FEATURES
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LTC2442
24-Bit High Speed
4-Channel
DS
ADC
with Integrated Amplifier
DESCRIPTION
The
LTC
®
2442
is an ultra high precision, variable speed,
24-bit
DS
™
ADC with integrated amplifier. The amplifier
can be configured as a buffer for easy input drive of high
impedance sensors. 1 part-per-million (ppm) linearity is
achievable when the amplifier is configured in unity gain.
External resistors can be used to set a gain for increased
resolution of low level input signals. The positive and
negative amplifier supply pins may be tied directly to V
CC
(4.5V to 5.5V) and GND or biased above V
CC
and below
GND for rail-to-rail input signals.
The proprietary
DS
architecture ensures stable DC ac-
curacy through continuous transparent calibration. Ten
speed/resolution combinations from 6.9Hz/220nV
RMS
to
3.5kHz/25µV
RMS
can be selected with no latency or shift
in DC accuracy. Additionally, a 2X speed mode can be
selected enabling output rates up to 7kHz (8kHz with an
external oscillator) with one cycle latency.
Any combination of single-ended (up to 4 inputs) or dif-
ferential (up to 2 inputs) can be selected with a common
mode input range from ground to V
CC
. While operating in
the 1X speed mode the first conversion following a new
speed/resolution or channel selection is valid.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. No Latency
DS
and SoftSpan are trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners. Protected by U.S.
Patents including 6140950, 6169506, 6411242, 6639526.
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1ppm Linearity with No Missing Codes
Integrated Amplifier for Direct Sensor Digitization
2 Differential or 4 Single-Ended Input Channels
Up to 8kHz Output Rate (External f
O
)
Up to 4kHz Multiplexing Rate (External f
O
)
Selectable Speed/Resolution
2.1µV
RMS
Noise at 1.76kHz Output Rate
220nV
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
<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
36-Lead SSOP Package
APPLICATIONS
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Auto Ranging 6-Digit DVMs
High Speed Multiplexing
Weight Scales
Direct Temperature Measurement
High Speed Data Acquisition
TYPICAL APPLICATION
0.1µF
High Precision Data Acquisition System
5
4
4.5V TO 15V
4.5V TO 5.5V
V
CC
F
O
SDI
SCK
SDO
CS
LTC2442 Integral Non-Linearity
V
INCM
= 2.048V
V
REF
= 4.096V
V
CC
= 5V
V
+
= 5V
V
–
= 0V
3
INL ERROR (ppm)
= EXTERNAL OSCILLATOR
= INTERNAL OSCILLATOR
(SIMULTANEOUS 50Hz/60Hz
REJECTION AT 6.9Hz OUTPUT RATE)
4-WIRE
SPI INTERFACE
V
+
V
REF
+
CH0
HIGH Z
2-CHANNEL
DIFFERENTIAL/
4-CHANNEL
SINGLE ENDED
CH1
CH2
CH3
COM
V
–
V
REF
–
–15V TO 0V
AUTO-CAL
–
VARIABLE SPEED/
RESOLUTION
DIFFERENTIAL
24-BIT
∆Σ
ADC
2
1
0
–1
–2
–3
–4
–
+
+
0.1µF
GND LTC2442
2442 TA01
–5
–2.048
0
–1.024
1.024
V
IN
DIFFERENTIAL (V)
2.048
2442 TA02
2442fb
For more information
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1
LTC2442
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
PIN CONFIGURATION
TOP VIEW
SCK
BUSY
EXT
DGND
AGND
CH0
CH1
CH2
CH3
1
2
3
4
5
6
7
8
9
36 SDO
35
CS
34 F
O
33 SDI
32 GND
31 REF
–
30 REF
+
29 V
CC
28 COM
27 MUXOUTA
26 MUXOUTB
25 +INA
24 V–
23 NC
22 NC
21 V+
20 NC
19 +INB
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
LTC2442CG .................................................. 0°C to 70°C
LTC2442IG ...............................................–40°C to 85°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
Amplifier Supply Voltage (V
+
to V
–
) ..........................36V
ADCINB 10
ADCINA 11
OUTA 12
–INA 13
NC 14
NC 15
NC 16
OUTB 17
–INB 18
G PACKAGE
36-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 160°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC2442CG#PBF
LTC2442IG#PBF
TAPE AND REEL
LTC2442CG#TRPBF
LTC2442IG#TRPBF
http://www.linear.com/product/LTC2442#orderinfo
PART MARKING
LTC2442CG
LTC2442IG
PACKAGE DESCRIPTION
36-Lead Plastic SSOP
36-Lead Plastic SSOP
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on nonstandard lead based finish parts.
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.
2442fb
2
For more information
www.linear.com/LTC2442
LTC2442
ELECTRICAL CHARACTERISTICS
PARAMETER
Resolution (No Missing Codes)
Integral Nonlinearity
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, 14)
V
CC
= 5V, REF
+
= 2.5V, REF
–
= GND, V
INCM
= 1.25V (Note 6, 14)
REF
+
= 4.096V, REF
–
= GND, V
INCM
= 2.048V (Note 6, 14)
2.5V ≤ REF
+
≤ V
CC
, REF
–
= GND,
GND ≤ SEL
+
= SEL
–
≤ V
CC
(Note 12)
2.5V ≤ REF
+
≤ V
CC
, REF
–
= GND,
GND ≤ SEL
+
= SEL
–
≤ V
CC
REF
+
= 5V, REF
–
= GND, SEL
+
= 3.75V, SEL
–
= 1.25V
REF
+
= 2.5V, REF
–
= GND, SEL
+
= 1.875V, SEL
–
= 0.625V
2.5V ≤ REF
+
≤ V
CC
, REF
–
= GND,
SEL
+
= 0.75 • REF
+
, SEL
–
= 0.25 • REF
+
REF
+
= 5V, REF
–
= GND, SEL
+
= 1.25V, SEL
–
= 3.75V
REF
+
= 2.5V, REF
–
= GND, SEL
+
= 0.625V, SEL
–
= 1.875V
2.5V ≤ REF
+
≤ V
CC
, REF
–
= GND,
SEL
+
= 0.25 • REF
+
, SEL
–
= 0.75 • REF
+
5V ≤ V
CC
≤ 5.5V, REF
+
= 2.5V, REF
–
= GND, V
INCM
= 1.25V (Note 6)
5V ≤ V
CC
≤ 5.5V, 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 ≤ SEL
–
= SEL
+
≤ V
CC
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The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4, 15)
MIN
24
2
2
1
2.5
20
10
10
0.2
10
10
0.2
12
12
12
120
50
50
50
50
10
7
5
TYP
MAX
UNITS
Bits
ppm of V
REF
ppm of V
REF
ppm of V
REF
µV
nV/°C
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
/°C
ppm of V
REF
ppm of V
REF
ppm of V
REF
dB
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
Input Common Mode Rejection DC
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 15)
SYMBOL
SEL
+
SEL
–
V
IN
REF
+
REF
–
V
REF
C
S(ADCINA)
C
S(ADCINB)
C
S(REF
+
)
C
S(REF
–
)
I
DC_LEAK(SEL
+
, SEL
–
,
REF , REF )
+
–
ANALOG INPUT AND REFERENCE
PARAMETER
Absolute/Common Mode SEL
+
Voltage
Absolute/Common Mode SEL
–
Voltage
Input Differential Voltage Range
(SEL
+
– SEL
–
)
Absolute/Common Mode REF
+
Voltage
Absolute/Common Mode REF
–
Voltage
Reference Differential Voltage Range
(REF
+
– REF
–
)
ADCINA Sampling Capacitance
ADCINB Sampling Capacitance
REF
+
Sampling Capacitance
REF
–
Sampling Capacitance
Leakage Current, Inputs and Reference
MUX Break-Before-Make
MUX Off Isolation
CONDITIONS
SEL
+
is the Positive Selected
Input Channel, see Table 3
SEL
–
is the Negative Selected
Input Channel, see Table 3
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MIN
GND – 0.3
GND – 0.3
–V
REF
/2
0.1
GND
0.1
TYP
MAX
V
CC
+ 0.3
V
CC
+ 0.3
V
REF
/2
V
CC
V
CC
– 0.1
V
CC
UNITS
V
V
V
V
V
V
pF
pF
pF
pF
2
2
2
2
CS
= V
CC
, SEL
+
= GND, SEL
–
=
GND, REF
+
= 5V, REF
–
= GND
V
IN
= 2V
P-P
DC to 1.8MHz
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–15
1
50
120
15
nA
ns
dB
t
OPEN
QIRR
2442fb
For more information
www.linear.com/LTC2442
3
LTC2442
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
,
EXT,
SDI
Low Level Input Voltage
CS,
F
O
,
EXT,
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
,
EXT,
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
= 1.6µA
I
O
= –800µA (Note 9)
I
O
= 1.6µA (Note 9)
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DIGITAL INPUTS AND DIGITAL OUTPUTS
CONDITIONS
4.5V ≤ V
CC
≤ 5.5V
4.5V ≤ V
CC
≤ 5.5V
MIN
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TYP
MAX
UNITS
V
2.5
0.8
2.5
0.8
–10
–10
10
10
V
CC
– 0.5
0.4
V
CC
– 0.5
0.4
–10
10
10
10
V
V
V
µA
µA
pF
pF
V
V
V
V
µA
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)
POWER REQUIREMENTS
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Notes 3)
SYMBOL
V
CC
V
+
V
–
I
CC
PARAMETER
Supply Voltage
Amplifier Positive Supply
Amplifier Negative Supply
Supply Current
Amplifiers and ADC
CONDITIONS
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MIN
4.5
4.5
–15
TYP
MAX
5.5
15
0
UNITS
V
V
V
mA
10
13
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For more information
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LTC2442
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
fLESCK
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 Setup Before
CS
↓
SCK Hold After
CS
↓
SDI Setup 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)
(Note 8, 12)
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TIMING CHARACTERISTICS
CONDITIONS
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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
30.9
0.9
f
EOSC
/10
1
55
20
MHz
Hz
%
MHz
ns
ns
35.3
320/f
EOSC
32/f
ESCK
41.6
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
= SEL
+
– SEL
–
, V
INCM
= (SEL
+
+ SEL
–
)/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
O
cycles
to the conversion time.
Note 14:
In order to achieve optimum linearity, the amplifier power
positive supply input (V
+
) must exceed the maximum input voltage level by
2V or greater. The negative amplifier power supply input (V
–
) must be at
least 200mV below the minimum input voltage level.
Note 15:
Amplifiers are externally compensated with 0.1µF.
2442fb
For more information
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5
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