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PDF LT1021 Data sheet ( Hoja de datos )
| Número de pieza | LT1021 | |
| Descripción | Precision Reference | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LT1021
Precision Reference
FEATURES
■ 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
■ Minimum Input/Output Differential of 1V
■ Available in 5-Lead Can, N8 and S8 Packages
U
APPLICATIO S
■ 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
VIN IN
OUT VOUT
GND
LT1021
(7 AND 10 ONLY)
NC IN
OUT
GND
R1 =
VOUT – (V – )
ILOAD + 1.5mA
–VOUT
R1
–15V
(V –)
1021 TA01
DESCRIPTIO
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 can be used as shunt regulators (two-terminal zeners)
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.
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.
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 LT1021-
10 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
DISTRIBUTION
21 OF THREE RUNS
18
15
12
9
6
3
–0
–5 –4 –3 –2 –1 0 1 2 3 4 5
OUTPUT DRIFT (ppm/°C)
1021 TA01
1021fc
1
1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
Ripple Rejection
115
f = 150Hz
110
LT1021-7
LT1021-10
105
100
LT1021-5
95
90
85
0
5 10 15 20 25 30 35 40
INPUT VOLTAGE (V)
LT1021 G01
Start-Up (Series Mode)
13
12 VIN = 0V TO 12V
11
LT1021-10
10
9
8
LT1021-7
7
6
LT1021-5
5
4
3
0 2 4 6 8 10
TIME (µs)
12 14
LT1021 G04
Output Voltage Noise
16
COUT = 0
14
FILTER = 1 POLE
fLOW = 0.1Hz
12
10
8
LT1021-7
6
LT1021-10
4
LT1021-5
2
0
10 100 1k 10k
BANDWIDTH (Hz)
LT1021 G07
Ripple Rejection
130
VIN = 15V
120 COUT = 0
110
LT1021-7
100
LT1021-10
90
LT1021-5
80
70
60
50
10
100 1k
FREQUENCY (Hz)
10k
LT1021 G02
Start-Up (Shunt Mode)
LT1021-7, LT1021-10
11
LT1021-10
10
9
VOUT + 2V
0V
1k
OUT
VOUT
NC IN
8 GND
7
LT1021-7
6
5
0 2 4 6 8 10 12
TIME (µs)
LT1021 G05
Output Voltage Temperature Drift
LT1021-5
5.006
5.004
5.002
5.000
4.998
4.996
4.994
– 50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
LT1021 G08
LT1021
Minimum Input/Output Differential
LT1021-7, LT1021-10
1.6
TJ = 125 °C
1.4
1.2 TJ = –55 °C
1.0 TJ = 25 °C
0.8
0.6
0.4
0.2
0
0 2 4 6 8 10 12 14 16 18 20
OUTPUT CURRENT (mA)
1021 G03
Output Voltage Noise Spectrum
400
350
300
250
200
150 LT1021-10
100 LT1021-7
50 LT1021-5
0
10 100 1k 10k
FREQUENCY (Hz)
LT1021 G06
Load Regulation LT1021-5
5
VIN = 8V
4
3
2
1
0
–1
–2
–3
–4
–5
–10 – 8 – 6 – 4 – 2 0 2 4 6 8 10
SOURCING
SINKING
OUTPUT CURRENT (mA) LT1021 G09
1021fc
5
5 Page 
LT1021
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 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
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 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
02
46 8
TIME (MINUTES)
10 12
1021 AI07
TYPICAL APPLICATIONS
Restricted Trim Range for Improved
Resolution, 10V, “C” Version Only
LT1021-10 Full Trim Range (±0.7%)
LT1021C-10
VIN IN
OUT
GND TRIM
R1
75k
10.000V
R2
50k
1021 TA11
TRIM RANGE ≈ ±10mV
LT1021-10
VIN IN
OUT
GND TRIM
VOUT
R1*
10k
1021 TA03
*CAN BE RAISED TO 20k FOR
LESS CRITICAL APPLICATIONS
Negative Series Reference
15V
R1
4.7k LT1021-10
IN OUT
D1
R2 15V GND
4.7k
–15V
Q1
2N2905
–10V AT 50mA
LT1021 TA04
1021fc
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LT1021.PDF ] | |
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