LTC2440 Datasheet, PDF (1/28 Pages) Linear Technology – 24-Bit High Speed Differential delta-sigma ADC with Selectable Speed/Resolution

LTC2440
24-Bit High Speed
Differential ∆Σ ADC with
Selectable Speed/Resolution
FEATURES
■ _{Up to 3.5kHz Output Rate}
■ _{Selectable Speed/Resolution}
■ _{2µVRMS Noise at 880Hz Output Rate}
■ _{200nVRMS Noise at 6.9Hz Output Rate with}
Simultaneous 50/60Hz Rejection
■ _{0.0005% INL, No Missing Codes}
■ _{Autosleep Enables 20µA Operation at 6.9Hz}
■ _{< 5µV Offset (4.5V < VCC < 5.5V, – 40°C to 85°C)}
■ _{Differential Input and Differential Reference with}
GND to V_CC Common Mode Range
■ _{No Latency, Each Conversion is Accurate Even After}
an Input Step
■ _{Internal Oscillator—No External Components}
■ _{Pin Compatible with the LTC2410}
■ _{24-Bit ADC in Narrow 16-Lead SSOP Package}
U
APPLICATIO S
■ _{High Speed Multiplexing}
■ _{Weight Scales}
■ _{Auto Ranging 6-Digit DVMs}
■ _{Direct Temperature Measurement}
■ _{High Speed Data Acquisition}
DESCRIPTIO
The LTC^®2440 is a high speed 24-bit No Latency ∆Σ^TM ADC
with 5ppm INL and 5µV offset. It uses proprietary delta-
sigma architecture enabling variable speed and resolution
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/resolution
combination can be easily selected. The accuracy (offset,
full-scale, linearity, drift) and power dissipation are inde-
pendent of the speed selected. Since there is no latency,
a speed/resolution change may be made between conver-
sions 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 com-
municates through a flexible 3-wire or 4-wire digital inter-
face that is compatible with the LTC2410 and is available
in a narrow 16-lead SSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
No Latency ∆Σ is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
Simple 24-Bit 2-Speed Acquisition System
4.5V TO 5.5V
2
V_CC
BUSY ¹⁵
REFERENCE VOLTAGE
0.1V TO V_CC
LTC2440
3 _REF+
F_O ¹⁴
4 _REF–
13
SCK
ANALOG INPUT
–0.5V_REF TO 0.5V_REF
5 _IN+
6 _IN–
12
SDO
11
CS
1, 8, 9, 16
GND
7
SDI
EXT ¹⁰
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
sn2440, 2440fas
1