ented sampling scheme eliminates dynamic input current
errors and the shortcomings of on-chip buffering through
automatic cancellation of differential input current. This
allows large external source impedances, and rail-to-rail
input signals to be directly digitized while maintaining
exceptional DC accuracy.
The LTC2494 includes programmable gain, a high accu-
racy temperature sensor and an integrated oscillator. This
device can be configured to measure an external signal
(from combinations of 16 analog input channels operat-
ing in single ended or differential modes) or its internal
temperature sensor. The integrated temperature sensor
offers 1/2°C resolution and 2°C absolute accuracy. The
LTC2494 can be configured to provide a progammable
gain from 1 to 256 in 8 steps.
The LTC2494 allows a wide common mode input range
(0V to V
CC
), independent of the reference voltage. Any
combination of single-ended or differential inputs can be
selected and the first conversion, after a new channel is
selected, is valid.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
No Latency
ΔΣ
and Easy Drive are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
■
■
■
■
■
■
■
■
■
■
■
■
■
Up to 8 Differential or 16 Single-Ended Inputs
Easy Drive Technology Enables Rail-to-Rail Inputs
with Zero Differential Input Current
Directly Digitizes High Impedance Sensors with
Full Accuracy
600nV RMS Noise
Programmable Gain from 1 to 256
Integrated High Accuracy Temperature Sensor
GND to V
CC
Input/Reference Common Mode Range
Programmable 50Hz, 60Hz or Simultaneous
50Hz/60Hz Rejection Mode
2ppm INL, No Missing Codes
1ppm Offset and 15ppm Full-Scale Error
2x Speed Mode/Reduced Power Mode (15Hz Using
Internal Oscillator and 80μA at 7.5Hz Output)
No Latency: Digital Filter Settles in a Single Cycle,
Even After a New Channel is Selected
Single Supply 2.7V to 5.5V Operation
Internal Oscillator
Tiny 5mm
×
7mm QFN Package
APPLICATIONS
■
■
■
■
Direct Sensor Digitizer
Direct Temperature Measurement
Instrumentation
Industrial Process Control
TYPICAL APPLICATION
Data Acquisition System with Temperature Compensation
2.7V TO 5.5V
0.1μF
10μF
ABSOLUTE ERROR (°C)
5
4
CH0
CH1
•
•
•
CH7
CH8 16-CHANNEL
MUX
•
•
•
CH15
COM
TEMPERATURE
SENSOR
F
O
MUXOUT/
ADCIN
OSC
2494 TA01a
Absolute Temperature Error
MUXOUT/
ADCIN
REF
+
V
CC
3
2
1
0
–1
–2
–3
–4
–5
–55
–30
–5
20
45
70
TEMPERATURE (°C)
95
120
IN
+
16-BIT
ΔΣ
ADC
WITH EASY-DRIVE
IN
–
REF
–
SDI
SCK
SDO
CS
4-WIRE
SPI INTERFACE
2494 TA01b
2494fb
1
LTC2494
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
PIN CONFIGURATION
TOP VIEW
GND
GND
31 GND
30 REF
–
29 REF
+
28 V
CC
27 MUXOUTN
39
26 ADCINN
25 ADCINP
24 MUXOUTP
23 CH15
22 CH14
21 CH13
20 CH12
13 14 15 16 17 18 19
CH5
CH6
CH7
CH8
CH9
CH10
CH11
SDO
SCK
SDI
CS
F
O
38 37 36 35 34 33 32
GND 1
NC 2
GND 3
GND 4
GND 5
GND 6
COM 7
CH0 8
CH1 9
CH2 10
CH3 11
CH4 12
Supply Voltage (V
CC
) ................................... –0.3V to 6V
Analog Input Voltage
(CH0 to CH15, COM) ................–0.3V to (V
CC
+ 0.3V)
REF
+
, REF
–
................................–0.3V to (V
CC
+ 0.3V)
ADCINN, ADCINP, MUXOUTP,
MUXOUTN ................................–0.3V to (V
CC
+ 0.3V)
Digital Input Voltage......................–0.3V to (V
CC
+ 0.3V)
Digital Output Voltage ...................–0.3V to (V
CC
+ 0.3V)
Operating Temperature Range
LTC2494C ................................................ 0°C to 70°C
LTC2494I ............................................. –40°C to 85°C
Storage Temperature Range................... –65°C to 150°C
UHF PACKAGE
38-LEAD (5mm
×
7mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 34°C/W
EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC2494CUHF#PBF
LTC2494IUHF#PBF
TAPE AND REEL
LTC2494CUHF#TRPBF
LTC2494IUHF#TRPBF
PART MARKING*
2494
2494
PACKAGE DESCRIPTION
38-Lead (5mm
×
7mm) Plastic QFN
38-Lead (5mm
×
7mm) Plastic QFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard 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/
2494fb
2
LTC2494
ELECTRICAL CHARACTERISTICS (NORMAL SPEED)
PARAMETER
Resolution (No Missing Codes)
Integral Nonlinearity
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
CONDITIONS
0.1V ≤ V
REF
≤ V
CC
, –FS ≤ V
IN
≤ +FS (Note 5)
5V ≤ V
CC
≤ 5.5V, V
REF
= 5V, V
IN(CM)
= 2.5V (Note 6)
2.7V ≤ V
CC
≤ 5.5V, V
REF
= 2.5V, V
IN(CM)
= 1.25V (Note 6)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
(Note 14)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
2.5V ≤ V
REF
≤ V
CC
, IN
+
= 0.75V
REF
, IN
–
= 0.25V
REF
2.5V ≤ V
REF
≤ V
CC
, IN
+
= 0.75V
REF
, IN
–
= 0.25V
REF
2.5V ≤ V
REF
≤ V
CC
, IN
+
= 0.25V
REF
, IN
–
= 0.75V
REF
2.5V ≤ V
REF
≤ V
CC
, IN
+
= 0.25V
REF
, IN
–
= 0.75V
REF
5V ≤ V
CC
≤ 5.5V, V
REF
= 2.5V, V
IN(CM)
= 1.25V
5V ≤ V
CC
≤ 5.5V, V
REF
= 5V, V
IN(CM)
= 2.5V
2.7V ≤ V
CC
≤ 5.5V, V
REF
= 2.5V, V
IN(CM)
= 1.25V
2.7V ≤ V
CC
≤ 5.5V, 2.5V ≤ V
REF
≤ V
CC
,
GND ≤ IN
+
= IN
–
≤ V
CC
(Note 13)
T
A
= 27°C (Note 14)
●
●
●
The
●
denotes the specifications which
apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
MIN
16
TYP
2
1
0.5
10
0.1
●
MAX
20
5
32
32
Output Noise
Internal PTAT Signal
Internal PTAT Temperature Coefficient
Programmable Gain
0.1
15
15
15
0.6
27.8
●
UNITS
Bits
ppm of V
REF
ppm of V
REF
μV
nV/°C
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
ppm of V
REF
μV
RMS
mV
μV/°C
28.0
93.5
28.2
256
1
ELECTRICAL CHARACTERISTICS (2X SPEED)
PARAMETER
Resolution (No Missing Codes)
Integral Nonlinearity
Offset Error
Offset Error Drift
Positive Full-Scale Error
Positive Full-Scale Error Drift
Negative Full-Scale Error
Negative Full-Scale Error Drift
Output Noise
Programmable Gain
The
●
denotes the 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
, –FS ≤ V
IN
≤ +FS (Note 5)
5V ≤ V
CC
≤ 5.5V, V
REF
= 5V, V
IN(CM)
= 2.5V (Note 6)
2.7V ≤ V
CC
≤5.5V, V
REF
= 2.5V, V
IN(CM)
= 1.25V (Note 6)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
(Note 14)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
2.5V ≤ V
REF
≤ V
CC
, IN
+
= 0.75V
REF
, IN
–
= 0.25V
REF
2.5V ≤ V
REF
≤ V
CC
, IN
+
= 0.75V
REF
, IN
–
= 0.25V
REF
2.5V ≤ V
REF
≤ V
CC
, IN
+
= 0.25V
REF
, IN
–
= 0.75V
REF
2.5V ≤ V
REF
≤ V
CC
, IN
+
= 0.25V
REF
, IN
–
= 0.75V
REF
5V ≤ V
CC
≤ 2.5V, V
REF
= 5V, GND ≤ IN
+
= IN
–
≤ V
CC
MIN
16
●
●
●
TYP
2
1
0.2
100
0.1
MAX
20
2
32
32
●
0.1
0.85
●
UNITS
Bits
ppm of V
REF
ppm of V
REF
mV
nV/°C
ppm of V
REF
ppm of V
REF
/°C
ppm of V
REF
ppm of V
REF
/°C
μV
RMS
1
128
CONVERTER CHARACTERISTICS
PARAMETER
Input Common Mode Rejection DC
Input Common Mode Rejection 60Hz ±2%
Input Common Mode Rejection 50Hz ±2%
Input Normal Mode Rejection 50Hz ±2%
Input Normal Mode Rejection 60Hz ±2%
Input Normal Mode Rejection 50Hz/60Hz ±2%
Reference Common Mode Rejection DC
Power Supply Rejection DC
Power Supply Rejection, 50Hz ±2%
Power Supply Rejection, 60Hz ±2%
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
(Note 5)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
(Note 5)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
(Note 5)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
(Notes 5, 7)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
(Notes 5, 8)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
(Notes 5, 9)
2.5V ≤ V
REF
≤ V
CC
, GND ≤ IN
+
= IN
–
≤ V
CC
(Note 5)
V
REF
= 2.5V, IN
+
= IN
–
= GND
V
REF
= 2.5V, IN
+
= IN
–
= GND (Notes 7, 9)
V
REF
= 2.5V, IN
+
= IN
–
= GND (Notes 8, 9)
●
●
●
●
●
●
●
MIN
140
140
140
110
110
87
120
TYP
MAX
120
120
140
120
120
120
UNITS
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
2494fb
3
LTC2494
ANALOG INPUT AND REFERENCE
SYMBOL
IN
+
IN
–
V
IN
FS
LSB
REF
+
REF
–
V
REF
C
S(IN+)
C
S(IN–)
C
S(VREF)
I
DC_LEAK(IN+)
I
DC_LEAK(IN–)
PARAMETER
Absolute/Common Mode IN
+
Voltage
(IN
+
Corresponds to the Selected Positive Input Channel)
Absolute/Common Mode IN
–
Voltage
(IN
–
Corresponds to the Selected Negative Input Channel)
Input Differential Voltage Range (IN
+
– IN
–
)
Full Scale of the Differential Input (IN
+
– IN
–
)
Least Significant Bit of the Output Code
Absolute/Common Mode REF
+
Voltage
Absolute/Common Mode REF
–
Voltage
Reference Voltage Range (REF
+
– REF
–
)
IN
+
Sampling Capacitance
IN
–
Sampling Capacitance
V
REF
Sampling Capacitance
IN
+
DC Leakage Current
IN
–
DC Leakage Current
Sleep Mode, IN
+
= GND
Sleep Mode, IN
–
= GND
Sleep Mode, REF
+
= V
CC
Sleep Mode, REF
–
= GND
V
IN
= 2V
P-P
DC to 1.8MHz
●
●
●
●
●
●
●
●
●
●
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
MIN
GND – 0.3V
GND – 0.3V
–FS
0.5V
REF
/Gain
FS/2
16
0.1
GND
0.1
11
11
11
–10
–10
–100
–100
1
1
1
1
50
120
10
10
100
100
V
CC
REF
+
– 0.1V
V
CC
V
V
V
pF
pF
pF
nA
nA
nA
nA
ns
dB
TYP
MAX
V
CC
+ 0.3V
V
CC
+ 0.3V
+FS
UNITS
V
V
V
V
I
DC_LEAK(REF+)
REF
+
DC Leakage Current
I
DC_LEAK(REF–)
REF
–
DC Leakage Current
t
OPEN
QIRR
MUX Break-Before-Make
MUX Off Isolation
DIGITAL INPUTS AND 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
, SDI)
Low Level Input Voltage (CS, F
O
, SDI)
High Level Input Voltage (SCK)
Low Level Input Voltage (SCK)
Digital Input Current (CS, F
O
, SDI)
Digital Input Current (SCK)
Digital Input Capacitance (CS, F
O
, SDI)
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)
(Notes 10, 15)
I
O
= –800μA
I
O
= 1.6mA
CONDITIONS
2.7V ≤ V
CC
≤ 5.5V
2.7V ≤ V
CC
≤ 5.5V
The
●
denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
MIN
●
●
●
●
●
●
TYP
MAX
0.5
UNITS
V
V
V
V
μA
μA
pF
pF
V
V
CC
– 0.5
V
CC
– 0.5
0.5
–10
–10
10
10
10
10
2.7V ≤ V
CC
≤ 5.5V (Notes 10, 15)
2.7V ≤ V
CC
≤ 5.5V (Notes 10, 15)
0V ≤ V
IN
≤ V
CC
0V ≤ V
IN
≤ V
CC
(Notes 10, 15)
●
●
●
●
●
V
CC
– 0.5
0.4
V
CC
– 0.5
0.4
–10
10
V
V
V
μA
I
O
= –800μA (Notes 10, 17)
I
O
= 1.6mA (Notes 10, 17)
POWER REQUIREMENTS
SYMBOL
V
CC
I
CC
PARAMETER
Supply Voltage
Supply Current
The
●
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
●
MIN
2.7
●
●
●
TYP
160
200
1
MAX
5.5
275
300
2
UNITS
V
μA
μA
μA
2494fb
Conversion Current (Note 12)
Temperature Measurement (Note 12)
Sleep Mode (Note 12)
4
LTC2494
DIGITAL INPUTS AND DIGITAL OUTPUTS
SYMBOL
f
EOSC
t
HEO
t
LEO
t
CONV_1
PARAMETER
External Oscillator Frequency Range
External Oscillator High Period
External Oscillator Low Period
Conversion Time for 1x Speed Mode
50Hz Mode
60Hz Mode
Simultaneous 50/60Hz Mode
External Oscillator
50Hz Mode
60Hz Mode
Simultaneous 50/60Hz Mode
External Oscillator
Internal Oscillator (Notes 10, 17)
External Oscillator (Notes 10, 11, 15)
(Notes 10, 17)
(Notes 10, 11, 15)
(Notes 10, 11, 15)
(Notes 10, 11, 15)
Internal Oscillator (Notes 10, 17)
External Oscillator (Notes 10, 11, 15)
(Notes 10, 11, 15)
●
●
●
●
●
●
●
The
●
denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
(Note 16)
●
●
●
●
●
●
●
●
●
MIN
10
0.125
0.125
157.2
131
144.1
78.7
65.6
72.2
TYP
MAX
4000
50
50
UNITS
kHz
μs
μs
ms
ms
ms
ms
ms
ms
ms
ms
kHz
kHz
160.3
133.6
146.9
41036/f
EOSC
(in kHz)
80.3
66.9
73.6
20556/f
EOSC
(in kHz)
38.4
f
EOSC
/8
163.5
136.3
149.9
81.9
68.2
75.1
t
CONV_2
Conversion Time for 2x Speed Mode
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
7
t
8
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
External SCK 24-Bit Data Output Time
CS↓
to SDO Low
CS↑
to SDO High Z
CS↓
to SCK↑
CS↓
to SCK↑
SCK↓ to SDO Valid
SDO Hold After SCK↓
SCK Set-Up Before
CS↓
SDI Setup Before SCK↑
SDI Hold After SCK↑
45
125
125
0.61
0.625
192/f
EOSC
(in kHz)
24/f
ESCK
(in kHz)
0
0
0
50
55
4000
%
kHz
ns
ns
0.64
ms
ms
ms
ns
ns
ns
ns
ns
ns
ns
ns
ns
200
200
200
200
Internal SCK Mode
External SCK Mode
(Note 5)
(Note 5)
(Note 5)
●
●
●
●
●
●
●
15
50
100
100
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
= 2.7V to 5.5V unless otherwise specified.
V
REFCM
= V
REF
/2, F
S
= 0.5V
REF
/Gain
V
IN
= IN
+
– IN
–
, V
IN(CM)
= (IN
+
– IN
–
)/2,
where IN
+
and IN
–
are the selected input channels.
Note 4:
Use internal conversion clock or external conversion clock source
with f
EOSC
= 307.2kHz unless other wise 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:
50Hz mode (internal oscillator) or f
EOSC
= 256kHz ±2% (external
oscillator).
Note 8:
60Hz mode (internal oscillator) or f
EOSC
= 307.2kHz ±2% (external
oscillator).
Note 9:
Simultaneous 50Hz/60Hz mode (internal oscillator) or f
EOSC
=
280kHz ±2% (external oscillator).
Note 10:
The SCK can be configured in external SCK mode or internal SCK
mode. In external SCK mode, the SCK pin is used as a digital input and the
driving clock is f
ESCK
. In the internal SCK mode, the SCK pin is used as a
digital output and the output clock signal during the data output is f
ISCK
.
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 its internal oscillator.
Note 13:
The output noise includes the contribution of the internal
calibration operations.
Note 14:
Guaranteed by design and test correlation.
Note 15:
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 16:
Refer to Applications Information section for performance vs
data rate graphs.
Note 17:
The converter is in internal SCK mode of operation such that the
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