LTC2400
24-Bit
µPower
No Latency
∆Σ
TM
ADC in SO-8
FEATURES
s
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DESCRIPTIO
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24-Bit ADC in SO-8 Package
4ppm INL, No Missing Codes
4ppm Full-Scale Error
Single Conversion Settling Time
for Multiplexed Applications
0.5ppm Offset
0.3ppm Noise
Internal Oscillator—No External Components
Required
110dB Min, 50Hz/60Hz Notch Filter
Reference Input Voltage: 0.1V to V
CC
Live Zero—Extended Input Range Accommodates
12.5% Overrange and Underrange
Single Supply 2.7V to 5.5V Operation
Low Supply Current (200µA) and Auto Shutdown
The LTC
®
2400 is a 2.7V to 5.5V micropower 24-bit
converter with an integrated oscillator, 4ppm INL and
0.3ppm RMS noise. It uses delta-sigma technology and
provides single cycle settling time for multiplexed appli-
cations. Through a single pin the LTC2400 can be config-
ured for better than 110dB rejection at 50Hz or 60Hz
±2%,
or it can be driven by an external oscillator for a user
defined rejection frequency in the range 1Hz to 120Hz.
The internal oscillator requires no external frequency
setting components.
The converter accepts any external reference voltage from
0.1V to V
CC
. With its extended input conversion range of
–12.5% V
REF
to 112.5% V
REF
, the LTC2400 smoothly
resolves the offset and overrange problems of preceding
sensors or signal conditioning circuits.
The LTC2400 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
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
V
CC
LTC2400
REFERENCE
VOLTAGE
0.1V TO V
CC
ANALOG
INPUT RANGE
–0.12V
REF
TO 1.12V
REF
V
REF
SCK
F
O
Total Unadjusted Error vs Output Code
10
V
CC
8
LINEARITY ERROR (ppm)
= INTERNAL OSC/50Hz REJECTION
= EXTERNAL CLOCK SOURCE
= INTERNAL OSC/60Hz REJECTION
6
4
2
0
–2
–4
–6
–8
V
IN
GND
SDO
CS
3-WIRE
SPI INTERFACE
2400 TA01
–10
0
8,338,608
OUTPUT CODE (DECIMAL)
16,777,215
2400 TA02
U
V
CC
= 5V
V
REF
= 5V
T
A
= 25°C
F
O
= LOW
U
U
1
LTC2400
ABSOLUTE
MAXIMUM
RATINGS
(Notes 1, 2)
PACKAGE/ORDER INFORMATION
TOP VIEW
V
CC
1
V
REF
2
V
IN
3
GND 4
8
7
6
5
F
O
SCK
SDO
CS
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
LTC2400C ............................................... 0°C to 70°C
LTC2400I ............................................ – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART NUMBER
LTC2400CS8
LTC2400IS8
S8 PART MARKING
2400
2400I
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 130°C/W
Consult factory for Military grade parts.
CONVERTER CHARACTERISTICS
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
Offset Error
Offset Error Drift
Full-Scale Error
Full-Scale Error Drift
Total Unadjusted Error
Output Noise
Normal Mode Rejection 60Hz
±2%
Normal Mode Rejection 50Hz
±2%
Power Supply Rejection, DC
Power Supply Rejection, 60Hz
±2%
Power Supply Rejection, 50Hz
±2%
CONDITIONS
0.1V
≤
V
REF
≤
V
CC
, (Note 5)
V
REF
= 2.5V (Note 6)
V
REF
= 5V (Note 6)
2.5V
≤
V
REF
≤
V
CC
2.5V
≤
V
REF
≤
V
CC
2.5V
≤
V
REF
≤
V
CC
2.5V
≤
V
REF
≤
V
CC
V
REF
= 2.5V
V
REF
= 5V
V
IN
= 0V (Note 13)
(Note 7)
(Note 8)
V
REF
= 2.5V, V
IN
= 0V
V
REF
= 2.5V, V
IN
= 0V, (Notes 7, 15)
V
REF
= 2.5V, V
IN
= 0V, (Notes 8, 15)
q
q
q
q
q
q
q
MIN
24
TYP
2
4
0.5
0.01
4
0.02
5
10
1.5
MAX
10
15
2
10
UNITS
Bits
ppm of V
REF
ppm of V
REF
ppm of V
REF
ppm of V
REF
/°C
ppm of V
REF
ppm of V
REF
/°C
ppm of V
REF
ppm of V
REF
µV
RMS
dB
dB
dB
dB
dB
110
110
130
130
100
110
110
A ALOG I PUT A D REFERE CE
SYMBOL
V
IN
V
REF
C
S(IN)
C
S(REF)
I
IN(LEAK)
I
REF(LEAK)
PARAMETER
Input Voltage Range
Reference Voltage Range
Input Sampling Capacitance
Reference Sampling Capacitance
Input Leakage Current
Reference Leakage Current
CS = V
CC
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
(Note 14)
q
q
MIN
– 0.125 • V
REF
0.1
TYP
MAX
1.125 • V
REF
V
CC
UNITS
V
V
pF
pF
10
15
q
q
–10
– 10
1
1
10
10
V
REF
= 2.5V, CS = V
CC
2
U
W
U
U
U
W W
U
W
U
U
U
nA
nA
LTC2400
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
High-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
The
q
denotes specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
q
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
0.4V
V
CC
– 0.5V
0.4V
–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
CS = 0V (Note 12)
CS = V
CC
(Note 12)
q
q
200
20
300
30
3
LTC2400
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
= 2.7 to 5.5V unless otherwise specified.
Note 4:
Internal Conversion Clock source with the 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).
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.
4
UW
MIN
2.56
0.5
0.5
TYP
MAX
307.2
390
390
UNITS
kHz
µs
µs
ms
ms
ms
kHz
kHz
130.66
133.33
136
156.80
160
163.20
20480/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
200
15
50
50
150
150
150
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 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:
For reference voltage values V
REF
> 2.5V the extended input
of – 0.125 • V
REF
to 1.125 • V
REF
is limited by the absolute maximum
rating of the Analog Input Voltage pin (Pin 3). For 2.5V < V
REF
≤
0.267V + 0.89 • V
CC
the input voltage range is – 0.3V to 1.125 • V
REF
.
For 0.267V + 0.89 • V
CC
< V
REF
≤
V
CC
the input voltage range is – 0.3V
to V
CC
+ 0.3V.
Note 15:
The DC voltage at V
CC
= 4.1V, and the AC voltage applied to
V
CC
is 2.8V
P-P
LTC2400
TYPICAL PERFOR A CE CHARACTERISTICS
Total Unadjusted Error
(3V Supply)
10
V
CC
= 3V
V
REF
= 3V
10
5
ERROR (ppm)
ERROR (ppm)
0
T
A
= –55°C, –45°C, 25°C, 90°C
–5
0
ERROR (ppm)
–10
0
0.5
1.0
1.5
2.0
INPUT VOLTAGE (V)
2.5
3.0
2400 G01
Positive Input Extended Total
Unadjusted Error (3V Supply)
10
V
CC
= 3V
V
REF
= 3V
5
ERROR (ppm)
ERROR (ppm)
2
0
–2
–4
–6
–8
T
A
= –55°C, –45°C, 25°C, 90°C
0
T
A
= 90°C
–5
T
A
= – 45°C
T
A
= 25°C
ERROR (ppm)
T
A
= – 55°C
–10
3.0
3.1
3.2
INPUT VOLTAGE (V)
3.3
2400 G04
Negative Input Extended Total
Unadjusted Error (5V Supply)
10
V
CC
= 5V
V
REF
= 5V
10
T
A
= 90°C
5
OFFSET ERROR (ppm)
5
ERROR (ppm)
T
A
= 25°C
0
T
A
= – 45°C
–5
T
A
= – 55°C
ERROR (ppm)
–10
0
– 0.05 – 0.10 – 0.15 – 0.20 – 0.25 – 0.30
INPUT VOLTAGE (V)
2400 G07
U W
INL (3V Supply)
V
CC
= 3V
V
REF
= 3V
10
Negative Input Extended Total
Unadjusted Error (3V Supply)
V
CC
= 3V
V
REF
= 3V
T
A
= 90°C
5
T
A
= –55°C, –45°C, 25°C, 90°C
5
T
A
= 25°C
0
T
A
= – 45°C
–5
T
A
= – 55°C
–5
–10
0
0.5
1.0
1.5
2.0
INPUT VOLTAGE (V)
2.5
3.0
2400 G02
–10
0
– 0.05 – 0.10 – 0.15 – 0.20 – 0.25 – 0.30
INPUT VOLTAGE (V)
2400 G03
Total Unadjusted Error
(5V Supply)
10
V
CC
= 5V
8 V
REF
= 5V
6
4
10
INL (5V Supply)
V
CC
= 5V
V
REF
= 5V
5
0
T
A
= –55°C, –45°C, 25°C, 90°C
–5
–10
0
1
3
2
INPUT VOLTAGE (V)
4
5
2400 G05
–10
0
1
3
2
INPUT VOLTAGE (V)
4
5
2400 G06
Positive Input Extended Total
Unadjusted Error (5V Supply)
6
V
CC
= 5V
V
REF
= 5V
T
A
= – 55°C
Offset Error vs Reference Voltage
5
4
3
2
1
0
V
CC
= 5V
T
A
= 25°C
0
T
A
= 90°C
–5
T
A
= – 45°C
T
A
= 25°C
–10
5.0
5.1
5.2
INPUT VOLTAGE (V)
5.3
2400 G08
–1
0
1
3
4
REFERENCE VOLTAGE
2
5
2400 G09
5
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