LTC2412
2-Channel Differential Input
24-Bit No Latency
∆Σ
ADC
FEATURES
s
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
2-Channel Differential Input with Automatic
Channel Selection (Ping-Pong)
Low Supply Current: 200µA, 4µA in Autosleep
Differential Input and Differential Reference with
GND to V
CC
Common Mode Range
2ppm INL, No Missing Codes
2.5ppm Full-Scale Error and 0.1ppm Offset
0.16ppm Noise, 22.5 Effective Number of Bits
No Latency: Digital Filter Settles in a Single Cycle and
Each Channel Conversion is Accurate
Internal Oscillator—No External Components
Required
110dB Min, 50Hz or 60Hz Notch Filter
Narrow SSOP-16 Package
Single Supply 2.7V to 5.5V Operation
The LTC
®
2412 is a 2-channel differential input micropower
24-bit No Latency
∆Σ
TM
analog-to-digital converter with
an integrated oscillator. It provides 2ppm INL and 0.16ppm
RMS noise over the entire supply range. The two differen-
tial channels are converted alternately with channel ID
included in the conversion results. It uses delta-sigma
technology and provides single conversion settling of the
digital filter. Through a single pin, the LTC2412 can be
configured for better than 110dB input differential mode
rejection at 50Hz or 60Hz
±2%,
or it can be driven by an
external oscillator for a user defined rejection frequency.
The internal oscillator requires no external frequency
setting components.
The converter accepts any external differential reference
voltage from 0.1V to V
CC
for flexible ratiometric and
remote sensing measurement configurations. The full-
scale differential input range is from – 0.5V
REF
to 0.5V
REF
.
The reference common mode voltage, V
REFCM
, and the
input common mode voltage, V
INCM
, may be indepen-
dently set anywhere within the GND to V
CC
. The DC
common mode input rejection is better than 140dB.
The LTC2412 communicates through a flexible 3-wire
digital interface which is compatible with SPI and
MICROWIRE
TM
protocols.
, LTC and LT are registered trademarks of Linear Technology Corporation.
No Latency
∆Σ
is a trademark of Linear Technology Corporation.
MICROWIRE is a trademark of National Semiconductor Corporation.
APPLICATIO S
s
s
s
s
s
s
s
s
s
Direct Sensor Digitizer
Weight Scales
Direct Temperature Measurement
Gas Analyzers
Strain-Gage Transducers
Instrumentation
Data Acquisition
Industrial Process Control
6-Digit DVMs
TYPICAL APPLICATIO
2.7V TO 5.5V
1µF
1
2
4
V
CC
1.5
V
CC
F
O
14
REF
+
CH0
+
LTC2412
CH0
–
REF
–
CH1
+
CH1
–
GND
2412 TA01
TUE (ppm OF V
REF
)
= INTERNAL OSC/50Hz REJECTION
= EXTERNAL CLOCK SOURCE
= INTERNAL OSC/60Hz REJECTION
1.0
0.5
0
V
CC
= 5V
REF
+
= 5V
REF
–
= GND
V
REF
= 5V
V
INCM
= 2.5V
F
O
= GND
T
A
= 90°C
T
A
= 25°C
T
A
= –45°C
5
THERMOCOUPLE
3
6
7
8, 9, 10, 15, 16
SCK
SDO
CS
13
12
11
3-WIRE
SPI INTERFACE
–0.5
–1.0
–1.5
–2.5 –2 –1.5 –1 –0.5 0 0.5
V
IN
(V)
U
Total Unadjusted Error vs Input
1 1.5
2
2.5
2412f
2412 TA02
U
U
1
LTC2412
ABSOLUTE
(Notes 1, 2)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
CC
REF
+
REF
–
CH0
+
CH0
–
CH1
+
CH1
–
GND
1
2
3
4
5
6
7
8
16 GND
15 GND
14 F
O
13 SCK
12 SDO
11 CS
10 GND
9
GND
Supply Voltage (V
CC
) to GND .......................– 0.3V to 7V
Analog Input Voltage
to GND .................................... – 0.3V to (V
CC
+ 0.3V)
Reference Input 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
LTC2412C ............................................... 0°C to 70°C
LTC2412I ............................................ – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART NUMBER
LTC2412CGN
LTC2412IGN
GN PART MARKING
2412
2412I
GN PACKAGE
16-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 110°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
q
denotes 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
CONDITIONS
0.1V
≤
V
REF
≤
V
CC
, –0.5 • V
REF
≤
V
IN
≤
0.5 • V
REF
, (Note 5)
q
ELECTRICAL CHARACTERISTICS
MIN
24
TYP
1
2
5
0.5
10
MAX
UNITS
Bits
ppm of V
REF
ppm of V
REF
ppm of V
REF
µV
nV/°C
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)
q
+
= 2.5V, REF
–
= GND, V
REF
INCM
= 1.25V, (Note 6)
2.5V
≤
REF
+
≤
V
CC
, REF
–
= GND,
GND
≤
IN
+
= IN
–
≤
V
CC
, (Note 14)
2.5V
≤
REF
+
≤
V
CC
, REF
–
= GND,
GND
≤
IN
+
= IN
–
≤
V
CC
2.5V
≤
REF
+
≤
V
CC
, REF
–
= GND,
IN
+
= 0.75REF
+
, IN
–
= 0.25 • REF
+
2.5V
≤
REF
+
≤
V
CC
, REF
–
= GND,
IN
+
= 0.75REF
+
, IN
–
= 0.25 • REF
+
2.5V
≤
REF
+
≤
V
CC
, REF
–
= GND,
IN
+
= 0.25 • REF
+
, IN
–
= 0.75 • REF
+
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)
5V
≤
V
CC
≤
5.5V, REF
+
= 5V, REF
–
= GND,
GND
≤
IN
–
= IN
+
≤
V
CC
, (Note 13)
q
q
q
14
2.5
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
2.5
0.03
2.5
0.03
3
3
4
0.8
12
ppm of V
REF
ppm of V
REF
/°C
12
ppm of V
REF
ppm of V
REF
/°C
ppm of V
REF
ppm of V
REF
ppm of V
REF
µV
RMS
Output Noise
2
U
2412f
W
U
U
W W
W
LTC2412
CO VERTER CHARACTERISTICS
PARAMETER
Input Common Mode Rejection DC
Input Common Mode Rejection
60Hz
±2%
Input Common Mode Rejection
50Hz
±2%
Input Normal Mode Rejection
60Hz
±2%
Input Normal Mode Rejection
50Hz
±2%
Reference Common Mode
Rejection DC
Power Supply Rejection, DC
CONDITIONS
2.5V
≤
REF
+
≤
V
CC
, REF
–
= GND,
GND
≤
IN
–
= IN
+
≤
V
CC
(Note 5)
2.5V
≤
REF
+
≤
V
CC
, REF
–
= GND,
GND
≤
IN
–
= IN
+
≤
V
CC
, (Notes 5, 7)
2.5V
≤
REF
+
≤
V
CC
, REF
–
= GND,
GND
≤
IN
–
= IN
+
≤
V
CC
, (Notes 5, 8)
(Notes 5, 7)
(Note 5, 8)
2.5V
≤
REF
+
≤
V
CC
, GND
≤
REF
–
≤
2.5V,
V
REF
= 2.5V, IN
–
= IN
+
= GND (Note 5)
REF
+
= 2.5V, REF
–
= GND, IN
–
= IN
+
= GND
q
q
q
q
q
q
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
MIN
130
140
140
110
110
130
140
140
140
120
120
120
TYP
140
MAX
UNITS
dB
dB
dB
dB
dB
dB
dB
dB
dB
Power Supply Rejection, 60Hz
±2%
REF
+
= 2.5V, REF
–
= GND, IN
–
= IN
+
= GND, (Note 7)
Power Supply Rejection, 50Hz
±2%
REF
+
= 2.5V, REF
–
= GND, IN
–
= IN
+
= GND, (Note 8)
A ALOG I PUT A D REFERE CE
The
q
denotes 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
–
)
I
DC_LEAK
(IN
+
)
I
DC_LEAK
(IN
–
)
I
DC_LEAK
(REF
+
)
I
DC_LEAK
(REF
–
)
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
IN
+
DC Leakage Current
IN
–
DC Leakage Current
REF
+
DC Leakage Current
REF
–
DC Leakage Current
CS = V
CC
= 5.5V, IN
+
= GND
CS = V
CC
= 5.5V, IN
–
= 5.5V
CS = V
CC
= 5.5V, REF
+
= 5.5V
CS = V
CC
= 5.5V, REF
–
= GND
q
q
q
q
U
U
U
U
U
CONDITIONS
q
q
q
q
q
q
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
18
18
18
18
–10
–10
–10
–10
1
1
1
1
10
10
10
10
nA
nA
nA
nA
2412f
3
LTC2412
DIGITAL I PUTS A D DIGITAL OUTPUTS
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
Low Level Input Voltage
CS, F
O
High Level Input Voltage
SCK
Low Level Input Voltage
SCK
Digital Input Current
CS, F
O
Digital Input Current
SCK
Digital Input Capacitance
CS, F
O
Digital Input Capacitance
SCK
High Level Output Voltage
SDO
Low Level Output Voltage
SDO
High Level Output Voltage
SCK
Low Level Output Voltage
SCK
Hi-Z Output Leakage
SDO
(Note 9)
I
O
= –800µA
I
O
= 1.6mA
I
O
= –800µA (Note 10)
I
O
= 1.6mA (Note 10)
q
q
q
q
q
The
q
denotes specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
2.7V
≤
V
CC
≤
5.5V
2.7V
≤
V
CC
≤
3.3V
4.5V
≤
V
CC
≤
5.5V
2.7V
≤
V
CC
≤
5.5V
2.7V
≤
V
CC
≤
5.5V (Note 9)
2.7V
≤
V
CC
≤
3.3V (Note 9)
4.5V
≤
V
CC
≤
5.5V (Note 9)
2.7V
≤
V
CC
≤
5.5V (Note 9)
0V
≤
V
IN
≤
V
CC
0V
≤
V
IN
≤
V
CC
(Note 9)
q
q
q
q
q
q
POWER REQUIRE E TS
SYMBOL
V
CC
I
CC
PARAMETER
Supply Voltage
Supply Current
Conversion Mode
Sleep Mode
Sleep Mode
The
q
denotes specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
q
4
U W
U
U
MIN
2.5
2.0
TYP
MAX
UNITS
V
V
0.8
0.6
2.5
2.0
0.8
0.6
–10
–10
10
10
V
CC
– 0.5
0.4
V
CC
– 0.5
0.4
–10
10
10
10
V
V
V
V
V
V
µA
µA
pF
pF
V
V
V
V
µA
MIN
2.7
TYP
MAX
5.5
UNITS
V
µA
µA
µA
CS = 0V
CS = V
CC
(Note 12)
CS = V
CC
, 2.7V
≤
V
CC
≤
3.3V
(Note 12)
q
q
200
4
2
300
13
2412f
LTC2412
TI I G CHARACTERISTICS
SYMBOL
f
EOSC
t
HEO
t
LEO
t
CONV
PARAMETER
External Oscillator Frequency Range
External Oscillator High Period
External Oscillator Low Period
Conversion Time
F
O
= 0V
F
O
= V
CC
External Oscillator (Note 11)
Internal Oscillator (Note 10)
External Oscillator (Notes 10, 11)
(Note 10)
(Note 9)
(Note 9)
(Note 9)
Internal Oscillator (Notes 10, 12)
External Oscillator (Notes 10, 11)
(Note 9)
q
q
q
q
q
q
q
q
q
The
q
denotes specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
q
q
q
q
q
q
f
ISCK
D
ISCK
f
ESCK
t
LESCK
t
HESCK
t
DOUT_ISCK
t
DOUT_ESCK
t
1
t2
t3
t4
t
KQMAX
t
KQMIN
t
5
t
6
Note 1:
Absolute Maximum Ratings are those values beyond which the
life of the device may be impaired.
Note 2:
All voltage values are with respect to GND.
Note 3:
V
CC
= 2.7V to 5.5V unless otherwise specified.
V
REF
= REF
+
– REF
–
, V
REFCM
= (REF
+
+ REF
–
)/2; V
IN
= IN
+
– IN
–
,
V
INCM
= (IN
+
+ IN
–
)/2, IN
+
and IN
–
are defined as the selected positive
(CH0
+
or CH1
+
) and negative (CH0
–
or CH1
–
) input respectively.
Note 4:
F
O
pin tied to GND or to V
CC
or to external conversion clock
source with f
EOSC
= 153600Hz 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:
F
O
= 0V (internal oscillator) or f
EOSC
= 153600Hz
±2%
(external oscillator).
UW
MIN
2.56
0.25
0.25
TYP
MAX
2000
390
390
UNITS
kHz
µs
µs
ms
ms
ms
kHz
kHz
130.86
133.53
136.20
157.03
160.23
163.44
20510/f
EOSC
(in kHz)
19.2
f
EOSC
/8
45
250
250
1.64
1.67
1.70
256/f
EOSC
(in kHz)
32/f
ESCK
(in kHz)
0
0
0
50
220
15
50
50
200
200
200
55
2000
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
↓
%
kHz
ns
ns
ms
ms
ms
ns
ns
ns
ns
ns
ns
ns
ns
(Note 10)
(Note 9)
(Note 5)
q
q
q
q
q
q
Note 8:
F
O
= V
CC
(internal oscillator) or f
EOSC
= 128000Hz
±2%
(external oscillator).
Note 9:
The converter is in external SCK mode of operation such that
the SCK pin is used as digital input. The frequency of the clock signal
driving SCK during the data output is f
ESCK
and is expressed in kHz.
Note 10:
The converter is in internal SCK mode of operation such that
the SCK pin is used as digital output. In this mode of operation the
SCK pin has a total equivalent load capacitance C
LOAD
= 20pF.
Note 11:
The external oscillator is connected to the F
O
pin. The external
oscillator frequency, f
EOSC
, is expressed in kHz.
Note 12:
The converter uses the internal oscillator.
F
O
= 0V or F
O
= V
CC
.
Note 13:
The output noise includes the contribution of the internal
calibration operations.
Note 14:
Guaranteed by design and test correlation.
2412f
5
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