LT1461
Micropower Precision
Low Dropout Series
Voltage Reference Family
FEATURES
DESCRIPTION
Trimmed to High Accuracy: 0.04% Max
nn Low Drift: 3ppm/°C Max
nn Low Supply Current: 50µA Max
nn High Output Current: 50mA Min
nn Low Dropout Voltage: 300mV Max
nn Excellent Thermal Regulation
nn Power Shutdown
nn Thermal Limiting
nn All Parts Guaranteed Functional from –40°C to 125°C
nn Voltage Options: 2.5V, 3V, 3.3V, 4.096V and 5V
nn AEC-Q100 Qualified for Automotive Applications
The LT®1461 is a family of low dropout micropower bandgap references that combine very high accuracy and low
drift with low supply current and high output drive. These
series references use advanced curvature compensation
techniques to obtain low temperature coefficient and
trimmed precision thin-film resistors to achieve high
output accuracy. The LT1461 family draws only 35µA
of supply current, making them ideal for low power and
portable applications, however their high 50mA output
drive makes them suitable for higher power requirements,
such as precision regulators.
nn
In low power applications, a dropout voltage of less than
300mV ensures maximum battery life while maintaining
full reference performance. Line regulation is nearly immeasurable, while the exceedingly good load and thermal regulation will not add significantly to system error
budgets. The shutdown feature can be used to switch full
load currents and can be used for system power down.
Thermal shutdown protects the part from overload conditions. The LT1461 is available in 2.5V, 3V, 3.3V 4.096V
and 5V options.
APPLICATIONS
A/D and D/A Converters
Precision Regulators
nn Handheld Instruments
nn Power Supplies
nn
nn
All registered trademarks and trademarks are the property of their respective owners.
TYPICAL APPLICATION
Basic Connection
(VOUT + 0.3V) ≤ VIN ≤ 20V
CIN
1µF
LT1461-2.5 Load Regulation, PDISS = 200mW
VOUT
LT1461
CL
2µF
0mA
VOUT
1461 TA01
20mA
VOUT LOAD REG
1mV/DIV
10ms/DIV
1461 TA02
Rev. C
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1
LT1461
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
Input Voltage .............................................................20V
Output Short-Circuit Duration........................... Indefinite
Operating Temperature Range
(Note 2).............................................. –40°C to 125°C
Storage Temperature Range (Note 3)...... –65°C to 150°C
Specified Temperature Range
Commercial.............................................. 0°C to 70°C
Industrial..............................................–40°C to 85°C
High.................................................... –40°C to 125°C
Lead Temperature (Soldering, 10 sec).................... 300°C
TOP VIEW
DNC* 1
8
DNC*
VIN 2
7
DNC*
SHDN 3
6
VOUT
GND 4
5
DNC*
S8 PACKAGE
8-LEAD PLASTIC SO
*DNC: DO NOT CONNECT
TJMAX = 150°C, θJA = 190°C/W
(Note 3)
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
SPECIFIED TEMPERATURE RANGE
LT1461ACS8-2.5#PBF
LT1461ACS8-2.5#TRPBF
461A25
8-LEAD PLASTIC SO
0°C to 70°C
LT1461ACS8-3#PBF
LT1461ACS8-3#TRPBF
1461A3
8-LEAD PLASTIC SO
0°C to 70°C
LT1461ACS8-3.3#PBF
LT1461ACS8-3.3#TRPBF
461A33
8-LEAD PLASTIC SO
0°C to 70°C
LT1461ACS8-4#PBF
LT1461ACS8-4#TRPBF
1461A4
8-LEAD PLASTIC SO
0°C to 70°C
LT1461ACS8-5#PBF
LT1461ACS8-5#TRPBF
1461A5
8-LEAD PLASTIC SO
0°C to 70°C
LT1461BCS8-2.5#PBF
LT1461BCS8-2.5#TRPBF
461B25
8-LEAD PLASTIC SO
0°C to 70°C
LT1461BCS8-3#PBF
LT1461BCS8-3#TRPBF
1461B3
8-LEAD PLASTIC SO
0°C to 70°C
LT1461BCS8-3.3#PBF
LT1461BCS8-3.3#TRPBF
461B33
8-LEAD PLASTIC SO
0°C to 70°C
LT1461BCS8-4#PBF
LT1461BCS8-4#TRPBF
1461B4
8-LEAD PLASTIC SO
0°C to 70°C
LT1461BCS8-5#PBF
LT1461BCS8-5#TRPBF
1461B5
8-LEAD PLASTIC SO
0°C to 70°C
LT1461CCS8-2.5#PBF
LT1461CCS8-2.5#TRPBF
461C25
8-LEAD PLASTIC SO
0°C to 70°C
LT1461CCS8-3#PBF
LT1461CCS8-3#TRPBF
1461C3
8-LEAD PLASTIC SO
0°C to 70°C
LT1461CCS8-3.3#PBF
LT1461CCS8-3.3#TRPBF
461C33
8-LEAD PLASTIC SO
0°C to 70°C
LT1461CCS8-4#PBF
LT1461CCS8-4#TRPBF
1461C4
8-LEAD PLASTIC SO
0°C to 70°C
LT1461CCS8-5#PBF
LT1461CCS8-5#TRPBF
1461C5
8-LEAD PLASTIC SO
0°C to 70°C
LT1461AIS8-2.5#PBF
LT1461AIS8-2.5#TRPBF
61AI25
8-LEAD PLASTIC SO
–40°C to 85°C
LT1461AIS8-3#PBF
LT1461AIS8-3#TRPBF
461AI3
8-LEAD PLASTIC SO
–40°C to 85°C
LT1461AIS8-3.3#PBF
LT1461AIS8-3.3#TRPBF
61AI33
8-LEAD PLASTIC SO
–40°C to 85°C
LT1461AIS8-4#PBF
LT1461AIS8-4#TRPBF
461AI4
8-LEAD PLASTIC SO
–40°C to 85°C
LT1461AIS8-5#PBF
LT1461AIS8-5#TRPBF
461AI5
8-LEAD PLASTIC SO
–40°C to 85°C
LT1461BIS8-2.5#PBF
LT1461BIS8-2.5#TRPBF
61BI25
8-LEAD PLASTIC SO
–40°C to 85°C
LT1461BIS8-3#PBF
LT1461BIS8-3#TRPBF
461BI3
8-LEAD PLASTIC SO
–40°C to 85°C
LT1461BIS8-3.3#PBF
LT1461BIS8-3.3#TRPBF
61BI33
8-LEAD PLASTIC SO
–40°C to 85°C
LT1461BIS8-4#PBF
LT1461BIS8-4#TRPBF
461BI4
8-LEAD PLASTIC SO
–40°C to 85°C
LT1461BIS8-5#PBF
LT1461BIS8-5#TRPBF
461BI5
8-LEAD PLASTIC SO
–40°C to 85°C
LT1461CIS8-2.5#PBF
LT1461CIS8-2.5#TRPBF
61CI25
8-LEAD PLASTIC SO
–40°C to 85°C
LT1461CIS8-3#PBF
LT1461CIS8-3#TRPBF
461CI3
8-LEAD PLASTIC SO
–40°C to 85°C
LT1461CIS8-3.3#PBF
LT1461CIS8-3.3#TRPBF
61CI33
8-LEAD PLASTIC SO
–40°C to 85°C
Rev. C
2
For more information www.analog.com
LT1461
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
SPECIFIED TEMPERATURE RANGE
LT1461CIS8-4#PBF
LT1461CIS8-4#TRPBF
461CI4
8-LEAD PLASTIC SO
–40°C to 85°C
LT1461CIS8-5#PBF
LT1461CIS8-5#TRPBF
461CI5
8-LEAD PLASTIC SO
–40°C to 85°C
LT1461DHS8-2.5#PBF
LT1461DHS8-2.5#TRPBF
61DH25
8-LEAD PLASTIC SO
–40°C to 125°C
LT1461DHS8-3#PBF
LT1461DHS8-3#TRPBF
461DH3
8-LEAD PLASTIC SO
–40°C to 125°C
LT1461DHS8-3.3#PBF
LT1461DHS8-3.3#TRPBF
61DH33
8-LEAD PLASTIC SO
–40°C to 125°C
LT1461DHS8-4#PBF
LT1461DHS8-4#TRPBF
461DH4
8-LEAD PLASTIC SO
–40°C to 125°C
LT1461DHS8-5#PBF
LT1461DHS8-5#TRPBF
461DH5
8-LEAD PLASTIC SO
–40°C to 125°C
LT1461DHS8-2.5#WPBF
LT1461DHS8-2.5#WTRPBF
61DH25
8-LEAD PLASTIC SO
–40°C to 125°C
LT1461DHS8-3#WPBF
LT1461DHS8-3#WTRPBF
461DH3
8-LEAD PLASTIC SO
–40°C to 125°C
LT1461DHS8-3.3#WPBF
LT1461DHS8-3.3#WTRPBF
61DH33
8-LEAD PLASTIC SO
–40°C to 125°C
LT1461DHS8-4#WPBF
LT1461DHS8-4#WTRPBF
461DH4
8-LEAD PLASTIC SO
–40°C to 125°C
LT1461DHS8-5#WPBF
LT1461DHS8-5#WTRPBF
461DH5
8-LEAD PLASTIC SO
–40°C to 125°C
AUTOMOTIVE PRODUCTS**
Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
**Versions of this part are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. These
models are designated with a #W suffix. Only the automotive grade products shown are available for use in automotive applications. Contact your
local Analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for
these models.
AVAILABLE OPTIONS
OUTPUT VOLTAGE
INITIAL
ACCURACY
TEMPERATURE
COEFFICIENT
TEMPERATURE
RANGE
2.5V
3.0V
3.3V
4.096V
5.0V
0.04% Max
3ppm/°C Max
0°C to 70°C
LT1461ACS8-2.5
LT1461ACS8-3
LT1461ACS8-3.3
LT1461ACS8-4
LT1461ACS8-5
0.04% Max
3ppm/°C Max
–40°C to 85°C
LT1461AIS8-2.5
LT1461AIS8-3
LT1461AIS8-3.3
LT1461AIS8-4
LT1461AIS8-5
0.06% Max
7ppm/°C Max
0°C to 70°C
LT1461BCS8-2.5
LT1461BCS8-3
LT1461BCS8-3.3
LT1461BCS8-4
LT1461BCS8-5
0.06% Max
7ppm/°C Max
–40°C to 85°C
LT1461BIS8-2.5
LT1461BIS8-3
LT1461BIS8-3.3
LT1461BIS8-4
LT1461BIS8-5
0.08% Max
12ppm/°C Max
0°C to 70°C
LT1461CCS8-2.5
LT1461CCS8-3
LT1461CCS8-3.3
LT1461CCS8-4
LT1461CCS8-5
0.08% Max
12ppm/°C Max
–40°C to 85°C
LT1461CIS8-2.5
LT1461CIS8-3
LT1461CIS8-3.3
LT1461CIS8-4
LT1461CIS8-5
0.15% Max
20ppm/°C Max
–40°C to 125°C
LT1461DHS8-2.5
LT1461DHS8-3
LT1461DHS8-3.3
LT1461DHS8-4
LT1461DHS8-5
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified
temperature range, otherwise specifications are at TA = 25°C. VIN – VOUT = 0.5V, Pin 3 = 2.4V, CL = 2µF, unless otherwise specified.
PARAMETER
CONDITIONS
MIN
Output Voltage (Note 4)
LT1461ACS8/LT1461AIS8
LT1461BCS8/LT1461BIS8
LT1461CCS8/LT1461CIS8
LT1461DHS8
–0.04
–0.06
–0.08
–0.15
Output Voltage Temperature Coefficient (Note 5)
LT1461ACS8/LT1461AIS8
LT1461BCS8/LT1461BIS8
LT1461CCS8/LT1461CIS8
LT1461DHS8
l
l
l
l
TYP
1
3
5
7
MAX
UNITS
0.04
0.06
0.08
0.15
%
%
%
%
3
7
12
20
ppm/°C
ppm/°C
ppm/°C
ppm/°C
Rev. C
For more information www.analog.com
3
LT1461
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified
temperature range, otherwise specifications are at TA = 25°C. VIN – VOUT = 0.5V, Pin 3 = 2.4V, CL = 2µF, unless otherwise specified.
PARAMETER
CONDITIONS
Line Regulation
(VOUT + 0.5V) ≤ VIN ≤ 20V
MIN
TYP
MAX
UNITS
2
8
12
ppm/V
ppm/V
15
50
ppm/V
12
l
30
40
ppm/mA
ppm/mA
LT1461DHS8, 0 ≤ IOUT ≤ 10mA
l
50
ppm/mA
VIN – VOUT, VOUT Error = 0.1%
IOUT = 0mA
IOUT = 1mA
IOUT = 10mA
IOUT = 50mA, I and C Grades Only
l
l
l
0.3
0.4
2.0
V
V
V
V
l
LT1461DHS8
Load Regulation Sourcing (Note 6)
Dropout Voltage
l
VIN = VOUT + 2.5V
0 ≤ IOUT ≤ 50mA
Output Current
Short VOUT to GND
Shutdown Pin
Logic High Input Voltage
Logic High Input Current, Pin 3 = 2.4V
l
l
Logic Low Input Voltage
Logic Low Input Current, Pin 3 = 0.8V
l
l
Supply Current
0.06
0.13
0.20
1.50
100
No Load
2.4
2
15
V
µA
0.5
0.8
4
V
µA
35
50
70
µA
µA
25
35
55
µA
µA
l
Shutdown Current
RL = 1k
mA
l
Output Voltage Noise (Note 7)
0.1Hz ≤ f ≤ 10Hz
10Hz ≤ f ≤ 1kHz
8
9.6
ppmP-P
ppmRMS
Long-Term Drift of Output Voltage, SO-8 Package (Note 8)
See Applications Information
60
ppm/√kHr
Thermal Hysteresis (Note 9)
∆T = 0°C to 70°C
∆T = –40°C to 85°C
∆T = –40°C to 125°C
40
75
120
ppm
ppm
ppm
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: The LT1461 is guaranteed functional over the operating
temperature range of –40°C to 125°C.
Note 3: Output may shift due to thermal hysteresis. Thermal hysteresis
affects parts during storage as well as operation.
Note 4: ESD (Electrostatic Discharge) sensitive device. Extensive use of
ESD protection devices are used internal to the LT1461, however, high
electrostatic discharge can damage or degrade the device. Use proper ESD
handling precautions.
Note 5: Temperature coefficient is calculated from the minimum and
maximum output voltage measured at TMIN, Room and TMAX as follows:
TC = (VOMAX – VOMIN)/(TMAX – TMIN)
Incremental slope is also measured at 25°C.
Note 6: Load regulation is measured on a pulse basis from no load to the
specified load current. Output changes due to die temperature change
must be taken into account separately.
Note 7: Peak-to-peak noise is measured with a single pole 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. The test
time is 10 seconds. RMS noise is measured with a single 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. A correction factor of 1.1 is used
to convert from average to RMS and a second correction of 0.88 is used to
correct for the nonideal bandpass of the filters.
Note 8: Long-term drift typically has a logarithmic characteristic and
therefore, changes after 1000 hours tend to be much smaller than before
that time. Total drift in the second thousand hours is normally less than
one third that of the first thousand hours with a continuing trend toward
reduced drift with time. Long-term drift will also be affected by differential
stresses between the IC and the board material created during board
assembly. See the Applications Information section.
Note 9: Hysteresis in output voltage is created by package stress
that depends on whether the IC was previously at a higher or lower
temperature. Output voltage is always measured at 25°C, but the IC is
cycled hot or cold before successive measurements. Hysteresis is roughly
proportional to the square of the temperature change. Hysteresis is not
normally a problem for operational temperature excursions where the
instrument might be stored at high or low temperature. See Applications
Information section.
Rev. C
4
For more information www.analog.com
LT1461
TYPICAL PERFORMANCE CHARACTERISTICS
Characteristic curves are similar for most LT1461s.
Curves from the LT1461-2.5 and the LT1461-5 represent the extremes of the voltage options. Characteristic curves for other output
voltages fall between these curves and can be estimated based on their output.
2.5V Reference Voltage
vs Temperature
2.5005
2.5000
2.4995
2.4990
2.4985
2.4980
– 60 – 40 – 20
0
VIN = 7.5V
–1
1200
125°C
25°C
800
400
– 55°C
0
0.1
0 20 40 60 80 100 120
TEMPERATURE (°C)
1
10
OUTPUT CURRENT (mA)
–2
–3
–4
–5
–6
–7
SUPPLY ∆ = 15V
5V – 20V
–8
–40 – 20
100
0
20 40 60 80
TEMPERATURE (°C)
1461 G02
1461 G01
2.5V Minimum Input/Output
Voltage Differential vs Load Current
10
LINE REGULATION (ppm/V)
2.5010
100 120
1461 G03
2.5V Supply Current
vs Input Voltage
2.5V Ripple Rejection Ratio
vs Frequency
100
1000
125°C
25°C
RIPPLE REJECTION RATIO (dB)
1
SUPPLY CURRENT (µA)
INPUT/OUTPUT VOLTAGE (V)
90
100
125°C
25°C
– 55°C
– 55°C
0.1
0.1
1
10
OUTPUT CURRENT (mA)
80
70
60
50
40
30
20
10
10
100
0
5
10
15
20
INPUT VOLTAGE (V)
1461 G04
0
0.01
25
0.1
1
10
FREQUENCY (kHz)
1461 G05
2.5V Output Impedance
vs Frequency
100
1000
1641 G06
2.5V Turn-On Time
2.5V Turn-On Time
1000
COUT = 2µF
COUT = 1µF
10
10
10
0
0
2
1
VOUT
CIN = 1µF
CL = 2µF
RL = ∞
0
1
0.01
0.1
1
FREQUENCY (kHz)
10
VIN
20
VOLTAGE (V)
100
VIN
20
VOLTAGE (V)
OUTPUT IMPEDANCE (Ω)
REFERENCE VOLTAGE (V)
2.5015
1600
TEMPCO –60°C TO 120°C
3 TYPICAL PARTS
OUTPUT VOLTAGE CHANGE (ppm)
2.5020
2.5V Line Regulation
vs Temperature
2.5V Load Regulation
TIME (100µs/DIV)
1
VOUT
CIN = 1µF
CL = 2µF
RL = 50Ω
0
TIME (100µs/DIV)
1461 G08
1461 G07
2
1461 G09
Rev. C
For more information www.analog.com
5
LT1461
TYPICAL PERFORMANCE CHARACTERISTICS
Characteristic curves are similar for most LT1461s.
Curves from the LT1461-2.5 and the LT1461-5 represent the extremes of the voltage options. Characteristic curves for other output
voltages fall between these curves and can be estimated based on their output.
2.5V Transient Response to 10mA
Load Step
VIN
5V
OUTPUT NOISE (10µV/DIV)
IOUT
0mA
10mA/DIV
VOUT
50mV/DIV
2.5V Output Noise
0.1Hz ≤ f ≤ 10Hz
2.5V Line Transient Response
4V
VOUT
50mV/DIV
1461 G10
CL = 2µF
1461 G11
CIN = 0.1µF
TIME (2SEC/DIV)
1461 G12
5V Reference Voltage
vs Temperature
5.0040
2000
VIN = 10V
0
125°C
–1
5.0010
5.0000
4.9990
4.9980
4.9970
4.9960
4.9950
1600
–55°C
1200
800
25°C
400
–55°C
4.9940
0
0.1
0 20 40 60 80 100 120
TEMPERATURE (°C)
125°C
1
10
OUTPUT CURRENT (mA)
–2
–3
–4
–5
–6
–7
SUPPLY ∆ = 14V
6V TO 20V
–8
–40 –20 0
20 40 60 80
TEMPERATURE (°C)
100
100 120
1461 G14
1461 G13
5V Minimum Input/Output Voltage
Differential vs Load Current
10
LINE REGULATION (ppm/V)
25°C
LOAD REGULATION (ppm)
REFERENCE VOLTAGE (V)
TEMPCO –60°C TO 120°C
5.0030 3 TYPICAL PARTS
5.0020
4.9930
–60 –40 –20
5V Line Regulation
vs Temperature
5V Load Regulation
1461 G15
5V Supply Current
vs Input Voltage
5V Ripple Rejection Ratio
vs Frequency
100
10000
1
25°C
125°C
–55°C
0.1
RIPPLE REJECTION RATIO (dB)
SUPPLY CURRENT (µA)
INPUT/OUTPUT VOLTAGE (V)
90
1000
100
125°C
–55°C
10
25°C
80
70
60
50
40
30
20
10
0.01
0.1
1
10
OUTPUT CURRENT (mA)
100
1
0
5
10
15
INPUT VOLTAGE (V)
20
1461 G16
6
25
1461 G17
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0
0.01
0.1
1
10
FREQUENCY (kHz)
100
1000
1461
G18
Rev.
C
LT1461
TYPICAL PERFORMANCE CHARACTERISTICS
Characteristic curves are similar for most LT1461s.
Curves from the LT1461-2.5 and the LT1461-5 represent the extremes of the voltage options. Characteristic curves for other output
voltages fall between these curves and can be estimated based on their output.
5V Output Impedance vs
Frequency
5V Turn-On Time
5V Turn-On Time
1000
VIN
COUT = 1µF
4
4
2
2
0
VOUT
4
10
VOUT
2
CIN = 1µF
COUT = 2µF
IOUT = 0
0
0.1
1
FREQUENCY (kHz)
0
4
2
1
0.01
VIN
6
2V/DIV
COUT = 2µF
100
2V/DIV
OUTPUT IMPEDANCE (Ω)
6
10
CIN = 1µF
COUT = 2µF
IOUT = 50mA
0
200µs/DIV
200µs/DIV
1461 G20
1461 G21
1461 G19
5V Transient Response to 10mA
Load Step
7V
VIN
6V
OUTPUT NOISE (10µV/DIV)
IOUT
5V Output Noise
0.1Hz ≤ f ≤ 10Hz
5V Line Transient Response
0mA
10mA
VOUT
50mV/DIV
VOUT
50mV/DIV
1461 G22
CL = 2µF
1461 G23
CIN = 0.1µF
TIME (2SEC/DIV)
1461 G24
Supply Current
vs Temperature
50
200
120
160
30
20
10
SHDN PIN CURRENT (µA)
IS(SHDN)
CURRENT LIMIT (mA)
SUPPLY CURRENT (µA)
140
180
IS
40
SHDN Pin Current
vs SHDN Input Voltage
Current Limit vs Temperature
100
80
60
140
125°C
120
25°C
100
– 55°C
80
60
40
20
0
– 40 –20
0
20 40
60 80
TEMPERATURE (°C)
100 120
40
–50
–25
50
0
75
25
TEMPERATURE (°C)
100
1461 G25
125
1461 G26
For more information www.analog.com
0
0
15
10
5
SHDN PIN INPUT VOLTAGE (V)
20
Rev.
1461
G27
C
7
LT1461
TYPICAL PERFORMANCE CHARACTERISTICS
Characteristic curves are similar for most LT1461s.
Curves from the LT1461-2.5 and the LT1461-5 represent the extremes of the voltage options. Characteristic curves for other output
voltages fall between these curves and can be estimated based on their output.
0°C to 70°C Hysteresis
20
18
WORST-CASE HYSTERESIS
ON 35 UNITS
NUMBER OF UNITS
16
14
70°C TO 25°C
12
0°C TO 25°C
10
8
6
4
2
0
–100
– 80
– 60
– 40
– 20
0
20
HYSTERESIS (ppm)
40
60
80
100
1461 G29
–40°C to 85°C Hysteresis
20
18
WORST-CASE HYSTERESIS
ON 35 UNITS
NUMBER OF UNITS
16
14
85°C TO 25°C
12
– 40°C TO 25°C
10
8
6
4
2
0
–100
– 80
– 60
– 40
– 20
0
20
HYSTERESIS (ppm)
40
60
80
100
1461 G30
–40°C to 125°C Hysteresis
16
14
NUMBER OF UNITS
12
WORST-CASE HYSTERESIS
ON 35 UNITS
125°C TO 25°C
– 40°C TO 25°C
10
8
6
4
2
0
–200
–160
–120
–80
–40
0
40
HYSTERESIS (ppm)
80
120
160
200
1461 G31
8
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Rev. C
LT1461
TYPICAL PERFORMANCE CHARACTERISTICS
Characteristic curves are similar for most LT1461s.
Curves from the LT1461-2.5 and the LT1461-5 represent the extremes of the voltage options. Characteristic curves for other output
voltages fall between these curves and can be estimated based on their output.
Long-Term Drift (Number of Data Points Reduced at 650 Hours)*
250
LT1461S8
3 TYPICAL PARTS SOLDERED ONTO PCB
TA = 30°C
200
ppm
150
100
50
0
–50
0
200
400
600
800
1000
HOURS
1200
1400
1600
1800
2000
1461 G28
*SEE APPLICATIONS INFORMATION FOR DETAILED EXPLANATION OF LONG-TERM DRIFT
Rev. C
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9
LT1461
APPLICATIONS INFORMATION
Examples shown in this Applications section use the
LT1461-2.5. The response of other voltage options can
be estimated by proper scaling.
Bypass and Load Capacitors
The LT1461 family requires a capacitor on the input and
on the output for stability. The capacitor on the input is
a supply bypass capacitor and if the bypass capacitors
from other components are close (within 2 inches) they
should be sufficient. The output capacitor acts as frequency
compensation for the reference and cannot be omitted.
For light loads ≤1mA, a 1µF nonpolar output capacitor
is usually adequate, but for higher loads (up to 75mA),
the output capacitor should be 2µF or greater. Figures 1
and 2 show the transient response to a 1mA load step
with a 1µF output capacitor and a 50mA load step with a
2µF output capacitor.
IOUT 0mA
1mA/DIV
1mA
IOUT
50mA/DIV
VOUT
200mV/DIV
VOUT
20mV/DIV
1461 F01
Figure 1. 1mA Load Step with CL = 1µF
1461 F02
Figure 2. 50mA Load Step with CL = 2µF
Rev. C
10
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LT1461
APPLICATIONS INFORMATION
Precision Regulator
PC Board Layout
The LT1461 will deliver 50mA with VIN = VOUT + 2.5V and
higher load current with higher VIN. Load regulation is
typically 12ppm/mA, which means for a 50mA load step,
the output will change by only 1.5mV. Thermal regulation,
caused by die temperature gradients and created from
load current or input voltage changes, is not measurable.
This often overlooked parameter must be added to normal
line and load regulation errors. The load regulation photo,
on the first page of this data sheet, shows the output
response to 200mW of instantaneous power dissipation
and the reference shows no sign of thermal errors. The
reference has thermal shutdown and will turn off if the
junction temperature exceeds 150°C.
In 13- to 16-bit systems where initial accuracy and
temperature coefficient calibrations have been done, the
mechanical and thermal stress on a PC board (in a card
cage for instance) can shift the output voltage and mask
the true temperature coefficient of a reference. In addition,
the mechanical stress of being soldered into a PC board
can cause the output voltage to shift from its ideal value.
Surface mount voltage references are the most susceptible
to PC board stress because of the small amount of plastic
used to hold the lead frame.
Shutdown
The shutdown (Pin 3 low) serves to shut off load current
when the LT1461 is used as a regulator. The LT1461 operates normally with Pin 3 open or greater than or equal
to 2.4V. In shutdown, the reference draws a maximum
supply current of 35µA. Figure 3 shows the transient
response of shutdown while the part is delivering 25mA.
After shutdown, the reference powers up in about 200µs.
5V
A simple way to improve the stress-related shifts is to
mount the reference near the short edge of the PC board,
or in a corner. The board edge acts as a stress boundary,
or a region where the flexure of the board is minimum.
The package should always be mounted so that the leads
absorb the stress and not the package. The package is
generally aligned with the leads parallel to the long side
of the PC board as shown in Figure 5a.
A qualitative technique to evaluate the effect of stress on
voltage references is to solder the part into a PC board and
deform the board a fixed amount as shown in Figure 4.
The flexure #1 represents no displacement, flexure #2 is
concave movement, flexure #3 is relaxation to no displacement and finally, flexure #4 is a convex movement. This
motion is repeated for a number of cycles and the relative
PIN 3
1
0V
2
VOUT
3
0V
4
1461 F03
Figure 3. Shutdown While Delivering 25mA, RL = 100Ω
1461 F04
Figure 4. Flexure Numbers
Rev. C
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11
LT1461
APPLICATIONS INFORMATION
output deviation is noted. The result shown in Figure 5a is
for two LT1461S8-2.5s mounted vertically and Figure 5b
is for two LT1461S8-2.5s mounted horizontally. The parts
oriented in Figure 5a impart less stress into the package
because stress is absorbed in the leads. Figures 5a and
5b show the deviation to be between 125µV and 250µV
and implies a 50ppm and 100ppm change respectively.
This corresponds to a 13- to 14-bit system and is not a
problem for most 10- to 12-bit systems unless the system has a calibration. In this case, as with temperature
hysteresis, this low level can be important and even more
careful techniques are required.
The most effective technique to improve PC board stress
is to cut slots in the board around the reference to serve
as a strain relief. These slots can be cut on three sides of
the reference and the leads can exit on the fourth side. This
“tongue” of PC board material can be oriented in the long
direction of the board to further reduce stress transferred
to the reference.
The results of slotting the PC boards of Figures 5a and
5b are shown in Figures 6a and 6b. In this example the
slots can improve the output shift from about 100ppm
to nearly zero.
2
OUTPUT DEVIATION (mV)
OUTPUT DEVIATION (mV)
2
1
LONG DIMENSION
0
–1
0
10
20
FLEXURE NUMBER
0
10
20
30
FLEXURE NUMBER
40
1461 F06a
Figure 6a. Same Two LT1461S8-2.5s in Figure 5a, but with Slots
2
OUTPUT DEVIATION (mV)
2
OUTPUT DEVIATION (mV)
SLOT
1461 F05a
Figure 5a. Two Typical LT1461S8-2.5s,
Vertical Orientation without Slots
1
LONG DIMENSION
0
–1
0
–1
40
30
1
0
10
20
40
30
FLEXURE NUMBER
1
0
SLOT
–1
0
Figure 5b. Two Typical LT1461S8-2.5s,
Horizontal Orientation without Slots
10
20
FLEXURE NUMBER
1461 F05b
30
40
1461 F06b
Figure 6b. Same Two LT1461S8-2.5s in Figure 5b, but with Slots
Rev. C
12
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LT1461
APPLICATIONS INFORMATION
Long-Term Drift
Long-term drift cannot be extrapolated from accelerated
high temperature testing. This erroneous technique gives
drift numbers that are wildly optimistic. The only way
long-term drift can be determined is to measure it over
the time interval of interest. The erroneous technique
uses the Arrhenius Equation to derive an acceleration factor from elevated temperature readings. The equation is:
AF = e
EA ⎛ 1 1 ⎞
⎜ – ⎟
K ⎝ T1 T2⎠
where: EA = Activation Energy (Assume 0.7)
K = Boltzmann’s Constant
T2 = Test Condition in °Kelvin
T1 = Use Condition Temperature in °Kelvin
To show how absurd this technique is, compare the LT1461
data. Typical 1000 hour long-term drift at 30°C = 60ppm.
The typical 1000 hour long-term drift at 130°C = 120ppm.
From the Arrhenius Equation the acceleration factor is:
AF = e
1 ⎞
0.7
⎛ 1
–
⎜
⎟
0.0000863 ⎝ 303 403⎠
= 767
As an additional accuracy check on the DVM, a Fluke 732A
laboratory reference was also scanned. Figure 7 shows
the long-term drift measurement system. The data taken
is shown at the end of the Typical Performance Characteristics section of this data sheet. The long-term drift is
the trend line that asymptotes to a value at 2000 hours.
Note the slope in output shift between 0 hours and 1000
hours compared to the slope between 1000 hours and
2000 hours. Long-term drift is affected by differential
stresses between the IC and the board material created
during board assembly.
PCB3
PCB2
PCB1
SCANNER
8.5 DIGIT
DVM
COMPUTER
1461 F07
FLUKE
732A
LABORATORY
REFERENCE
Figure 7. Long-Term Drift Measurement Setup
The erroneous projected long-term drift is:
120ppm/767 = 0.156ppm/1000 hr
Hysteresis
For a 2.5V reference, this corresponds to a 0.39µV shift
after 1000 hours. This is pretty hard to determine (read
impossible) if the peak-to-peak output noise is larger than
this number. As a practical matter, one of the best laboratory
references available is the Fluke 732A and its long-term
drift is 1.5µV/mo. This performance is only available from
the best subsurface zener references utilizing specialized
heater techniques.
The hysteresis curves found in the Typical Performance
Characteristics represent the worst-case data taken on
35 typical parts after multiple temperature cycles. As
expected, the parts that are cycled over the wider –40°C
to 125°C temperature range have more hysteresis than
those cycled over lower ranges. Note that the hysteresis
coming from 125°C to 25°C has an influence on the –40°C
to 25°C hysteresis. The –40°C to 25°C hysteresis is different depending on the part’s previous temperature. This is
because not all of the high temperature stress is relieved
during the 25°C measurement.
The LT1461 long-term drift data was taken with parts that
were soldered onto PC boards similar to a “real world”
application. The boards were then placed into a constant
temperature oven with TA = 30°C, their outputs were
scanned regularly and measured with an 8.5 digit DVM.
The typical performance hysteresis curves are for parts
mounted in a socket and represent the performance of the
Rev. C
For more information www.analog.com
13
LT1461
APPLICATIONS INFORMATION
parts alone. What is more interesting are parts IR soldered
onto a PC board. If the PC board is then temperature cycled
several times from –40°C to 85°C, the resulting hysteresis
curve is shown in Figure 8. This graph shows the influence
of the PC board stress on the reference.
When the LT1461 is soldered onto a PC board, the output
shifts due to thermal hysteresis. Figure 9 shows the effect
of soldering 40 pieces onto a PC board using standard
IR reflow techniques. The average output voltage shift is
–110ppm. Remeasurement of these parts after 12 days
shows the outputs typically shift back 45ppm toward their
initial value. This second shift is due to the relaxation of
stress incurred during soldering.
12
11
10
WORST-CASE HYSTERESIS
ON 35 UNITS
85°C TO 25°C
9
NUMBER OF UNITS
The LT1461 is capable of dissipating high power, i.e.,
for the LT1461-2.5, 17.5V • 50mA = 875mW. The SO-8
package has a thermal resistance of 190°C/W and this
dissipation causes a 166°C internal rise producing a junction temperature of TJ = 25°C + 166°C = 191°C. What will
actually occur is the thermal shutdown will limit the junction temperature to around 150°C. This high temperature
excursion will cause the output to shift due to thermal
hysteresis. Under these conditions, a typical output shift is
–135ppm, although this number can be higher. This high
dissipation can cause the 25°C output accuracy to exceed
its specified limit. For best accuracy and precision, the
LT1461 junction temperature should not exceed 125°C.
– 40°C TO 25°C
8
7
6
5
4
3
2
1
0
– 200
–160
–120
– 80
– 40
0
40
HYSTERESIS (ppm)
80
120
160
200
1461 F08
Figure 8. –40°C to 85°C Hysteresis of 35 Parts Soldered Onto a PC Board
12
NUMBER OF UNITS
10
8
6
4
2
0
–300
200
0
100
–200 –100
OUTPUT VOLTAGE SHIFT (ppm)
300
1461 F09
Figure 9. Typical Distribution of Output Voltage Shift After Soldering Onto PC Board
Rev. C
14
For more information www.analog.com
LT1461
SIMPLIFIED SCHEMATIC
2 VIN
6 VOUT
100k
SHDN 3
4 GND
1461 SS
Rev. C
For more information www.analog.com
15
LT1461
PACKAGE DESCRIPTION
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610 Rev G)
.050 BSC
.189 – .197
(4.801 – 5.004)
NOTE 3
.045 ±.005
8
.245
MIN
.160 ±.005
.010 – .020
× 45°
(0.254 – 0.508)
NOTE:
1. DIMENSIONS IN
5
.150 – .157
(3.810 – 3.988)
NOTE 3
1
RECOMMENDED SOLDER PAD LAYOUT
.053 – .069
(1.346 – 1.752)
0°– 8° TYP
.016 – .050
(0.406 – 1.270)
6
.228 – .244
(5.791 – 6.197)
.030 ±.005
TYP
.008 – .010
(0.203 – 0.254)
7
.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)
4. PIN 1 CAN BE BEVEL EDGE OR A DIMPLE
2
3
4
.004 – .010
(0.101 – 0.254)
.050
(1.270)
BSC
SO8 REV G 0212
Rev. C
16
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LT1461
REVISION HISTORY
REV
DATE
DESCRIPTION
A
04/15
Features modified
PAGE NUMBER
1
Correction to VIN description, Typical Application schematic
1
Order Information updated
2
Note 3 thermal hysteresis description updated
4
Related Parts list updated
18
B
09/15
Removed unneeded Pin Functions section
10
C
10/19
Added automotive note to Order Information
3
Rev. C
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
subject to change without notice. No license For
is granted
implication or
otherwise under any patent or patent rights of Analog Devices.
more by
information
www.analog.com
17
LT1461
TYPICAL APPLICATION
Low Power 16-Bit A/D
VCC
35µA
200µA
VCC
1µF
VCC
FO
LTC2400
SCK
VREF
SD0
CS
VIN
LT1461-2.5
VOUT
1µF
INPUT
0.1µF
GND
GND
SPI
INTERFACE
1461 TA03
NOISE PERFORMANCE*
VIN = 0V, VNOISE = 1.1ppmRMS = 2.25µVRMS = 16µVP-P
VIN = VREF/2, VNOISE = 1.6ppmRMS = 4µVRMS = 24µVP-P
VIN = VREF, VNOISE = 2.5ppmRMS = 6.25µVRMS = 36µVP-P
*FOR 24-BIT PERFORMANCE USE LT1236 REFERENCE
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
LT1460
Micropower Series References
0.075% Accuracy, 10ppm/°C Drift, 20mA Drive
LT1790
Micropower Series References
0.05% Accuracy, 10ppm/°C Drift, 60µA Supply Current
LTC 1798
Micropower Series Reference
200mV Dropout at 10mA Drive, Sinks 2mA, 4μA Supply Current
LT6650
Micropower Reference and Buffer
0.5% Accuracy, 5.6μA Supply Current, SOT23 Package
LTC6652
Micropower Series Reference
0.05% Accuracy, 5ppm/°C Drift, –40°C to 125°C Operation
LT6654
All Purpose, Rugged and Precise Micropower References 0.05% Accuracy, 10ppm/°C Drift, –55°C to 125°C Operation, ±10mA Output
Drive, 100mV Dropout, 1.6ppmP-P Noise
LT6656
1µA Precision Voltage Reference
0.05% Accuracy, 10ppm/°C, 800nA Supply Current, SOT-23 Package
LT6660
Tiny Micropower Series Reference
0.2% Accuracy, 20ppm/°C Drift, 20mA Drive, 2mm × 2mm DFN Package
®
Rev. C
18
10/19
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