LTC2485 Datasheet, PDF (1/40 Pages) Linear Technology – 24-Bit ΔΣ ADC with Easy Drive Input Current Cancellation and I2C Interface

LTC2485
24-Bit ∆Σ ADC with Easy Drive
Input Current Cancellation and I²C Interface
FEATURES
■ _{Easy Drive}^TM _{Technology Enables Rail-to-Rail}
Inputs with Zero Differential Input Current
■ _{Directly Digitizes High Impedance Sensors with}
Full Accuracy
■ _{Integrated Temperature Sensor}
■ _{GND to VCC Input/Reference Common Mode Range}
■ _{2-Wire I}²_{C Interface}
■ _{Programmable 50Hz, 60Hz or Simultaneous}
50Hz/60Hz Rejection Mode
■ _{2ppm (0.25LSB) INL, No Missing Codes}
■ _{1ppm Offset and 15ppm Full-Scale Error}
■ _{Selectable 2x Speed Mode}
■ _{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
U
APPLICATIO S
■ _{Direct Sensor Digitizer}
■ _{Weight Scales}
■ _{Direct Temperature Measurement}
■ _{Strain Gauge Transducers}
■ _{Instrumentation}
■ _{Industrial Process Control}
■ _{DVMs and Meters}
DESCRIPTIO
The LTC^®2485 combines a 24-bit plus sign No Latency ∆Σ^TM
analog-to-digital converter with patented Easy Drive tech-
nology and I²C 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 LTC2485 includes on-chip temperature sensor and an
oscillator. The LTC2485 can be configured through an I²C
interface to measure an external signal or internal tem-
perature 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 LTC2485 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 LTC2485 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.
TYPICAL APPLICATIO
V_CC
1µF
10k
SENSE
10k
I_DIFF = 0
1µF
REF⁺
V_IN+
V_CC
LTC2485
V_IN–
GND
REF^–
SCL
2-WIRE
SDA I²C INTERFACE
CA0/F₀
CA1
2485 TA01
6 ADDRESSES
+FS Error vs R_SOURCE at IN⁺ and IN^–
80
V_CC = 5V
60
40
VVV_{RIINNE+–F}
=
=
=
5V
3.75V
1.25V
F_O = GND
20 ^{TA = 25°C}
0
C_IN = 1µF
–20
–40
–60
–80
1
10
100 1k
10k 100k
R_SOURCE (Ω)
2485 TA02
2485fa
1