channel (4-/8-differential) high speed 24-bit No Latency
∆Σ
™
ADCs. They use a proprietary delta-sigma architec-
ture enabling variable speed/resolution. Through a simple
4-wire serial interface, ten speed/resolution combinations
6.9Hz/280nV
RMS
to 3.5kHz/25µV
RMS
(4kHz with external
oscillator) can be selected with no latency between con-
version results or shift in DC accuracy (offset, full-scale,
linearity, drift). Additionally, a 2X speed mode can be
selected enabling output rates up to 7kHz (8kHz if an
external oscillator is used) with one cycle latency.
Any combination of single-ended or differential inputs
can be selected with a common mode input range from
ground to V
CC
, independent of V
REF
. While operating in
the 1X speed mode the first conversion following a new
speed, resolution, or channel selection is valid. Since
there is no settling time between conversions, all 8 dif-
ferential channels can be scanned at a rate of 500Hz.
At the conclusion of each conversion, the converter is
internally reset eliminating any memory effects between
successive conversions and assuring stability of the high
order delta-sigma modulator.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
No Latency ∆∑ and SoftSpan are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
n
n
n
n
n
n
n
n
n
Up to 8 Differential or 16 Single-Ended Input Channels
Up to 8kHz Output Rate (External f
O
)
Up to 4kHz Multiplexing Rate (External f
O
)
Selectable Speed/Resolution
2µV
RMS
Noise at 1.76kHz Output Rate
200nV
RMS
Noise at 13.8Hz Output Rate with
Simultaneous 50Hz/60Hz Rejection
Guaranteed Modulator Stability and Lock-Up
Immunity for any Input and Reference Conditions
0.0005% INL, No Missing Codes
Autosleep Enables 20µA Operation at 6.9Hz
< 5µV Offset (4.5V < V
CC
< 5.5V, –40°C to 85°C)
Differential Input and Differential Reference with
GND to V
CC
Common Mode Range
No Latency Mode, Each Conversion is Accurate Even
After a New Channel is Selected
Internal Oscillator—No External Components
LTC2445/LTC2449 Include MUXOUT/ADCIN for
External Buffering or Gain
Tiny QFN 5mm × 7mm Package
High Speed Multiplexing
Weight Scales
Auto Ranging 6-Digit DVMs
Direct Temperature Measurement
High Speed Data Acquisition
applicaTions
n
n
n
n
n
Typical applicaTion
Simple 24-Bit Variable Speed Data Acquisition System
4.5V TO 5.5V
1µF
CH0
CH1
•
•
•
CH7
CH8
•
•
•
CH15
COM
0.1
REF
–
GND
LTC2448
2444 TA01a
LTC2444/LTC2448
RMS Noise vs Speed
100
V
CC
= 5V
V
REF
= 5V
V
IN+
= V
IN–
= 0V
2X SPEED MODE
NO LATENCY MODE
2.8µV AT 880Hz
280nV AT 6.9Hz
(50/60Hz REJECTION)
REF
+
V
CC
F
O
SDI
SCK
SDO
CS
THERMOCOUPLE
16-CHANNEL
MUX
+
–
VARIABLE SPEED/
RESOLUTION
DIFFERENTIAL
24-BIT ∆∑ ADC
4-WIRE
SPI INTERFACE
RMS NOISE (µV)
= EXTERNAL OSCILLATOR
= INTERNAL OSCILLATOR
(SIMULTANEOUS 50Hz/60Hz
REJECTION AT 6.9Hz OUTPUT RATE)
10
1
1
1000
10
100
CONVERSION RATE (Hz)
10000
2440 TA01b
2444589fc
For more information
www.linear.com/LTC2444
1
LTC2444/LTC2445/
LTC2448/LTC2449
absoluTe MaxiMuM raTings
(Notes 1, 2)
Supply Voltage (V
CC
) to GND ....................... – 0.3V to 6V
Analog Input Pins Voltage
to GND ......................................–0.3V to (V
CC
+ 0.3V)
Reference Input Pins 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
LTC2444C/LTC2445C/
LTC2448C/LTC2449C............................... 0°C to 70°C
LTC2444I/LTC2445I/
LTC2448I/LTC2449I .............................–40°C to 85°C
Storage Temperature Range .................. –65°C to 150°C
pin conFiguraTion
LTC2444
TOP VIEW
GND
GND
SDO
SDO
SCK
SCK
SDI
CS
F
O
LTC2445
TOP VIEW
GND
GND
31 GND
30 REF
–
29 REF
+
28 V
CC
27 MUXOUTN
39
26 ADCINN
25 ADCINP
24 MUXOUTP
23 NC
22 CH7
21 CH6
20 NC
13 14 15 16 17 18 19
NC
NC
CH2
CH3
CH4
SDI
CH5
GND
NC
GND
31 GND
30 REF
–
29 REF
+
28 V
CC
27 MUXOUTN
39
26 ADCINN
25 ADCINP
24 MUXOUTP
23 CH15
22 CH14
21 CH13
20 CH12
13 14 15 16 17 18 19
CH5
CH6
CH7
CH8
CH9
CH10
CH11
SDI
CS
CS
F
O
F
O
38 37 36 35 34 33 32
GND 1
BUSY 2
EXT
3
GND 4
GND 5
GND 6
COM 7
NC 8
CH0 9
CH1 10
NC 11
NC 12
13 14 15 16 17 18 19
NC
NC
CH2
CH3
CH4
CH5
NC
39
31 GND
30 REF
–
29
REF
+
28 V
CC
27 NC
26 NC
25 NC
24 NC
23 NC
22 CH7
21 CH6
20 NC
GND 1
BUSY 2
EXT
3
GND 4
GND 5
GND 6
COM 7
NC 8
CH0 9
CH1 10
NC 11
NC 12
38 37 36 35 34 33 32
UHF PACKAGE
38-LEAD (5mm × 7mm) PLASTIC QFN
UHF PACKAGE
38-LEAD (5mm × 7mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 34°C/W
EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB
T
JMAX
= 125°C,
θ
JA
= 34°C/W
EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB
LTC2448
TOP VIEW
GND
GND
SDO
SCK
SDI
CS
F
O
LTC2449
TOP VIEW
SDO
SCK
31 GND
30 REF
–
29
REF
+
28 V
CC
27 NC
39
26 NC
25 NC
24 NC
23 CH15
22 CH14
21 CH13
20 CH12
13 14 15 16 17 18 19
CH5
CH6
CH7
CH8
CH9
CH10
CH11
GND 1
BUSY 2
EXT
3
GND 4
GND 5
GND 6
COM 7
CH0 8
CH1 9
CH2 10
CH3 11
CH4 12
38 37 36 35 34 33 32
GND 1
BUSY 2
EXT
3
GND 4
GND 5
GND 6
COM 7
CH0 8
CH1 9
CH2 10
CH3 11
CH4 12
38 37 36 35 34 33 32
UHF PACKAGE
38-LEAD (5mm × 7mm) PLASTIC QFN
UHF PACKAGE
38-LEAD (5mm × 7mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 34°C/W
EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB
T
JMAX
= 125°C,
θ
JA
= 34°C/W
EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB
2444589fc
2
For more information
www.linear.com/LTC2444
LTC2444/LTC2445/
LTC2448/LTC2449
orDer inForMaTion
LEAD FREE FINISH
LTC2444CUHF#PBF
LTC2444IUHF#PBF
LTC2445CUHF#PBF
LTC2445IUHF#PBF
LTC2448CUHF#PBF
LTC2448IUHF#PBF
LTC2449CUHF#PBF
LTC2449IUHF#PBF
TAPE AND REEL
LTC2444CUHF#TRPBF
LTC2444IUHF#TRPBF
LTC2445CUHF#TRPBF
LTC2445IUHF#TRPBF
LTC2448CUHF#TRPBF
LTC2448IUHF#TRPBF
LTC2449CUHF#TRPBF
LTC2449IUHF#TRPBF
http://www.linear.com/product/LTC2444#orderinfo
PART MARKING*
2444
2444
2445
2445
2448
2448
2449
2449
PACKAGE DESCRIPTION
38-Lead Plastic QFN
38-Lead Plastic QFN
38-Lead Plastic QFN
38-Lead Plastic QFN
38-Lead Plastic QFN
38-Lead Plastic QFN
38-Lead Plastic QFN
38-Lead Plastic QFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
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
0.1V ≤ V
REF
≤ V
CC
, –0.5
•
V
REF
≤ V
IN
≤ 0.5
•
V
REF
, (Note 5)
V
CC
= 5V, REF
+
= 5V, REF
–
= GND, V
INCM
= 2.5V, (Note 6)
REF
+
= 2.5V, REF
–
= GND, V
INCM
= 1.25V, (Note 6)
2.5V ≤ REF
+
≤ V
CC
, REF
–
= GND,
GND ≤ IN
+
= IN
–
≤ V
CC
(Note 12)
2.5V ≤ REF
+
≤ V
CC
, REF
–
= GND,
GND ≤ IN
+
= IN
–
≤ V
CC
REF
+
= 5V, REF
–
= GND, IN
+
= 3.75V, IN
–
= 1.25V
REF
+
= 2.5V, REF
–
= GND, IN
+
= 1.875V, IN
–
= 0.625V
2.5V ≤ REF
+
≤ V
CC
, REF
–
= GND,
IN
+
= 0.75
•
REF
+
, IN
–
= 0.25
•
REF
+
REF
+
= 5V, REF
–
= GND, IN
+
= 1.25V, IN
–
= 3.75V
REF
+
= 2.5V, REF
–
= GND, IN
+
= 0.625V, IN
–
= 1.875V
2.5V ≤ REF
+
≤ V
CC
, REF
–
= GND,
IN
+
= 0.25
•
REF
+
, IN
–
= 0.75
•
REF
+
5V ≤ V
CC
≤ 5.5V, REF
+
= 2.5V, REF
–
= GND, V
INCM
= 1.25V
5V ≤ V
CC
≤ 5.5V, REF
+
= 5V, REF
–
= GND, V
INCM
= 2.5V
REF
+
= 2.5V, REF
–
= GND, V
INCM
= 1.25V, (Note 6)
2.5V ≤ REF
+
≤ V
CC
, REF
–
= GND,
GND ≤ IN
–
= IN
+
≤ V
CC
l
l
l
l
l
l
l
elecTrical characTerisTics
MIN
24
TYP
5
3
2.5
20
10
10
0.2
10
10
0.2
15
15
15
120
MAX
15
5
UNITS
Bits
ppm of V
REF
ppm of V
REF
µV
nV/°C
50
50
ppm of V
REF
ppm of V
REF
ppm of V
REF
/°C
50
50
ppm of V
REF
ppm of V
REF
ppm of V
REF
/°C
ppm of V
REF
ppm of V
REF
ppm of V
REF
dB
Input Common Mode Rejection DC
2444589fc
For more information
www.linear.com/LTC2444
3
LTC2444/LTC2445/
LTC2448/LTC2449
The
l
denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
SYMBOL
IN
+
IN
–
V
IN
REF
+
REF
–
V
REF
C
S(IN+)
C
S(IN–)
C
S(REF+)
C
S(REF–)
REF+, REF–)
analog inpuT anD reFerence
PARAMETER
Absolute/Common Mode IN
+
Voltage
Absolute/Common Mode IN
–
Voltage
Input Differential Voltage Range
(IN
+
– IN
–
)
Absolute/Common Mode REF
+
Voltage
Absolute/Common Mode REF
–
Voltage
Reference Differential Voltage Range
(REF
+
– REF
–
)
IN
+
Sampling Capacitance
IN
–
Sampling Capacitance
REF
+
Sampling Capacitance
REF
–
Sampling Capacitance
CONDITIONS
l
l
l
l
l
l
MIN
GND – 0.3V
GND – 0.3V
–V
REF
/2
0.1
GND
0.1
TYP
MAX
V
CC
+ 0.3V
V
CC
+ 0.3V
V
REF
/2
V
CC
V
CC
– 0.1V
V
CC
UNITS
V
V
V
V
V
V
pF
pF
pF
pF
2
2
2
2
CS
= V
CC
, IN
+
= GND, IN
–
= GND,
REF
+
= 5V, REF
–
= GND
l
I
DC_LEAK(IN+, IN–,
Leakage Current, Inputs and Reference
I
SAMPLE(IN+, IN–,
Average Input/Reference Current
During Sampling
REF+, REF–)
t
OPEN
QIRR
MUX Break-Before-Make
MUX Off Isolation
–15
1
15
nA
nA
ns
dB
Varies, See Applications Section
50
V
IN
= 2V
P-P
DC to 1.8MHz
120
The
l
denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
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
,
EXT,
SDI
Digital Input Current, SCK
Digital Input Capacitance,
CS,
F
O
, SDI
Digital Input Capacitance, SCK
High Level Output Voltage, SDO, BUSY
Low Level Output Voltage, SDO, BUSY
High Level Output Voltage, SCK
Low Level Output Voltage, SCK
Hi-Z Output Leakage, SDO
(Note 8)
I
O
= –800µA
I
O
= 1.6mA
I
O
= –800µA (Note 9)
I
O
= 1.6mA (Note 9)
l
l
l
l
l
DigiTal inpuTs anD DigiTal ouTpuTs
CONDITIONS
4.5V ≤ V
CC
≤ 5.5V
4.5V ≤ V
CC
≤ 5.5V
MIN
l
l
l
l
l
l
TYP
MAX
0.8
UNITS
V
V
V
V
µA
µA
pF
pF
V
2.5
2.5
0.8
–10
–10
10
10
V
CC
– 0.5V
0.4V
V
CC
– 0.5V
0.4V
–10
10
10
10
4.5V ≤ V
CC
≤ 5.5V (Note 8)
4.5V ≤ V
CC
≤ 5.5V (Note 8)
0V ≤ V
IN
≤ V
CC
0V ≤ V
IN
≤ V
CC
(Note 8)
V
V
V
µA
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 3)
SYMBOL
V
CC
I
CC
PARAMETER
Supply Voltage
Supply Current
Conversion Mode
Sleep Mode
CS
= 0V (Note 7)
CS
= V
CC
(Note 7)
CONDITIONS
l
l
l
power requireMenTs
MIN
4.5
TYP
MAX
5.5
UNITS
V
mA
µA
2444589fc
8
8
11
30
4
For more information
www.linear.com/LTC2444
LTC2444/LTC2445/
LTC2448/LTC2449
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 3)
SYMBOL
f
EOSC
t
HEO
t
LEO
t
CONV
PARAMETER
External Oscillator Frequency Range
External Oscillator High Period
External Oscillator Low Period
Conversion Time
OSR = 256 (SDI = 0)
OSR = 32768 (SDI = 1)
External Oscillator, 1X Mode
(Notes 10, 13)
f
ISCK
D
ISCK
f
ESCK
t
LESCK
t
HESCK
t
DOUT_ISCK
t
DOUT_ESCK
t
1
t
2
t
3
t
4
t
KQMAX
t
KQMIN
t
5
t
6
t
7
t
8
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 Z
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 Set-Up Before SCK
↑
SDI Hold After SCK
↑
(Note 5)
(Note 5)
(Note 5)
Internal Oscillator (Note 9)
External Oscillator (Notes 9, 10)
(Note 9)
(Note 8)
(Note 8)
(Note 8)
Internal Oscillator (Notes 9, 11)
External Oscillator (Notes 9, 10)
(Note 8)
(Note 12)
(Note 12)
(Note 9)
(Notes 8, 12)
l
l
l
l
l
l
l
TiMing characTerisTics
CONDITIONS
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
MIN
0.1
25
25
0.99
126
TYP
MAX
12
10000
10000
UNITS
MHz
ns
ns
ms
ms
ms
1.13
145
40 • OSR +178
f
EOSC
(kHz)
1.33
170
0.8
45
25
25
41.6
0.9
f
EOSC
/10
1
55
20
MHz
Hz
%
MHz
ns
ns
35.3
320/f
EOSC
32/f
EOSC
30.9
µs
s
s
ns
ns
µs
ns
0
0
5
25
25
25
25
15
50
50
10
10
ns
ns
ns
ns
ns
ns
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
= 4.5V to 5.5V unless otherwise specified.
V
REF
= REF
+
– REF
–
, V
REFCM
= (REF
+
+ REF
–
)/2;
V
IN
= IN
+
– IN
–
, V
INCM
= (IN
+
+ IN
–
)/2.
Note 4:
F
O
pin tied to GND or to external conversion clock source with
f
EOSC
= 10MHz 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:
The converter uses the internal oscillator.
Note 8:
The converter is in external SCK mode of operation such that the
SCK pin is used as a digital input. The frequency of the clock signal driving
SCK during the data output is f
ESCK
and is expressed in Hz.
Note 9:
The converter is in internal SCK mode of operation such that the
SCK pin is used as a digital output. In this mode of operation, the SCK pin
has a total equivalent load capacitance of C
LOAD
= 20pF.
Note 10:
The external oscillator is connected to the F
O
pin. The external
oscillator frequency, f
EOSC
, is expressed in Hz.
Note 11:
The converter uses the internal oscillator. F
O
= 0V.
Note 12:
Guaranteed by design and test correlation.
Note 13:
There is an internal reset that adds an additional 5 to 15 f
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