No Latency: Digital Filter Settles in a Single Cycle
Single Supply 2.7V to 5.5V Operation
Internal Oscillator
Six Addresses Available and One Global Address for
Synchronization
Available in a Tiny (3mm
×
3mm) 10-Lead DFN Package
Direct Sensor Digitizer
Weight Scales
Direct Temperature Measurement
Strain Gauge Transducers
Instrumentation
Industrial Process Control
DVMs and Meters
LTC2481
16-Bit
∆Σ
ADC with Easy Drive
Input Current Cancellation
and I
2
C Interface
DescripTion
The
LTC
®
2481
combines a 16-bit plus sign No Latency
∆Σ
™
analog-to-digital converter with patented Easy Drive
technology and I
2
C digital interface. The patented sampling
scheme eliminates dynamic input current errors and the
shortcomings of on-chip buffering through automatic
cancellation of differential input current. This allows large
external source impedances and input signals, with rail-to-
rail input range to be directly digitized while maintaining
exceptional DC accuracy.
The LTC2481 includes on-chip programmable gain and
an oscillator. The LTC2481 can be configured through an
I
2
C interface to provide a programmable gain from 1 to
256 in 8 steps, to digitize an external signal or internal
temperature sensor, reject line frequencies (50Hz, 60Hz or
simultaneous 50Hz/60Hz) as well as a 2x speed-up mode.
The LTC2481 allows a wide common mode input range
(0V to V
CC
) independent of the reference voltage. The
reference can be as low as 100mV or can be tied directly
to V
CC
. The LTC2481 includes an on-chip trimmed oscil-
lator eliminating the need for external crystals or oscil-
lators. Absolute accuracy and low drift are automatically
maintained through continuous, transparent, offset and
full-scale calibration.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
No Latency ∆∑ and Easy Drive are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Patents Pending.
applicaTions
n
n
n
n
n
n
n
Typical applicaTion
V
CC
0.1µF
10k
SENSE
10k
V
IN–
0.1µF
I
DIFF
= 0
REF
+
LTC2481
GND
REF
–
V
CC
1µF
SCL
SDA
CA0/f
0
CA1
2481 TA01a
+FS Error vs R
SOURCE
at IN
+
and IN
–
V
CC
= 5V
60 V
REF
= 5V
V
IN+
= 3.75V
V
IN–
= 1.25V
40
f
O
= GND
20 T
A
= 25°C
0
–20
–40
–60
–80
1
10
100
1k
R
SOURCE
( )
10k
100k
2481 TA01b
80
V
IN+
2-WIRE
I
2
C INTERFACE
6 ADDRESSES
+FS ERROR (ppm)
C
IN
= 1µF
2481fd
For more information
www.linear.com/LTC2481
1
LTC2481
absoluTe MaxiMuM raTings
(Notes 1, 2)
pin conFiguraTion
TOP VIEW
REF
+
REF
–
IN
+
Supply Voltage (V
CC
) to GND ...................... – 0.3V to 6V
Analog Input Voltage to GND ....... –0.3V to (V
CC
+ 0.3V)
Reference Input Voltage to GND .. –0.3V to (V
CC
+ 0.3V)
Digital Input Voltage to GND ....... – 0.3V to (V
CC
+ 0.3V)
Digital Output Voltage to GND...... –0.3V to (V
CC
+ 0.3V)
Operating Temperature Range
LTC2481C.................................................... 0°C to 70°C
LTC2481I .................................................– 40°C to 85°C
LTC2481H .............................................. –40°C to 125°C
Storage Temperature Range ................. –65°C to 125°C
1
2
3
4
5
11
V
CC
10 CA0/f
0
9 CA1
8 GND
7 SDA
6 SCL
IN
–
DD PACKAGE
10-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC2481CDD#PBF
LTC2481IDD#PBF
LTC2481HDD#PBF
TAPE AND REEL
LTC2481CDD#TRPBF
LTC2481IDD#TRPBF
LTC2481HDD#TRPBF
PART MARKING*
LBPV
LBPV
LBPV
PACKAGE DESCRIPTION
10-Lead (3mm
×
3mm) Plastic DFN
10-Lead (3mm
×
3mm) Plastic DFN
10-Lead (3mm
×
3mm) Plastic DFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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 (norMal speeD)
PARAMETER
Resolution (No Missing Codes)
Integral Nonlinearity
Offset Error
Offset Error Drift
Positive Full-Scale Error
Positive Full-Scale Error Drift
Negative Full-Scale Error
Negative Full-Scale Error Drift
Total Unadjusted Error
CONDITIONS
0.1 ≤ V
REF
≤ V
CC
, –FS ≤ V
IN
≤ +FS (Note 5)
5V ≤ V
CC
≤ 5.5V, V
REF
= 5V, V
IN(CM)
= 2.5V (Note 6)
2.7V ≤ V
CC
≤ 5.5V, V
REF
= 2.5V, V
IN(CM)
= 1.25V (Note 6)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
(Note 13)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
2.5V ≤ V
REF
≤ V
CC
, IN
+
= 0.75V
REF
, IN
–
= 0.25V
REF
2.5V ≤ V
REF
≤ V
CC
, IN
+
= 0.75V
REF
, IN
–
= 0.25V
REF
(H-Grade)
2.5V ≤ V
REF
≤ V
CC
, IN
+
= 0.75V
REF
, IN
–
= 0.25V
REF
2.5V ≤ V
REF
≤ V
CC
, IN
–
= 0.75V
REF
, IN
+
= 0.25V
REF
2.5V ≤ V
REF
≤ V
CC
, IN
–
= 0.75V
REF
, IN
+
= 0.25V
REF
(H-Grade)
2.5V ≤ V
REF
≤ V
CC
, IN
–
= 0.75V
REF
, IN
+
= 0.25V
REF
5V ≤ V
CC
≤ 5.5V, V
REF
= 2.5V, V
IN(CM)
= 1.25V (Note 6)
5V ≤ V
CC
≤ 5.5V, V
REF
= 5V, V
IN(CM)
= 2.5V (Note 6)
2.7V ≤ V
CC
≤ 5.5V, V
REF
= 2.5V, V
IN(CM)
= 1.25V (Note 6)
5V ≤ V
CC
≤ 5.5V, V
REF
= 5V, GND ≤ IN
–
= IN
+
≤ V
CC
(Note 12)
T
A
= 27°C
See Table 2a
The
l
denotes the specifications which
apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
MIN
l
l
l
TYP
2
1
0.5
10
MAX
10
2.5
25
40
UNITS
Bits
ppm of V
REF
ppm of V
REF
µV
nV/°C
ppm of V
REF
ppm
ppm of V
REF
/°C
ppm of V
REF
ppm
ppm of V
REF
/°C
ppm of V
REF
ppm of V
REF
ppm of V
REF
µV
RMS
16
l
0.1
l
25
40
0.1
15
15
15
0.6
390
450
256
Output Noise
Internal PTAT Signal
Programmable Gain
mV
l
1
2
2481fd
For more information
www.linear.com/LTC2481
LTC2481
elecTrical characTerisTics (2x speeD)
PARAMETER
Integral Nonlinearity
Offset Error
Offset Error Drift
Positive Full-Scale Error
Positive Full-Scale Error Drift
Negative Full-Scale Error
Negative Full-Scale Error Drift
Output Noise
Programmable Gain
CONDITIONS
l
l
l
The
l
denotes the specifications which apply over
the full operating temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
MIN
16
2
1
0.5
100
l
TYP
MAX
10
2
25
UNITS
Bits
ppm of V
REF
mV
nV/°C
ppm of V
REF
ppm of V
REF
/°C
ppm of V
REF
ppm of V
REF
/°C
µV
RMS
Resolution (No Missing Codes) 0.1 ≤ V
REF
≤ V
CC
, –FS ≤ V
IN
≤ +FS (Note 5)
5V ≤ V
CC
≤ 5.5V, V
REF
= 5V, V
IN(CM)
= 2.5V (Note 6)
2.7V ≤ V
CC
≤ 5.5V, V
REF
= 2.5V, V
IN(CM)
= 1.25V (Note 6)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
(Note 13)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
2.5V ≤ V
REF
≤ V
CC
, IN
+
= 0.75V
REF
, IN
–
= 0.25V
REF
2.5V ≤ V
REF
≤ V
CC
, IN
+
= 0.75V
REF
, IN
–
= 0.25V
REF
2.5V ≤ V
REF
≤ V
CC
, IN
–
= 0.75V
REF
, IN
+
= 0.25V
REF
2.5V ≤ V
REF
≤ V
CC
, IN
–
= 0.75V
REF
, IN
+
= 0.25V
REF
5V ≤ V
CC
≤ 5.5V, V
REF
= 5V, GND ≤ IN
–
= IN
+
≤ V
CC
See Table 2b
0.1
l
25
0.1
0.84
l
1
128
converTer characTerisTics
PARAMETER
Input Common Mode Rejection DC
Input Common Mode Rejection
50Hz ± 2%
Input Common Mode Rejection
60Hz ±2%
Input Normal Mode Rejection
50Hz ±2%
Input Normal Mode Rejection
60Hz ±2%
Input Normal Mode Rejection
50Hz/60Hz ±2%
Reference Common Mode Rejection DC
Power Supply Rejection DC
Power Supply Rejection, 50Hz ±2%
Power Supply Rejection, 60Hz ±2%
CONDITIONS
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
MIN
l
l
l
l
l
l
l
l
l
TYP
MAX
UNITS
dB
dB
dB
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
–
= IN
+
≤ V
CC
(Note 5)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
–
= IN
+
≤ V
CC
(Note 5)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
–
= IN
+
≤ V
CC
(Note 5)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
–
= IN
+
≤ V
CC
(Notes 5, 7)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
–
= IN
+
≤ V
CC
(H-Grade)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
–
= IN
+
≤ V
CC
(Notes 5, 8)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
–
= IN
+
≤ V
CC
(H-Grade)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
–
= IN
+
≤ V
CC
(Notes 5, 9)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
–
= IN
+
≤ V
CC
(Note 5)
V
REF
= 2.5V, IN
–
= IN
+
= GND
V
REF
= 2.5V, IN
–
= IN
+
= GND (Notes 7, 9)
V
REF
= 2.5V, IN
–
= IN
+
= GND (Notes 8, 9)
140
140
140
110
104
110
104
87
120
140
120
120
120
120
120
dB
dB
dB
dB
dB
dB
dB
dB
dB
analog inpuT anD reFerence
SYMBOL
IN
+
IN
–
FS
LSB
V
IN
V
REF
C
S
(IN
+
)
PARAMETER
Absolute/Common Mode IN
+
Voltage
Absolute/Common Mode IN
–
Voltage
Full Scale of the Differential Input (IN
+
– IN
–
)
Least Significant Bit of the Output Code
Input Differential Voltage Range (IN
+
– IN
–
)
Reference Voltage Range (REF
+
– REF
–
)
IN
+
Sampling Capacitance
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
MIN
GND – 0.3V
GND – 0.3V
l
l
l
l
TYP
MAX
V
CC
+ 0.3V
V
CC
+ 0.3V
UNITS
V
V
V
0.5V
REF
/GAIN
FS/2
16
–FS
0.1
11
+FS
V
CC
V
V
pF
2481fd
For more information
www.linear.com/LTC2481
3
LTC2481
analog inpuT anD reFerence
SYMBOL
C
S
(IN
–
)
C
S
(V
REF
)
I
DC_LEAK
(IN
+
)
I
DC_LEAK
(IN
–
)
PARAMETER
IN
–
Sampling Capacitance
V
REF
Sampling Capacitance
IN
+
DC Leakage Current
IN
–
DC Leakage Current
Sleep Mode, IN
+
= GND
Sleep Mode, IN
–
= GND
Sleep Mode, V
REF
= V
CC
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
MIN
TYP
11
11
–10
–10
–100
1
1
1
10
10
100
MAX
UNITS
pF
pF
nA
nA
nA
I
DC_LEAK
(V
REF
) REF
+
, REF
–
DC Leakage Current
i
2
c DigiTal inpuTs anD DigiTal ouTpuTs
SYMBOL
V
IH
V
IL
V
IL(CA1)
V
IH(CA0/f0,CA1)
R
INH
R
INL
R
INF
I
I
V
HYS
V
OL
t
OF
t
SP
I
IN
C
I
C
B
C
CAX
V
IH(EXT,OSC)
V
IL(EXT,OSC)
PARAMETER
High Level Input Voltage
Low Level Input Voltage
Low Level Input Voltage for Address Pin
High Level Input Voltage for Address Pins
Resistance from CA0/f
0
, CA1 to V
CC
to Set
Chip Address Bit to 1
Resistance from CA1 to GND to Set Chip
Address Bit to 0
Resistance from CA0/f
0
, CA1 to V
CC
or
GND to Set Chip Address Bit to Float
Digital Input Current
Hysteresis of Schmitt Trigger Inputs
Low Level Output Voltage SDA
Output Fall Time from V
IHMIN
to V
ILMAX
Input Spike Suppression
Input Leakage
Capacitance for Each I/O Pin
Capacitance Load for Each Bus Line
External Capacitive Load On-Chip Address
Pins (CA0/f
0
,CA1) for Valid Float
High Level CA0/f
0
External Oscillator
Low Level CA0/f
0
External Oscillator
2.7V ≤ V
CC
< 5.5V
2.7V ≤ V
CC
< 5.5V
0.1V
CC
≤ V
IN
≤ V
CC
(Note 5)
I = 3mA
CONDITIONS
The
l
denotes the specifications which apply over
the full operating temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
MIN
l
l
l
l
l
l
l
l
TYP
MAX
0.3V
CC
0.05V
CC
UNITS
V
V
V
V
kΩ
kΩ
MΩ
0.7V
CC
0.95V
CC
10
10
2
–10
0.05V
CC
10
0.4
20+0.1C
B
250
50
1
10
400
10
V
CC
– 0.5V
0.5
µA
V
V
ns
ns
µA
pF
pF
pF
V
V
l
l
l
l
l
l
l
l
l
Bus Load C
B
10pF to 400pF (Note 14)
power requireMenTs
SYMBOL
V
CC
I
CC
PARAMETER
Supply Voltage
Supply Current
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
l
MIN
2.7
l
l
l
TYP
160
1
MAX
5.5
250
2
20
UNITS
V
µA
µA
µA
Conversion Mode (Note 11)
Sleep Mode (Note 11)
H-Grade
4
2481fd
For more information
www.linear.com/LTC2481
LTC2481
TiMing characTerisTics
SYMBOL
f
EOSC
t
HEO
t
LEO
t
CONV_1
PARAMETER
External Oscillator Frequency Range
External Oscillator High Period
External Oscillator Low Period
Conversion Time for 1x Speed Mode
50Hz Mode
50Hz Mode (H-Grade)
60Hz Mode
60Hz Mode (H-Grade)
Simultaneous 50Hz/60Hz Mode
Simultaneous 50Hz/60Hz Mode (H-Grade)
External Oscillator (Note 10)
50Hz Mode
50Hz Mode (H-Grade)
60Hz Mode
60Hz Mode (H-Grade)
Simultaneous 50Hz/60Hz Mode
Simultaneous 50Hz/60Hz Mode (H-Grade)
External Oscillator (Note 10)
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
MIN
10
0.125
0.125
157.2
157.2
131.0
131.0
144.1
144.1
78.7
65.6
72.2
TYP
MAX
1000
100
100
UNITS
kHz
µs
µs
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
160.3
160.3
133.6
133.6
146.9
146.9
41036/f
EOSC
80.3
66.9
73.6
20556/f
EOSC
163.5
165.1
136.3
137.6
149.9
151.0
81.9
82.7
68.2
68.9
75.1
75.6
t
CONV_2
Conversion Time for 2x Speed Mode
i
2
c TiMing characTerisTics
SYMBOL
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)
PARAMETER
SCL Clock Frequency
Hold Time (Repeated) START Condition
LOW Period of the SCL Clock Pin
HIGH Period of the SCL Clock Pin
Set-Up Time for a Repeated START Condition
Data Hold Time
Data Set-Up Time
Rise Time for Both SDA and SCL Signals
Fall Time for Both SDA and SCL Signals
Set-Up Time for STOP Condition
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 15)
CONDITIONS
l
l
l
l
l
l
l
MIN
0
0.6
1.3
0.6
0.6
0
100
20+0.1C
B
20+0.1C
B
0.6
TYP
MAX
400
UNITS
kHz
µs
µs
µs
µs
0.9
300
300
µs
ns
ns
ns
µs
(Note 14)
(Note 14)
l
l
l
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.
Note 3:
V
CC
= 2.7V to 5.5V unless otherwise specified.
V
REF
= REF
+
– REF
–
, V
REFCM
= (REF
+
+ REF
–
)/2, FS = 0.5V
REF
/GAIN;
V
IN
= IN
+
– IN
–
, V
INCM
= (IN
+
+ IN
–
)/2.
Note 4:
Use internal conversion clock or external conversion clock source
with f
EOSC
= 307.2kHz unless otherwise specified.
Note 5:
Guaranteed by design, not subject to test.
Note 6:
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.
Note 7:
50Hz mode (internal oscillator) or f
EOSC
= 256kHz ±2% (external
oscillator).
Note 8:
60Hz mode (internal oscillator) or f
EOSC
= 307.2kHz ±2% (external
oscillator).
Note 9:
Simultaneous 50Hz/60Hz mode (internal oscillator) or f
EOSC
=
280kHz ±2% (external oscillator).
Note 10:
The external oscillator is connected to the CA0/f
0
pin. The
external oscillator frequency, f
EOSC
, is expressed in kHz.
Note 11:
The converter uses the internal oscillator.
Note 12:
The output noise includes the contribution of the internal
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