FEATURES
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LTC2450
Easy-to-Use, Ultra-Tiny
16-Bit
ΔΣ
ADC
DESCRIPTION
The LTC
®
2450 is an ultra-tiny 16-bit analog-to-digital
converter. The LTC2450 uses a single 2.7V to 5.5V supply,
accepts a single-ended analog input voltage, and commu-
nicates through an SPI interface. 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 applica-
tions. The converter is available in a 6-pin, 2mm
×
2mm
DFN package. The internal oscillator does not require any
external components. The LTC2450 includes a proprietary
input sampling scheme that reduces the average input
sampling current several orders of magnitude.
The LTC2450 is capable of up to 30 conversions per sec-
ond and, due to the very large oversampling ratio, has
extremely relaxed antialiasing requirements. The LTC2450
includes continuous internal offset and full-scale calibra-
tion algorithms which are transparent to the user, ensuring
accuracy over time and over the operating temperature
range. The converter uses its power supply voltage as the
reference voltage and the single-ended, rail-to-rail input
voltage range extends from GND to V
CC
.
Following a conversion, the LTC2450 can automatically
enter a sleep mode and reduce its power to less than
200nA. If the user samples the ADC once a second, the
LTC2450 consumes an average of less than 50μW from
a 2.7V supply.
GND to V
CC
Single-Ended Input Range
0.02LSB RMS Noise
2LSB INL, No Missing Codes
2LSB Offset Error
4LSB Full-Scale Error
Single Conversion Settling Time for Multiplexed
Applications
Single Cycle Operation with Auto Shutdown
350μA Supply Current
50nA Sleep Current
30 Conversions Per Second
Internal Oscillator—No External Components
Required
Single Supply, 2.7V to 5.5V Operation
SPI Interface
Ultra-Tiny 2mm
×
2mm DFN 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 and LTM are registered trademarks of Linear Technology Corporation. East Drive
is a trademark 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
3.0
2.5
2.0
Integral Nonlinearity, V
CC
= 3V
V
CC
= V
REF
= 3V
0.1μF
10μF
INL (LSB)
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
–2.5
–3.0
0
0.5
1.0
1.5
2.0
INPUT VOLTAGE (V)
2.5
3.0
2450 G02
1k
SENSE
CLOSE TO
CHIP
V
IN
0.1μF
V
CC
LTC2450
GND
CS
SCK
SDO
2450 TA01
T
A
= –45°C, 25°C, 90°C
3-WIRE SPI
INTERFACE
2450fb
1
LTC2450
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
PIN CONFIGURATION
TOP VIEW
V
CC
1
V
IN
2
GND 3
7
6 SCK
5 SDO
4
CS
Supply Voltage (V
CC
) ................................... –0.3V to 6V
Analog Input Voltage (V
IN
) ............–0.3V to (V
CC
+ 0.3V)
Digital Input Voltage......................–0.3V to (V
CC
+ 0.3V)
Digital Output Voltage ...................–0.3V to (V
CC
+ 0.3V)
Operating Temperature Range
LTC2450C ................................................ 0°C to 70°C
LTC2450I.............................................. –40°C to 85°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10sec) ................... 300°C
DC PACKAGE
6-LEAD (2mm × 2mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 102°C/W
EXPOSED PAD (PIN7) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
Lead Free Finish
TAPE AND REEL (MINI)
LTC2450CDC#TRMPBF
TAPE AND REEL
LTC2450CDC#TRPBF
PART MARKING*
LCTR
PACKAGE DESCRIPTION
6-Lead (2mm
×
2mm) Plastic DFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
LTC2450IDC#TRMPBF
LTC2450IDC#TRPBF
LCTR
6-Lead (2mm
×
2mm) Plastic DFN
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/
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
PARAMETER
Resolution (No missing codes)
Integral Nonlinearity
Offset Error
Offset Error Drift
Gain Error
Gain Error Drift
Transition Noise
l
ELECTRICAL CHARACTERISTICS
(Note 3)
(Note 4)
CONDITIONS
l
l
l
MIN
16
TYP
2
2
0.02
0.01
0.02
1.4
MAX
10
8
0.02
UNITS
Bits
LSB
LSB
LSB/°C
% of FS
LSB/°C
μV
RMS
ANALOG INPUT
The
l
denotes the specifications which apply over the full operating temperature range,otherwise
specifications are at T
A
= 25°C.
SYMBOL
V
IN
C
IN
I
DC_LEAK
(V
IN
)
I
CONV
PARAMETER
Input Voltage Range
IN Sampling Capacitance
IN DC Leakage Current
Input Sampling Current (Note 9)
V
IN
= GND (Note 5)
V
IN
= V
CC
(Note 5)
l
l
CONDITIONS
l
MIN
0
TYP
0.35
MAX
V
CC
UNITS
pF
–10
–10
1
1
50
10
10
nA
nA
nA
2450fb
2
LTC2450
POWER REQUIREMENTS
The
l
denotes the specifications which apply over the full operating temperature
range,otherwise specifications are at T
A
= 25°C.
SYMBOL
V
CC
I
CC
PARAMETER
Supply Voltage
Supply Current
Conversion
Sleep
CS
= GND (Note 6)
CS
= VCC (Note 6)
CONDITIONS
l
l
l
MIN
2.7
TYP
MAX
5.5
UNITS
V
μA
μA
350
0.05
600
0.5
DIGITAL INPUTS AND DIGITAL OUTPUTS
The
l
denotes the specifications which apply over the full
operating temperature range,otherwise specifications are at T
A
= 25°C. (Note 2)
SYMBOL
V
IH
V
IL
I
IN
C
IN
V
OH
V
OL
I
OZ
PARAMETER
High Level Input Voltage
Low Level Input Voltage
Digital Input Current
Digital Input Capacitance
High Level Output Voltage
Low Level Output Voltage
Hi-Z Output Leakage Current
I
O
= –800μA
I
O
= –1.6mA
l
l
l
CONDITIONS
l
l
l
MIN
V
CC
– 0.3
TYP
MAX
0.3
UNITS
V
V
μA
pF
V
–10
10
V
CC
– 0.5
10
0.4
–10
10
V
μA
TIMING CHARACTERISTICS
The
l
denotes the specifications which apply over the full operating temperature
range,otherwise specifications are at T
A
= 25°C.
SYMBOL
t
CONV
f
SCK
t
lSCK
t
hSCK
t
1
t
2
t
3
t
KQ
PARAMETER
Conversion Time
SCK Frequency Range
SCK Low Period
SCK High Period
CS
Falling Edge to SDO Low Z
CS
Rising Edge to SDO High Z
CS
Falling Edge to SCK Falling Edge
SCK Falling Edge to SDO Valid
(Note 7)
(Notes 7, 8)
(Notes 7, 8)
CONDITIONS
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l
l
l
l
l
l
l
MIN
29
250
250
0
0
100
0
TYP
33.3
MAX
42
2
UNITS
ms
MHz
ns
ns
100
100
100
ns
ns
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.
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:
CS
= V
CC
. A positive current is flowing into the DUT pin.
Note 6:
SCK = V
CC
or GND. SDO is high impedance.
Note 7:
See Figure 3.
Note 8:
See Figure 4.
Note 9:
Input sampling current is the average input current drawn from the
input sampling network while the LTC2450 is actively sampling the input.
2450fb
3
LTC2450
TYPICAL PERFORMANCE CHARACTERISTICS
Integral Nonlinearity, V
CC
= 5V
3.0
2.5
2.0
1.5
1.0
INL (LSB)
0.5
0
–0.5
–1.0
–1.5
–2.0
–2.5
–3.0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
INPUT VOLTAGE (V)
2450 G01
Integral Nonlinearity, V
CC
= 3V
3.0
2.5
2.0
1.5
1.0
INL (LSB)
0.5
0
–0.5
–1.0
–1.5
–2.0
–2.5
–3.0
0
0.5
1.0
1.5
2.0
INPUT VOLTAGE (V)
2.5
3.0
2450 G02
V
CC
= V
REF
= 5V
V
CC
= V
REF
= 3V
T
A
= –45°C, 25°C, 90°C
T
A
= –45°C, 25°C, 90°C
Maximum INL vs Temperature
5.0
4.5
4.0
3.5
OFFSET (LSB)
INL (LSB)
3.0
2.5
2.0
1.5
1.0
0.5
0
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
2450 G03
Offset Error vs Temperature
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
2450 G04
V
CC
= 3V
V
CC
= 5V
V
CC
= 4.1V
V
CC
= 3V
V
CC
= 4.1V
V
CC
= 5V
Gain Error vs Temperature
5.0
4.5
4.0
GAIN ERROR (LSB)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
2450 G05
Transition Noise vs Temperature
3.00
2.75
TRANSITION NOISE RMS (μV)
2.50
2.25
2.00
1.75
1.50 V
CC
= 4.1V
1.25
1.00
0.50
0.75
0.25
0
–50 –30
50
–10 10 30
TEMPERATURE (°C)
70
90
2450 G06
V
CC
= 5V
V
CC
= 4.1V
V
CC
= 5V
V
CC
= 3V
V
CC
= 3V
2450fb
4
LTC2450
TYPICAL PERFORMANCE CHARACTERISTICS
Transition Noise vs Output Code
3.00
2.75
TRANSITION NOISE RMS (μV)
2.50
2.25
2.00
1.75
1.50
1.25
1.00
0.50
0.75
0.25
0
0.80
1.00
0.40
0.60
0
0.20
OUTPUT CODE (NORMALIZED TO FULL SCALE)
2450 G07
Conversion Mode Power Supply
Current vs Temperature
500
V
CC
= 5V
V
CC
= 3V
300
V
CC
= 4.1V
T
A
= 25°C
CONVERSION CURRENT (μA)
400
V
CC
= 5V
V
CC
= 3V
200
100
0
–45
–25
35
15
–5
55
TEMPERATURE (°C)
75
95
2450 G08
Sleep Mode Power Supply
Current vs Temperature
250
10000
AVERAGE POWER DISSIPATION (μW)
Average Power Dissipation
vs Temperature, V
CC
= 3V
SLEEP MODE CURRENT (nA)
200
V
CC
= 5V
150
V
CC
= 4.1V
25Hz OUTPUT SAMPLE RATE
1000
10Hz OUTPUT SAMPLE RATE
100
1Hz OUTPUT SAMPLE RATE
100
50
V
CC
= 3V
0
–45
–25
35
15
–5
55
TEMPERATURE (°C)
75
95
10
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
2450 G10
2450 G09
Conversion Period vs
Temperature
42
40
CONVERSION TIME (ms)
38
V
CC
= 5V, 4.1V, 3V
36
34
32
30
–45 –25
35
15
55
–5
TEMPERATURE (°C)
75
95
2450 G11
2450fb
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