ANALOG DEVICES LT 1021 DCS8-10 Datasheet

Page 1
FEATURES
Ultralow Drift: 5ppm/°C Max Slope
Very Low Noise: <1ppm
100% Noise Tested
Pin Compatible with Most Bandgap Reference
(0.1Hz to 10Hz)
P-P
Applications, Including Ref 01, Ref 02, LM368, MC1400 and MC1404 with Greatly Improved Stability, Noise and Drift
Trimmed Output Voltage
Operates in Series or Shunt Mode
Output Sinks and Sources in Series Mode
>100dB Ripple Rejection
Minimum Input/Output Differential of 1V
Available in 5-Lead Can, N8 and S8 Packages
U
APPLICATIO S
LT1021
Precision Reference
U
The LT and noise, extremely good long term stability and almost total immunity to input voltage variations. The reference output will both source and sink up to 10mA. Three voltages are available: 5V, 7V and 10V. The 7V and 10V units can be used as shunt regulators (two-terminal zeners) with the same precision characteristics as the three­terminal connection. Special care has been taken to mini­mize thermal regulation effects and temperature induced hysteresis.
The LT1021 references are based on a buried zener diode structure that eliminates noise and stability problems associated with surface breakdown devices. Further, a subsurface zener exhibits better temperature drift and time stability than even the best bandgap references.
®
1021 is a precision reference with ultralow drift
A/D and D/A Converters
Precision Regulators
Digital Voltmeters
Inertial Navigation Systems
Precision Scales
Portable Reference Standard
TYPICAL APPLICATIO
Basic Positive and Negative Connections
LT1021
IN
V
IN
OUT
GND
V
OUT
R1 =
NC
V
I
LOAD
U
(7 AND 10 ONLY)
IN
– (V–)
OUT
+ 1.5mA
LT1021
GND
–15V
(V
Unique circuit design makes the LT1021 the first IC reference to offer ultralow drift without the use of high power on-chip heaters.
The LT1021-7 uses no resistive divider to set output voltage, and therefore exhibits the best long term stability and temperature hysteresis. The LT1021-5 and LT1021­10 are intended for systems requiring a precise 5V or 10V reference with an initial tolerance as low as ±0.05%.
, LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Typical Distribution of Temperature Drift
24
21
18
OUT
–V
OUT
R1
)
1021 TA01
15
12
UNITS (%)
9
6
3
– 0
–5
–3 –1 1 52–4 –2 0 4
OUTPUT DRIFT (ppm/°C)
DISTRIBUTION OF THREE RUNS
3
1021 TA01
1021fc
1
Page 2
LT1021
A
W
O
LUTEXI TIS
S
A
WUW
U
ARB
G
(Note 1)
Input Voltage .......................................................... 40V
Input/Output Voltage Differential ............................ 35V
Output-to-Ground Voltage (Shunt Mode Current Limit)
LT1021-5............................................................. 10V
LT1021-7............................................................. 10V
LT1021-10........................................................... 16V
Trim Pin-to-Ground Voltage
Positive ............................................... Equal to V
OUT
Negative ........................................................... – 20V
WU
/
PACKAGE
*CONNECTED INTERNALLY. DO NOT CONNECT EXTERNAL CIRCUITRY TO THESE PINS. **NO TRIM PIN ON LT1021-7. DO NOT CONNECT EXTERNAL CIRCUITRY TO PIN 5 ON LT1021-7
O
RDER I FOR ATIO
TOP VIEW
NC*
8
1
NC*
2
V
IN
3
NC*
GND
H PACKAGE
8-LEAD TO-5 METAL CAN
T
= 150°C, θJA = 150°C/W,θJC = 45°C/W
JMAX
NC*
7
6
V
OUT
5
TRIM
4
**
U
Output Short-Circuit Duration
VIN = 35V ......................................................... 10 sec
V
20V ................................................... Indefinite
IN
Operating Temperature Range
Commercial ............................................ 0°C to 70°C
Industrial ........................................... – 40°C to 85°C
Military ............................................ –55°C to 125°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................ 300°C
TOP VIEW
DNC*
1
V
2
IN
DNC*
3
GND
4
N8 PACKAGE 8-LEAD PDIP
*CONNECTED INTERNALLY. DO NOT CONNECT EXTERNAL CIRCUITRY TO THESE PINS. **NO TRIM PIN ON LT1021-7. DO NOT CONNECT EXTERNAL CIRCUITRY TO PIN 5 ON LT1021-7
T
= 130°C, θJA = 130°C/W (N)
JMAX
T
= 130°C, θJA = 150°C/W (S)
JMAX
8-LEAD PLASTIC SO
DNC*
8
DNC*
7
V
6
TRIM**
5
S8 PACKAGE
0UT
ORDER PART NUMBER
LT1021BCH-5 LT1021BMH-5 LT1021CCH-5 LT1021CMH-5 LT1021BMH-10
LT1021DCH-5 LT1021DMH-5 LT1021BCH-7 LT1021BMH-7 LT1021DCH-7 LT1021DMH-7 LT1021BCH-10 LT1021CMH-10 LT1021DCH-10 LT1021DMH-10
OBSOLETE
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
N8 ORDER PART NUMBER
LT1021BCN8-5 LT1021CCN8-5 LT1021CIN8-5 LT1021DCN8-5 LT1021DIN8-5 LT1021BCN8-7 LT1021DCN8-7 LT1021BCN8-10 LT1021CCN8-10 LT1021CIN8-10 LT1021DCN8-10 LT1021DIN8-10
S8 ORDER PART NUMBER
LT1021DCS8-5 LT1021DCS8-7 LT1021DCS8-10
S8 PART MARKING
2105 2107 2110
1021fc
2
Page 3
LT1021
LECTRICAL C CHARA TERIST
E
range, otherwise specifications are T
PARAMETER CONDITIONS MIN TYP MAX UNITS
Output Voltage (Note 2) LT1021C-5 4.9975 5.000 5.0025 V
Output Voltage Temperature Coefficient (Note 3) T
Line Regulation (Note 4) 7.2V ≤ VIN 10V 4 12 ppm/V
Load Regulation (Sourcing Current) 0 ≤ I
Load Regulation (Sinking Current) 0 ≤ I
Supply Current 0.8 1.2 mA
Output Voltage Noise (Note 6) 0.1Hz f 10Hz 3.0 µV
Long Term Stability of Output Voltage (Note 7) t = 1000Hrs Noncumulative 15 ppm Temperature Hysteresis of Output T = ± 25°C 10 ppm
= 25°C. VIN = 10V, I
A
ICS
LT1021B-5/LT1021D-5 4.9500 5.000 5.0500 V
TJ T
MIN
LT1021B-5 LT1021C-5/LT1021D-5
10V V
OUT
(Note 4)
OUT
(Note 4)
10Hz f 1kHz 2.2 3.5 µV
The ● denotes specifications that apply over the full operating temperature
= 0, unless otherwise noted.
OUT
LT1021-5
MAX
40V 2 6 ppm/V
IN
10mA 10 20 ppm/mA
10mA 60 100 ppm/mA
2 5 ppm/°C 3 20 ppm/°C
20 ppm/V
10 ppm/V
35 ppm/mA
150 ppm/mA
1.5 mA
P-P
RMS
The
denotes specifications that apply over the full operating temperature range, otherwise specifications are TA = 25°C.
VIN = 12V, I
PARAMETER CONDITIONS MIN TYP MAX UNITS
Output Voltage (Note 2) 6.95 7.00 7.05 V
Output Voltage Temperature Coefficient (Note 3) T
Line Regulation (Note 4) 8.5V ≤ VIN 12V 1.0 4 ppm/V
Load Regulation (Sourcing Current) 0 ≤ I
Load Regulation (Shunt Mode) 1.2mA ≤ I
Supply Current (Series Mode) 0.75 1.2 mA
Minimum Current (Shunt Mode) VIN is Open 0.7 1.0 mA
Output Voltage Noise (Note 6) 0.1Hz f 10Hz 4.0 µV
Long Term Stability of Output Voltage (Note 7) t = 1000Hrs Noncumulative 7 ppm Temperature Hysteresis of Output T = ± 25°C 3 ppm
= 0, unless otherwise noted.
OUT
LT1021-7
TJ T
MIN
LT1021B-7 LT1021D-7
12V V
(Note 4)
(Notes 4, 5)
10Hz f 1kHz 2.5 4.0 µV
MAX
40V 0.5 2 ppm/V
IN
10mA 12 25 ppm/mA
OUT
10mA 50 100 ppm/mA
SHUNT
2 5 ppm/°C 3 20 ppm/°C
2.0 8 ppm/V
1.0 4 ppm/V
40 ppm/mA
150 ppm/mA
1.5 mA
1.2 mA
P-P
RMS
1021fc
3
Page 4
LT1021
LECTRICAL C CHARA TERIST
E
range, otherwise specifications are T
PARAMETER CONDITIONS MIN TYP MAX UNITS
Output Voltage (Note 2) LT1021C-10 9.995 10.00 10.005 V
Output Voltage Temperature Coefficient (Note 3) T
Line Regulation (Note 4) 11.5V ≤ VIN 14.5V 1.0 4 ppm/V
Load Regulation (Sourcing Current) 0 ≤ I
Load Regulation (Shunt Mode) 1.7mA ≤ I
Supply Current (Series Mode) 1.2 1.7 mA
Minimum Current (Shunt Mode) VIN is Open 1.1 1.5 mA
Output Voltage Noise (Note 6) 0.1Hz f 10Hz 6.0 µV
Long Term Stability of Output Voltage (Note 7) t = 1000Hrs Noncumulative 15 ppm Temperature Hysteresis of Output T = ± 25°C 5 ppm
= 25°C. VIN = 15V, I
A
ICS
LT1021B-10/LT1021D-10 9.950 10.00 10.050 V
TJ T
MIN
LT1021B-10 LT1021C-10/LT1021D-10
14.5V V
OUT
(Note 4)
(Notes 4, 5)
10Hz f 1kHz 3.5 6 µV
The ● denotes specifications that apply over the full operating temperature
= 0, unless otherwise noted.
OUT
LT1021-10
MAX
40V 0.5 2 ppm/V
IN
10mA 12 25 ppm/mA
10mA 50 100 ppm/mA
SHUNT
2 5 ppm/°C 5 20 ppm/°C
6 ppm/V
4 ppm/V
40 ppm/mA
150 ppm/mA
2.0 mA
1.7 mA
P-P
RMS
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
Note 2: Output voltage is measured immediately after turn-on. Changes due to chip warm-up are typically less than 0.005%.
Note 3: Temperature coefficient is measured by dividing the change in output voltage over the temperature range by the change in temperature. Separate tests are done for hot and cold; T
Incremental slope is also measured at 25°C. Note 4: Line and load regulation are measured on a pulse basis. Output
changes due to die temperature change must be taken into account separately. Package thermal resistance is 150°C/W for TO-5 (H), 130°C/W for N and 150°C/W for the SO-8.
to 25°C and 25°C to T
MIN
MAX
.
Note 5: Shunt mode regulation is measured with the input open. With the input connected, shunt mode current can be reduced to 0mA. Load regulation will remain the same.
Note 6: RMS noise is measured with a 2-pole highpass filter at 10Hz and a 2-pole lowpass filter at 1kHz. The resulting output is full-wave rectified and then integrated for a fixed period, making the final reading an average as opposed to RMS. Correction factors are used to convert from average to RMS and correct for the non-ideal bandpass of the filters.
Peak-to-peak noise is measured with a single highpass filter at 0.1Hz and a 2-pole lowpass filter at 10Hz. The unit is enclosed in a still-air environment to eliminate thermocouple effects on the leads. Test time is 10 seconds.
Note 7: Consult factory for units with long term stability data.
4
1021fc
Page 5
LPER
OUTPUT CURRENT (mA)
0
INPUT/OUTPUT VOLTAGE (V)
1.2
1.6
16
1021 G03
0.8
0.4
0
4
8
12
20
1.0
1.4
0.6
0.2
14
2
6
10
18
TJ = 125 °C
TJ = –55 °C
TJ = 25 °C
FREQUENCY (Hz)
100
NOISE VOLTAGE (nV/Hz)
200
250
350
400
10 1k 10k
LT1021 G06
0
100
300
150
50
LT1021-10
LT1021-5
LT1021-7
)
Ripple Rejection
115
f = 150Hz
110
105
100
REJECTION (dB)
95
90
85
0
515
10 20
INPUT VOLTAGE (V)
Start-Up (Series Mode)
13
VIN = 0V TO 12V
12
11
10
9
8
7
6
OUTPUT VOLTAGE (V)
5
4
3
04
2
F
LT1021-10
LT1021-7
LT1021-5
6
TIME (µs)
R
O
LT1021-7
LT1021-10
LT1021-5
25
8
LT1021
UW
ATYPICA
30
35
LT1021 G01
12
10
LT1021 G04
CCHARA TERIST
E
C
Ripple Rejection
130
VIN = 15V C
OUT
120
110
100
90
80
REJECTION (dB)
70
60
50
40
10
Start-Up (Shunt Mode) LT1021-7, LT1021-10
11
10
9
8
7
OUTPUT VOLTAGE (V)
6
14
5
ICS
= 0
LT1021-7
LT1021-5
100 1k 10k
FREQUENCY (Hz)
LT1021-10
+ 2V
V
OUT
0V
NC
LT1021-7
61012
02
48
TIME (µs)
LT1021-10
1k
OUT
IN
GND
LT1021 G02
V
OUT
LT1021 G05
Minimum Input/Output Differential LT1021-7, LT1021-10
Output Voltage Noise Spectrum
Output Voltage Noise
16
C
= 0
OUT
FILTER = 1 POLE
14
= 0.1Hz
f
LOW
12
10
8
6
RMS NOISE (µV)
4
2
0
10
LT1021-10
100 1k 10k
BANDWIDTH (Hz)
LT1021-7
LT1021-5
LT1021 G07
Output Voltage Temperature Drift LT1021-5
5.006
5.004
5.002
5.000
4.998
OUTPUT VOLTAGE (V)
4.996
4.994 –50
0
–25
TEMPERATURE (°C)
50
25
Load Regulation LT1021-5
5
VIN = 8V
4
3
2
1
0
–1
–2
OUTPUT CHANGE (mV)
–3
–4
100
LT1021 G08
125
75
–5
–6–8 –4 0 4 8
–10
–2
SOURCING SINKING
OUTPUT CURRENT (mA
2
6
10
LT1021 G09
1021fc
5
Page 6
LT1021
)
LPER
Quiescent Current LT1021-5
1.8
1.6
1.4
1.2
1.0
0.8
0.6
INPUT CURRENT (mA)
0.4
0.2
= 0
I
OUT
TJ = – 55°C
TJ = 25°C
TJ = 125°C
0
5 10152025 40
0
INPUT VOLTAGE (V)
UW
R
F
O
ATYPICA
3530
LT1021 G10
CCHARA TERIST
E
C
Sink Mode* Current Limit LT1021-5
60
VIN = 8V
50
40
30
20
CURRENT INTO OUTPUT (mA)
10
0
26
0
4
*NOTE THAT AN INPUT VOLTAGE IS REQUIRED
FOR 5V UNITS.
ICS
10 18
12
8
OUTPUT VOLTAGE (V)
14
16
LT1021 G11
Thermal Regulation LT1021-5
VIN = 25V POWER = 200mW
0
– 0.5
–1.0
OUTPUT CHANGE (mV)
LOAD REGULATION
I
LOAD
0
20
= 10mA
40
TIME (ms)
60
THERMAL REGULATION
80
100
120
LT1021 G12
140
Load Transient Response LT1021-5, C
I
SOURCE
I
SOURCE
I
SOURCE
OUTPUT CHANGE (50mV/DIV)
I
SOURCE
LOAD
= 0
50mV 50mV
= 0.5mA
= 2-10mA
= 100µA
P-P
102413
3
TIME (µs)
Output Voltage Temperature Drift LT1021-7
7.003
7.002
7.001
7.000
6.999
OUTPUT VOLTAGE (V)
6.998
6.997 –50
–25
25
0
TEMPERATURE (°C)
= 0
Output Noise 0.1Hz to 10Hz LT1021-5
FILTERING = 1 ZERO AT 0.1Hz
OUTPUT VOLTAGE NOISE (5µV/DIV)
035
2 POLES AT 10Hz
5µV (1ppm)
12
TIME (MINUTES)
46
LT1021 G15
I
I
SINK
0
I
SINK
SINK
I
= 0
= 0.2mA
SINK
= 2-10mA
= 100µA
2
P-P
LT1021 G13
Load Transient Response LT1021-5, C
I
= 0
SOURCE
20mV 20mV
I
SOURCE
I
= 2-10mA
SOURCE
OUTPUT CHANGE (20mV/DIV)
I
= 100µA
SOURCE
4
501020515
LOAD
= 0.2mA
P-P
15
TIME (µs)
= 1000pF
I
= 0
SINK
I
SINK
I
SINK
I
SINK
0
= 0.2mA
= 2-10mA
= 100µA
10
LT1021 G14
P-P
20
Load Regulation LT1021-7, LT1021-10
5
VIN = 12V
4
3
2
1
0
–1
–2
OUTPUT CHANGE (mV)
–3
–4
50
75
100
LT1021 G16
125
–5
–6–8 –4 0 4 8
–10
SOURCING SINKING
–2
OUTPUT CURRENT (mA
2
6
10
LT1021 G17
Quiescent Current LT1021-7
1.8
1.6
1.4
1.2
1.0
0.8
0.6
INPUT CURRENT (mA)
0.4
0.2
= 0
I
OUT
TJ = – 55°C
TJ = 25°C
TJ = 125°C
0
5 10152025 40
0
INPUT VOLTAGE (V)
3530
LT1021 G18
1021fc
6
Page 7
LPER
)
INPUT VOLTAGE (V)
0
0
INPUT CURRENT (mA)
0.2
0.6
0.8
1.0
3530
1.8
1021 G27
0.4
5 10152025 40
1.2
1.4
1.6
TJ = – 55°C
TJ = 25°C
TJ = 125°C
I
OUT
= 0
F
O
Shunt Characteristics LT1021-7
1.2 INPUT PIN OPEN
1.0
0.8
0.6
0.4
CURRENT INTO OUTPUT (mA)
0.2
TJ = 25°C
TJ = –55°C
T
= 125°C
J
R
ATYPICA
UW
CCHARA TERIST
E
C
Shunt Mode Current Limit LT1021-7
60
INPUT PIN OPEN
50
40
30
20
CURRENT INTO OUTPUT (mA)
10
ICS
Thermal Regulation LT1021-7
VIN = 27V POWER = 200mW
0
–0.5
–1.0
–1.5
OUTPUT CHANGE (mV)
LOAD
REGULATION
I
= 10mA
LOAD
LT1021
THERMAL REGULATION*
0
10.006
10.004
10.002
10.000
9.998
OUTPUT VOLTAGE (V)
9.996
9.994
13
2
0
OUTPUT TO GROUND VOLTAGE (V)
59
6
4
Load Transient Response LT1021-7, C
I
= 0
SOURCE
5mV
I
SOURCE
OUTPUT VOLTAGE CHANGE
I
SOURCE
I
= 100µA
SOURCE
102413
NOTE VERTICAL SCALE CHANGE BETWEEN SOURCING AND SINKING
LOAD
= 0.5mA
= 2-10mA
P-P
3
TIME (µs)
= 0
I
0
I
SINK
SINK
I
SINK
I
SINK
I
Output Voltage Temperature Drift LT1021-10
50
–50
–25
25
0
TEMPERATURE (°C)
7
= 0.8mA
= 1.2mA
50mV
= 1.4mA
SINK
= 2-10mA
= 100µA
2
75
8
1021 G19
P-P
LT1021 G22
100
LT1021 G25
4
125
0
26
0
4
8
OUTPUT VOLTAGE (V)
Load Transient Response LT1021-7, C
I
SOURCE
OUTPUT VOLTAGE CHANGE
I
SOURCE
NOTE VERTICAL SCALE CHANGE BETWEEN SOURCING AND SINKING
LOAD
= 0
5mV
I
= 0.5mA
SOURCE
I
= 2-10mA
SOURCE
= 100µA
P-P
501020515
15
5µs/DIV
Load Regulation LT1021-7, LT1021-10
5
VIN = 12V
4
3
2
1
0
–1
–2
OUTPUT CHANGE (mV)
–3
–4
–5
–6–8 –4 0 4 8
–10
SOURCING SINKING
–2
OUTPUT CURRENT (mA
14
10 18
16
12
LT1021 G20
= 1000pF
I
= 0.6mA
SINK
20mV
I
= 0.8mA
SINK
= 1mA
I
SINK
I
= 2-10mA
SINK
= 100µA
I
SINK
0
10
LT1021 G23
2
6
P-P
1021 G26
80
0
20
*INDEPENDENT OF TEMPERATURE COEFFICIENT
60
40
TIME (ms)
100
120
LT1021 G21
140
Output Noise 0.1Hz to 10Hz LT1021-7
FILTERING = 1 ZERO AT 0.1Hz
OUTPUT VOLTAGE NOISE (5µV/DIV)
20
035
2 POLES AT 10Hz
5µV (0.7ppm)
12
TIME (MINUTES)
46
LT1021 G24
Input Supply Current LT1021-10
10
1021fc
7
Page 8
LT1021
TIME (ms)
OUTPUT CHANGE (mV)
–1.0
–0.5
0
140
1021 G30
–1.5
20
60
100
0
40
80
120
LOAD
REGULATION
THERMAL REGULATION*
I
LOAD
= 10mA
*INDEPENDENT OF TEMPERATURE COEFFICIENT
VIN = 30V POWER = 200mW
LPER
Shunt Characteristics LT1021-10
1.8 INPUT PIN OPEN
1.6
1.4
1.2
1.0
0.8
0.6
0.4
CURRENT INTO OUTPUT (mA)
0.2
0
TJ = – 55°C
0
OUTPUT TO GROUND VOLTAGE (V)
F
O
TJ = 125°C
42 6 10 12
8
R
ATYPICA
TJ = 25°C
1021 G28
UW
CCHARA TERIST
E
C
Shunt Mode Current Limit LT1021-10
60
INPUT PIN OPEN
50
40
30
20
CURRENT INTO OUTPUT (mA)
10
0
26
0
4
ICS
10 18
12
8
OUTPUT VOLTAGE (V)
Thermal Regulation LT1021-10
14
16
1021 G29
Load Transient Response LT1021-10, C
I
= 0
SOURCE
10mV
I
= 0.2mA
SOURCE
OUTPUT VOLTAGE CHANGE
I
SOURCE
I
= 100µA
SOURCE
102413
NOTE VERTICAL SCALE CHANGE
BETWEEN SOURCING AND SINKING
LOAD
= 2-10mA
P-P
3
TIME (µs)
= 0
I
I
0
SINK
I
SINK
= 0.6mA
50mV
I
SINK
I
SINK
SINK
= 100µA
= 0.8mA
= 1mA
= 2-10mA
2
1021 G31
P-P
Load Transient Response LT1021-10, C
I
= 0
SOURCE
5mV
I
= 0.5mA
SOURCE
OUTPUT VOLTAGE CHANGE
I
SOURCE
I
= 100µA
SOURCE
4
102413
NOTE VERTICAL SCALE CHANGE
BETWEEN SOURCING AND SINKING
LOAD
I
SINK
= 2-10mA
P-P
3
TIME (µs)
= 1000pF
I
SINK
20mV
= 1.2mA
I
I
SINK
I
SINK
0
= 0.8mA
= 1.4mA
SINK
= 2-10mA
= 100µA
2
P-P
4
1021 G32
Output Noise 0.1Hz to 10Hz LT1021-10
FILTERING = 1 ZERO AT 0.1Hz
OUTPUT VOLTAGE NOISE (10µV/DIV)
035
2 POLES AT 10Hz
10µV (1ppm)
12
TIME (MINUTES)
46
1021 G33
8
1021fc
Page 9
LT1021
U
WUU
APPLICATIONS INFORMATION
Effect of Reference Drift on System Accuracy
A large portion of the temperature drift error budget in many systems is the system reference voltage. This graph indicates the maximum temperature coefficient allowable if the reference is to contribute no more than 0.5LSB error to the overall system performance. The example shown is a 12-bit system designed to operate over a temperature range from 25°C to 65°C. Assuming the system calibra­tion is performed at 25°C, the temperature span is 40°C. It can be seen from the graph that the temperature coeffi­cient of the reference must be no worse than 3ppm/°C if it is to contribute less than 0.5LSB error. For this reason, the LT1021 family has been optimized for low drift.
Maximum Allowable Reference Drift
100
8-BIT
The LT1021-10 “C” version is pre-trimmed to ± 5mV and therefore can utilize a restricted trim range. A 75k resistor in series with a 20k 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 100k and attenuation to the output is 13:1. The technique shown below is suggested for trimming the output of the LT1021-5 while maintaining minimum shift in output temperature coefficient. The R1/R2 ratio is chosen to minimize interaction of trimming and TC shifts, so the exact values shown should be used.
10-BIT
10
0.5LSB ERROR (ppm/°C)
MAXIMUM TEMPERATURE COEFFICIENT FOR
1.0 100
12-BIT
14-BIT
20 100
40
50
30
TEMPERATURE SPAN (°C)
807060
90
LT1021 AI01
Trimming Output Voltage
LT1021-10
The LT1021-10 has a trim pin for adjusting output voltage. The impedance of the trim pin is about 12k with a nominal open-circuit voltage of 5V. It is designed to be driven from a source impedance of 3k 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 10k potentiometer is recom­mended, preferably a 20 turn cermet type with stable characteristics over time and temperature.
LT1021-5
IN
GND
OUT
TRIM
R1 27k
1N4148
V
R2 50k
1021 AI02
OUT
LT1021-7
The 7V version of the LT1021 has no trim pin because the internal architecture does not have a point which could be driven conveniently from the output. Trimming must therefore be done externally, as is the case with ordinary reference diodes. Unlike these diodes, however, the out­put of the LT1021 can be loaded with a trim potentiometer. The following trim techniques are suggested; one for voltage output and one for current output. The voltage output is trimmed for 6.95V. Current output is 1mA, as shown, into a summing junction, but all resistors may be scaled for currents up to 10mA.
Both of these circuits use the trimmers in a true potentio­metric mode to reduce the effects of trimmer TC. The voltage output has a 200 impedance, so loading must be
1021fc
9
Page 10
LT1021
U
WUU
APPLICATIONS INFORMATION
minimized. In the current output circuit, R1 determines output current. It should have a TC commensurate with the LT1021 or track closely with the feedback resistor around the op amp.
LT1021-7
IN
LT1021-7
IN
GND
OUT
GND
50k
OUT
R3
R3
10k
TC TRACKING TO 50ppm/°C
R2**
182k
R2*
14k
1%
R1*
7.15k
1.000mA
R1* 200 1%
V
OUT
6.950V
1021 AI03
Kelvin Connections
Although the LT1021 does not have true force/sense capability at its outputs, significant improvements in ground loop and line loss problems can be achieved with proper hook-up. In series mode operation, the ground pin of the LT1021 carries only 1mA and can be used as a sense line, greatly reducing ground loop and loss problems on the low side of the reference. The high side supplies load current so line resistance must be kept low. Twelve feet of #22 gauge hook-up wire or 1 foot of 0.025 inch printed circuit trace will create 2mV loss at 10mA output current. This is equivalent to 1LSB in a 10V, 12-bit system.
The following circuits show proper hook-up to minimize errors due to ground loops and line losses. Losses in the output lead can be greatly reduced by adding a PNP boost transistor if load currents are 5mA or higher. R2 can be added to further reduce current in the output sense lead.
Standard Series Mode
OP AMP
+
1021 AI04
RESISTOR TC DETERMINES I
*
TC (10 • R1) TC. R2 AND R3 SCALE
**
WITH R1 FOR DIFFERENT OUTPUT CURRENTS
OUT
TC
Capacitive Loading and Transient Response
The LT1021 is stable with all capacitive loads, but for optimum settling with load transients, output capacitance should be under 1000pF. The output stage of the reference is class AB with a fairly low idling current. This makes transient response worst-case at light load currents. Be­cause of internal current drain on the output, actual worst­case occurs at I –0.8mA (sinking) on LT1021-7 and I
= 0 on LT1021-5, I
LOAD
LOAD
=
LOAD
= 1.4mA (sink­ing) on LT1021-10. Significantly better load transient response is obtained by moving slightly away from these points. See Load Transient Response curves for details. In general, best transient response is obtained when the output is sourcing current. In critical applications, a 10µF solid tantalum capacitor with several ohms in series provides optimum output bypass.
INPUT
GROUND
RETURN
LT1021
IN
GND
KEEP THIS LINE RESISTANCE LOW
OUT
Series Mode with Boost Transistor
INPUT
R1 220
2N3906
IN
LT1021
OUT
GND
GROUND
RETURN
*OPTIONAL—REDUCES CURRENT IN OUTPUT SENSE LEAD R2 = 2.4k (LT1021-5), 3k (LT1021-7), 5.6k (LT1021-10)
R2*
1021 AI06
+
LOAD
1021 AI05
LOAD
1021fc
10
Page 11
LT1021
U
WUU
APPLICATIONS INFORMATION
Effects of Air Movement on Low Frequency Noise
The LT1021 has very low noise because of the buried zener used in its design. In the 0.1Hz to 10Hz band, peak-to-peak noise is about 0.5ppm of the DC output. To achieve this low noise, however, care must be taken to shield the reference from ambient air turbulence. Air movement can create noise because of thermoelectric differences between IC package leads (especially kovar lead TO-5) and printed circuit board materials and/or sockets. Power dissipation in the reference, even though it rarely exceeds 20mW, is enough to cause small temperature gradients in the package leads. Variations in thermal resistance, caused by uneven air flow, create differential lead temperatures, thereby causing thermoelectric voltage noise at the output of the reference. The following XY plotter trace dramati­cally illustrates this effect. The first half of the plot was done with the LT1021 shielded from ambient air with a small foam cup. The cup was then removed for the second half of the trace. Ambient in both cases was a lab environ­ment with no excessive air turbulence from air condition­ers, opening/closing doors, etc. Removing the foam cup increases the output noise by almost an order of magni­tude in the 0.01Hz to 1Hz band! The kovar leads of the TO-5 (H) package are the primary culprit. Alloy 42 and
copper lead frames used on dual-in-line packages are not nearly as sensitive to thermally generated noise because they are intrinsically matched.
There is nothing magical about foam cups—any enclo­sure which blocks air flow from the reference will do. Smaller enclosures are better since they do not allow the build-up of internally generated air movement. Naturally, heat generating components external to the reference itself should not be included inside the enclosure.
Noise Induced By Air Turbulence (TO-5 Package)
LT1021-7 (TO-5 PACKAGE) f = 0.01Hz TO 10Hz
20µV
OUTPUT VOLTAGE NOISE (20µV/DIV)
0610
24
TIME (MINUTES)
FOAM CUP REMOVED
812
1021 AI07
U
TYPICAL APPLICATIONS
Restricted Trim Range for Improved
Resolution, 10V, “C” Version Only
LT1021C-10
IN 10.000V
IN
OUT V
GND TRIM
TRIM RANGE ±10mV
R1
75k
R2 50k
1021 TA11
LT1021-10 Full Trim Range (± 0.7%)
LT1021-10
V
IN
GND
OUT
TRIM
IN
*CAN BE RAISED TO 20k FOR LESS CRITICAL APPLICATIONS
R1* 10k
1021 TA03
V
OUT
–15V
Negative Series Reference
15V
R2
4.7k
Q1
2N2905
R1
4.7k
D1 15V
LT1021-10
IN
GND
LT1021 TA04
OUT
–10V AT 50mA
1021fc
11
Page 12
LT1021
LT1021-10
OUT
IN
TRIM
GND
4.32k
V
OUT
= 10.24V
V
IN
5k
V
= –15V*
*MUST BE WELL REGULATED
dV
OUT
dV
=
15mV
V
1021 TA12
U
TYPICAL APPLICATIONS
Boosted Output Current
with No Current Limit
V+ (V
OUT
+ 1.8V)
LT1021
2-Pole Lowpass Filtered Reference
LT1021
IN
V
IN
OUT
GND
IN
GND
R1 220
OUT
R1
36k
+
f = 10Hz
2N2905
10V AT 100mA
2µF SOLID TANT
1021 TA05
1µF
MYLAR
R2
36k
+
V
V
LT1001
+
0.5µF MYLAR
Boosted Output Current
with Current Limit
+ 2.8V
OUT
D1* LED
LT1021
*GLOWS IN CURRENT LIMIT, DO NOT OMIT
V
IN
V
REF
TOTAL NOISE 2µV
RMS
1Hz f 10kHz
IN
GND
Ultraprecise Current Source
R1 220
OUT
+
8.2
2N2905
10V AT 100mA
2µF SOLID TANT
1021 TA06
15V
LT1021-7
IN
OUT
GND
6
Operating 5V Reference from 5V Supply
C1*
5µF
+
1N914
1N914
+
CMOS LOGIC GATE**
2kHz*
f
IN
FOR HIGHER FREQUENCIES C1 AND C2 MAY BE DECREASED
*
PARALLEL GATES FOR HIGHER REFERENCE CURRENT LOADING
**
TRIM
100
8.5V
C2* 5µF
17.4k 1%
15V
7
2
LT1001
–15V
3
+
4
REGULATION < 1ppm/V
COMPLIANCE = –13V TO 7V
LT1021-5
IN
OUT
GND
I
OUT
6.98k*
0.1%
*LOW TC
= 1mA
5V LOGIC SUPPLY
5V REFERENCE
1021 TA07
1021 TA16
LT1021-10
12
OUT
GND
–15V
TRIM
1.2k
–V
REF
1021 TA13
CMOS DAC with Low Drift Full-Scale Trimming**
4.02K
R1
4.99k 1%
R2
40.2 1%
TC LESS THAN 200ppm/°C
*
NO ZERO ADJUST REQUIRED
**
WITH LT1007 (V
REF
7520, ETC
CMOS
DAC
0S
FB
60µV)
I
OUT
30pF
LT1007C
+
R3
1%
Trimming 10V Units to 10.24V
R4* 100 FULL-SCALE ADJUST
10V F.S.
LT1236 TA15
1021fc
Page 13
U
LT1021-10
OUT
GND
IN
1021 TA08
R
L
30mA
15V
R1* 169
V
OUT
10V
TYPICAL LOAD CURRENT = 30mA
SELECT R1 TO DELIVER TYPICAL LOAD CURRENT. LT1021 WILL THEN SOURCE OR SINK AS NECESSARY TO MAINTAIN PROPER OUTPUT. DO NOT REMOVE LOAD AS OUTPUT WILL BE DRIVEN UNREGULATED HIGH. LINE REGULATION IS DEGRADED IN THIS APPLICATION
*
TYPICAL APPLICATIONS
LT1021
Strain Gauge Conditioner for 350 Bridge
R1
357
1/2W
LM301A
1
100pF
OF AMPLIFIER
IN
28mA
+
8
28.5mA
3
2
LT1021-10
15V
*
THIS RESISTOR PROVIDES POSITIVE FEEDBACK TO THE BRIDGE TO ELIMINATE LOADING EFFECT OF THE AMPLIFIER. EFFECTIVE Z STAGE IS 1M. IF R2 TO R5 ARE CHANGED, SET R6 = R3
IN
OUT
GND
6 6
5V
350 STRAIN GAUGE BRIDGE**
R2
20k
R4
20k
R5 2M
–5V
357 1/2W
–15V
BRIDGE IS ULTRALINEAR WHEN ALL LEGS ARE
**
ACTIVE, TWO IN COMPRESSION AND TWO IN TENSION, OR WHEN ONE SIDE IS ACTIVE WITH ONE COMPRESSED AND ONE TENSIONED LEG
OFFSET AND DRIFT OF LM301A ARE VIRTUALLY ELIMINATED BY DIFFERENTIAL CONNECTION OF LT1012C
2
3
LT1012C
+
R6*
2M
R3
2M
1021 TA09
Negative Shunt Reference Driven
by Current Source
LT1021-10
OUT
GND
V
OUT
× 100
LM334
–11V TO – 40V
2.5mA
–10V (I
LOAD
27
1mA)
1021 TA14
Precision DAC Reference with System TC Trim
LT1021-10
15V
IN
OUT
GND
TRIMS 1mA REFERENCE CURRENT
*
TC BY ± 40ppm/°C. THIS TRIM SCHEME HAS VERY LITTLE EFFECT ON ROOM TEMPERATURE CURRENT TO MINIMIZE ITERATIVE TRIMMING
8.87k 1%
1.24k 1%
D1 1N457
50k
TC TRIM*
10k 1%
10k 1%
D2 1N457
50k
50k ROOM TEMP TRIM
200k 1%
10.36k 1%
1mA
Handling Higher Load Currents
8.45k
DAC
1021 TA17
1021fc
13
Page 14
LT1021
U
TYPICAL APPLICATIONS
Ultralinear Platinum Temperature Sensor*
LT1021-10
IN
OUT
20V
100k
R2* 5k
R1** 253k
R8
R9
10M
–15V
R3** 5k
R7 392k 1%
R
S
100 AT 0°C
R10
182k
1%
4.75k
R4
1%
GND
R14 5k
R11
6.65M 1%
2
R5 200k 1%
3
R6
619k
STANDARD INDUSTRIAL 100 PLATINUM 4-WIRE SENSOR,
1%
ROSEMOUNT 78S OR EQUIVALENT. α = 0.00385 TRIM R9 FOR V
TRIM R12 FOR V TRIM R14 FOR V USE TRIM SEQUENCE AS SHOWN. TRIMS ARE NONINTERACTIVE SO THAT ONLY ONE TRIM SEQUENCE IS NORMALLY REQUIRED.
*
FEEDBACK LINEARIZES OUTPUT TO ±0.005°C FROM –50°C TO 150°C
**
WIREWOUND RESISTORS WITH LOW TC
LT1001
+
R
654k
20V
–15V
**
F
7
4
6
= 0V AT 0°C
OUT
= 10V AT 100°C
OUT
= 5V AT 50°C
OUT
R15 10k
R13
24.3k
R12 1k
=100mV/°C
V
OUT
–50°C T 150°C
1021 TA10
U
W
EQUIVALE T SCHE ATIC
D4
6.3V
INPUT
Q3
D1
D2
OUTPUT
D3
R1
Q1
+
A1
Q2
R2
LT1021 ES
GND
1021fc
14
Page 15
PACKAGE DESCRIPTION
SEATING
PLANE
45°
U
H Package
8-Lead TO-5 Metal Can (.200 Inch PCD)
(Reference LTC DWG # 05-08-1320)
.335 – .370
(8.509 – 9.398)
DIA
.305 – .335
(7.747 – 8.509)
.016 – .021**
(0.406 – 0.533)
.050
(1.270)
MAX
.027 – .045
(0.686 – 1.143)
PIN 1
GAUGE PLANE
(5.080)
.010 – .045*
(0.254 – 1.143)
.028 – .034
(0.711 – 0.864)
.040
(1.016)
MAX
(12.700 – 19.050)
.200
TYP
.165 – .185
(4.191 – 4.699)
.500 – .750
REFERENCE PLANE
LT1021
.110 – .160
(2.794 – 4.064)
INSULATING
STANDOFF
*
LEAD DIAMETER IS UNCONTROLLED BETWEEN THE REFERENCE PLANE AND THE SEATING PLANE
**
FOR SOLDER DIP LEAD FINISH, LEAD DIAMETER IS
N8 Package
8-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510)
87 6
.255 ± .015*
(6.477 ± 0.381)
1234
.300 – .325
(7.620 – 8.255)
.065
(1.651)
.008 – .015
(0.203 – 0.381)
+.035
.325
–.015 +0.889
8.255
()
–0.381
NOTE:
1. DIMENSIONS ARE
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
INCHES
MILLIMETERS
TYP
.045 – .065
(1.143 – 1.651)
.100
(2.54)
BSC
.016 – .024
(0.406 – 0.610)
.400*
(10.160)
MAX
H8(TO-5) 0.200 PCD 0204
5
.130 ± .005
(3.302 ± 0.127)
(3.048)
.018 ± .003
(0.457 ± 0.076)
.120
MIN
.020
(0.508)
MIN
N8 1002
1021fc
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen­tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
Page 16
LT1021
PACKAGE DESCRIPTION
8-Lead Plastic Small Outline (Narrow .150 Inch)
.050 BSC
U
S8 Package
(Reference LTC DWG # 05-08-1610)
.045 ±.005
.189 – .197
(4.801 – 5.004)
8
NOTE 3
7
5
6
.245 MIN
.030 ±.005
TYP
RECOMMENDED SOLDER PAD LAYOUT
.010 – .020
(0.254 – 0.508)
.008 – .010
(0.203 – 0.254)
NOTE:
1. DIMENSIONS IN
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
× 45°
.016 – .050
(0.406 – 1.270)
INCHES
(MILLIMETERS)
.160 ±.005
0°– 8° TYP
.228 – .244
(5.791 – 6.197)
.053 – .069
(1.346 – 1.752)
.014 – .019
(0.355 – 0.483)
TYP
.150 – .157
(3.810 – 3.988)
1
3
2
4
(0.101 – 0.254)
.050
(1.270)
BSC
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
LT1019 Precision Bandgap Reference 0.05%, 5ppm/°C
LT1027 Precision 5V Reference 0.02%, 2ppm/°C
LT1236 Precision Reference SO-8, 5V and 10V, 0.05%, 5ppm/°C
LTC®1258 Micropower Reference 200mV Dropout, MSOP
LT1389 Nanopower Shunt Reference 800nA Operating Current
LT1460 Micropower Reference SOT-23, 2.5V, 5V, 10V
LT1634 Micropower Shunt Reference 0.05%, 10ppm/°C, MSOP
NOTE 3
.004 – .010
SO8 0303
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
www.linear.com
1021fc
LT 1005 REV C • PRINTED IN USA
© LINEAR TECHNOLOGY CORPORATION 1995
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