LTZ1000/LTZ1000A
Ultra Precision Reference
FEATURES
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DESCRIPTION
The LTZ1000 and LTZ1000A are ultra-stable temperature
controllable references. They are designed to provide 7V
outputs with temperature drifts of 0.05ppm/°C, about
1.2μV
P-P
of noise and long-term stability of 2μV/√kHr.
Included on the chip is a subsurface zener reference, a
heater resistor for temperature stabilization, and a tem-
perature sensing transistor. External circuitry is used to
set operating currents and to temperature stabilize the
reference. This allows maximum flexibility and best long-
term stability and noise.
The LTZ1000 and LTZ1000A references can provide su-
perior performance to older devices such as the LM199,
provided that the user implements the heater control and
properly manages the thermal layout. To simplify thermal
insulation, the LTZ1000A uses a proprietary die attach
method to provide significantly higher thermal resistance
than the LTZ1000.
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
1.2μV
P-P
Noise
2μV/√kHr Long-Term Stability
Very Low Hysteresis
0.05ppm/°C Drift
Temperature Stabilized
400°C/W Thermal Resistance for LTZ1000A Reduces
Insulation Requirements
Specified for –55°C to 125°C Temperature Range
Offered in TO-99 package
APPLICATIONS
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Voltmeters
Calibrators
Standard Cells
Scales
Low Noise RF Oscillators
TYPICAL APPLICATION
Low Noise Reference
LTZ1000
V
IN
≥ 10V
OUTPUT
30k
3
1N4148
(ppm)
6
0
2
Long-Term Stability
+
–
7
LT
®
1006
2
4
120Ω
0.02μF
–2
1000 TA01
0
10
DAYS
20
30
LONG-TERM STABILITY OF A TYPICAL DEVICE FROM TIME = 0
WITH NO PRECONDITIONING OR AGING
1000 TA01b
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LTZ1000/LTZ1000A
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
BOTTOM VIEW
8
7
Q2
6
Q1
7V
5
4
H8 PACKAGE
TO-5 METAL CAN
T
JMAX
= 80°C,
θ
JA
= 400°C/W
3
2
1
Heater to Substrate ...................................................35V
Collector Emitter Breakdown Q1 ...............................15V
Collector Emitter Breakdown Q2 ...............................35V
Emitter Base Reverse Bias ..........................................2V
Operating Temperature Range..........–55°C ≤ T
A
≤ 125°C
Storage Temperature Range.............–65°C ≤ T
A
≤ 150°C
Substrate Forward Bias ............................................0.1V
ORDER INFORMATION
LEAD FREE FINISH
LTZ1000ACH#PBF
LTZ1000CH#PBF
LEAD BASED FINISH
LTZ1000ACH
LTZ1000CH
TAPE AND REEL
LTZ1000ACH#TRPBF
LTZ1000CH#TRPBF
TAPE AND REEL
LTZ1000ACH#TR
LTZ1000CH#TR
PART MARKING
PART MARKING
PACKAGE DESCRIPTION
8-Lead TO-5 Metal Can (.200 Inch PCD)
8-Lead TO-5 Metal Can (.200 Inch PCD)
PACKAGE DESCRIPTION
8-Lead TO-5 Metal Can (.200 Inch PCD)
8-Lead TO-5 Metal Can (.200 Inch PCD)
TEMPERATURE RANGE
–55°C to 125°C
–55°C to 125°C
TEMPERATURE RANGE
–55°C to 125°C
–55°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS
PARAMETER
Zener Voltage
Zener Change with Current
Zener Leakage Current
Zener Noise
Heater Resistance
Heater Breakdown Voltage
Transistor Q1 Breakdown
Transistor Q2 Breakdown
Q1, Q2 Current Gain
Thermal Resistance
Long-Term Stability
CONDITIONS
(Note 2)
MIN
7.0
6.9
TYP
7.2
7.15
80
20
1.2
200
35
15
35
80
Time = 5 Minutes
Time = 5 Minutes
300
20
50
200
80
400
2
450
°C/W
°C/W
μV√kHr
MAX
7.5
7.45
240
200
2
420
UNITS
V
V
mV
μA
μV
P-P
Ω
V
V
V
l
Z
= 5mA, (V
Z
+ VBE
Q1
) I
Q1
= 100μA
l
Z
= 1mA, (V
Z
+ VBE
Q1
) I
Q1
= 100μA
1mA ≤ I
Z
< 5mA
V
Z
= 5V
l
Z
= 5mA, 0.1Hz < f < 10Hz
1
Q1
= 100μA
I
L
≤ 100μA
I
C
= 10μA, LVCEO
I
C
= 10μA, LVCEO
I
C
= 100μA
LTZ1000
LTZ1000A
T = 65°C
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
All testing is done at 25°C. Pulse testing is used for LTZ1000A to
minimize temperature rise during testing. LTZ1000 and LTZ1000A devices
are QA tested at –55°C and 125°C.
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LTZ1000/LTZ1000A
TYPICAL PERFORMANCE CHARACTERISTICS
Zener Voltage vs Current
100
90
ZENER VOLTAGE NOISE (nV/√Hz)
ZENER VOLTAGE CHANGE (mV)
80
70
60
50
40
30
20
10
0
0
ZENER WITH KELVIN
SENSED Q1
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
ZENER CURRENT (mA)
1000 G01
Zener Voltage Noise Spectrum
500
450
Zener Noise
I
Z
= 4mA
ZENER ALONE
400
350
300
250
200
150
100
50
0
0.1
ZENER CURRENT = 4mA
ZENER CURRENT = 0.5mA
ZENER VOLTAGE NOISE (2μV/D)
I
Z
= 0.5mA
1
10
FREQUENCY (Hz)
100
0
10
20
30
40
TIME (SECONDS)
50
60
1000 G02
1000 G03
Die Temperature Rise
vs Heater Power
0.8
0.7
HEATER POWER (W)
0.6
0.5
0.4
0.3
0.2
0.1
0
25 35 45 55 65 75 85 95 105 115 125
DIE TEMPERATURE ABOVE AMBIENT (°C)
1000 G04
Die Temperature vs Time
125
LTZ1000A
DIE TEMPERATURE RISE (°C)
HEATER POWER = 0.3W
125
Die Temperature Rise vs Time
LTZ1000
100
LTZ1000
DIE TEMPERATURE RISE (°C)
100
75
HEATER POWER = 0.2W
75
HEATER POWER = 0.7W
HEATER POWER = 0.5W
50
50
LTZ1000A
25
HEATER POWER = 0.1W
25
HEATER POWER = 0.3W
0
0.1
1
10
100
TIME (SECONDS)
1000
0
0.1
1
10
100
TIME (SECONDS)
1000 G06
1000
1000 G05
PIN FUNCTIONS
Pin 1:
Heater Positive. Must have a higher positive value
than Pin 2 and Pin 4.
Pin 2:
Heater Negative. Must have a higher positive value
than Pin 4. Must have equal or lower potential than Pin 1.
Pin 3:
Zener Positive. Must have a higher positive value
than Pin 4.
Pin 4:
Substrate and Zener Negative. Must have a higher
positive value than Pin 7. If Q1 is zenered (about 7V) a
permanent degradation in beta will result.
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Pin 5:
Temperature Compensating Transistor Collector.
Pin 6:
Temperature Sensing Transistor Base. If the base
emitter junction is zenered (about 7V) the transistor will
suffer permanent beta degradation.
Pin 7:
Emitter of Sensing and Compensating Transistors.
Pin 8:
Collector of Sensing Transistor.
3
LTZ1000/LTZ1000A
BLOCK DIAGRAM
1
8
3
5
*
*
Q2
Q1
2
6
4
7
1000 TA07
*SUBSTRATE DEVICES–DO NOT FORWARD BIAS
APPLICATIONS INFORMATION
LTZ1000 and LTZ1000A are capable of providing ultimate
voltage reference performance. Temperature drifts of better
than 0.03ppm/°C and long-term stability on the order of
1μV per month can be achieved. Noise of about 0.15ppm
can also be obtained. This performance is at the expense
of circuit complexity, since external influences can easily
cause output voltage shifts of more than 1ppm.
Thermocouple effects are one of the worst problems and
can give apparent drifts of many ppm/°C as well as cause
low frequency noise. The kovar input leads of the TO-5
package form thermocouples when connected to copper
PC boards. These thermocouples generate outputs of
35μV/°C. It is mandatory to keep the zener and transistor
leads at the same temperature, otherwise 1ppm to 5ppm
shifts in the output voltage can easily be expected from
these thermocouples.
Air currents blowing across the leads can also cause small
temperature variations, especially since the package is
heated. This will look like 1ppm to 5ppm of low frequency
noise occurring over a several minute period. For best
results, the device should be located in an enclosed area
and well shielded from air currents.
Certainly, any temperature gradient externally generated,
say from a power supply, should not appear across the
critical circuitry. The leads to the transistor and zener
should be connected to equal size PC traces to equalize
the heat loss and maintain them at similar temperatures.
The bottom portion of the PC board should be shielded
against air currents as well.
Resistors, as well as having resistance temperature coef-
ficients, can generate thermocouple effects. Some types of
resistors can generate hundreds of microvolts of thermo-
couple voltage. These thermocouple effects in the resistor
can also interfere with the output voltage. Wire wound
resistors usually have the lowest thermocouple voltage,
while tin oxide type resistors have very high thermocouple
voltage. Film resistors, especially Vishay precision film
resistors, can have low thermocouple voltage.
Ordinary breadboarding techniques are not good enough
to give stable output voltage with the LTZ1000 family
devices. For breadboarding, it is suggested that a small
printed circuit board be made up using the reference, the
amplifier and wire wound resistors. Care must be taken to
ensure that heater current does not flow through the same
ground lead as the negative side of the reference (emitter
of Q1). Current changes in the heater could add to, or
subtract from, the reference voltage causing errors with
temperature. Single point grounding using low resistance
wiring is suggested.
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LTZ1000/LTZ1000A
APPLICATIONS INFORMATION
Setting Control Temperature
The emitter-base voltage of the control transistor sets the
stabilization temperature for the LTZ1000. With the values
given in the applications, temperature is normally 60°C.
This provides 15°C of margin above a maximum ambient
of 45°C, for example. Production variations in emitter-base
voltage will typically cause about ±10°C variation. Since
the emitter-base voltage changes about 2mV/°C and is
very predictable, other temperatures are easily set.
Because higher temperatures accelerate aging and decrease
long-term stability, the lowest temperature consistent with
the operating environment should be used. The LTZ1000A
should be set about 10°C higher than the LTZ1000. This
is because normal operating power dissipation in the
LTZ1000A causes a temperature rise of about 10°C. Of
course both types of devices should be insulated from
ambient. Several minutes of warm-up is usual.
For applications not requiring the extreme precision or
the low noise of the LTZ1000, Linear Technology makes a
broad line of voltage references. Devices like the LT1021
can provide drifts as low as 2ppm/°C and devices such as
the LM399A can provide drifts of 1ppm/°C. Only applica-
tions requiring the very low noise or low drift with time
of the LTZ1000 should use this device. See Application
Notes AN-82 and AN-86 for further information. Consult
the Linear Technology Applications department for ad-
ditional help.
TYPICAL APPLICATIONS
Negative Voltage Reference
ZENER + SENSE
V
+
15V
GND
0.1μF
1
1k
2N3904
7
LT1013
R4
13k
8
3
6
10k
1M
2
0.1μF
3
400k*
R5
1k
R1
120
4
7
8
1
LT1013
4
1N4148
0.022μF
ZENER – FORCE
ZENER – SENSE
*PROVIDE TEMPERATURE COMPENSATION, DELETE FOR LTZ1000A
APPROXIMATE CHANGE IN REFERENCE VOLTAGE FOR A 100ppm CHANGE IN RESISTOR VALUES:
R1
R2
R3
R4/R5 RATIO
100ppm = R(Ω)
0.012Ω
7Ω
7Ω
R = 0.01%
V
Z
1ppm
0.3ppm
0.2ppm
1ppm
1000 TA02
R3
70k
5
R2
70k
+
–
5
2
–
+
V
–
≥ 10V
BOTH A1 AND A2 CONTRIBUTE LESS THAN 2μV OF OUTPUT DRIFT OVER A 50°C RANGE
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