LINER LT6656BCS6-2.048TRPBF 1î¼a precision series voltage reference Datasheet

LT6656
1µA Precision Series
Voltage Reference
Features
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Description
Low Drift
A Grade: 10 ppm/°C Max
B Grade: 20 ppm/°C Max
High Accuracy
A Grade: 0.05% Max
B Grade: 0.1% Max
Ultralow Supply Current: 850nA
High Output Drive Current: 5mA Min
Low Dropout Voltage: 10mV Max
Fully Specified from –40°C to 85°C
Operational from –55°C to 125°C
Wide Supply Range to 18V
Reverse Input/Output Protection
Available Output Voltage Options:
1.25V, 2.048V, 2.5V, 3V, 3.3V, 4.096V and 5V
Thermal Hysteresis: 25ppm
Low Profile (1mm) ThinSOT™ Package
Applications
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Precision A/D and D/A Converters
Portable Gas Monitors
Battery- or Solar-Powered Systems
Precision Regulators
Low Voltage Signal Processing
Micropower Remote Sensing
The LT®6656 is a small precision voltage reference that
draws less than 1µA of supply current and can operate
with a supply voltage within 10mV of the output voltage.
The LT6656 offers an initial accuracy of 0.05% and temperature drift of 10ppm/°C. The combined low power and
precision characteristics are ideal for portable and battery
powered instrumentation.
The LT6656 can supply up to 5mA of output drive with
65ppm/mA of load regulation, allowing it to be used as
the supply voltage and the reference input to a low power
ADC. The LT6656 can accept a supply voltage up to 18V
and withstand the reversal of the input connections.
The LT6656 output is stable with 1µF or larger output
capacitance and operates with a wide range of output
capacitor ESR.
This reference is fully specified for operation from –40°C
to 85°C, and is functional over the extreme temperature
range of –55°C to 125°C. Low hysteresis and a consistent
temperature drift are obtained through advanced design,
processing and packaging techniques.
The LT6656 is offered in the 6-lead SOT-23 package.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ThinSOT is
a trademark of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
Typical Application
Output Voltage Temperature Drift
LT6656-2.5
2.503
Basic Connection
0.1µF
2.502
VOUT
2.5V
1µF
6656 TA01a
VOUT (V)
2.51V ≤ VIN ≤ 18V
LT6656-2.5
VIN
VOUT
GND
38 TYPICAL UNITS
2.501
2.500
2.499
2.498
–40
–20
0
20
40
TEMPERATURE (°C)
60
80
6652 TA01b
6656fa
LT6656
Absolute Maximum Ratings
Pin Configuration
(Note 1)
Input Voltage............................................................±20V
Output Voltage............................................ –0.3V to 20V
Output Voltage Above Input Voltage..........................20V
Specified Temperature Range
Commercial.............................................. 0°C to 70°C
Industrial..............................................–40°C to 85°C
Operating Temperature Range................ –55°C to 125°C
Output Short Circuit Duration .......................... Indefinite
Junction Temperature ........................................... 150°C
Storage Temperature Range (Note 2)...... –65°C to 150°C
Lead Temperature (Soldering, 10 sec.)
(Note 3).................................................................. 300°C
TOP VIEW
GND* 1
6 VOUT
GND 2
5 NC
NC 3
4 VIN
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
TJMAX = 150°C, θJA = 230°C/W
*CONNECT PIN TO DEVICE GND (PIN 2)
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
SPECIFIED TEMPERATURE RANGE
LT6656ACS6-1.25#PBF
LT6656ACS6-1.25#TRPBF
LTFNK
6-Lead Plastic TSOT-23
0°C to 70°C
LT6656BCS6-1.25#PBF
LT6656BCS6-1.25#TRPBF
LTFNK
6-Lead Plastic TSOT-23
0°C to 70°C
LT6656AIS6-1.25#PBF
LT6656AIS6-1.25#TRPBF
LTFNK
6-Lead Plastic TSOT-23
–40°C to 85°C
LT6656BIS6-1.25#PBF
LT6656BIS6-1.25#TRPBF
LTFNK
6-Lead Plastic TSOT-23
–40°C to 85°C
LT6656ACS6-2.048#PBF
LT6656ACS6-2.048#TRPBF
LTFNN
6-Lead Plastic TSOT-23
0°C to 70°C
LT6656BCS6-2.048#PBF
LT6656BCS6-2.048#TRPBF
LTFNN
6-Lead Plastic TSOT-23
0°C to 70°C
LT6656AIS6-2.048#PBF
LT6656AIS6-2.048#TRPBF
LTFNN
6-Lead Plastic TSOT-23
–40°C to 85°C
LT6656BIS6-2.048#PBF
LT6656BIS6-2.048#TRPBF
LTFNN
6-Lead Plastic TSOT-23
–40°C to 85°C
LT6656ACS6-2.5#PBF
LT6656ACS6-2.5#TRPBF
LTFGW
6-Lead Plastic TSOT-23
0°C to 70°C
LT6656BCS6-2.5#PBF
LT6656BCS6-2.5#TRPBF
LTFGW
6-Lead Plastic TSOT-23
0°C to 70°C
LT6656AIS6-2.5#PBF
LT6656AIS6-2.5#TRPBF
LTFGW
6-Lead Plastic TSOT-23
–40°C to 85°C
LT6656BIS6-2.5#PBF
LT6656BIS6-2.5#TRPBF
LTFGW
6-Lead Plastic TSOT-23
–40°C to 85°C
LT6656ACS6-3#PBF
LT6656ACS6-3#TRPBF
LTFNQ
6-Lead Plastic TSOT-23
0°C to 70°C
LT6656BCS6-3#PBF
LT6656BCS6-3#TRPBF
LTFNQ
6-Lead Plastic TSOT-23
0°C to 70°C
LT6656AIS6-3#PBF
LT6656AIS6-3#TRPBF
LTFNQ
6-Lead Plastic TSOT-23
–40°C to 85°C
LT6656BIS6-3#PBF
LT6656BIS6-3#TRPBF
LTFNQ
6-Lead Plastic TSOT-23
–40°C to 85°C
LT6656ACS6-3.3#PBF
LT6656ACS6-3.3#TRPBF
LTFNS
6-Lead Plastic TSOT-23
0°C to 70°C
LT6656BCS6-3.3#PBF
LT6656BCS6-3.3#TRPBF
LTFNS
6-Lead Plastic TSOT-23
0°C to 70°C
LT6656AIS6-3.3#PBF
LT6656AIS6-3.3#TRPBF
LTFNS
6-Lead Plastic TSOT-23
–40°C to 85°C
LT6656BIS6-3.3#PBF
LT6656BIS6-3.3#TRPBF
LTFNS
6-Lead Plastic TSOT-23
–40°C to 85°C
6656fa
LT6656
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
SPECIFIED TEMPERATURE RANGE
LT6656ACS6-4.096#PBF
LT6656ACS6-4.096#TRPBF
LTFNV
6-Lead Plastic TSOT-23
0°C to 70°C
LT6656BCS6-4.096#PBF
LT6656BCS6-4.096#TRPBF
LTFNV
6-Lead Plastic TSOT-23
0°C to 70°C
LT6656AIS6-4.096#PBF
LT6656AIS6-4.096#TRPBF
LTFNV
6-Lead Plastic TSOT-23
–40°C to 85°C
LT6656BIS6-4.096#PBF
LT6656BIS6-4.096#TRPBF
LTFNV
6-Lead Plastic TSOT-23
–40°C to 85°C
LT6656ACS6-5#PBF
LT6656ACS6-5#TRPBF
LTFNX
6-Lead Plastic TSOT-23
0°C to 70°C
LT6656BCS6-5#PBF
LT6656BCS6-5#TRPBF
LTFNX
6-Lead Plastic TSOT-23
0°C to 70°C
LT6656AIS6-5#PBF
LT6656AIS6-5#TRPBF
LTFNX
6-Lead Plastic TSOT-23
–40°C to 85°C
LT6656BIS6-5#PBF
LT6656BIS6-5#TRPBF
LTFNX
6-Lead Plastic TSOT-23
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
*The temperature and performance grades are identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
Available Options
SPECIFIED TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
OUTPUT VOLTAGE
INITIAL ACCURACY
TEMPERATURE
COEFFICIENT
ORDER PART NUMBER**
ORDER PART NUMBER**
1.250V
0.05%
0.1%
10ppm/°C
20ppm/°C
LT6656ACS6-1.25
LT6656BCS6-1.25
LT6656AIS6-1.25
LT6656BIS6-1.25
2.048V
0.05%
0.1%
10ppm/°C
20ppm/°C
LT6656ACS6-2.048
LT6656BCS6-2.048
LT6656AIS6-2.048
LT6656BIS6-2.048
2.500V
0.05%
0.1%
10ppm/°C
20ppm/°C
LT6656ACS6-2.5
LT6656BCS6-2.5
LT6656AIS6-2.5
LT6656BIS6-2.5
3.000V
0.05%
0.1%
10ppm/°C
20ppm/°C
LT6656ACS6-3
LT6656BCS6-3
LT6656AIS6-3
LT6656BIS6-3
3.300V
0.05%
0.1%
10ppm/°C
20ppm/°C
LT6656ACS6-3.3
LT6656BCS6-3.3
LT6656AIS6-3.3
LT6656BIS6-3.3
4.096V
0.05%
0.1%
10ppm/°C
20ppm/°C
LT6656ACS6-4.096
LT6656BCS6-4.096
LT6656AIS6-4.096
LT6656BIS6-4.096
5.000V
0.05%
0.1%
10ppm/°C
20ppm/°C
LT6656ACS6-5
LT6656BCS6-5
LT6656AIS6-5
LT6656BIS6-5
**See Order Information section for complete part number listing.
6656fa
LT6656
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 (for LT6656-1.25, VIN = 2.2V), CL = 1μF, IL = 0,unless
otherwise noted.
PARAMETER
CONDITIONS
MIN
Output Voltage Error
LT6656A
LT6656B
–0.05
–0.10
Output Voltage Temperature Coefficient (Note 4)
LT6656A
LT6656B
l
l
Line Regulation
VIN = (VOUT + 0.5V) to 18V
LT6656-2.048, LT6656-2.5, LT6656-3,
LT6656-3.3, LT6656-4.096, LT6656-5
l
VIN = 2.2V to 18V
LT6656-1.25
Load Regulation (Note 5)
IL = 5mA, Sourcing
LT6656-2.048, LT6656-2.5, LT6656-3,
LT6656-3.3, LT6656-4.096, LT6656-5
IL = 5mA, Sourcing
LT6656-1.25
Dropout Voltage (Note 6)
VIN – VOUT, ∆VOUT Error ≤ 0.1%
IL = 0
LT6656-2.048, LT6656-2.5, LT6656-3,
LT6656-3.3, LT6656-4.096, LT6656-5
IL = 5mA, Sourcing
LT6656-2.048, LT6656-2.5, LT6656-3,
LT6656-3.3, LT6656-4.096, LT6656-5
Minimum Input Voltage
IL = 0, ∆VOUT Error ≤ 0.1%
LT6656-1.25
0°C ≤ TA ≤ 70°C
–40°C ≤ TA ≤ 85°C
TYP
UNITS
0.05
0.10
%
%
5
12
10
20
ppm/°C
ppm/°C
2
25
40
ppm/V
ppm/V
2
25
40
ppm/V
ppm/V
65
150
375
ppm/mA
ppm/mA
80
175
425
ppm/mA
ppm/mA
3
10
40
mV
mV
250
370
500
mV
mV
1.35
1.5
1.6
1.8
V
V
V
0.85
1.0
1.5
µA
µA
l
l
l
l
l
l
l
Supply Current
MAX
l
Output Short Circuit Current
Short VOUT to GND
Short VOUT to VIN
18
4
mA
mA
Input Reverse Leakage Current
VIN = –18V, VOUT = GND
80
µA
Reverse Output Current
VIN = GND, VOUT = 18V
30
µA
Output Voltage Noise (Note 7)
0.1Hz to 10Hz
10Hz to 1kHz, LT6656-1.25
10Hz to 1kHz, LT6656-2.5
10Hz to 1kHz, LT6656-5
30
50
80
140
ppmP-P
µVRMS
µVRMS
µVRMS
Turn-On Time
LT6656-1.25, 0.1% Settling
LT6656-2.5, 0.1% Settling
LT6656-5, 0.1% Settling
15
30
60
ms
ms
ms
50
ppm/√kHr
25
70
ppm
ppm
Long Term Drift of Output Voltage (Note 8)
Hysteresis (Note 9)
∆T = 0°C to 70°C
∆T = –40°C to 85°C
6656fa
LT6656
Electrical Characteristics
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: If the parts are stored outside of the specified temperature range,
the output may shift due to hysteresis.
Note 3: The stated temperature is typical for soldering of the leads during
manual rework. For detailed IR reflow recommendations, refer to the
Applications section.
Note 4: Temperature coefficient is measured by dividing the maximum
change in output voltage by the specified temperature range.
Note 5: Load regulation is measured with a pulse from no load to the
specified load current. Output changes due to die temperature change
must be taken into account separately.
Note 6: Excludes load regulation errors.
Note 7: Peak-to-peak noise is measured with a 3-pole highpass filter at
0.1Hz and a 4-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 on a spectrum analyzer in a
shielded environment.
Note 8: Long term stability 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 stability will also be affected by
differential stresses between the IC and the board material created during
board assembly.
Note 9: Hysteresis in output voltage is created by mechanical stress
that differs depending 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 to the hot or cold temperature limit before successive
measurements. For instruments that are stored at well controlled
temperatures (within 20 or 30 degrees of operational temperature)
hysteresis is usually not a dominant error source.
Typical Performance Characteristics
Output Voltage Temperature Drift
200
6000
5000
4000
3000
2000
120
100
80
60
40
0
20
6652 G01
Supply Current vs Input Voltage
100
ALL OPTIONS
180 CL = 1µF
I =0
160 TL = 25°C
A
140
1000
–1000
–60 –40 –20 0 20 40 60 80 100 120
TEMPERATURE (°C)
Typical VOUT Distribution
SUPPLY CURRENT (µA)
ALL OPTIONS
9000 25 TYPICAL UNITS
8000 NORMALIZED AT 25°C
CL = 1µF
7000 IL = 0
NUMBER OF UNITS
CHANGE IN OUTPUT VOLTAGE (ppm)
10000
0
–0.10
–0.06
–0.02 0 0.02
0.06
OUTPUT VOLTAGE ERROR (%)
0.10
6656 G02
1.25V OPTION
10
TA = 125°C
TA = 85°C
TA = 25°C
TA = –40°C
TA = –55°C
1
0.1
0
2
4
6 8 10 12 14 16 18 20
INPUT VOLTAGE (V)
6656 G17
6656fa
LT6656
Typical Performance Characteristics
Minimum Supply Voltage
vs Load Current
Supply Current vs Input Voltage
VON
1
2.5V OPTION SHOWN
VON MOVES WITH VOLTAGE OPTION
0.1
0
2
4
1.25V OPTION
INITIAL VIN = 2.2V
1.8 ∆VOUT = 0.1%
1.6
1.4
1.2
TA = 125°C
TA = 85°C
TA = 25°C
TA = –40°C
TA = –55°C
1.0
0.8
0.1µ
6 8 10 12 14 16 18 20
INPUT VOLTAGE (V)
1µ
10µ
100µ
1m
LOAD CURRENT (A)
6656 G03
Load Regulation (Sourcing)
TA = 125°C
TA = 85°C
TA = 25°C
TA = –40°C
TA = –55°C
1µ
10µ
100µ
1m
LOAD CURRENT (A)
10m
0
–250
–500
–750
0.1µ
600 2.5V OPTION SHOWN
VON MOVES WITH
500 VOLTAGE OPTION
400
VON
300
200
100
0
–100
–200
0
2
4
TA = 125°C
TA = 85°C
TA = 25°C
TA = –55°C
1µ
6 8 10 12 14 16 18 20
INPUT VOLTAGE (V)
6656 G08
90
3.5
3.0
TA = 85°C, 125°C
TA = 25°C
TA = –40°C
TA = –55°C
2.5
2.0
1.5
1.0
0.5
0
10µ
100µ
1m
LOAD CURRENT (A)
10m
–0.5
10µ
100µ
LOAD CURRENT (A)
70
60
50
40
30
20
1.25V OPTION
2.5V OPTION
5V OPTION
10
0
10
100
1k
FREQUENCY (Hz)
1m
6656 G06
Power Supply Rejection Ratio
vs Frequency
VIN = VOUT + 0.5V
CL = 1µF
IL = 0
80
10m
ALL OPTIONS
4.5 VIN = VOUT + 0.5V
4.0 CL = 1µF
6656 G05
POWER SUPPLY REJECTION RATIO (dB)
OUTPUT VOLTAGE CHANGE (ppm)
700
10µ
100µ
1m
LOAD CURRENT (A)
6656 G04
Power Supply Rejection Ratio
vs Frequency
TA = 125°C
TA = 85°C
TA = 25°C
TA = –55°C
1µ
Load Regulation (Sinking)
250
Line Regulation
ALL OPTIONS
900 I = 0
L
800 CL = 1µF
TA = 125°C
TA = 85°C
TA = 25°C
TA = –55°C
5.0
2.048V TO 5V OPTIONS
VIN = VOUT + 0.5V
500 CL = 1µF
6656 G19
1000
1
0.1µ
10m
OUTPUT VOLTAGE CHANGE (%)
OUTPUT VOLTAGE CHANGE (ppm)
OUTPUT VOLTAGE CHANGE (ppm)
–250
–1000
0.1µ
10
Load Regulation (Sourcing)
0
–750
100
750
1.25V OPTION
VIN = 1.75V
250 CL = 1µF
2.048V TO 5V OPTIONS
VIN – VOUT
INITIAL VIN = VOUT + 0.5V
∆VOUT = 0.1%
6656 G18
500
–500
DROPOUT VOLTAGE (mV)
10
TA = 125°C
TA = 85°C
TA = 25°C
TA = –55°C
1000
10k
6656 G09
90
POWER SUPPLY REJECTION RATIO (dB)
2.048V TO 5V OPTIONS
Dropout Voltage vs Load Current
2.0
MINIMUM SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
100
2.5V OPTION
VIN = 3V
80
70
60
50
40
30
20
IL = 0, CL = 1µF
IL = 0, CL = 10µF
IL = 1mA, CL = 1µF
IL = 1mA, CL = 10µF
10
0
–10
10
100
1k
FREQUENCY (Hz)
10k
6656 G20
6656fa
LT6656
Typical Performance Characteristics
Output Impedance vs Frequency
100
10
1.25V OPTION
2.5V OPTION
5V OPTION
100
1k
FREQUENCY (Hz)
1k
100
10
1
10k
IL = 0, CL = 1µF
IL = 0, CL = 10µF
IL = 100µA, CL = 1µF
IL = 100µA, CL = 10µF
10
100
1k
FREQUENCY (Hz)
6656 G21
TA = 125°C
TA = 85°C
TA = 25°C
TA = –55°C
0
ALL OPTIONS
VIN = GND
TA = 125°C
TA = 85°C
TA = 25°C
TA = –55°C
0
5
10
15
OUTPUT VOLTAGE (V)
15
10
2.5V OPTION
5
100
1k
FREQUENCY (Hz)
TIME (1s/DIV)
6656 G13
Output Noise Voltage Spectrum
vs Load Capacitance
IL = 0
IL = 10µA
IL = 250µA
IL = 1mA
12
10
8
6
4
10k
6656 G24
0
40
2.5V OPTION
35 VIN = 3V
CL = 47µF
IL = 0
30
25
20
CL = 4.7µF
15
CL = 0.47µF
10
5
2
1.25V OPTION
10
2.5V OPTION
14 VIN = 3V
CL = 1µF
NOISE VOLTAGE (µV/√Hz)
NOISE VOLTAGE (µVRMS/√Hz)
5V OPTION
0
16
VIN = VOUT + 5V
CL = 1µF
IL = 0
20
ALL OPTIONS
VIN = VOUT + 0.5V
CL = 1µF
IL = 0
20
Output Voltage Noise Spectrum
vs Load Current
Output Voltage Noise Spectrum
25
10m
6656 G12
6656 G11
30
100µ
1m
LOAD CURRENT (A)
Output Noise 0.1Hz to 10Hz
10
1
–2 –4 –6 –8 –10 –12 –14 –16 –18 –20
INPUT VOLTAGE (V)
TA = 125°C
TA = 85°C
TA = 25°C
TA = –55°C
6656 G07
OUTPUT NOISE (20ppm/DIV)
10
REVERSE OUTPUT CURRENT (µA)
REVERSE INPUT CURRENT (µA)
ALL OPTIONS
VOUT = GND
100
0
10
Reverse Output Current
100
1
100
6656 G22
Reverse Input Current
1000
ALL OPTIONS
VIN = VOUT + 0.5V
CL = 1µF
1
10µ
10k
NOISE VOLTAGE (µV/√Hz)
10
2.5V OPTION
VIN = 3V
1000
GROUND CURRENT (µA)
VIN = VOUT + 0.5V
CL = 1µF
IL = 0
1k
1
Ground Current vs Load Current
Output Impedance vs Frequency
10k
OUTPUT IMPEDANCE (Ω)
OUTPUT IMPEDANCE (Ω)
10k
10
100
1k
FREQUENCY (Hz)
10k
6656 G14
0
1
10
100
FREQUENCY (Hz)
1k
6656 G15
6656fa
LT6656
Typical Performance Characteristics
250
VIN = VOUT + 0.5V
CL = 1µF
400
INTEGRATED NOISE (µVRMS)
INTEGRATED NOISE (µVRMS)
500
Integrated 10Hz to 1kHz Noise
vs Load Current
300
5V OPTION
200
2.5V OPTION
100
ALL OPTIONS
150 CL = 1µF
IL = 0
2.5V OPTION
200
150
100
CL = 0.47µF
CL = 1µF
CL = 10µF
CL = 47µF
50
1.25V OPTION
0
0.1µ
1µ
10µ
100µ
LOAD CURRENT (A)
1m
10m
Long-Term Drift
200
0
0.1µ
1µ
10µ
100µ
LOAD CURRENT (A)
6656 G25
1m
10m
LONG TERM DRIFT (ppm)
Integrated 10Hz to 1kHz Noise
vs Load Current
100
50
0
–50
–100
–150 5 TYPICAL PARTS
SOLDERED ONTO PCB
–200
0 100 200 300 400 500 600 700 800 900 1000
HOURS
6656 G16
6656 G23
Pin Functions
GND* (Pin 1): Internal Function. This pin must be tied
to ground.
NC (Pin 5): Not internally connected. May be tied to VIN,
VOUT, GND or floated.
GND (Pin 2): Device Ground.
VOUT (Pin 6): Output Voltage. An output capacitor of 1µF
minimum is required for stable operation.
NC (Pin 3): Not internally connected. May be tied to VIN,
VOUT, GND or floated.
VIN (Pin 4): Power Supply. Bypass VIN with a 0.1µF
capacitor to ground.
Block Diagram
VIN
NC
VOUT
ERROR
AMP
BANDGAP
NC
GND
GND
6656 BD
6656fa
LT6656
Applications Information
Long Battery Life
Output Voltage Options
Series references have a large advantage over shunt style
references. Shunt references require a resistor from the
power supply to operate. This resistor must be chosen
to supply the maximum current that can be demanded by
the load. When the load is not operating at this maximum
current, the shunt reference must always sink this current,
resulting in high dissipation and shortened battery life.
The performance of the LT6656 is consistent for the 2.048V
to 5V options. The 1.25V option has slightly reduced load
regulation, and unlike the higher voltage options, the
minimum operating supply voltage is limited by internal
circuitry rather than the output voltage.
The LT6656 series reference does not require a current
setting resistor and is specified to operate with any supply
from 1.5V to 18V, depending on the output voltage option,
load current and operating temperature (see Dropout
Voltage and Minimum Input Voltage in the Typical Performance Characteristics). When the load does not demand
current, the LT6656 reduces its dissipation and battery life
is extended. If the reference is not delivering load current,
it dissipates only a few µW, yet the same connection can
deliver 5mA of load current when required.
Start-Up
To ensure proper start-up, the output voltage should be
between –0.3V and the rated output voltage. If the output
load may be driven more than 0.3V below ground, a low
forward voltage schottky diode from the output to ground
is required. The turn-on characteristics can be seen in
Figure 1.
VIN
1V/DIV
VOUT
1ms/DIV
6656 F01
Parameters that are based on changes in the output voltage,
such as load regulation and hysteresis, remain proportional
to the output voltage and are specified in relative units,
for example, parts per million (ppm). Parameters that
are not based on changes in the output voltage, such as
supply current and reverse input current, are the same
for all options.
The bandwidth of the LT6656 decreases with higher output
voltage. This causes parameters that are affected by both
bandwidth and output voltage, such as wideband noise
and output impedance, to increase less with higher output
voltage.
Bypass and Load Capacitance
The LT6656 voltage reference needs a 0.1μF input bypass
capacitor placed within an inch of the input pin. An additional 2.2μF capacitor should be used when the source
impedance of the input supply is high or when driving
heavy loads. The bypassing of other local devices may
serve as the required components. The output of the
LT6656 requires a capacitance of 1µF or larger. The LT6656
is stable with a wide variety of capacitor types including
ceramic, tantalum and electrolytic due to its low sensitivity
to ESR (5Ω or less).
The test circuit in Figure 2 was used to test the response
and stability of the LT6656 to various load currents. The
resultant transient responses can be seen in Figure 3 and
Figure 4. The large scale output response to a 500mV input
step is shown in Figure 5 with a more detailed photo and
description in the Output Settling section.
Figure 1. LT6656-2.5 Turn-On Characteristics, CL = 1µF
VIN
3V
CIN
0.1µF
R2
LT6656-2.5
3V
VGEN
CL
1µF
R1
2N7000
6656 F02
Figure 2. Transient Load Test Circuit
6656fa
LT6656
Applications Information
0µA
IOUT
100µA
2.52V
VOUT 2.50V
2.48V
5ms/DIV
6656 F03
Figure 3. Transient Response, 0µA to 100µA Load Step
(R2 = 24.9k, R1 = Open)
1mA
IOUT
2mA
In application circuits where the LT6656 is experiencing
a load step greater than 5µA, such as an ADC reference
and supply implementation, the settling time will typically
remain less than 8ms, regardless of the output settling
from a previous load step.
The settling time can be estimated by the following
equation:
2.52V
VOUT 2.50V
Settling time ≈
2.48V
5ms/DIV
6656 F04
Figure 4. Transient Response, 1mA to 2mA Load Step
(R1 = R2 = 2.49k)
VIN
The settling time is typically less than 8ms for output loads
up to 5mA, however the time required to settle when the
load is turned off or in response to an input transient can be
significantly longer due to the dead band (shown in Figure
7). During this interval the output stage is neither sourcing
nor sinking current so the settling time is dominated by
the ability of the application circuit to discharge the output
capacitor to the voltage at which the sourcing circuitry
in the output stage reactivates. Larger load currents will
decrease the settling time and higher output capacitance
will increase the settling time.
The deadband is ≈7mV for the 2.5V option, is proportional
to the voltage option (i.e., ≈14mV for the 5V option) and
can double due to variations in processing.
The graph in Figure 6 shows the settling time versus load
step with no load and with a constant 2µA load applied.
Note the settling time can be longer with load steps that
are not large enough to activate the sinking side of the
output stage.
3.25V
2.75V
2.7V
30
2.3V
5ms/DIV
6656 F05
Figure 5. Output Response to 0.5VP-P Step on VIN, CL = 1µF, IL = 0
Output Settling
The output of the LT6656 is primarily designed to source
current into a load, but is capable of sinking current to
aid in output transient recovery. The output stage uses a
class B architecture to minimize quiescent current and
has a crossover dead band as the output transitions from
sourcing to sinking current.
OUTPUT SETTLING TIME (ms)
VOUT 2.5V
10
2(Deadband)(CL )
+ ( VOUT )(0.8ms / V)
IL
2.5V OPTION
VIN = 3V
25 CL = 1µF
∆IL = LOAD
STEP TO ZERO
20
15
∆IL = LOAD
STEP TO 2µA
10
5
0
0.001
∆IL = ZERO TO
LOAD STEP
0.01
0.1
LOAD STEP (mA)
1
10
6656 F06
Figure 6. Output Settling Time to 0.05% vs Load Step
6656fa
LT6656
Applications Information
VIN
input pulled to ground, the reverse output protection of
the LT6656 limits the output current to typically less than
30µA. The current versus reverse voltage is shown in the
Typical Performance Characteristics section.
3.25V
2.75V
IL = 0
Long-Term Drift
VOUT
10mV/DIV
The photo in Figure 7 shows the output response to a 0.5V
input step in both a no-load and 5µA load condition. In
the no-load condition only the bias current of the internal
bandgap reference (about 400nA) is available to discharge
the output capacitor.
Long-term drift cannot be extrapolated from accelerated
high temperature testing. This erroneous technique gives
drift numbers that are wildly optimistic. A more realistic
way to determine long-term drift is to measure it over the
time interval of interest. The LT6656 drift data was taken
over 100 parts that were soldered onto PC boards in a
typical application configuration. The boards were then
placed into a constant temperature oven with TA = 30°C,
their outputs scanned regularly and measured with an
8.5 digit DVM. The parts chosen in the Long Term Drift
curves in the Typical Performance Characteristics section
represent high, low and typical units.
Output Noise
Hysteresis
IL = 5µA
5ms/DIV
6656 F07
Figure 7. Detailed Output Response to a 0.5V Input Step,
CIN = CL = 1µF
Low frequency noise is proportional to the output voltage
and is insensitive to output current and moderate levels
of output capacitance.
Wideband noise increases less with higher output voltage
and is proportional to the bandwidth of the output stage,
increasing with higher load current and lower output
capacitance.
Peaking in the noise response is another factor contributing to the output noise level for a given frequency range.
Noise peaking can be reduced by increasing the size of the
output capacitor when driving heavier loads, or conversely,
reducing the size of the output capacitor when driving
lighter loads. Noise plots in the Typical Performance Curves
section show noise spectrum with various load currents
and output capacitances.
Internal Protection
The LT6656 incorporates several internal protection
features that make it ideal for use in battery powered
systems. Reverse input protection limits the input current to typically less than 40µA when either the LT6656
or the battery is installed backwards. In systems where
the output can be held up by a backup battery with the
Hysteresis on the LT6656 is measured in two steps, for
example, from 25°C to –40°C to 25°C, then from 25°C to
85°C to 25°C, for the industrial temperature range. This
two-step cycle is repeated several times and the maximum
hysteresis from all the partial cycles is noted. Unlike other
commonly used methods for specifying hysteresis, this
ensures the worst-case hysteresis is included, whether it
occurs in the first temperature excursion or the last.
Results over both commercial and industrial temperature
ranges are shown in Figure 8 and Figure 9. The parts cycled
over the higher temperature range have a higher hysteresis
than those cycled over the lower range.
Power Dissipation
The LT6656 will not exceed the maximum junction temperature when operating within its specified temperature
range of –40°C to 85°C, maximum input voltage of 18V
and specified load current of 5mA.
IR Reflow Shift
The different expansion and contraction rates of the materials that make up the LT6656 package may induce small
stresses on the die that can cause the output to shift during
6656fa
11
LT6656
Applications Information
30
NUMBER OF UNITS
2.5V OPTION
VIN = 3V
25 CL = 1µF
IL = 0
0°C TO 25°C
70°C TO 25°C
300
380s
TP = 260°C
TL = 217°C
TS(MAX) = 200°C
225
20
TS = 190°C
15
RAMP
DOWN
tP
30s
T = 150°C
150
tL
130s
RAMP TO
150°C
10
75
40s
5
120s
0
–60
–40
–20
0
20
HYSTERESIS (ppm)
40
0
60
0
2
6656 F08
Figure 8. 0°C to 70°C Hysteresis
20
18
12
10
8
6
4
10
6656 F10
2.5V OPTION
VIN = 3V
6 C = 1µF
L
IL = 0
5
3 CYCLES
1 CYCLE
4
3
2
1
2
0
7
2.5V OPTION
VIN = 3V
CL = 1µF
IL = 0
14
8
Figure 10. Lead Free Reflow Profile Due to IR Reflow
NUMBER OF UNITS
NUMBER OF UNITS
16
–40°C TO 25°C
85°C TO 25°C
4
6
MINUTES
–160 –120 –80 –40 0 40 80 120 160
HYSTERESIS (ppm)
0
0 20
60
100
140
180
220
CHANGE IN OUTPUT VOLTAGE (ppm)
6656 F11
6656 F09
Figure 9. –40°C to 85°C Hysteresis
IR reflow. Common lead free IR reflow profiles reach over
250°C, considerably more than lead solder profiles. The
higher reflow temperature of the lead free parts exacerbates
the issue of thermal expansion and contraction causing
the output shift to generally be greater than with a leaded
reflow process.
The lead free IR reflow profile used to experimentally
measure the output voltage shift in the LT6656-2.5 is
shown in Figure 10. Similar results can be expected using
a convection reflow oven. Figure 11 shows the change
in output voltage that was measured for parts that were
run through the reflow process for 1 cycle and also 3
cycles. The results indicate that the standard deviation
of the output voltage increases with a positive mean shift
of 120ppm. While there can be up to 220ppm of output
voltage shift, additional drift of the LT6656 after IR reflow
does not vary significantly.
Figure 11. Output Voltage Shift Due to IR Reflow,
Peak Temperature = 260°C
PC Board Layout
The mechanical stress of soldering a surface mount voltage reference to a PC board can cause the output voltage
to shift and temperature coefficient to change.
To reduce the effects of stress-related shifts, position
the reference near the short edge of the PC board or in a
corner. In addition, slots can be cut into the board on two
sides of the device. See Application Note AN82 for more
information. http://www.linear.com
The input and output capacitors should be mounted close
to the package. The GND and VOUT traces should be as
short as possible to minimize the voltage drops caused
by load and ground currents. Excessive trace resistance
directly impacts load regulation.
6656fa
12
LT6656
Typical Applications
Regulator Reference
Low Power ADC Reference
The robust input and output of the LT6656 along with its
high output current make it an excellent precision low
power regulator as well as a reference. The LT6656 would
be a good match with a small, low power microcontroller.
Using the LT6656 as a regulator reduces power consumption, decreases solution size and increases the accuracy
of the microcontroller’s on board ADC.
Low power ADCs draw only a few µAs during their idle
period and well over 100µA during conversions. Despite
these surges of current, the ADC in reality can have very
low power consumption. Figure 13 shows the LTC2480, a
low power delta sigma ADC. When the ADC is disabled its
quiescent current (IQ) is roughly 1µA, during conversion the
IQ jumps up to 160µA. In reality, the power consumption
is not only based on the IQ during conversion, but the real
power consumption of the ADC is set by the conversion
time and the sample rate. The LTC2480 shown in Figure 13
has a conversion time of 160ms which sets the maximum
sample rate of 6 samples per second. The maximum sample
rate also sets the maximum current consumption to 160µA,
but at slower sample rates the ADC will have significantly
lower average current draw. If the ADC is sampled at 1
sample per second the average current drawn by the ADC
during a 1 second interval would only be 26.4µA. When
taking into consideration the current drawn by the reference, the total current draw is only 27.4µA. This system is
greatly simplified because the precision reference does not
need to be cycled on and off to save power. Furthermore,
leaving the reference on continuously eliminates concern
for turn-on settling time.
3V ≤ VIN ≤ 18V
0.1µF
IN
LT6656-2.5
OUT
MCU
VCC/VREF
10µF
PB0/AIN0/AREF/MOSI
PB1/INT0/AIN1/MISO/OC1A
PB2/ADC1/SCK/T0/INT0
PB3/ADC2
PB4/ADC3
PB5/RESET/ADC0
5
6
7
2
3
1
GND
6656 TA02
Figure 12. Microcontroller Reference and Regulator
5.1V ≤ VIN ≤ 18V
0.1µF
IN
LT6656-5
OUT
4.7µF
IN+
DIFFERENTIAL INPUT
±VREF • 0.5 (±2.5V)
REF
VCC
LTC2480
IN–
AT 1sps, IQ = 27.4µA
CS
SCK
SDO
6656 TA05
Figure 13. Low Power ADC Reference
6656fa
13
LT6656
Typical Applications
Extended Supply Range Reference
VCC
UP TO 160V
330k
MMBT5551
BZX584C12
0.1µF
2.2µF
IN
VOUT
OUT
LT6656-2.5
1µF
6656 TA03
Boosted Output Current Reference
3.6V ≤ VCC ≤ 18V
2207
+
10µF
2N2905
0.1µF
IN
VOUT
40mA MAX
OUT
LT6656-2.5
1µF
6656 TA04
Micropower Regulator, IQ = 2µA, Sink Up to 8mA
3V ≤ VCC ≤ 18V
IN
LT6656-2.5
+
OUT
0.1µF
1µF
2.5V
LT6003
–
6656 TA06
ADC Reference and Bridge Excitation Supply
3.8V ≤ VIN ≤ 18V
IN
0.1µF
LT6656-3.3
3.3V ≤ VCC ≤ 5.5V
OUT
1µF
10k
0.1µF
10k
0.1µF
IN–
VCC
LTC2452
IN+
10k
VREF
10µF
CS
SCK
SDO
0.1µF
6656fa
14
LT6656
Typical Applications
Low Power Precision High Voltage Supply Monitor, IQ = 1.4µA, High Voltage Supply Load = 10µA
100V
105V OVERVOLTAGE THRESHOLD
VCC
9.53M
3
+
4
–
6.5V ≤ VCC ≤ 10V
IN
LT6656-5
OUT
0.1µF
1µF
475k
7
OVERVOLTAGE FLAG
LTC1540
5
6
1, 2
6656 TA08
2-Terminal Current Source
+
+
IN
LT6656-1.25
GND
0.1µF
OUT
VREF
LT6003
R1
–
1µF
R3
R2
–
IOUT 6656 TA09
VREF ¥ R2 ´
1
R1 §¦ R3 ¶µ
Precision Current and Boosted Reference, IQ = 5.5µA
249k
2N5086
VCC
1k
+
+
–
–
LT6004
2.75V
LT6004
200k
1µA OUT
3V ≤ VCC ≤ 16V
IN
0.1µF
LT6656-2.5
2M
OUT
2.5V
1µF
6656 TA10
6656fa
15
LT6656
Package Description
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
0.62
MAX
2.90 BSC
(NOTE 4)
0.95
REF
1.22 REF
3.85 MAX 2.62 REF
1.4 MIN
2.80 BSC
1.50 – 1.75
(NOTE 4)
PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.30 – 0.45
6 PLCS (NOTE 3)
0.95 BSC
0.80 – 0.90
0.20 BSC
0.01 – 0.10
1.00 MAX
DATUM ‘A’
0.30 – 0.50 REF
0.09 – 0.20
(NOTE 3)
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
1.90 BSC
S6 TSOT-23 0302 REV B
6656fa
16
LT6656
Revision History
REV
DATE
DESCRIPTION
PAGE NUMBER
A
7/10
Voltage options added (1.25, 2.048, 3, 3.3), reflected throughout the data sheet
1 to 18
6656fa
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.
17
LT6656
Typical Application
Reference Regulator for Micropower DAC, Total IQ = 4.8µA
5.1V ≤ VIN ≤ 18V
IN
LT6656-5
OUT
0.1µF
5V
10µF
VREF
VCC
CS
SCK
SDI
DAC A
0V TO 5V OUTPUT
DAC B
0V TO 5V OUTPUT
LTC1662
GND
6656 TA07
Related Parts
PART NUMBER
DESCRIPTION
COMMENTS
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Micropower Comparator with Reference
3.7µA Max Supply Current, 1% 1.182V Reference, MSOP, PDIP and SO-8 Packages
LT1460
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0.075% Max, 10ppm/°C Max Drift, 2.5V, 5V and 10V Versions,MSOP, PDIP, SO-8,
SOT-23 and TO-92 Packages
LT1461
Micropower Precision LDO Series Reference
3ppm/°C Max Drift, 0°C to 70°C, –40°C to 85°C, –40°C to 125°C Options in SO-8
LT1495
1.5µA Precision Rail-to-Rail Dual Op Amp
1.5µA Max Supply Current, 100pA Max IOS
LTC1540
Nanopower Comparator with Reference
600nA Max Supply Current, 2% 1.182V Reference, MSOP and SO-8 Packages
LT1634
Micropower Precision Shunt Voltage
Reference
0.05% Max, 10ppm/°C Max Drift, 1.25V, 2.5V, 4.096V, 5V, 10µA Maximum Supply
Current
LT1790
Micropower Precision Series Reference
0.05% Max, 10ppm/°C Max, 60µA Supply, SOT23 Package
LTC1798
6µA Low Dropout Series Reference
Available in Adjustable, 2.5V, 3V, 4.096V and 5V
LT6003
1.6V, 1µA Precision Rail-to-Rail Op Amp
1µA Max Supply Current, 1.6V Minimum Operating Voltage, SOT-23 Package
LT6650
Micropower Reference with Buffer Amplifier
0.05% Max, 5.6µA Supply, SOT-23 Package
LT6660
Tiny Micropower Series Reference
0.2% Max, 20ppm/°C Max, 20mA Output Current, 2mm × 2mm DFN
LT6700
Micropower, Low Voltage Dual Comparator
with 40mV Reference
6.5µA Supply Current, 1.4V Minimum Operating Voltage
6656fa
18 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
LT 0710 REV A • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 2010
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