LTC2435/LTC2435-1
20-Bit No Latency
∆Σ
TM
ADCs with Differential Input and
Differential Reference
DESCRIPTIO
The LTC
®
2435/2435-1 are 2.7V to 5.5V micropower
20-bit differential
∆Σ
analog to digital converters with
integrated oscillator, 3ppm INL and 0.8ppm RMS noise.
They use delta-sigma technology and provide single cycle
settling time for multiplexed applications. Through a
single pin, the LTC2435 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 LTC2435-1 can be con-
figured for better than 87dB input differential mode rejec-
tion over the range of 49Hz to 61.2Hz (50Hz and 60Hz
±2%
simultaneously). The internal oscillator 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 the GND to V
CC
range of the
LTC2435/LTC2435-1. The DC common mode input rejec-
tion is better than 120dB.
The LTC2435/LTC2435-1 communicate 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.
Protected by U.S. Patents including 6140950, 6169506.
FEATURES
■
■
■
■
■
■
■
■
■
■
2× Speed Up Version of the LTC2430: 15Hz Output
×
Rate, 60Hz Notch—LTC2435; 13.75Hz Output Rate,
Simultaneous 50Hz/60Hz Notch—LTC2435-1
Differential Input and Differential Reference with
GND to V
CC
Common Mode Range
3ppm INL, No Missing Codes
10ppm Gain Error
0.8ppm Noise
Single Conversion Settling Time for Multiplexed
Applications
Internal Oscillator—No External Components
Required
Single Supply 2.7V to 5.5V Operation
Low Supply Current (200µA,4µA in Auto Sleep)
20-Bit ADC in Narrow SSOP-16 Package
(SO-8 Footprint)
APPLICATIO 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 S
2.7V TO 5.5V
2
14
INL (ppm OF V
REF
)
10
8
6
V
CC
1µF
V
CC
F
O
LTC2435/
LTC2435-1
REFERENCE
VOLTAGE
0.1V TO V
CC
ANALOG INPUT RANGE
–0.5V
REF
TO 0.5V
REF
3
4
5
6
REF
+
REF
–
IN
+
IN
–
= INTERNAL OSC/50Hz REJECTION (LTC2435)
= EXTERNAL CLOCK SOURCE
= INTERNAL OSC/60Hz REJECTION (LTC2435)
= INTERNAL 50Hz/60Hz REJECTION (LTC2435-1)
SCK
13
3-WIRE
SPI INTERFACE
–2
–4
–6
–8
F
O
= GND
V
CC
= 5V
V
REF
= 5V
V
INCM
= V
INCM
= 2.5V
–1.5
SDO
CS
12
11
1, 7, 8, 9, 10, 15, 16
GND
–10
–2.5
2435 TA01
U
4
2
0
U
U
Integral Nonlinearity vs Input
T
A
= 25°C
T
A
= 85°C
T
A
= –45°C
–0.5
0.5
1.5
INPUT VOLTAGE (V)
2.5
2435 G04
24351fa
1
LTC2435/LTC2435-1
ABSOLUTE
(Notes 1, 2)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
GND
V
CC
REF
+
REF
–
IN
+
IN
–
GND
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 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
LTC2435C/LTC2435-1C ........................... 0°C to 70°C
LTC2435I/LTC2435-1I ........................ – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART NUMBER
LTC2435CGN
LTC2435IGN
LTC2435-1CGN
LTC2435-1IGN
GN PART MARKING
2435
2435I
24351
24351I
GN PACKAGE
16-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 95°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
●
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
PARAMETER
Integral Nonlinearity
CONDITIONS
●
●
●
ELECTRICAL CHARACTERISTICS
MIN
20
TYP
2
3
10
2
100
MAX
UNITS
Bits
ppm of V
REF
ppm of V
REF
ppm of V
REF
mV
nV/°C
Resolution (No Missing Codes) 0.1V
≤
V
REF
≤
V
CC
, –0.5 • V
REF
≤
V
IN
≤
0.5 • V
REF
, (Note 5)
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)
2.7V
≤
V
CC
≤
5.5V, 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
+
5V
≤
V
CC
≤
5.5V, REF
+
= 5V, REF
–
= GND,
GND
≤
IN
–
= IN
+
≤
V
CC
, (Note 13)
20
5
Offset Error
Offset Error Drift
Positive Gain Error
Positive Gain Error Drift
Negative Gain Error
Negative Gain Error Drift
Output Noise
●
10
0.1
25
ppm of V
REF
ppm of V
REF
/°C
●
10
0.1
4
25
ppm of V
REF
ppm of V
REF
/°C
µV
RMS
CO VERTER CHARACTERISTICS
PARAMETER
Input Common Mode Rejection DC
CONDITIONS
The
●
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
MIN
●
TYP
120
MAX
UNITS
dB
2.5V
≤
REF
+
≤
V
CC
, REF
–
= GND,
GND
≤
IN
–
= IN
+
≤
V
CC
(Note 5)
110
24351fa
2
U
W
U
U
W W
W
U
LTC2435/LTC2435-1
CO VERTER CHARACTERISTICS
PARAMETER
Input Common Mode Rejection
60Hz
±2%
(LTC2435)
Input Common Mode Rejection
50Hz
±2%
(LTC2435)
Input Normal Mode Rejection
60Hz
±2%
(LTC2435)
Input Normal Mode Rejection
50Hz
±2%
(LTC2435)
Input Common Mode Rejection
49Hz to 61.2Hz (LTC2435-1)
Input Normal Mode Rejection
49Hz to 61.2Hz (LTC2435-1)
Input Normal Mode Rejection
External Clock f
EOSC
/2560
±14%
Input Normal Mode Rejection
External Clock f
EOSC
/2560
±4%
Reference Common Mode
Rejection DC
Power Supply Rejection, DC
CONDITIONS
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)
(Notes 5, 8)
2.5V
≤
REF
+
≤
V
CC
, REF
–
= GND,
GND
≤
IN
–
= IN
+
≤
V
CC
, (Notes 5, 7)
F
O
= GND (Note 5)
External Oscillator (Note 5)
External Oscillator (Note 5)
2.5V
≤
REF
+
≤
V
CC
, GND
≤
REF
–
≤
2.5V,
V
REF
= 2.5V, IN
–
= IN
+
= GND (Note 5)
REF
+
= V
CC
, REF
–
= GND, IN
–
= IN
+
= GND
●
●
●
●
●
●
●
●
●
The
●
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
MIN
140
140
110
110
120
87
87
110
130
120
140
100
120
120
120
120
TYP
MAX
UNITS
dB
dB
dB
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
●
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
, IN
+
= GND
CS = V
CC
, IN
–
= V
CC
CS = V
CC
, REF
+
= V
CC
CS = V
CC
, REF
–
= GND
●
●
●
●
U
U
U
U
U
CONDITIONS
●
●
●
●
●
●
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
–10
–10
–10
–10
1
1
1
1
10
10
10
10
nA
nA
nA
nA
24351fa
3
LTC2435/LTC2435-1
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)
●
●
●
●
●
The
●
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)
●
●
●
●
●
●
POWER REQUIRE E TS
SYMBOL
V
CC
I
CC
PARAMETER
Supply Voltage
Supply Current
Conversion Mode
Sleep Mode
Sleep Mode
The
●
denotes specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
●
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 (Note 12)
CS = V
CC
(Note 12)
CS = V
CC
, 2.7V
≤
V
CC
≤
3.3V (Note 12)
●
●
●
200
4
2
300
10
24351fa
LTC2435/LTC2435-1
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 (LTC2435)
The
●
denotes specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
●
●
●
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.
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 measured from the center of the quantization
band.
Note 7:
F
O
= 0V (internal oscillator) or f
EOSC
= 153600Hz
±2%
(external oscillator) for the LTC2435 or f
EOSC
= 139800Hz
±2%
for the
LTC2435-1.
UW
MIN
5
0.25
0.25
65.6
78.7
72
TYP
MAX
2000
200
200
UNITS
kHz
µs
µs
ms
ms
ms
ms
ms
kHz
kHz
kHz
F
O
= 0V
F
O
= V
CC
External Oscillator (Note 11)
F
O
= 0V
External Oscillator (Note 11)
Internal Oscillator (Note 10), LTC2435
Internal Oscillator (Note 10), LTC2435-1
External Oscillator (Notes 10, 11)
(Note 10)
(Note 9)
(Note 9)
(Note 9)
●
●
●
●
●
68.3
81.9
10278/f
EOSC
(in kHz)
75
10278/f
EOSC
(in kHz)
19.2
17.5
f
EOSC
/8
73.5
66.9
80.3
Conversion Time (LTC2435-1)
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
●
●
●
●
45
250
250
1.22
1.34
55
2000
%
kHz
ns
ns
Internal Oscillator (Notes 10, 12), LTC2435
●
Internal Oscillator (Notes 10, 12), LTC2435-1
●
●
External Oscillator (Notes 10, 11)
●
●
●
1.25
1.28
1.37
1.40
192/f
EOSC
(in kHz)
24/f
ESCK
(in kHz)
200
200
200
220
ms
ms
ms
ms
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)
0
0
0
50
15
50
●
●
●
●
●
●
50
ns
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:
Refer to Offset Accuracy and Drift in the Applications
Information section.
24351fa
5
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