LTC2440_15 Datasheet, PDF (1/28 Pages) Linear Technology – 24-Bit High Speed Differential ADC with Selectable Speed/Resolution

LTC2440
FEATURES
24-Bit High Speed
Differential Δ∑ ADC with
Selectable Speed/Resolution
DESCRIPTION
n _{Up to 3.5kHz Output Rate}
n _{Selectable Speed/Resolution}
n _{2μVRMS Noise at 880Hz Output Rate}
n _{200nVRMS Noise at 6.9Hz Output Rate with}
Simultaneous 50/60Hz Rejection
n _{0.0005% INL, No Missing Codes}
n _{Autosleep Enables 20μA Operation at 6.9Hz}
n _{<5μV Offset (4.5V < VCC < 5.5V, –40°C to 85°C)}
n _{Differential Input and Differential Reference with}
GND to V_CC Common Mode Range
n _{No Latency, Each Conversion is Accurate Even After}
an Input Step
n _{Internal Oscillator—No External Components}
n _{Pin Compatible with the LTC2410}
n _{24-Bit ADC in Narrow 16-Lead SSOP Package}
APPLICATIONS
n _{High Speed Multiplexing}
n _{Weight Scales}
n _{Auto Ranging 6-Digit DVMs}
n _{Direct Temperature Measurement}
n _{High Speed Data Acquisition}
The LTC^®2440 is a high speed 24-bit No Latency Δ∑^TM
ADC with 5ppm INL and 5μV offset. It uses proprietary
delta-sigma architecture enabling variable speed and reso-
lution with no latency. Ten speed/resolution combinations
(6.9Hz/200nV_RMS to 3.5kHz/25μV_RMS) are programmed
through a simple serial interface. Alternatively, by tying a
single pin HIGH or LOW, a fast (880Hz/2μV_RMS) or ultralow
noise (6.9Hz, 200nV_RMS, 50/60Hz rejection) speed/reso-
lution combination can be easily selected. The accuracy
(offset, full-scale, linearity, drift) and power dissipation
are independent of the speed selected. Since there is no
latency, a speed/resolution change may be made between
conversions with no degradation in performance.
Following each conversion cycle, the LTC2440 automati-
cally enters a low power sleep state. Power dissipation
may be reduced by increasing the duration of this sleep
state. For example, running at the 3.5kHz conversion speed
but reading data at a 100Hz rate draws 240μA average
current (1.1mW) while reading data at a 7Hz output rate
draws only 25μA (125μW).The LTC2440 communicates
through a flexible 3-wire or 4-wire digital interface that is
compatible with the LTC2410 and is available in a narrow
16-lead SSOP package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
No Latency Δ∑ is a trademark of Linear Technology Corporation. All other trademarks are
the property of their respective owners.
TYPICAL APPLICATION
Simple 24-Bit 2-Speed Acquisition System
4.5V TO 5.5V
REFERENCE VOLTAGE
0.1V TO V_CC
ANALOG INPUT
–0.5V_REF TO 0.5V_REF
V_CC BUSY
LTC2440
REF⁺
f_O
4 _REF–
SCK
IN⁺
SDO
IN^–
CS
SDI
GND
EXT
3-WIRE
V_CC
SPI INTERFACE 6.9Hz, 200nV NOISE,
50/60Hz REJECTION
2440 TA01
10-SPEED SERIAL
PROGRAMMABLE
880Hz OUTPUT RATE,
2μV NOISE
2440 TA01
Speed vs RMS Noise
100
V_CC = 5V
VV^RINE+F
=
=
5V
V_IN–
=
0V
10
2μV AT 880Hz
200nV AT 6.9Hz
1 (50/60Hz REJECTION)
0.1
1
10
100
1000
CONVERSION RATE (Hz)
10000
2440 TA02
2440fd
1