LT1021
Precision Reference
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DESCRIPTIO
FEATURES
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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
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APPLICATIO S
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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 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.
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
Precision Scales
Portable Reference Standard
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.
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TYPICAL APPLICATIO
Typical Distribution of Temperature Drift
24
Basic Positive and Negative Connections
21
VIN
IN
OUT
VOUT
NC
LT1021
(7 AND 10 ONLY)
18
IN
15
OUT
GND
GND
–VOUT
– (V – )
V
R1 = OUT
ILOAD + 1.5mA
12
9
6
R1
–15V
(V – )
UNITS (%)
LT1021
DISTRIBUTION
OF THREE RUNS
3
1021 TA01
–0
– 5 – 4 – 3 – 2 –1 0 1 2 3
OUTPUT DRIFT (ppm/°C)
4
5
1021 TA01
1021fc
1
LT1021
W W
W
AXI U
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ABSOLUTE
RATI GS
(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 VOUT
Negative ........................................................... – 20V
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
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W
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PACKAGE/ORDER I FOR ATIO
TOP VIEW
TOP VIEW
NC*
8
NC* 1
7 NC*
6
VIN 2
NC* 3
VOUT
5 TRIM**
4
8
DNC*
VIN 2
7
DNC*
DNC* 3
6
V0UT
GND 4
5
TRIM**
N8 PACKAGE
8-LEAD PDIP
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
TJMAX = 150°C, θJA = 150°C/W,θJC = 45°C/W
ORDER PART NUMBER
LT1021BCH-5
LT1021BMH-5
LT1021CCH-5
LT1021CMH-5
LT1021BMH-10
DNC* 1
LT1021DCH-5
LT1021DMH-5
LT1021BCH-7
LT1021BMH-7
LT1021DCH-7
LT1021DMH-7
LT1021BCH-10
LT1021CMH-10
LT1021DCH-10
LT1021DMH-10
OBSOLETE
S8 PACKAGE
8-LEAD PLASTIC SO
*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)
TJMAX = 130°C, θJA = 150°C/W (S)
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
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
ELECTRICAL CHARACTERISTICS
The ● denotes specifications that apply over the full operating temperature
range, otherwise specifications are TA = 25°C. VIN = 10V, IOUT = 0, unless otherwise noted.
PARAMETER
CONDITIONS
Output Voltage (Note 2)
LT1021C-5
LT1021B-5/LT1021D-5
Output Voltage Temperature Coefficient (Note 3)
TMIN ≤ TJ ≤ TMAX
LT1021B-5
LT1021C-5/LT1021D-5
Line Regulation (Note 4)
MIN
LT1021-5
TYP
MAX
4.9975
4.9500
5.000
5.000
5.0025
5.0500
2
3
5
20
ppm/°C
ppm/°C
4
12
20
6
10
ppm/V
ppm/V
ppm/V
ppm/V
10
20
35
ppm/mA
ppm/mA
60
100
150
ppm/mA
ppm/mA
0.8
1.2
1.5
mA
mA
3.5
µVP-P
µVRMS
●
●
7.2V ≤ VIN ≤ 10V
10V ≤ VIN ≤ 40V
●
2
●
Load Regulation (Sourcing Current)
Load Regulation (Sinking Current)
0 ≤ IOUT ≤ 10mA
(Note 4)
●
0 ≤ IOUT ≤ 10mA
(Note 4)
●
Supply Current
●
Output Voltage Noise (Note 6)
0.1Hz ≤ f ≤ 10Hz
10Hz ≤ f ≤ 1kHz
3.0
2.2
UNITS
V
V
Long Term Stability of Output Voltage (Note 7)
∆t = 1000Hrs Noncumulative
15
ppm
Temperature Hysteresis of Output
∆T = ±25°C
10
ppm
The ● denotes specifications that apply over the full operating temperature range, otherwise specifications are TA = 25°C.
VIN = 12V, IOUT = 0, unless otherwise noted.
PARAMETER
CONDITIONS
Output Voltage (Note 2)
Output Voltage Temperature Coefficient (Note 3)
Line Regulation (Note 4)
TMIN ≤ TJ ≤ TMAX
LT1021B-7
LT1021D-7
●
●
8.5V ≤ VIN ≤ 12V
12V ≤ VIN ≤ 40V
●
●
Load Regulation (Sourcing Current)
Load Regulation (Shunt Mode)
0 ≤ IOUT ≤ 10mA
(Note 4)
●
1.2mA ≤ ISHUNT ≤ 10mA
(Notes 4, 5)
●
Supply Current (Series Mode)
MIN
LT1021-7
TYP
MAX
UNITS
6.95
7.00
7.05
V
2
3
5
20
ppm/°C
ppm/°C
1.0
2.0
0.5
1.0
4
8
2
4
ppm/V
ppm/V
ppm/V
ppm/V
12
25
40
ppm/mA
ppm/mA
50
100
150
ppm/mA
ppm/mA
0.75
1.2
1.5
mA
mA
0.7
1.0
1.2
mA
mA
4.0
µVP-P
µVRMS
●
Minimum Current (Shunt Mode)
VIN is Open
●
Output Voltage Noise (Note 6)
0.1Hz ≤ f ≤ 10Hz
10Hz ≤ f ≤ 1kHz
4.0
2.5
Long Term Stability of Output Voltage (Note 7)
∆t = 1000Hrs Noncumulative
7
ppm
Temperature Hysteresis of Output
∆T = ±25°C
3
ppm
1021fc
3
LT1021
ELECTRICAL CHARACTERISTICS
The ● denotes specifications that apply over the full operating temperature
range, otherwise specifications are TA = 25°C. VIN = 15V, IOUT = 0, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
LT1021-10
TYP
MAX
Output Voltage (Note 2)
LT1021C-10
LT1021B-10/LT1021D-10
9.995
9.950
10.00
10.00
10.005
10.050
Output Voltage Temperature Coefficient (Note 3)
TMIN ≤ TJ ≤ TMAX
LT1021B-10
LT1021C-10/LT1021D-10
2
5
5
20
ppm/°C
ppm/°C
1.0
4
6
2
4
ppm/V
ppm/V
ppm/V
ppm/V
12
25
40
ppm/mA
ppm/mA
50
100
150
ppm/mA
ppm/mA
1.2
1.7
2.0
mA
mA
1.1
1.5
1.7
mA
mA
Line Regulation (Note 4)
●
●
11.5V ≤ VIN ≤ 14.5V
●
14.5V ≤ VIN ≤ 40V
0.5
●
Load Regulation (Sourcing Current)
Load Regulation (Shunt Mode)
0 ≤ IOUT ≤ 10mA
(Note 4)
●
1.7mA ≤ ISHUNT ≤ 10mA
(Notes 4, 5)
●
Supply Current (Series Mode)
●
Minimum Current (Shunt Mode)
VIN is Open
●
UNITS
V
V
0.1Hz ≤ f ≤ 10Hz
10Hz ≤ f ≤ 1kHz
6.0
3.5
Long Term Stability of Output Voltage (Note 7)
∆t = 1000Hrs Noncumulative
15
ppm
Temperature Hysteresis of Output
∆T = ±25°C
5
ppm
Output Voltage Noise (Note 6)
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; TMIN to 25°C and 25°C to TMAX.
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.
6
µVP-P
µVRMS
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.
1021fc
4
LT1021
U W
TYPICAL PERFOR A CE CHARACTERISTICS
VIN = 15V
COUT = 0
LT1021-7
120
REJECTION (dB)
105
LT1021-7
110
LT1021-10
100
LT1021-5
95
100
LT1021-10
90
LT1021-5
80
70
90
60
0
5
10
15 20 25 30
INPUT VOLTAGE (V)
35
VIN = 0V TO 12V
6
LT1021-5
VOUT + 2V
0V
9
NC
8
7
1k
VOUT
OUT
IN
GND
LT1021-7
6
4
2
4
6
8
TIME (µs)
10
12
0
14
2
6
4
TIME (µs)
8
150
LT1021-10
100
LT1021-7
50
LT1021-5
12
Load Regulation LT1021-5
5
LT1021-7
LT1021-10
4
LT1021-5
5.002
5.000
4.998
2
1
0
–1
–2
–3
4.996
2
VIN = 8V
3
OUTPUT CHANGE (mV)
OUTPUT VOLTAGE (V)
8
10k
LT1021 G06
5.004
10
100
1k
FREQUENCY (Hz)
10
4
12
RMS NOISE (µV)
10
5.006
COUT = 0
FILTER = 1 POLE
fLOW = 0.1Hz
6
200
Output Voltage Temperature Drift
LT1021-5
Output Voltage Noise
14
250
LT1021 G05
LT1021 G04
16
300
0
5
3
0
6 8 10 12 14 16 18 20
OUTPUT CURRENT (mA)
350
NOISE VOLTAGE (nV/√Hz)
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
LT1021-7
7
4
Output Voltage Noise Spectrum
LT1021-10
9
2
400
10
11
LT1021-10
0
1021 G03
11
5
0.4
Start-Up (Shunt Mode)
LT1021-7, LT1021-10
13
8
0.6
LT1021 G02
Start-Up (Series Mode)
10
0.8
10k
LT1021 G01
12
TJ = 25 °C
1.0
0
100
1k
FREQUENCY (Hz)
10
40
TJ = –55 °C
1.2
0.2
50
85
TJ = 125 °C
1.4
INPUT/OUTPUT VOLTAGE (V)
f = 150Hz
110
REJECTION (dB)
1.6
130
115
Minimum Input/Output Differential
LT1021-7, LT1021-10
Ripple Rejection
Ripple Rejection
–4
0
10
100
1k
BANDWIDTH (Hz)
10k
LT1021 G07
4.994
– 50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
LT1021 G08
–5
–10 – 8 – 6 – 4 – 2
SOURCING
0
2
4 6 8
SINKING
OUTPUT CURRENT (mA)
10
LT1021 G09
1021fc
5
LT1021
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Sink Mode* Current Limit
LT1021-5
Quiescent Current LT1021-5
60
IOUT = 0
CURRENT INTO OUTPUT (mA)
1.6
INPUT CURRENT (mA)
1.4
1.2
TJ = – 55°C
1.0
TJ = 25°C
0.8
TJ = 125°C
0.6
0.4
Thermal Regulation LT1021-5
VIN = 8V
VIN = 25V
∆POWER = 200mW
50
OUTPUT CHANGE (mV)
1.8
40
30
20
LOAD
REGULATION
0
– 0.5
THERMAL
REGULATION
– 1.0
ILOAD = 10mA
10
0.2
0
0
5
10
15 20 25 30
INPUT VOLTAGE (V)
35
0
40
2
4
6
8 10 12 14
OUTPUT VOLTAGE (V)
∆ISOURCE = 100µAP-P
0
1
2
OUTPUT CHANGE (20mV/DIV)
OUTPUT CHANGE (50mV/DIV)
50mV
ISINK = 0.2mA
ISINK = 2-10mA
ISOURCE = 2-10mA
1
3
2
20mV
20mV
ISOURCE = 2-10mA
0
4
ISINK = 0.2mA
ISOURCE = 0.2mA
ISINK = 2-10mA
∆ISOURCE = 100µAP-P
∆ISINK = 100µAP-P
3 4 0
TIME (µs)
5
10 15 20 0
TIME (µs)
5
7.003
5
4
7.002
6.999
6.998
100
125
LT1021 G16
4
3
2
TIME (MINUTES)
1
6
5
LT1021 G15
Quiescent Current LT1021-7
1.8
VIN = 12V
IOUT = 0
1.6
1.4
INPUT CURRENT (mA)
7.000
5µV (1ppm)
0
3
OUTPUT CHANGE (mV)
OUTPUT VOLTAGE (V)
10 15 20
Load Regulation
LT1021-7, LT1021-10
7.001
FILTERING = 1 ZERO AT 0.1Hz
2 POLES AT 10Hz
LT1021 G14
Output Voltage Temperature
Drift LT1021-7
50
25
0
75
TEMPERATURE (°C)
100 120 140
∆ISINK = 100µAP-P
LT1021 G13
6.997
– 50 –25
40 60 80
TIME (ms)
Output Noise 0.1Hz to 10Hz
LT1021-5
ISINK = 0
ISOURCE = 0
ISINK = 0
ISOURCE = 0.5mA
20
LT1021 G12
Load Transient Response
LT1021-5, CLOAD = 1000pF
Load Transient Response
LT1021-5, CLOAD = 0
50mV
0
18
*NOTE THAT AN INPUT VOLTAGE IS REQUIRED
FOR 5V UNITS.
LT1021 G11
LT1021 G10
ISOURCE = 0
16
OUTPUT VOLTAGE NOISE (5µV/DIV)
0
2
1
0
–1
–2
1.2
1.0
TJ = – 55°C
0.8
TJ = 25°C
–3
0.4
–4
0.2
–5
–10 – 8 – 6 – 4 – 2
SOURCING
0
2
4 6 8
SINKING
OUTPUT CURRENT (mA)
10
LT1021 G17
TJ = 125°C
0.6
0
0
5
10
15 20 25 30
INPUT VOLTAGE (V)
35
40
LT1021 G18
1021fc
6
LT1021
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Shunt Mode Current Limit
LT1021-7
Shunt Characteristics LT1021-7
60
0.8
TJ = – 55°C
TJ = 25°C
0.6
0.4
TJ = 125°C
0.2
0
Thermal Regulation LT1021-7
VIN = 27V
∆POWER = 200mW
INPUT PIN OPEN
50
OUTPUT CHANGE (mV)
INPUT PIN OPEN
1.0
CURRENT INTO OUTPUT (mA)
CURRENT INTO OUTPUT (mA)
1.2
40
30
20
LOAD
REGULATION
0
– 0.5
THERMAL
REGULATION*
–1.0
–1.5
ILOAD = 10mA
10
0
0
7
1
3
8
2
5
6
4
OUTPUT TO GROUND VOLTAGE (V)
9
0
2
4
6
8 10 12 14
OUTPUT VOLTAGE (V)
16
0
18
40 60 80
TIME (ms)
100 120 140
*INDEPENDENT OF TEMPERATURE COEFFICIENT
LT1021 G20
1021 G19
20
LT1021 G21
Load Transient Response
LT1021-7, CLOAD = 0
Load Transient Response
LT1021-7, CLOAD = 1000pF
ISOURCE = 0
ISINK = 0.6mA
OUTPUT VOLTAGE CHANGE
OUTPUT VOLTAGE CHANGE
ISOURCE = 0
ISINK = 1.2mA
5mV
50mV
ISOURCE = 0.5mA
ISINK = 1.4mA
0
1
2
ISINK = 0.8mA
ISINK = 1mA
1
3
2
ISINK = 2-10mA
ISOURCE = 2-10mA
∆ISOURCE = 100µAP-P
∆ISINK = 100µAP-P
3 4 0
TIME (µs)
20mV
ISOURCE = 0.5mA
ISINK = 2-10mA
ISOURCE = 2-10mA
∆ISOURCE = 100µAP-P
5mV
0
4
NOTE VERTICAL SCALE CHANGE
BETWEEN SOURCING AND SINKING
5
10 15 20 0
5µs/DIV
5
4
3
2
TIME (MINUTES)
1
LT1021 G24
Load Regulation
LT1021-7, LT1021-10
5
4
10.004
Input Supply Current LT1021-10
1.8
VIN = 12V
10.000
9.998
9.996
100
125
LT1021 G25
INPUT CURRENT (mA)
OUTPUT CHANGE (mV)
3
10.002
6
5
LT1021 G23
10.006
OUTPUT VOLTAGE (V)
0
10 15 20
NOTE VERTICAL SCALE CHANGE
BETWEEN SOURCING AND SINKING
Output Voltage Temperature
Drift LT1021-10
50
25
0
75
TEMPERATURE (°C)
5µV (0.7ppm)
∆ISINK = 100µAP-P
LT1021 G22
9.994
– 50 –25
FILTERING = 1 ZERO AT 0.1Hz
2 POLES AT 10Hz
OUTPUT VOLTAGE NOISE (5µV/DIV)
ISINK = 0.8mA
Output Noise 0.1Hz to 10Hz
LT1021-7
2
1
0
–1
–2
TJ = – 55°C
1.4
TJ = 25°C
1.2
0.8
0.6
–3
–4
0.2
0
2
4 6 8
SINKING
OUTPUT CURRENT (mA)
10
1021 G26
TJ = 125°C
1.0
0.4
–5
–10 – 8 – 6 – 4 – 2
SOURCING
IOUT = 0
1.6
0
0
5
10
15 20 25 30
INPUT VOLTAGE (V)
35
40
1021 G27
1021fc
7
LT1021
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Shunt Mode Current Limit
LT1021-10
Shunt Characteristics LT1021-10
60
INPUT PIN OPEN
CURRENT INTO OUTPUT (mA)
CURRENT INTO OUTPUT (mA)
1.6
1.4
1.2
TJ = – 55°C
1.0
0.8
TJ = 25°C
0.6
0.4
TJ = 125°C
Thermal Regulation LT1021-10
VIN = 30V
∆POWER = 200mW
INPUT PIN OPEN
50
OUTPUT CHANGE (mV)
1.8
40
30
20
LOAD
REGULATION
0
– 0.5
–1.0
THERMAL
REGULATION*
–1.5
ILOAD = 10mA
10
0.2
0
0
0
2
4
6
10
8
OUTPUT TO GROUND VOLTAGE (V)
12
0
2
4
6
8 10 12 14
OUTPUT VOLTAGE (V)
16
1021 G29
1021 G28
0
18
20
40 60 80
TIME (ms)
100 120 140
*INDEPENDENT OF TEMPERATURE COEFFICIENT
1021 G30
Load Transient Response
LT1021-10, CLOAD = 0
Load Transient Response
LT1021-10, CLOAD = 1000pF
ISINK = 0.8mA
ISOURCE = 0
OUTPUT VOLTAGE CHANGE
OUTPUT VOLTAGE CHANGE
ISOURCE = 0
50mV
10mV
ISINK = 0.8mA
ISOURCE = 0.2mA
ISINK = 1mA
0
1
2
5mV
ISOURCE = 2-10mA
∆ISOURCE = 100µAP-P
∆ISINK = 100µAP-P
3 4 0
TIME (µs)
1
3
2
ISINK = 1.2mA
ISOURCE = 0.5mA
ISINK = 2-10mA
ISOURCE = 2-10mA
∆ISOURCE = 100µAP-P
20mV
4
NOTE VERTICAL SCALE CHANGE
BETWEEN SOURCING AND SINKING
1021 G31
0
1
2
ISINK = 1.4mA
ISINK = 2-10mA
∆ISINK = 100µAP-P
3 4 0
TIME (µs)
1
3
2
4
NOTE VERTICAL SCALE CHANGE
BETWEEN SOURCING AND SINKING
FILTERING = 1 ZERO AT 0.1Hz
2 POLES AT 10Hz
OUTPUT VOLTAGE NOISE (10µV/DIV)
ISINK = 0.6mA
Output Noise 0.1Hz to 10Hz
LT1021-10
10µV (1ppm)
0
1
4
3
2
TIME (MINUTES)
5
6
1021 G33
1021 G32
1021fc
8
LT1021
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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 TEMPERATURE COEFFICIENT FOR
0.5LSB ERROR (ppm/°C)
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
LT1021-5
10
IN
12-BIT
GND
VOUT
OUT
TRIM
R1
27k
R2
50k
14-BIT
1N4148
1.0
0 10 20 30 40 50 60 70 80 90 100
TEMPERATURE SPAN (°C)
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.
1021 AI02
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
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LT1021
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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
OUT
R2*
14k
1%
GND
R3
10k
R1*
200Ω
1%
VOUT
6.950V
TC TRACKING TO 50ppm/°C
1021 AI03
OUT
GND
R3
50k
R2**
182k
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.
LT1021-7
IN
Kelvin Connections
R1*
7.15k
1.000mA
Standard Series Mode
–
OP AMP
+
LT1021
INPUT
1021 AI04
*RESISTOR TC DETERMINES IOUT TC
**TC ≤ (10 • R1) TC. R2 AND R3 SCALE
WITH R1 FOR DIFFERENT OUTPUT CURRENTS
IN
KEEP THIS LINE RESISTANCE LOW
OUT
+
GND
LOAD
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
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 LOAD = 0 on LT1021-5, I LOAD =
– 0.8mA (sinking) on LT1021-7 and ILOAD = 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.
Series Mode with Boost Transistor
INPUT
R1
220Ω
2N3906
IN
LT1021
OUT
GND
GROUND
RETURN
R2*
LOAD
1021 AI06
*OPTIONAL—REDUCES CURRENT IN OUTPUT SENSE LEAD
R2 = 2.4k (LT1021-5), 3k (LT1021-7), 5.6k (LT1021-10)
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LT1021
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APPLICATIONS INFORMATION
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
OUTPUT VOLTAGE NOISE (20µV/DIV)
Effects of Air Movement on Low Frequency Noise
20µV
0
FOAM CUP
REMOVED
8
6
4
TIME (MINUTES)
2
12
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TYPICAL APPLICATIONS
Restricted Trim Range for Improved
Resolution, 10V, “C” Version Only
LT1021-10 Full Trim Range (±0.7%)
Negative Series Reference
15V
LT1021-10
LT1021C-10
VIN
IN
10.000V
OUT
GND
VIN
IN
GND
TRIM
R1
75k
R2
50k
1021 TA11
TRIM RANGE ≈ ±10mV
OUT
R1
4.7k
VOUT
LT1021-10
IN
TRIM
R1*
10k
1021 TA03
*CAN BE RAISED TO 20k FOR
LESS CRITICAL APPLICATIONS
R2
4.7k
–15V
D1
15V
Q1
2N2905
OUT
GND
–10V AT 50mA
LT1021 TA04
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TYPICAL APPLICATIONS
Boosted Output Current
with No Current Limit
Boosted Output Current
with Current Limit
V + ≥ (VOUT + 1.8V)
Ultraprecise Current Source
V + ≥ VOUT + 2.8V
D1*
LED
R1
220Ω
R1
220Ω
LT1021-7
8.2Ω
15V
2N2905
IN
2N2905
IN
OUT
17.4k
1%
GND
TRIM
100Ω
IN
LT1021
10V AT
100mA
+
10V AT
100mA
OUT
2µF
SOLID
TANT
GND
+
6.98k*
0.1%
15V
7
2µF
SOLID
TANT
2
–
OUT
6
*LOW TC
LT1001
3
+
GND
LT1021
1021 TA05
4
1021 TA06
*GLOWS IN CURRENT LIMIT,
DO NOT OMIT
–15V
IOUT = 1mA
REGULATION < 1ppm/V
COMPLIANCE = –13V TO 7V
1021 TA07
Operating 5V Reference from 5V Supply
2-Pole Lowpass Filtered Reference
5V LOGIC
SUPPLY
1N914
VIN
CMOS LOGIC GATE**
–
VIN
R1
36k
R2
36k
f = 10Hz
TOTAL NOISE
≤2µVRMS
1Hz ≤ f ≤ 10kHz
0.5µF
MYLAR
+
C1*
5µF
+
OUT
GND
VREF
LT1001
LT1021
IN
fIN ≥ 2kHz*
1N914
+
1µF
MYLAR
≈ 8.5V
C2*
5µF
LT1021-5
IN
OUT
5V
REFERENCE
GND
*FOR HIGHER FREQUENCIES C1 AND C2 MAY BE DECREASED
**PARALLEL GATES FOR HIGHER REFERENCE CURRENT LOADING
1021 TA16
–VREF
1021 TA13
Trimming 10V Units to 10.24V
CMOS DAC with Low Drift Full-Scale Trimming**
LT1021-10
R3
4.02K
1%
OUT
LT1021-10
TRIM
GND
FB
R1
4.99k
1%
REF
CMOS
DAC
7520, ETC
30pF
IOUT
R2
40.2Ω
1%
1.2k
–15V
*TC LESS THAN 200ppm/°C
**NO ZERO ADJUST REQUIRED
WITH LT1007 (V0S ≤ 60µV)
VIN
R4*
100Ω
FULL-SCALE
ADJUST
–
LT1007C
+
10V
F.S.
IN
TRIM
OUT
VOUT = 10.24V
GND
4.32k
5k
V – = –15V*
LT1236 TA15
*MUST BE WELL REGULATED
dVOUT 15mV
=
dV –
V
1021 TA12
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LT1021
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TYPICAL APPLICATIONS
Negative Shunt Reference Driven
by Current Source
Strain Gauge Conditioner for 350Ω Bridge
R1
357Ω
1/2W
LT1021-10
15V
IN
OUT
28mA
LT1021-10
GND
28.5mA
OUT
5V
350Ω STRAIN
GAUGE BRIDGE**
GND
+
6
3
R2
20k
2
R4
20k
†
LM301A
–
1
100pF
–10V (ILOAD ≤ 1mA)
R3
2M
2
2.5mA
–
LM334
6
LT1012C
3
+
VOUT
× 100
27Ω
R5
2M
8
R6*
2M
–11V TO – 40V
–5V
1021 TA14
1021 TA09
357Ω
1/2W
–15V
*THIS RESISTOR PROVIDES POSITIVE FEEDBACK TO
THE BRIDGE TO ELIMINATE LOADING EFFECT OF
THE AMPLIFIER. EFFECTIVE ZIN OF AMPLIFIER
STAGE IS ≥1MΩ. IF R2 TO R5 ARE CHANGED,
SET R6 = R3
**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
Precision DAC Reference with System TC Trim
Handling Higher Load Currents
15V
30mA
LT1021-10
15V
IN
OUT
GND
IN
8.87k
1%
LT1021-10
D1
1N457
1.24k
1%
50k
TC TRIM*
10k
1%
10k
1%
D2
1N457
50k
*TRIMS 1mA REFERENCE CURRENT
TC BY ± 40ppm/°C. THIS TRIM SCHEME HAS
VERY LITTLE EFFECT ON ROOM TEMPERATURE
CURRENT TO MINIMIZE ITERATIVE TRIMMING
50k
ROOM TEMP
TRIM
R1*
169Ω
VOUT
10V
OUT
GND
10.36k
1%
RL
TYPICAL LOAD
CURRENT = 30mA
1021 TA08
200k
1%
8.45k
1mA
*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
DAC
1021 TA17
1021fc
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TYPICAL APPLICATIONS
Ultralinear Platinum Temperature Sensor*
LT1021-10
IN
OUT
R2*
5k
20V
GND
R10
182k
1%
R14
5k
R1**
253k
R9
100k
R11
6.65M
1%
R8
10M
R15
10k
RF**
654k
R12
1k
R13
24.3k
20V
R4
4.75k
1%
R3**
5k
RS†
100Ω AT
0°C
2
R5
200k
1%
LT1001
3
R6
619k
1%
R7
392k
1%
–15V
7
–
+
6
VOUT =100mV/°C
– 50°C ≤ T ≤ 150°C
4
–15V
†
STANDARD INDUSTRIAL 100Ω PLATINUM 4-WIRE SENSOR,
ROSEMOUNT 78S OR EQUIVALENT. α = 0.00385
TRIM R9 FOR VOUT = 0V AT 0°C
TRIM R12 FOR VOUT = 10V AT 100°C
TRIM R14 FOR VOUT = 5V AT 50°C
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
1021 TA10
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INPUT
Q3
D1
D2
OUTPUT
D3
R1
Q1
+
–
A1
R2
D4
6.3V
Q2
GND
LT1021 ES
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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
SEATING
PLANE
.165 – .185
(4.191 – 4.699)
GAUGE
PLANE
.010 – .045*
(0.254 – 1.143)
REFERENCE
PLANE
.500 – .750
(12.700 – 19.050)
.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
**FOR SOLDER DIP LEAD FINISH, LEAD DIAMETER IS
(0.406 – 0.610) 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
1
2
3
4
.255 ± .015*
(6.477 ± 0.381)
.300 – .325
(7.620 – 8.255)
.008 – .015
(0.203 – 0.381)
(
+.035
.325 –.015
8.255
+0.889
–0.381
)
.045 – .065
(1.143 – 1.651)
.130 ± .005
(3.302 ± 0.127)
.065
(1.651)
TYP
.100
(2.54)
BSC
.120
(3.048) .020
MIN
(0.508)
MIN
.018 ± .003
(0.457 ± 0.076)
N8 1002
NOTE:
1. DIMENSIONS ARE
INCHES
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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LT1021
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PACKAGE DESCRIPTION
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.189 – .197
(4.801 – 5.004)
NOTE 3
.045 ±.005
.050 BSC
8
.245
MIN
7
6
5
.160 ±.005
.150 – .157
(3.810 – 3.988)
NOTE 3
.228 – .244
(5.791 – 6.197)
.030 ±.005
TYP
1
RECOMMENDED SOLDER PAD LAYOUT
.010 – .020
× 45°
(0.254 – 0.508)
.008 – .010
(0.203 – 0.254)
2
3
4
.053 – .069
(1.346 – 1.752)
0°– 8° TYP
.016 – .050
(0.406 – 1.270)
NOTE:
1. DIMENSIONS IN
.014 – .019
(0.355 – 0.483)
TYP
INCHES
(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)
.004 – .010
(0.101 – 0.254)
.050
(1.270)
BSC
SO8 0303
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
®
1021fc
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Linear Technology Corporation
LT 1005 REV C • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 1995