LTC2484
24-Bit
∆Σ
ADC with
Easy Drive Input Current Cancellation
FEATURES
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■
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■
DESCRIPTIO
Easy Drive Technology Enables Rail-to-Rail Inputs
with Zero Differential Input Current
Directly Digitizes High Impedance Sensors with
Full Accuracy
600nV RMS Noise
Integrated Temperature Sensor
GND to V
CC
Input/Reference Common Mode Range
Programmable 50Hz, 60Hz or Simultaneous
50Hz/60Hz Rejection Mode
2ppm INL, No Missing Codes
1ppm Offset and 15ppm Total Unadjusted Error
Selectable 2x Speed Mode (15Hz Using Internal
Oscillator)
No Latency: Digital Filter Settles in a Single Cycle
Single Supply 2.7V to 5.5V Operation
Internal Oscillator
Available in a Tiny (3mm
×
3mm) 10-Lead
DFN Package
The LTC
®
2484 combines a 24-bit No Latency
∆Σ™
analog-
to-digital converter with patented Easy Drive™ technol-
ogy. 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 LTC2484 includes an on-chip temperature sensor and
oscillator. The LTC2484 can be configured to measure an
external signal or internal temperature sensor and reject
line frequencies. 50Hz, 60Hz or simultaneous 50Hz/60Hz
line frequency rejection can be selected as well as a 2x
speed-up mode.
The LTC2484 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 LTC2484 includes an on-chip trimmed oscil-
lator, eliminating the need for external crystals or oscilla-
tors. Absolute accuracy and low drift are automatically
maintained through continuous, transparent, offset and
full-scale calibration.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
No Latency
∆Σ
and Easy Drive are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Patent pending.
APPLICATIO S
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Direct Sensor Digitizer
Weight Scales
Direct Temperature Measurement
Strain Gauge Transducers
Instrumentation
Industrial Process Control
DVMs and Meters
TYPICAL APPLICATIO
V
CC
+FS Error vs R
SOURCE
at IN
+
and IN
–
V
CC
= 5V
60 V
REF
= 5V
V
IN+
= 3.75V
–
= 1.25V
40 V
IN
F
O
= GND
20 T
A
= 25°C
C
IN
= 1µF
0
–20
–40
–60
–80
1
10
1k
R
SOURCE
(Ω)
100
10k
100k
2484 TA02
80
10k
SENSE
10k
I
DIFF
= 0
1µF
V
IN+
V
REF
LTC2484
V
CC
SDI
SDO
SCK
4-WIRE
SPI INTERFACE
V
IN–
GND
F
O
CS
2484 TA01
+FS ERROR (ppm)
1µF
U
2484fa
U
U
1
LTC2484
ABSOLUTE
(Notes 1, 2)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SDI
V
CC
V
REF
IN
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
LTC2484C ................................................... 0°C to 70°C
LTC2484I ................................................ – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 125°C
1
2
3
4
5
11
10 F
O
9 SCK
8 GND
7 SDO
6 CS
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 PART NUMBER
LTC2484CDD
LTC2484IDD
DD PART MARKING*
LBSS
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
*The temperature grade is indicated by a label on the shipping container.
ELECTRICAL CHARACTERISTICS ( OR AL 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 14)
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
The
●
denotes specifications which apply
over the full operating temperature range, otherwise specifications are T
A
= 25°C. (Notes 3, 4)
MIN
●
●
●
●
TYP
2
1
0.5
10
MAX
10
2.5
25
UNITS
Bits
ppm of V
REF
ppm of V
REF
µV
nV/°C
ppm of V
REF
ppm of
V
REF
/°C
24
0.1
●
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
= 2.5V, V
IN(CM)
= 1.25V
5V
≤
V
CC
≤
5.5V, V
REF
= 5V, V
IN(CM)
= 2.5V
2.7V
≤
V
CC
≤
5.5V, V
REF
= 2.5V, V
IN(CM)
= 1.25V
5V
≤
V
CC
≤
5.5V, V
REF
= 5V, GND
≤
IN
–
= IN
+
≤
V
CC
(Note 13)
T
A
= 27°C
25
0.1
15
ppm of V
REF
ppm of
V
REF
/°C
ppm of V
REF
ppm of V
REF
ppm of V
REF
µV
RMS
mV
mV/°C
Output Noise
Internal PTAT Signal
Internal PTAT Temperature Coefficient
0.6
420
1.4
2
U
2484fa
W
U
W
U
U
W W
W
LTC2484
ELECTRICAL CHARACTERISTICS (2x 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
Output Noise
CONDITIONS
0.1
≤
V
REF
≤
V
CC
, –FS
≤
V
IN
≤
+FS (Note 5)
The
●
denotes specifications which apply over the full
operating temperature range, otherwise specifications are T
A
= 25°C. (Notes 3, 4)
MIN
●
●
●
●
TYP
2
1
0.5
100
MAX
10
2
25
UNITS
Bits
ppm of V
REF
mV
nV/°C
ppm of V
REF
ppm of
V
REF
/°C
24
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 14)
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
0.1
●
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
(Note 13)
25
0.1
0.84
ppm of V
REF
ppm of
V
REF
/°C
µV
RMS
CO VERTER 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
●
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
MIN
●
●
●
●
●
●
●
A ALOG I PUT A D REFERE CE
The
●
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
SYMBOL
IN
+
IN
–
FS
LSB
V
IN
V
REF
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
●
●
●
●
U
U
U
U
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
(Notes 5, 8)
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 (Note 7)
V
REF
= 2.5V, IN
–
= IN
+
= GND (Note 8)
140
140
140
110
110
87
120
140
120
120
120
120
120
dB
dB
dB
dB
dB
dB
dB
U
CONDITIONS
MIN
GND – 0.3V
GND – 0.3V
0.5V
REF
FS/2
24
–FS
0.1
TYP
MAX
V
CC
+ 0.3V
V
CC
+ 0.3V
UNITS
V
V
V
+FS
V
CC
V
V
2484fa
3
LTC2484
A ALOG I PUT A D REFERE CE
The
●
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
SYMBOL
C
S
(IN
+
)
C
S
(IN
–
)
C
S
(V
REF
)
I
DC_LEAK
(IN
+
)
I
DC_LEAK
(IN
–
)
I
DC_LEAK
(V
REF
)
PARAMETER
IN
+
Sampling Capacitance
IN
–
Sampling Capacitance
V
REF
Sampling Capacitance
IN
+
DC Leakage Current
IN
–
DC Leakage Current
V
REF
DC Leakage Current
Sleep Mode, IN
+
= GND
Sleep Mode, IN
–
= GND
Sleep Mode, V
REF
= V
CC
●
●
●
DIGITAL I PUTS A D DIGITAL OUTPUTS
SYMBOL
V
IH
V
IL
V
IH
V
IL
I
IN
I
IN
C
IN
C
IN
V
OH
V
OL
V
OH
V
OL
I
OZ
PARAMETER
High Level Input Voltage
CS, F
O
, SDI
Low Level Input Voltage
CS, F
O
, SDI
High Level Input Voltage
SCK
Low Level Input Voltage
SCK
Digital Input Current
CS, F
O
, SDI
Digital Input Current
SCK
Digital Input Capacitance
CS, F
O
, SDI
Digital Input Capacitance
SCK
High Level Output Voltage
SDO
Low Level Output Voltage
SDO
High Level Output Voltage
SCK
Low Level Output Voltage
SCK
Hi-Z Output Leakage
SDO
I
O
= –800µA
I
O
= 1.6mA
I
O
= –800µA
I
O
= 1.6mA
CONDITIONS
2.7V
≤
V
CC
≤
5.5V
2.7V
≤
V
CC
≤
5.5V
The
●
denotes specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
MIN
●
●
●
●
●
●
2.7V
≤
V
CC
≤
5.5V (Note 10)
2.7V
≤
V
CC
≤
5.5V (Note 10)
0V
≤
V
IN
≤
V
CC
0V
≤
V
IN
≤
V
CC
(Note 10)
POWER REQUIRE E TS
SYMBOL
V
CC
I
CC
PARAMETER
Supply Voltage
Supply Current
The
●
denotes specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
●
Conversion Mode (Note 12)
Sleep Mode (Note 12)
4
U
U W
U
U
U
U
U
CONDITIONS
MIN
TYP
11
11
11
MAX
UNITS
pF
pF
pF
–10
–10
–100
1
1
1
10
10
100
nA
nA
nA
TYP
MAX
UNITS
V
V
CC
– 0.5
0.5
V
CC
– 0.5
0.5
–10
–10
10
10
10
10
V
V
V
µA
µA
pF
pF
V
●
●
●
●
●
V
CC
– 0.5
0.4
V
CC
– 0.5
0.4
–10
10
V
V
V
µA
MIN
2.7
●
●
TYP
160
1
MAX
5.5
250
2
UNITS
V
µA
µA
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LTC2484
TI I G 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
The
●
denotes specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
(Note 15)
●
●
●
t
CONV_2
f
ISCK
D
ISCK
f
ESCK
t
LESCK
t
HESCK
t
DOUT_ISCK
t
DOUT_ESCK
t
1
t2
t3
t4
t
KQMAX
t
KQMIN
t
5
t
6
t
7
t
8
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
REFCM
= V
REF
/2, FS = 0.5V
REF
V
IN
= IN
+
– IN
–
, V
IN(CM)
= (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).
UW
MIN
10
0.125
0.125
157.2
131.0
144.1
78.7
65.6
72.2
TYP
MAX
4000
100
100
UNITS
kHz
µs
µs
ms
ms
ms
ms
ms
ms
ms
ms
kHz
kHz
50Hz Mode
60Hz Mode
Simultaneous 50Hz/60Hz Mode
External Oscillator
50Hz Mode
60Hz Mode
Simultaneous 50Hz/60Hz Mode
External Oscillator
Internal Oscillator (Note 10)
External Oscillator (Notes 10, 11)
(Note 10)
(Note 10)
(Note 10)
(Note 10)
Internal Oscillator (Notes 10, 12)
External Oscillator (Notes 10, 11)
(Note 10)
●
●
●
●
●
●
●
●
160.3
163.5
133.6
136.3
146.9
149.9
41036/f
EOSC
(in kHz)
81.9
68.2
75.1
20556/f
EOSC
(in kHz)
38.4
f
EOSC
/8
80.3
66.9
73.6
Conversion Time for 2x Speed Mode
Internal SCK Frequency
Internal SCK Duty Cycle
External SCK Frequency Range
External SCK Low Period
External SCK High Period
Internal SCK 32-Bit Data Output Time
External SCK 32-Bit Data Output Time
CS↓ to SDO Low
CS↑ to SDO High Z
CS↓ to SCK↓
CS↓ to SCK↑
SCK↓ to SDO Valid
SDO Hold After SCK↓
SCK Set-Up Before CS↓
SCK Hold After CS↓
SDI Setup Before SCK↑
SDI Hold After SCK↑
●
●
●
●
●
●
●
●
●
45
125
125
0.81
55
4000
%
kHz
ns
ns
0.83
0.85
256/f
EOSC
(in kHz)
32/f
ESCK
(in kHz)
200
200
200
200
ms
ms
ms
ns
ns
ns
ns
ns
ns
ns
0
0
0
50
15
50
(Note 10)
(Note 10)
(Note 5)
●
●
●
●
●
●
50
100
100
ns
ns
ns
(Note 5)
(Note 5)
●
●
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 SCK can be configured in external SCK mode or internal SCK
mode. In external SCK mode, the SCK pin is used as digital input and the
driving clock is f
ESCK
. In internal SCK mode, the SCK pin is used as digital
output and the output clock signal during the data output is f
ISCK
.
Note 11:
The external oscillator is connected to the F
O
pin. The external
oscillator frequency, f
EOSC
, is expressed in kHz.
Note 12:
The converter uses the internal oscillator.
Note 13:
The output noise includes the contribution of the internal
calibration operations.
Note 14:
Guaranteed by design and test correlation.
Note 15:
Refer to Applications Information section for performance vs
data rate graphs.
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