LTC2485_15 Datasheet, PDF (1/40 Pages) Linear Technology – 24-Bit ADC with Easy Drive Input Current Cancellation and I2C Interface

LTC2485
Features
n _{Easy Drive™ Technology Enables Rail-to-Rail Inputs}
with Zero Differential Input Current
n _{Directly Digitizes High Impedance Sensors with}
Full Accuracy
n _{GND to VCC Input/Reference Common Mode Range}
n _{2-Wire I}²_{C Interface}
n _{Programmable 50Hz, 60Hz or Simultaneous}
50Hz/60Hz Rejection Mode
n _{2ppm (0.25LSB) INL, No Missing Codes}
n _{1ppm Offset and 15ppm Full-Scale Error}
n _{Selectable 2x Speed Mode}
n _{No Latency: Digital Filter Settles in a Single Cycle}
n _{Single Supply 2.7V to 5.5V Operation}
n _{Internal Oscillator}
n _{Six Addresses Available and One Global Address for}
Synchronization
n _{Available in a Tiny (3mm × 3mm)}
10-Lead DFN Package
Applications
n _{Direct Sensor Digitizer}
n _{Weight Scales}
n _{Direct Temperature Measurement}
n _{Strain Gauge Transducers}
n _{Instrumentation}
n _{Industrial Process Control}
n _{DVMs and Meters}
24-Bit ∆Σ ADC with Easy Drive
Input Current Cancellation
and I²C Interface
Description
The LTC^®2485 combines a 24-bit plus sign No Latency
∆Σ™ analog-to-digital converter with patented Easy Drive
technology 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 an on-chip oscillator. The LTC2485
can be configured through an I²C interface to 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 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.
Typical Application
V_CC
0.1µF
1µF
10k
SENSE
10k
I_DIFF = 0
0.1µF
REF⁺
V_IN+
V_CC
LTC2485
V_IN–
GND
REF^–
SCL
2-WIRE
SDA I²C INTERFACE
CA0/f₀
CA1
2485 TA01a
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}
C_IN = 1µF
0
–20
–40
–60
–80
1
10
100 1k
10k 100k
R_SOURCE (Ω)
2485 TA01b
For more information www.linear.com/LTC2485
2485fd
1