FEATURES
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LTC2451
Ultra-Tiny, 16-Bit
∆∑
ADC
with I
2
C Interface
DESCRIPTION
The LTC
®
2451 is an ultra-tiny, 16-bit, analog-to-digital
converter. The LTC2451 uses a single 2.7V to 5.5V sup-
ply, accepts a single-ended analog input voltage and
communicates through an I
2
C interface. The converter
is available in an 8-pin, 3mm × 2mm DFN or TSOT-23
package. It includes an integrated oscillator that does not
require any external components. It uses a delta-sigma
modulator as a converter core and provides single-cycle
settling time for multiplexed applications. The LTC2451
includes a proprietary input sampling scheme that re-
duces the average input sampling current several orders
of magnitude lower than conventional ∆∑ converters.
The LTC2451 is capable of up to 60 conversions per
second and, due to the very large oversampling ratio,
has extremely relaxed antialiasing requirements. In the
30Hz mode, the LTC2451 includes continuous internal
offset calibration algorithms which are transparent to the
user, ensuring accuracy over time and over the operating
temperature range. The converter has external REF
+
and
REF
–
pins and the input voltage can range from V
REF–
to
V
REF+
. If V
REF+
= V
CC
and V
REF–
= GND, the input voltage
can range from GND to V
CC
.
Following a single conversion, the LTC2451 can auto-
matically enter sleep mode and reduce its power to less
than 0.2µA. If the user reads the ADC once per second,
the LTC2451 consumes an average of less than 50µW
from a 2.7V supply.
Integral Nonlinearity, V
CC
= 3V
3
2
2.7V TO 5.5V
0.1µF
10µF
INL (LSB)
1
0
–1
T
A
= – 45°C, 25°C
–2
2451 TA01a
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GND to V
CC
Single-Ended Input Range
0.02LSB RMS Noise
2LSB INL, No Missing Codes
1LSB Offset Error
4LSB Full-Scale Error
Programmable 30/60 Conversions per Second
Single Conversion Settling Time for Multiplexed
Applications
Single-Cycle Operation with Auto Shutdown
400µA Supply Current
0.2µA Sleep Current
Internal Oscillator—No External Components Required
Single Supply, 2.7V to 5.5V Operation
2-Wire I
2
C Interface
Ultra-Tiny 3mm × 2mm DFN or TSOT-23 Package
APPLICATIONS
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System Monitoring
Environmental Monitoring
Direct Temperature Measurements
Instrumentation
Industrial Process Control
Data Acquisition
Embedded ADC Upgrades
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. No Latency ∆∑ and Easy Drive are trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners. Protected by U.S.
Patents, including 6208279, 6411242, 7088280, 7164378.
TYPICAL APPLICATION
1k
IN
SENSOR
0.1µF
REF
+
V
CC
SCL
SDA
2-WIRE I
2
C
INTERFACE
LTC2451
REF
–
GND
T
A
= 90°C
–3
0
0.5
1
1.5
2
INPUT VOLTAGE (V)
2.5
3
2451 TA01b
2451fg
1
LTC2451
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
Supply Voltage (V
CC
) ................................... –0.3V to 6V
Analog Input Voltage (V
IN
) ............ –0.3V to (V
CC
+ 0.3V)
Reference Voltage (V
REF+
, V
REF –
) ...–0.3V to (V
CC
+ 0.3V)
Digital Voltage (V
SDA
, V
SCL
) .......... –0.3V to (V
CC
+ 0.3V)
Storage Temperature Range................... –65°C to 150°C
Operating Temperature Range
LTC2451C ................................................ 0°C to 70°C
LTC2451I.............................................. –40°C to 85°C
PIN CONFIGURATION
TOP VIEW
GND
REF
–
REF
+
V
CC
1
2
3
4
9
8
7
6
5
SDA
SCL
IN
GND
TOP VIEW
GND 1
REF
–
2
REF
+
3
V
CC
4
8 SDA
7 SCL
6 IN
5 GND
DDB PACKAGE
8-LEAD (3mm
×
2mm) PLASTIC DFN
C/I GRADE T
JMAX
= 125°C,
θ
JA
= 76°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
C/I GRADE T
JMAX
= 125°C,
θ
JA
= 140°C/W
ORDER INFORMATION
Lead Free Finish
TAPE AND REEL (MINI)
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
LTC2451CDDB#TRMPBF
LTC2451CDDB#TRPBF
LDGQ
8-Lead Plastic (3mm × 2mm) DFN
LTC2451IDDB#TRMPBF
LTC2451IDDB#TRPBF
LDGQ
8-Lead Plastic (3mm × 2mm) DFN
LTC2451CTS8#TRMPBF
LTC2451CTS8#TRPBF
LTDNS
8-Lead Plastic TSOT-23
LTC2451ITS8#TRMPBF
LTC2451ITS8#TRPBF
LTDNS
8-Lead Plastic TSOT-23
TRM = 500 pieces. *Temperature grades are identified by a label on the shipping container.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on 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/
ELECTRICAL CHARACTERISTICS
PARAMETER
Resolution (No Missing Codes)
Integral Nonlinearity
Offset Error
Offset Error
Offset Error Drift
Gain Error
Gain Error Drift
Transition Noise
Power Supply Rejection DC
Power Supply Rejection DC
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
CONDITIONS
(Note 3)
(Note 4)
30Hz Mode
60Hz Mode
l
l
l
l
MIN
16
TYP
2
0.08
0.5
0.02
0.01
0.02
1.4
80
80
MAX
10
0.5
2
0.02
UNITS
Bits
LSB
mV
mV
LSB/°C
% of FS
LSB/°C
µV
RMS
dB
dB
2451fg
l
30Hz Mode
60Hz Mode
2
LTC2451
ANALOG INPUT AND REFERENCES
SYMBOL
V
IN
V
REF+
V
REF–
C
IN
I
DC_LEAK(VIN)
PARAMETER
Input Voltage Range
Positive Reference Voltage Range
Negative Reference Voltage Range
IN Sampling Capacitance
IN DC Leakage Current
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
CONDITIONS
V
REF+
– V
REF–
≥ 2.5V
V
REF+
– V
REF–
≥ 2.5V
V
IN
= GND (Note 8)
V
IN
= V
CC
(Note 8)
V
REF
= 5V (Note 8)
MIN
l
V
REF–
l
V
CC
– 2.5
l
0
l
l
l
TYP
MAX
V
REF+
V
CC
V
CC
– 2.5
10
10
10
I
DC_LEAK(REF+, REF–)
REF
+
, REF
–
DC Leakage Current
I
CONV
Input Sampling Current (Note 5)
–10
–10
–10
0.35
1
1
1
50
UNITS
V
V
V
pF
nA
nA
nA
nA
POWER REQUIREMENTS
SYMBOL
V
CC
I
CC
PARAMETER
Supply Voltage
Supply Current
Conversion
Sleep
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 2)
CONDITIONS
l
l
l
MIN
2.7
TYP
MAX
5.5
700
0.5
UNITS
V
µA
µA
400
0.2
I
2
C INPUTS AND OUTPUTS
SYMBOL
V
IH
V
IL
V
HYS
V
OL
I
IN
C
I
C
B
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V
CC
= 2.7V to 5.5V. (Note 2)
PARAMETER
High Level Input Voltage
Low Level Input Voltage
Hysteresis of Schmidt Trigger Inputs
Low Level Output Voltage (SDA)
Input Leakage
Capacitance for Each I/O Pin
Capacitance Load for Each Bus Line
CONDITIONS
l
l
MIN
0.7V
CC
0.05V
CC
–1
10
TYP
MAX
0.3V
CC
0.4
1
400
(Note 3)
I = 3mA
0.1V
CC
≤ V
IN
≤ 0.9V
CC
l
l
l
l
l
UNITS
V
V
V
V
µA
pF
pF
I
2
C TIMING CHARACTERISTICS
SYMBOL
t
CONV
t
CONV
f
SCL
t
HD(SDA)
t
LOW
t
HIGH
t
SU(STA)
t
HD(DAT)
t
SU(DAT)
t
r
t
f
t
SU(STO)
t
BUF
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 2.7V to 5.5V. (Notes 2, 7)
PARAMETER
Conversion Time
Conversion Time
SCL Clock Frequency
Hold Time (Repeated) START Condition
LOW Period of the SCL Pin
HIGH Period of the SCL Pin
Set-Up Time for a Repeated START Condition
Data Hold Time
Data Set-Up Time
Rise Time for SDA/SCL Signals
Fall Time for SDA/SCL Signals
Set-Up Time for STOP Condition
Bus Free Time Between a STOP and START
Condition
CONDITIONS
30Hz Mode
60Hz Mode
l
l
l
l
l
l
l
l
l
(Note 6)
(Note 6)
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l
l
l
MIN
26
13
0
0.6
1.3
0.6
0.6
0
100
20 + 0.1C
B
20 + 0.1C
B
0.6
1.3
TYP
33.2
16.6
MAX
46
23
400
0.9
300
300
UNITS
ms
ms
kHz
µs
µs
µs
µs
µs
ns
ns
ns
µs
µs
2451fg
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LTC2451
I
2
C TIMING CHARACTERISTICS
SYMBOL
t
OF
t
SP
PARAMETER
Output Fall Time V
IH(MIN)
to V
IL(MAX)
Input Spike Suppression
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 2, 7)
CONDITIONS
Bus Load C
B
10pF to
400pF (Note 6)
l
l
MIN
20 + 0.1C
B
TYP
MAX
250
50
UNITS
ns
ns
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2.
All voltage values are with respect to GND. V
CC
= 2.7V to 5.5V,
unless otherwise specified. Specifications apply to both 30Hz and 60Hz
modes unless otherwise specified.
V
REF
= V
REF+
– V
REF–
, V
REFCM
= (V
REF+
+ V
REF–
)/2, FS = V
REF+
– V
REF–
;
V
REF–
≤ V
IN
≤ V
REF+
Note 3.
Guaranteed by design, not subject to test.
Note 4.
Integral nonlinearity is defined as the deviation of a code from
a straight line passing through the actual endpoints of the transfer
curve. The deviation is measured from the center of the quantization
band. Guaranteed by design, test correlation and 3-point transfer curve
measurement.
Note 5.
Input sampling current is the average input current drawn from
the input sampling network while the LTC2451 is actively sampling the
input. C
B
= capacitance of one bus line in pF.
Note 6.
C
B
= capacitance of one bus line in pF.
Note 7.
All values refer to V
IH(MIN
) and V
IL(MAX)
levels.
Note 8.
A positive current is flowing into the DUT pin.
TYPICAL PERFORMANCE CHARACTERISTICS
T
A
= 25°C; graphs apply to both 30Hz and 60Hz modes, unless otherwise noted.
Integral Nonlinearity
V
CC
= V
REF+
= 5V
Integral Nonlinearity
V
CC
= 5V, V
REF+
= 3V
Integral Nonlinearity
V
CC
= V
REF+
= 3V
3
2
1
INL (LSB)
3
2
1
INL (LSB)
0
–1
–2
–3
3
2
1
INL (LSB)
0
–1
0
–1
–2
–3
T
A
= – 45°C, 25°C, 90°C
T
A
= – 45°C, 25°C, 90°C
T
A
= 90°C
T
A
= – 45°C, 25°C
–2
–3
0
1
2
3
INPUT VOLTAGE (V)
4
5
2451 G01
0
0.5
1
1.5
2
INPUT VOLTAGE (V)
2.5
3
2451 G02
0
0.5
1
1.5
2
INPUT VOLTAGE (V)
2.5
3
2451 G03
2451fg
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LTC2451
TYPICAL PERFORMANCE CHARACTERISTICS
T
A
= 25°C; graphs apply to both 30Hz and 60Hz modes, unless otherwise noted.
Maximum INL vs Temperature
5.0
4.5
4.0
3.5
OFFSET (mV)
INL (LSB)
3.0
2.5
2.0
1.5
1.0
0.5
0
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
2451 G04
Offset Error vs Temperature
30Hz Mode
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
V
CC
= 3V
–25
25
50
0
TEMPERATURE (°C)
75
100
2451 G05
Offset Error vs Temperature
60Hz Mode
0.50
0.45
0.40
0.35
OFFSET (mV)
0.30
0.25
0.20
0.15
0.10
0.05
0.00
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
2451 G06
V
CC
= 4.1V
V
CC
= 5V
V
CC
= 3V
V
CC
= 4.1V
V
CC
= 5V
V
CC
= 5V, 4.1V, 3V
0.00
–50
Gain Error vs Temperature
10
9
7
6
5
4
3
2
1
0
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
2451 G07
Transition Noise vs Temperature
3.0
2.5
2.0
1.5
1.0
0.5
0
–50
V
CC
= 5V
V
CC
= 3V
3.0
2.5
2.0
1.5
1.0
0.5
0
Transition Noise vs Output Code
V
CC
= 3V
V
CC
= 4.1V
V
CC
= 5V
TRANSITION NOISE RMS (µV)
TRANSITION NOISE RMS (µV)
8
GAIN ERROR (LSB)
V
CC
= 5V
V
CC
= 3V
–25
0
25
50
TEMPERATURE (°C)
75
100
2451 G08
0
16384
32768
49152
OUTPUT CODE
65536
2451 G09
Conversion Mode Power Supply
Current vs Temperature
600
500
SLEEP CURRENT (nA)
400
300
200
100
0
–50
V
CC
= 5V
V
CC
= 4.1V
250
Sleep Mode Power Supply
Current vs Temperature
10000
V
CC
= 5V
AVERAGE POWER DISSIPATION (µW)
Average Power Dissipation vs
Temperature V
CC
= 3V, 30Hz Mode
CONVERSION CURRENT (µA)
200
1000
25Hz OUTPUT SAMPLE RATE
10Hz OUTPUT SAMPLE RATE
150
V
CC
= 4.1V
100
V
CC
= 3V
100
1Hz OUTPUT SAMPLE RATE
10
50
0
–50
V
CC
= 3V
–25
0
25
50
TEMPERATURE (°C)
75
100
2451 G10
–25
0
25
50
TEMPERATURE (°C)
75
100
2451 G11
1
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
2451 G12
2451fg
5
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