LT6656
1µA Precision Series
Voltage Reference
DESCRIPTION
FEATURES
Ultralow Supply Current: 850nA
n Low Drift
A Grade: 10 ppm/°C Max
B Grade: 20 ppm/°C Max
n High Accuracy
A Grade: 0.05% Max
B Grade: 0.1% Max
n Long-Term Drift: 15ppm/√kHr (LS8 Package)
n No Humidity Sensitivity (LS8 Package)
n High Output Drive Current: 5mA Min
n Low Dropout Voltage: 10mV Max
n Fully Specified from –40°C to 85°C
n Operational from –55°C to 125°C
n Wide Supply Range to 18V
n Reverse Input/Output Protection
n Available Output Voltage Options:
1.25V, 2.048V, 2.5V, 2.8V, 3V, 3.3V, 4.096V and 5V
n Available in Low Profile (1mm) ThinSOT™,
(2mm × 2mm) DFN and High Stability Hermetic
(5mm × 5mm) LS8 Packages
n
APPLICATIONS
The LT®6656 is a tiny 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, (2mm ×
2mm) DFN, and 8-lead LS8 Packages. The LS8 is a 5mm
× 5mm surface mount hermetic package that provides
outstanding stability.
Precision A/D and D/A Converters
n Portable Gas Monitors
n Battery- or Solar-Powered Systems
n Precision Regulators
n Low Voltage Signal Processing
n Micropower Remote Sensing
n
All registered trademarks and trademarks are the property of their respective owners.
TYPICAL APPLICATION
Output Voltage Temperature Drift
2.503
Basic Connection
0.1µF
VIN
LT6656-2.5
VOUT
GND
2.502
VOUT
2.5V
1µF
6656 TA01a
VOUT (V)
2.51V ≤ VIN ≤ 18V
38 TYPICAL UNITS
LT6656-2.5
2.501
2.500
2.499
2.498
–40
–20
0
20
40
TEMPERATURE (°C)
60
80
6652 TA01b
Rev D
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1
LT6656
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Voltage............................................................±20V
Output Voltage............................................ –0.3V to 20V
Output Voltage Above Input Voltage..........................20V
Specified Temperature Range (Note 2)
Commercial.............................................. 0°C to 70°C
Industrial..............................................–40°C to 85°C
Operating Temperature Range (Note 2).. –55°C to 125°C
Output Short Circuit Duration .......................... Indefinite
Junction Temperature ........................................... 150°C
Storage Temperature Range (Note 3)...... –65°C to 150°C
Lead Temperature (Soldering, 10 sec.)
TSOT-23 (Note 4)............................................... 300°C
PIN CONFIGURATION
TOP VIEW
GND* 1
TOP VIEW
VIN
TOP VIEW
NC 1
6 VOUT
GND 2
5 NC
GND 2
NC 3
4 VIN
GND* 3
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
TJMAX = 150°C, θJA = 230°C/W
*CONNECT PIN TO DEVICE GND (PIN 2)
7
GND*
6 VIN
NC
1
5 NC
NC
2
GND*
3
4 VOUT
DC PACKAGE
6-LEAD (2mm × 2mm) PLASTIC DFN
TJMAX = 125°C, θJA = 102°C/W
EXPOSED PAD (PIN 7) MUST BE CONNECTED TO GND
8
4
7
NC
6
VOUT
5
VOUT
GND
LS8 PACKAGE
8-PIN LEADLESS CHIP CARRIER (5mm × 5mm)
TJMAX = 150°C, θJA = 125°C/W
*CONNECT PIN TO DEVICE GND (PIN 4)
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL (MINI)
LT6656ACS6-1.25#TRMPBF
LT6656BCS6-1.25#TRMPBF
LT6656AIS6-1.25#TRMPBF
LT6656BIS6-1.25#TRMPBF
LT6656ACS6-2.048#TRMPBF
TAPE AND REEL
LT6656ACS6-1.25#TRPBF
LT6656BCS6-1.25#TRPBF
LT6656AIS6-1.25#TRPBF
LT6656BIS6-1.25#TRPBF
LT6656ACS6-2.048#TRPBF
PART MARKING*
LTFNK
LTFNK
LTFNK
LTFNK
LTFNN
PACKAGE DESCRIPTION
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
SPECIFIED TEMPERATURE RANGE
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
LT6656BCS6-2.048#TRMPBF
LT6656AIS6-2.048#TRMPBF
LT6656BIS6-2.048#TRMPBF
LT6656ACS6-2.5#TRMPBF
LT6656BCS6-2.5#TRMPBF
LT6656AIS6-2.5#TRMPBF
LT6656BIS6-2.5#TRMPBF
LT6656ACS6-3#TRMPBF
LT6656BCS6-3#TRMPBF
LT6656AIS6-3#TRMPBF
LT6656BIS6-3#TRMPBF
LT6656ACS6-3.3#TRMPBF
LT6656BCS6-3.3#TRMPBF
LT6656AIS6-3.3#TRMPBF
LT6656BIS6-3.3#TRMPBF
LT6656BCS6-2.048#TRPBF
LT6656AIS6-2.048#TRPBF
LT6656BIS6-2.048#TRPBF
LT6656ACS6-2.5#TRPBF
LT6656BCS6-2.5#TRPBF
LT6656AIS6-2.5#TRPBF
LT6656BIS6-2.5#TRPBF
LT6656ACS6-3#TRPBF
LT6656BCS6-3#TRPBF
LT6656AIS6-3#TRPBF
LT6656BIS6-3#TRPBF
LT6656ACS6-3.3#TRPBF
LT6656BCS6-3.3#TRPBF
LT6656AIS6-3.3#TRPBF
LT6656BIS6-3.3#TRPBF
LTFNN
LTFNN
LTFNN
LTFGW
LTFGW
LTFGW
LTFGW
LTFNQ
LTFNQ
LTFNQ
LTFNQ
LTFNS
LTFNS
LTFNS
LTFNS
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
2
Rev D
For more information www.analog.com
LT6656
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL (MINI)
TAPE AND REEL
PART MARKING* PACKAGE DESCRIPTION
LT6656ACS6-4.096#TRMPBF LT6656ACS6-4.096#TRPBF LTFNV
6-Lead Plastic TSOT-23
LT6656BCS6-4.096#TRMPBF LT6656BCS6-4.096#TRPBF LTFNV
6-Lead Plastic TSOT-23
LT6656AIS6-4.096#TRMPBF LT6656AIS6-4.096#TRPBF LTFNV
6-Lead Plastic TSOT-23
LT6656BIS6-4.096#TRMPBF LT6656BIS6-4.096#TRPBF LTFNV
6-Lead Plastic TSOT-23
LT6656ACS6-5#TRMPBF
LT6656ACS6-5#TRPBF
LTFNX
6-Lead Plastic TSOT-23
LT6656BCS6-5#TRMPBF
LT6656BCS6-5#TRPBF
LTFNX
6-Lead Plastic TSOT-23
LT6656AIS6-5#TRMPBF
LT6656AIS6-5#TRPBF
LTFNX
6-Lead Plastic TSOT-23
LT6656BIS6-5#TRMPBF
LT6656BIS6-5#TRPBF
LTFNX
6-Lead Plastic TSOT-23
LT6656ACDC-1.25#TRMPBF LT6656ACDC-1.25#TRPBF LFNM
6-Lead (2mm × 2mm) Plastic DFN
LT6656BCDC-1.25#TRMPBF LT6656BCDC-1.25#TRPBF LFNM
6-Lead (2mm × 2mm) Plastic DFN
LT6656AIDC-1.25#TRMPBF LT6656AIDC-1.25#TRPBF
LFNM
6-Lead (2mm × 2mm) Plastic DFN
LT6656BIDC-1.25#TRMPBF LT6656BIDC-1.25#TRPBF
LFNM
6-Lead (2mm × 2mm) Plastic DFN
LT6656ACDC-2.048#TRMPBF LT6656ACDC-2.048#TRPBF LFNP
6-Lead (2mm × 2mm) Plastic DFN
LT6656BCDC-2.048#TRMPBF LT6656BCDC-2.048#TRPBF LFNP
6-Lead (2mm × 2mm) Plastic DFN
LT6656AIDC-2.048#TRMPBF LT6656AIDC-2.048#TRPBF LFNP
6-Lead (2mm × 2mm) Plastic DFN
LT6656BIDC-2.048#TRMPBF LT6656BIDC-2.048#TRPBF LFNP
6-Lead (2mm × 2mm) Plastic DFN
LT6656ACDC-2.5#TRMPBF
LT6656ACDC-2.5#TRPBF
LFGX
6-Lead (2mm × 2mm) Plastic DFN
LT6656BCDC-2.5#TRMPBF
LT6656BCDC-2.5#TRPBF
LFGX
6-Lead (2mm × 2mm) Plastic DFN
LT6656AIDC-2.5#TRMPBF
LT6656AIDC-2.5#TRPBF
LFGX
6-Lead (2mm × 2mm) Plastic DFN
LT6656BIDC-2.5#TRMPBF
LT6656BIDC-2.5#TRPBF
LFGX
6-Lead (2mm × 2mm) Plastic DFN
LT6656AIDC-2.8#TRMPBF
LT6656AIDC-2.8#TRPBF
LHQX
6-Lead (2mm × 2mm) Plastic DFN
LT6656ACDC-3#TRMPBF
LT6656ACDC-3#TRPBF
LFNR
6-Lead (2mm × 2mm) Plastic DFN
LT6656BCDC-3#TRMPBF
LT6656BCDC-3#TRPBF
LFNR
6-Lead (2mm × 2mm) Plastic DFN
LT6656AIDC-3#TRMPBF
LT6656AIDC-3#TRPBF
LFNR
6-Lead (2mm × 2mm) Plastic DFN
LT6656BIDC-3#TRMPBF
LT6656BIDC-3#TRPBF
LFNR
6-Lead (2mm × 2mm) Plastic DFN
LT6656ACDC-3.3#TRMPBF
LT6656ACDC-3.3#TRPBF
LFNT
6-Lead (2mm × 2mm) Plastic DFN
LT6656BCDC-3.3#TRMPBF
LT6656BCDC-3.3#TRPBF
LFNT
6-Lead (2mm × 2mm) Plastic DFN
LT6656AIDC-3.3#TRMPBF
LT6656AIDC-3.3#TRPBF
LFNT
6-Lead (2mm × 2mm) Plastic DFN
LT6656BIDC-3.3#TRMPBF
LT6656BIDC-3.3#TRPBF
LFNT
6-Lead (2mm × 2mm) Plastic DFN
LT6656ACDC-4.096#TRMPBF LT6656ACDC-4.096#TRPBF LFNW
6-Lead (2mm × 2mm) Plastic DFN
LT6656BCDC-4.096#TRMPBF LT6656BCDC-4.096#TRPBF LFNW
6-Lead (2mm × 2mm) Plastic DFN
LT6656AIDC-4.096#TRMPBF LT6656AIDC-4.096#TRPBF LFNW
6-Lead (2mm × 2mm) Plastic DFN
LT6656BIDC-4.096#TRMPBF LT6656BIDC-4.096#TRPBF LFNW
6-Lead (2mm × 2mm) Plastic DFN
LT6656ACDC-5#TRMPBF
LT6656ACDC-5#TRPBF
LFNY
6-Lead (2mm × 2mm) Plastic DFN
LT6656BCDC-5#TRMPBF
LT6656BCDC-5#TRPBF
LFNY
6-Lead (2mm × 2mm) Plastic DFN
LT6656AIDC-5#TRMPBF
LT6656AIDC-5#TRPBF
LFNY
6-Lead (2mm × 2mm) Plastic DFN
LT6656BIDC-5#TRMPBF
LT6656BIDC-5#TRPBF
LFNY
6-Lead (2mm × 2mm) Plastic DFN
LEAD FREE FINISH
PART MARKING*
PACKAGE DESCRIPTION
LT6656AILS8-1.25#PBF†
656125
8-Lead (5mm × 5mm) Ceramic LCC
LT6656BILS8-1.25#PBF†
656125
8-Lead (5mm × 5mm) Ceramic LCC
TRM = 500 pieces. *Temperature grades are identified by a label on the shipping container.
Contact the factory for parts specified with wider operating temperature ranges.
Contact the factory for information on lead based finish parts.
SPECIFIED TEMPERATURE RANGE
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
SPECIFIED TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
†This product is only offered in trays.
Rev D
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3
LT6656
AVAILABLE OPTIONS
SPECIFIED TEMPERATURE RANGE
–40°C TO 85°C
INITIAL ACCURACY
TEMPERATURE
COEFFICIENT
0°C TO 70°C
OUTPUT VOLTAGE
ORDER PART NUMBER*
ORDER PART NUMBER*
1.250V
0.05%
10ppm/°C
LT6656ACS6-1.25
LT6656AIS6-1.25
0.05%
10ppm/°C
N/A
LT6656AILS8-1.25
0.10%
20ppm/°C
LT6656BCS6-1.25
LT6656BIS6-1.25
0.10%
10ppm/°C
LT6656ACDC-1.25
LT6656AIDC-1.25
0.10%
15ppm/°C
N/A
LT6656BILS8-1.25
0.20%
20ppm/°C
LT6656BCDC-1.25
LT6656BIDC-1.25
0.05%
10ppm/°C
LT6656ACS6-2.048
LT6656AIS6-2.048
0.10%
20ppm/°C
LT6656BCS6-2.048
LT6656BIS6-2.048
0.10%
10ppm/°C
LT6656ACDC-2.048
LT6656AIDC-2.048
0.20%
20ppm/°C
LT6656BCDC-2.048
LT6656BIDC-2.048
0.05%
10ppm/°C
LT6656ACS6-2.5
LT6656AIS6-2.5
0.10%
20ppm/°C
LT6656BCS6-2.5
LT6656BIS6-2.5
0.10%
10ppm/°C
LT6656ACDC-2.5
LT6656AIDC-2.5
0.20%
20ppm/°C
LT6656BCDC-2.5
LT6656BIDC-2.5
2.048V
2.500V
2.800V
0.10%
10ppm/°C
N/A
LT6656AIDC-2.8
3.000V
0.05%
10ppm/°C
LT6656ACS6-3
LT6656AIS6-3
0.10%
20ppm/°C
LT6656BCS6-3
LT6656BIS6-3
0.10%
10ppm/°C
LT6656ACDC-3
LT6656AIDC-3
0.20%
20ppm/°C
LT6656BCDC-3
LT6656BIDC-3
0.05%
10ppm/°C
LT6656ACS6-3.3
LT6656AIS6-3.3
0.10%
20ppm/°C
LT6656BCS6-3.3
LT6656BIS6-3.3
0.10%
10ppm/°C
LT6656ACDC-3.3
LT6656AIDC-3.3
0.20%
20ppm/°C
LT6656BCDC-3.3
LT6656BIDC-3.3
0.05%
10ppm/°C
LT6656ACS6-4.096
LT6656AIS6-4.096
0.10%
20ppm/°C
LT6656BCS6-4.096
LT6656BIS6-4.096
0.10%
10ppm/°C
LT6656ACDC-4.096
LT6656AIDC-4.096
0.20%
20ppm/°C
LT6656BCDC-4.096
LT6656BIDC-4.096
0.05%
10ppm/°C
LT6656ACS6-5
LT6656AIS6-5
0.10%
20ppm/°C
LT6656BCS6-5
LT6656BIS6-5
0.10%
10ppm/°C
LT6656ACDC-5
LT6656AIDC-5
0.20%
20ppm/°C
LT6656BCDC-5
LT6656BIDC-5
3.300V
4.096V
5.000V
*See Order Information section for complete part number listing.
4
Rev D
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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
LT6656ACS6, LT6656AIS6,
LT6656AILS8
LT6656BCS6, LT6656BIS6,
LT6656BILS8
LT6656ACDC, LT6656AIDC
LT6656BCDC, LT6656BIDC
–0.05
–0.1
–0.1
–0.2
Output Voltage Temperature Coefficient (Note 5)
LT6656A
LT6656B
Line Regulation
VIN = (VOUT + 0.5V) to 18V
LT6656-2.048, LT6656-2.5, LT6656-2.8,
LT6656-3, LT6656-3.3, LT6656-4.096,
LT6656-5
VIN = 2.2V to 18V
LT6656-1.25
Load Regulation (Note 6)
Dropout Voltage (Note 7)
IL = 5mA, Sourcing
LT6656-2.048, LT6656-2.5, LT6656-2.8,
LT6656-3, LT6656-3.3, LT6656-4.096,
LT6656-5
l
VIN – VOUT, ∆VOUT Error ≤ 0.1%
IL = 0
LT6656-2.048, LT6656-2.5, LT6656-2.8,
LT6656-3, LT6656-3.3, LT6656-4.096,
LT6656-5
IL = 0, ∆VOUT Error ≤ 0.1%
LT6656-1.25
0°C ≤ TA ≤ 70°C
–40°C ≤ TA ≤ 85°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
135
250
500
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
Supply Current
0.05
0.1
0.1
0.2
ppm/°C
ppm/°C
l
IL = 5mA, Sourcing
LT6656LS8-1.25
UNITS
10
20
l
l
MAX
5
12
l
IL = 5mA, Sourcing
LT6656S6-1.25, LT6656DC-1.25
IL = 5mA, Sourcing
LT6656-2.048, LT6656-2.5, LT6656-2.8,
LT6656-3, LT6656-3.3, LT6656-4.096,
LT6656-5
Minimum Input Voltage
l
l
TYP
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 8)
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
Rev D
For more information www.analog.com
5
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.
Long Term Drift of Output Voltage (Note 9)
LT6656S6, LT6656DC
LT6656LS8
50
15
ppm/√kHr
ppm/√kHr
Hysteresis (Note 10)
LT6656S6, LT6656DC
∆T = 0°C to 70°C
∆T = –40°C to 85°C
25
70
ppm
ppm
LT6656LS8
∆T = 0°C to 70°C
∆T = –40°C to 85°C
15
55
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 LT6656C is guaranteed to meet specified performance from
0°C to 70°C. The LT6656C is designed, characterized and expected to
meet specified performance from –40°C to 85°C but is not tested or
QA sampled at these temperatures. The LT6656I is guaranteed to meet
specified performance from –40°C to 85°C. By design, the LT6656 is
guaranteed functional over the operating temperature range of –55°C to
125°C.
Note 3: If the LT6656 is stored outside of the specified temperature range,
the output may shift due to hysteresis.
Note 4: The stated temperature is typical for soldering of the leads during
manual rework. For detailed IR reflow recommendations, refer to the
Applications section.
Note 5: Temperature coefficient is measured by dividing the maximum
change in output voltage by the specified temperature range.
Note 6: 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 7: Excludes load regulation errors.
Note 8: 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 9: 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 10: 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 hysteresis is the
worst-case of 25°C to cold to 25°C or 25°C to hot to 25°C, preconditioned
by one thermal cycle.
TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage Temperature Drift
200
6000
5000
4000
3000
2000
120
100
80
60
40
0
20
6652 G01
6
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
Rev D
For more information www.analog.com
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)
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)
6656 G08
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
1k
100
FREQUENCY (Hz)
10k
6656 G20
Rev D
For more information www.analog.com
7
LT6656
TYPICAL PERFORMANCE CHARACTERISTICS
Output Impedance vs Frequency
100
10
1.25V OPTION
2.5V OPTION
5V OPTION
1k
100
FREQUENCY (Hz)
1k
100
10
1
10k
IL = 0, CL = 1µF
IL = 0, CL = 10µF
IL = 100µA, CL = 1µF
IL = 100µA, CL = 10µF
10
1k
100
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
1k
100
FREQUENCY (Hz)
Output Noise Voltage Spectrum
vs Load Capacitance
IL = 0
IL = 10µA
IL = 250µA
IL = 1mA
12
10
8
6
4
10k
0
40
2.5V OPTION
35 VIN = 3V
CL = 47µF
IL = 0
30
25
20
CL = 4.7µF
15
CL = 0.47µF
10
5
10
100
1k
FREQUENCY (Hz)
6656 G24
8
TIME (1s/DIV)
6656 G13
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
1m
100µ
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
10k
6656 G14
0
1
10
100
FREQUENCY (Hz)
1k
6656 G15
Rev D
For more information www.analog.com
LT6656
TYPICAL PERFORMANCE CHARACTERISTICS
Integrated 10Hz to 1kHz Noise
vs Load Current
250
VIN = VOUT + 0.5V
CL = 1µF
400
300
5V OPTION
200
2.5V OPTION
100
INTEGRATED NOISE (µVRMS)
INTEGRATED NOISE (µVRMS)
500
Integrated 10Hz to 1kHz Noise
vs Load Current
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
0
0.1µ
10m
1µ
10µ
100µ
LOAD CURRENT (A)
6656 G25
10m
6656 G23
Long-Term Drift
Long-Term Drift (LS8)
200
100
50
0
–50
–100
OUTPUT VOLTAGE CHANGE (ppm)
200
ALL OPTIONS
150 CL = 1µF
IL = 0
LONG TERM DRIFT (ppm)
1m
1.25V OPTION
150 VIN = 2V
CLOAD =1µF
=0
I
100 LOAD
35 TYPICAL PARTS
SOLDERED ONTO PCB
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
–150
–200
0 100 200 300 400 500 600 700 800 900 1000
TIME (HOURS)
6656 G26
Rev D
For more information www.analog.com
9
LT6656
PIN FUNCTIONS
(TSOT-23/DFN)
(LS8)
GND* (Pin 1/Pin 3): Internal Function. This pin must be
tied to ground.
NC (Pins 1, 2, 7): Not Internally Connected. May be tied
to VIN, VOUT, GND or floated.
GND (Pin 2/Pin 2): Device Ground.
GND* (Pin 3): Internal Function. This pin must be tied
to ground.
NC (Pins 3, 5/Pins 1, 5): Not Internally Connected. May
be tied to VIN, VOUT, GND or floated.
VIN (Pin 4/Pin 6): Power Supply. The minimum supply varies with output load and voltage option, see the Dropout
Voltage specification in the Electrical Characteristics table
for further details. The maximum input voltage is 18V.
Bypass VIN with a 0.1µF capacitor to ground.
VOUT (Pin 6/Pin 4): Output Voltage. A minimum output
capacitor of 1µF is required for stable operation.
GND (Pin 4): Device Ground.
VOUT (Pin 5): Output Voltage. A minimum output capacitor of 1µF is required for stable operation.
VOUT (Pin 6): Output Voltage. Tie to pin 5 for best load
regulation.
VIN (Pin 8): Power Supply. Bypass VIN with a 0.1µF
capacitor to ground.
GND*(Exposed Pad Pin 7, DFN Only): This pin must be
tied to ground.
BLOCK DIAGRAM
8
VIN
LS8
VIN
TSOT-23/DFN
NC
1 NC
NC 7
VOUT
2 NC
VOUT
VOUT
ERROR
AMP
BANDGAP
6
5
ERROR
AMP
BANDGAP
NC
GND*
GND*
GND
6656 BD
10
3
GND
4
6656 BD (LS8)
Rev D
For more information www.analog.com
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.
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
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
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.
1V/DIV
VOUT
1ms/DIV
6656 F01
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
Rev D
For more information www.analog.com
11
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
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.
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
2.48V
5ms/DIV
6656 F04
Figure 4. Transient Response, 1mA to 2mA Load Step
(R1 = R2 = 2.49k)
VIN
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
12
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
For more information www.analog.com
Rev D
LT6656
APPLICATIONS INFORMATION
VIN
output can be held up by a backup battery with the 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
VOUT
10mV/DIV
Long-Term Drift
IL = 5µA
5ms/DIV
6656 F07
Figure 7. Detailed Output Response to a 0.5V Input Step,
CIN = CL = 1µF
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.
Output Noise
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
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.
Hysteresis
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. After
preconditioning by one thermal cycle, this two-step cycle
is repeated several times and the maximum hysteresis
from all the partial cycles is noted.
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
Rev D
For more information www.analog.com
13
LT6656
APPLICATIONS INFORMATION
30
20
0°C TO 25°C
70°C TO 25°C
1.25V OPTION
VIN = 2V
CL = 1µF
IL = 0
–40°C TO 25°C
85°C TO 25°C
15
20
NUMBER OF UNITS
NUMBER OF UNITS
2.5V OPTION
VIN = 3V
25 CL = 1µF
IL = 0
15
10
10
5
5
0
–60
–40
–20
0
20
HYSTERESIS (ppm)
40
0
60
6656 F08
6656 F11
Figure 8. LT6656 S6, DC 0°C to 70°C Hysteresis
20
–40°C TO 25°C
85°C TO 25°C
18
NUMBER OF UNITS
16
12
10
8
6
4
2
–160 –120 –80 –40 0 40 80 120 160
HYSTERESIS (ppm)
6656 F09
Figure 9. LT6656 S6, DC –40°C to 85°C Hysteresis
NUMBER OF UNITS
20
1.25V OPTION
VIN = 2V
CL = 1µF
15 IL = 0
0°C TO 25°C
70°C TO 25°C
The lead free IR reflow profile used to experimentally
measure the output voltage shift in the LT6656-2.5 is
shown in Figure 12. Similar results can be expected using
a convection reflow oven. Figure 13 and Figure 14 show
the change in output voltage that was measured for parts
that were run through the reflow process for 1 cycle and
also 3 cycles. Additional drift of the LT6656 after IR reflow
does not vary significantly.
300
380s
TP = 260°C
TL = 217°C
TS(MAX) = 200°C
225
10
TS = 190°C
–40
–20
0
20
HYSTERESIS (ppm)
40
tP
30s
tL
130s
RAMP TO
150°C
75
–60
RAMP
DOWN
T = 150°C
150
5
0
Figure 11. LT6656 LS8 –40°C to 85°C Hysteresis
during 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.
2.5V OPTION
VIN = 3V
CL = 1µF
IL = 0
14
0
–160 –120 –80 –40 0 40 80 120 160
HYSTERESIS (ppm)
40s
60
120s
6656 F10
0
Figure 10. LT6656 LS8 0°C to 70°C Hysteresis
0
2
4
6
MINUTES
8
10
6656 F12
Figure 12. Lead Free Reflow Profile Due to IR Reflow
14
Rev D
For more information www.analog.com
LT6656
APPLICATIONS INFORMATION
NUMBER OF UNITS
7
2.5V OPTION
VIN = 3V
6 C = 1µF
L
IL = 0
5
sides of the device. See Application Note AN82 for more
information. http://www.linear.com
SOT-23
3 CYCLES
1 CYCLE
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.
4
3
2
Humidity Sensitivity
1
0
Plastic mold compounds absorb water. With changes in
relative humidity, plastic packaging materials change the
amount of pressure they apply to the die inside, which
can cause slight changes in the output of a voltage reference, usually on the order of 100ppm. The LS8 package is
hermetic, so it is not affected by humidity, and is therefore
more stable in environments where humidity may be a
concern. However, PC board material may absorb water
and apply mechanical stress to the LT6656LS8. Proper
board materials and layout are essential.
0 20
60
100
140
180
220
CHANGE IN OUTPUT VOLTAGE (ppm)
6656 F13
Figure 13. ∆VOUT Due to IR Reflow,
Peak Temperature = 260°C, SOT-23
NUMBER OF UNITS
10
2.5V OPTION
9 VIN = 3V
C = 1µF
8 I L= 0
L
7
DFN
3 CYCLES
1 CYCLE
6
5
For best stability, the PC board layout is critical. Change
in temperature and position of the PC board, as well as
aging, can alter the mechanical stress applied to components soldered to the board. FR4 and similar materials
also absorb water, causing the board to swell. Even conformal coating or potting of the board does not always
eliminate this effect, though it may delay the symptoms
by reducing the rate of absorption. Removing power and
ground planes in the PC board under the voltage reference
can improve the stability significantly.
4
3
2
1
0
–160
240
–80
80
160
0
CHANGE IN OUTPUT VOLTAGE (ppm)
6656 F14
Figure 14. ∆VOUT Due to IR Reflow,
Peak Temperature = 260°C, DFN
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
Figure 15 shows a tab cut through the PC board on three
sides of an LT6656, which significantly reduces stress on
the IC, as described in Application Note 82.
An additional advantage of slotting the PC board is that the
LT6656 is thermally isolated from surrounding circuitry.
This can help reduce thermocouple effects and improve
accuracy.
Rev D
For more information www.analog.com
15
LT6656
APPLICATIONS INFORMATION
LS8
6656 F15
Figure 15. 3-Sided PCB Cutout
TYPICAL APPLICATIONS
Regulator 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.
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
IN
LT6656-2.5
OUT
MCU
0.1µF
PB0/AIN0/AREF/MOSI
Low Power ADC Reference
PB1/INT0/AIN1/MISO/OC1A
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 17 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 17 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
16
VCC/VREF
10µF
PB2/ADC1/SCK/T0/INT0
PB3/ADC2
PB4/ADC3
PB5/RESET/ADC0
5
6
7
2
3
1
GND
6656 F16
Figure 16. 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 F17
Figure 17. Low Power ADC Reference
Rev D
For more information www.analog.com
LT6656
TYPICAL APPLICATIONS
Extended Supply Range Reference
VCC
UP TO 160V
330k
MMBT5551
BZX584C12
0.1µF
2.2µF
IN
OUT
LT6656-2.5
VOUT
1µF
6656 TA03
Boosted Output Current Reference
3.6V ≤ VCC ≤ 18V
220Ω
+
10µF
2N2905
0.1µF
IN
VOUT
40mA MAX
OUT
LT6656-2.5
1µF
6656 TA04
Rev D
For more information www.analog.com
17
LT6656
TYPICAL APPLICATIONS
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–
18
VCC
LTC2452
IN+
10k
VREF
10µF
CS
SCK
SDO
0.1µF
Rev D
For more information www.analog.com
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
6.5V ≤ VCC ≤ 10V
IN
LT6656-5
4
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
R2
R3
–
IOUT =
6656 TA09
VREF R2
+1
R1 R3
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
Rev D
For more information www.analog.com
19
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
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
20
0.01 – 0.10
1.00 MAX
1.90 BSC
S6 TSOT-23 0302
Rev D
For more information www.analog.com
LT6656
PACKAGE DESCRIPTION
DC6 Package
6-Lead Plastic DFN (2mm × 2mm)
(Reference LTC DWG # 05-08-1703 Rev C)
0.70 ±0.05
2.55 ±0.05
1.15 ±0.05 0.60 ±0.10
(2 SIDES)
PACKAGE
OUTLINE
0.25 ±0.05
0.50 BSC
1.37 ±0.10
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
R = 0.125
TYP
0.60 ±0.10
(2 SIDES)
0.40 ±0.10
4
6
2.00 ±0.10
(4 SIDES)
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
PIN 1 NOTCH
R = 0.20 OR
0.25 × 45°
CHAMFER
R = 0.05
TYP
0.200 REF
0.75 ±0.05
3
(DC6) DFN REV C 0915
1
0.25 ±0.05
0.50 BSC
1.37 ±0.10
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WCCD-2)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
Rev D
For more information www.analog.com
21
LT6656
PACKAGE DESCRIPTION
LS8 Package
8-Pin Leadless Chip Carrier (5mm × 5mm)
(Reference LTC DWG # 05-08-1852 Rev B)
8
2.50 ±0.15
PACKAGE OUTLINE
7
1
0.5
2
6
2.54 ±0.15
1.4
3
1.50 ±0.15
4
0.70 ±0.05 × 8
e4
XYY ZZ
ABCDEF
Q12345
COMPONENT
PIN “A1”
5.00 SQ ±0.15
5.80 SQ ±0.15
TRAY PIN 1
BEVEL
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
5.00 SQ ±0.15
1.45 ±0.10
0.95 ±0.10
4.20 SQ ±0.10
8
1
PIN 1
TOP MARK
(SEE NOTE 5)
2
PACKAGE IN TRAY LOADING ORIENTATION
5.00 SQ ±0.15
8
R0.20 REF
2.00 REF
7
6
1
7
2
2.54 ±0.15
0.5
6
4.20 ±0.10
1.4
3
5
R0.20 REF
5
3
1.00 × 7 TYP
4
0.70 TYP
NOTE:
1. ALL DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS PACKAGE DO NOT INCLUDE PLATING BURRS
PLATING BURRS, IF PRESENT, SHALL NOT EXCEED 0.30mm ON ANY SIDE
4. PLATING—ELECTO NICKEL MIN 1.25UM, ELECTRO GOLD MIN 0.30UM
5. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
22
LS8 0113 REV B
4
0.10 TYP
0.64 × 8 TYP
Rev D
For more information www.analog.com
LT6656
REVISION HISTORY
REV
DATE
DESCRIPTION
A
07/10
Voltage options added (1.25, 2.048, 3, 3.3), reflected throughout the data sheet.
1 to 18
B
05/11
Added 6-lead DFN package reflected throughout the data sheet.
1 to 20
C
11/13
Addition of 1.25V option in the LS8 package.
1 to 4
Note 10 updated with additional explanation of hysteresis.
6
Pin Functions updated to show pin numbers and LS8 package.
10
Block Diagram updated to show pin numbers and LS8 package.
10
Hysteresis section updated with additional explanation.
13
Hysteresis graphs updated for SOT23 and LS8 packages.
New section added for Humidity Sensitivity.
D
05/21
PAGE NUMBER
Additon of the 2.8V option in the DFN package.
Removal of statements under Humidity Sensitivity (3rd paragraph).
Change Figure 15a to Figure 15 and remove Figure 15b.
Adding more related part numbers and descriptions in the Related Parts table.
14
15, 16
1, 3, 4, 5
15
15, 16
24
Rev D
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
23
LT6656
TYPICAL APPLICATION
Reference Regulator for Micropower DAC, Total IQ = 4.8µA
5.1V ≤ VIN ≤ 18V
IN
LT6656-5
0.1µF
OUT
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
LT1389
Nanopower Precision Shunt Voltage Reference 0.05% Max 10ppm/°C Max, 800nA Supply
LTC1440
Micropower Comparator with Reference
3.7µA Max Supply Current, 1% 1.182V Reference, MSOP, PDIP and SO-8 Packages
LT1460
Micropower Series Reference
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 and DFN Packages
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
ADR3425
Micropower, High-Accuracy Voltage Reference 100µA Supply Current, ±0.1% Max Initial Accuracy, 8ppm/°C Max drift
ADR3525
Micropower, Precision, Auto Qualified Voltage
Reference
AEC-Q100, 100µA Supply Current, ±0.1% Max Initial Accuracy, 5ppm/°C B-Grade Max
Drift
ADR5041
Precision Micropower Shunt Mode Voltage
Reference
AEC-Q100, SC70 or SOT-23 Package, 50µA to 15mA Supply Current, No External
Capacitor Required
AD4000/
AD4001
16-Bit, 2Msps Precision Pseudo Differential or INL: ±1.0LSB Maximum; 7mW/Msps, 70µW at 10ksps, 14mW at 2Msps from VDD Only
Differential SAR ADC
LTC2376-16/
LTC2378-16
18-Bit, 250ksps, Low Power SAR ADC with
102dB SNR
±1.75LSB INL (Max), 2.5V Supply, 3.4mW at 250ksps
LTC2400
24-Bit µPower No Latency ∆∑™ ADC in SO-8
200µA Supply Current, 12.5% Overrange and Underrange, 50Hz/60Hz Notch Filter with
110dB Min Attenuation
AD7980
16-Bit, 1Msps, PulSAR ADC in MSOP/LFCSP
INL: ±0.6LSB Typ, ±1.25LSB Max, 2.5V Supply with 1.8V/2.5V/3V/5V Logic Interface,
4mW at 1Msps (VDD Only)
AD4695/
AD4696
16-Channel 16-Bit 500ksps SAR ADC
8mW at fs = 1Msps (AD4696), 4mW at fs = 500ksps (AD4695 and AD4696)
24
Rev D
05/20
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