LTC2430/LTC2431
20-Bit No Latency
∆Σ
TM
ADCs
with Differential Input and
Differential Reference
FEATURES
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
Low Supply Current (200µA in Conversion Mode
and 4µA in Autosleep Mode)
Differential Input and Differential Reference
with GND to V
CC
Common Mode Range
3ppm INL, No Missing Codes
10ppm Full-Scale Error and 1ppm Offset
0.56ppm Noise, 20.8 ENOBs
No Latency: Digital Filter Settles in a Single Cycle.
Each Conversion Is Accurate, Even After an
Input Step
Single Supply 2.7V to 5.5V Operation
Internal Oscillator—No External Components
Required
110dB Min, 50Hz/60Hz Notch Filter
Pin Compatible with 24-Bit LTC2410/LTC2411
The LTC
®
2430/LTC2431 are 2.7V to 5.5V micropower
20-bit differential
∆Σ
analog-to-digital converters with an
integrated oscillator, 3ppm INL and 0.56ppm RMS noise.
They use delta-sigma technology and provide single cycle
settling time for multiplexed applications. Through a
single pin, the LTC2430/LTC2431 can be configured for
better than 110dB differential mode rejection at 50Hz or
60Hz
±2%,
or they can be driven by an external oscillator
for a user-defined rejection frequency. The internal oscil-
lator requires no external frequency setting components.
The converters accept 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 GND to V
CC
. The DC common
mode input rejection is better than 120dB.
The LTC2430/LTC2431 communicate through a flexible
3-wire digital interface that 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 Gauge Transducers
Instrumentation
Data Acquisition
Industrial Process Control
DVMs and Meters
TYPICAL APPLICATIO S
(V
OUT
+ 0.25V) TO 20V
V
OUT
3V TO 5V
4.7µF
6
LT1790
1
2
4
0.1µF
V
CC
TUE (ppm OF V
REF
)
V
CC
0.1µF
F
O
LTC2431
REF
+
SCK
REF
–
= INTERNAL OSC/50Hz REJECTION
= EXTERNAL CLOCK SOURCE
= INTERNAL OSC/60Hz REJECTION
ANALOG INPUT RANGE
–0.5V
REF
TO 0.5V
REF
IN
+
IN
–
GND
SDO
CS
24301 TA01
3-WIRE
SPI INTERFACE
U
Total Unadjusted Error
(V
CC
= 5V, V
REF
= 5V)
5
V
CC
= 5V
4 V
REF
= 5V
V
INCM
= V
INCM
= 2.5V
3 F = GND
O
2
1
0
–1
–2
–3
–4
–5
–2.5 –2 –1.5 –1 – 0.5 0 0.5 1 1.5
INPUT VOLTAGE (V)
2
2.5
–45°C
25°C
85°C
24301 G01
U
U
24301f
1
LTC2430/LTC2431
ABSOLUTE
AXI U
RATI GS
(Notes 1, 2)
Digital Output Voltage to GND ..... – 0.3V to (V
CC
+ 0.3V)
Operating Temperature Range
LTC2430C/LTC2431C .............................. 0°C to 70°C
LTC2430I/LTC2431I ........................... – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
Supply Voltage (V
CC
) to GND .......................– 0.3V to 7V
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)
PACKAGE/ORDER I FOR ATIO
TOP VIEW
GND
V
CC
REF
+
REF
–
ORDER PART NUMBER
16 GND
15 GND
14 F
O
13 SCK
12 SDO
11 CS
10 GND
9
GND
1
2
3
4
5
6
7
8
LTC2430CGN
LTC2430IGN
IN
+
IN
–
GN PART MARKING
2430
2430I
GND
GND
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.
ELECTRICAL CHARACTERISTICS
PARAMETER
Resolution (No Missing Codes)
Integral Nonlinearity
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
CONDITIONS
0.1V
≤
V
REF
≤
V
CC
, – 0.5 • V
REF
≤
V
IN
≤
0.5 • V
REF
(Note 5)
4.5V
≤
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
≤
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
+
4.5V
≤
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
5V
≤
V
CC
≤
5.5V, REF
+
= 5V, V
REF
– = GND,
GND
≤
IN
–
= IN
+
≤
5V, (Note 13)
q
q
q
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
Output Noise
2
U
U
W
W W
U
W
ORDER PART NUMBER
TOP VIEW
V
CC
REF
+
REF
–
IN
+
IN
–
1
2
3
4
5
10
9
8
7
6
F
O
SCK
SDO
CS
GND
LTC2431CMS
LTC2431IMS
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 120°C/W
MS PART MARKING
LTXD
LTXE
MIN
20
TYP
2
3
10
5
50
MAX
20
20
UNITS
Bits
ppm of V
REF
ppm of V
REF
ppm of V
REF
µV
nV/°C
q
10
0.1
20
ppm of V
REF
ppm of V
REF
/°C
q
10
0.1
3
6
15
2.8
20
ppm of V
REF
ppm of V
REF
/°C
ppm of V
REF
ppm of V
REF
ppm of V
REF
µV
RMS
24301f
LTC2430/LTC2431
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
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
MIN
q
q
q
q
q
q
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
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
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
U
U
U
U
TYP
120
MAX
UNITS
dB
dB
dB
2.5V
≤
REF
+
≤
V
CC
, REF
–
= GND,
GND
≤
IN
–
= IN
+
≤
5V (Note 5)
2.5V
≤
REF
+
≤
V
CC
, REF
–
= GND,
GND
≤
IN
–
= IN
+
≤
5V, (Notes 5, 7)
2.5V
≤
REF
+
≤
V
CC
, REF
–
= GND,
GND
≤
IN
–
= IN
+
≤
5V, (Notes 5, 8)
(Notes 5, 7)
(Notes 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
110
140
140
110
110
130
140
140
140
110
120
120
dB
dB
dB
dB
dB
dB
U
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
1.5
1.5
1.5
1.5
CS = V
CC
, IN
+
= GND
CS = V
CC
, IN
–
= V
CC
CS = V
CC
, REF
+
= V
CC
CS = V
CC
, REF
–
= GND
q
q
q
q
–10
–10
–10
–10
1
1
1
1
10
10
10
10
nA
nA
nA
nA
24301f
3
LTC2430/LTC2431
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
– 0.5V
0.4
V
CC
– 0.5V
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 (Note 12)
CS = V
CC
(Note 12)
CS = V
CC
, 2.7V
≤
V
CC
≤
3.3V
(Note 12)
q
q
200
4
2
300
10
24301f
LTC2430/LTC2431
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)
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
t
2
t
3
t
4
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.
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 calculated as the measured code minus the
expected value.
Note 7:
F
O
= 0V (internal oscillator) or f
EOSC
= 153600Hz
±2%
(external oscillator).
Note 8:
F
O
= V
CC
(internal oscillator) or f
EOSC
= 128000Hz
±2%
(external oscillator).
UW
MIN
5
0.25
0.25
TYP
MAX
2000
200
200
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
1.22
1.25
1.28
192/f
EOSC
(in kHz)
24/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 24-Bit Data Output Time
%
kHz
ns
ns
ms
ms
ms
ns
ns
ns
ns
ns
ns
ns
ns
External SCK 24-Bit Data Output Time (Note 9)
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
↓
(Note 5)
(Note 10)
(Note 9)
q
q
q
q
q
q
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.
24301f
5
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