK
I
= 2-10mA
I
= 2-10mA
SOURCE
SINK
SOURCE
∆I
= 100µA
∆I
= 100µA
SOURCE P-P
∆I
= 100µA
∆I
= 100µA
P-P
SOURCE
P-P
SINK
1
P-P
SINK
5
4
6
0
1
2
3
4
0
2
3
4
0
5
10 15 20
0
10 15 20
0
1
2
3
5
TIME (µs)
5µs/DIV
TIME (MINUTES)
NOTE VERTICAL SCALE CHANGE
NOTE VERTICAL SCALE CHANGE
LT1021 G24
BETWEEN SOURCING AND SINKING
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
SOURCING
0
2
4
6
8
10
0
5
10 15 20 25
INPUT VOLTAGE (V)
40
30 35
TEMPERATURE (°C)
SINKING
LT1021 G25
OUTPUT CURRENT (mA)
1021 G26
1021 G27
1021fc
7
LT1021
U W
TYPICAL PERFOR 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
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
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
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 = 0
Load Transient Response
LT1021-10, C = 1000pF
Output Noise 0.1Hz to 10Hz
LT1021-10
LOAD
LOAD
FILTERING = 1 ZERO AT 0.1Hz
2 POLES AT 10Hz
I
= 0.6mA
I
= 0.8mA
SINK
SINK
I
= 0
I
= 0
SOURCE
SOURCE
5mV
20mV
50mV
10µV (1ppm)
10mV
I
= 1.2mA
SINK
I
= 0.8mA
SINK
I
= 0.2mA
SOURCE
I
I
= 0.5mA
SOURCE
I
I
= 1.4mA
I
= 1mA
SINK
SINK
= 2-10mA
I
= 2-10mA
= 2-10mA
SOURCE
SINK
SOURCE
I
= 2-10mA
SINK
∆I
= 100µA
∆I
= 100µA
SOURCE P-P
∆I
= 100µA
∆I
= 100µA
P-P
SOURCE
P-P
SINK
1
P-P
SINK
0
1
2
3
4
0
2
3
4
0
1
2
4
0
1
3
0
1
2
3
4
5
6
3
2
4
TIME (µs)
TIME (µs)
TIME (MINUTES)
NOTE VERTICAL SCALE CHANGE
BETWEEN SOURCING AND SINKING
NOTE VERTICAL SCALE CHANGE
BETWEEN SOURCING AND SINKING
1021 G33
1021 G31
1021 G32
1021fc
8
LT1021
U
W U U
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
IN
GND TRIM
OUT
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
TheLT1021-10hasatrimpinforadjustingoutputvoltage.
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
voltageoutputhasa200Ωimpedance, soloadingmustbe
1021fc
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
capabilityatitsoutputs,significantimprovementsinground
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
10k
V
OUT
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*
GND
7.15k
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
OUT
TC
**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 ILOAD = 0 on LT1021-5, ILOAD
=
IN
–0.8mA (sinking) on LT1021-7 and ILOAD = 1.4mA (sink-
ing) on LT1021-10. Significantly better load transient
response is obtained by moving slightly away from these
points. SeeLoadTransientResponsecurvesfordetails. 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)
1021fc
10
LT1021
U
W U U
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.
TheLT1021hasverylownoisebecauseoftheburiedzener
usedinitsdesign.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.Variationsinthermalresistance,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
OUT
IN
10.000V
V
OUT
LT1021-10
4.7k
IN
IN
OUT
GND TRIM
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
1021fc
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)
OUT
V
≥ V + 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
IN
LT1021
OUT
100Ω
10V AT
6.98k*
0.1%
100mA
10V AT
100mA
GND
15V
+
2µF
SOLID
TANT
7
GND
–
+
2
3
+
2µF
SOLID
TANT
*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
1N914
V
IN
MYLAR
CMOS LOGIC GATE**
LT1021-5
+
1N914
≈8.5V
5V
–
+
f
≥ 2kHz*
IN
OUT
IN
REFERENCE
V
LT1021
LT1001
REF
+
C1*
5µF
C2*
5µF
GND
IN
OUT
V
IN
R1
36k
R2
36k
GND
TOTAL NOISE
RMS
1Hz ≤ f ≤10kHz
0.5µF
MYLAR
*FOR HIGHER FREQUENCIES C1 AND C2 MAY BE DECREASED
**PARALLEL GATES FOR HIGHER REFERENCE CURRENT LOADING
≤2µV
f = 10Hz
1021 TA16
–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
IN
R3
OUT
LT1021-10
TRIM
GND
4.02K
1%
TRIM GND
R4*
100Ω
FB
I
FULL-SCALE
ADJUST
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
1021fc
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
6
V
OUT
× 100
LM301A†
R4
20k
LT1012C
–
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,
†OFFSET AND DRIFT OF LM301A ARE VIRTUALLY
ELIMINATED BY DIFFERENTIAL CONNECTION OF LT1012C
SET R6 = R3
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
OUT
OUT
10V
50k
D1
GND
ROOM TEMP
1N457
10k
1%
TRIM
TYPICAL LOAD
CURRENT = 30mA
10.36k
1%
R
L
50k
TC TRIM*
1.24k
1%
1021 TA08
200k
1%
D2
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
1N457
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
1021fc
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
R **
F
654k
10M
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
TRIM R9 FOR V
TRIM R12 FOR V
TRIM R14 FOR V
R7
392k
1%
= 0V AT 0°C
= 10V AT 100°C
= 5V AT 50°C
OUT
OUT
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
1021fc
14
LT1021
U
PACKAGE DESCRIPTION
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)
.040
(1.016)
MAX
.050
(1.270)
MAX
.165 – .185
(4.191 – 4.699)
REFERENCE
PLANE
SEATING
PLANE
GAUGE
PLANE
.500 – .750
(12.700 – 19.050)
.010 – .045*
(0.254 – 1.143)
.016 – .021**
(0.406 – 0.533)
.027 – .045
(0.686 – 1.143)
45°
PIN 1
.028 – .034
(0.711 – 0.864)
.200
(5.080)
TYP
.110 – .160
(2.794 – 4.064)
INSULATING
STANDOFF
*LEAD DIAMETER IS UNCONTROLLED BETWEEN THE REFERENCE PLANE
AND THE SEATING PLANE
.016 – .024
(0.406 – 0.610)
**FOR SOLDER DIP LEAD FINISH, LEAD DIAMETER IS
H8(TO-5) 0.200 PCD 0204
N8 Package
8-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510)
.400*
(10.160)
MAX
8
7
6
5
4
.255 ± .015*
(6.477 ± 0.381)
1
2
3
.130 ± .005
.300 – .325
.045 – .065
(3.302 ± 0.127)
(1.143 – 1.651)
(7.620 – 8.255)
.065
(1.651)
TYP
.008 – .015
(0.203 – 0.381)
.120
.020
(0.508)
MIN
(3.048)
MIN
+.035
.325
–.015
.018 ± .003
(0.457 ± 0.076)
.100
(2.54)
BSC
+0.889
8.255
(
)
N8 1002
–0.381
NOTE:
INCHES
1. DIMENSIONS ARE
MILLIMETERS
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
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 represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
15
LT1021
PACKAGE DESCRIPTION
U
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.189 – .197
(4.801 – 5.004)
.045 ±.005
NOTE 3
.050 BSC
7
5
8
6
.245
MIN
.160 ±.005
.150 – .157
(3.810 – 3.988)
NOTE 3
.228 – .244
(5.791 – 6.197)
.030 ±.005
TYP
1
3
4
2
RECOMMENDED SOLDER PAD LAYOUT
.010 – .020
(0.254 – 0.508)
× 45°
.053 – .069
(1.346 – 1.752)
.004 – .010
(0.101 – 0.254)
.008 – .010
(0.203 – 0.254)
0°– 8° TYP
.016 – .050
(0.406 – 1.270)
.050
(1.270)
BSC
.014 – .019
(0.355 – 0.483)
TYP
NOTE:
INCHES
1. DIMENSIONS IN
(MILLIMETERS)
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)
SO8 0303
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
Nanopower Shunt Reference
Micropower Reference
Micropower Shunt Reference
LT1389
800nA Operating Current
SOT-23, 2.5V, 5V, 10V
LT1460
LT1634
0.05%, 10ppm/°C, MSOP
1021fc
LT 1005 REV C • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
16
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
© LINEAR TECHNOLOGY CORPORATION 1995
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