FeaTures
■
■
LTC2487
16-Bit 2-/4-Channel
DS
ADC
with PGA, Easy Drive and
I
2
C Interface
DescripTion
The LTC
®
2487 is a 4-channel (2 differential), 16-bit,
No Latency
DS™
ADC with Easy Drive technology and a
2-wire, I
2
C interface. The patented sampling scheme elimi-
nates 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 LTC2487 includes programmable gain, a high accuracy
temperature sensor and an integrated oscillator. This device
can be configured to measure an external signal (from com-
binations of 4 analog input channels operating 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 LTC2487 can
be configured to provide a programmable gain from 1 to
256 in 8 steps.
The LTC2487 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. Access to the multiplexer output en-
ables optional external amplifiers to be shared between all
analog inputs and auto calibration continuously removes
their associated offset and drift.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
No Latency
DS
and Easy Drive are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
■
■
■
■
■
■
■
■
■
■
■
■
■
■
Up to 2 Differential or 4 Single-Ended Inputs
Easy Drive
TM
Technology Enables Rail-to-Rail
Inputs with Zero Differential Input Current
Directly Digitizes High Impedance Sensors with
Full Accuracy
2-Wire I
2
C Interface with 9 Addresses Plus One
Global Address for Synchronization
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/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 (0.8mW)
Internal Oscillator
Tiny 4mm
×
3mm DFN 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
CH0
CH1
IN
+
Built-In High Performance Temperature Sensor
5
4
ABSOLUTE ERROR (°C)
V
CC
REF
+
16-BIT
∆Σ
ADC
WITH EASY-DRIVE
IN
–
REF
–
SDA
SCL
CA1
CA0
F
O
OSC
2487 TA01a
0.1µF
10µF
3
2
1
0
–1
–2
–3
–4
–5
–55
–30
–5
20
45
70
TEMPERATURE (°C)
95
120
2487 TA02
1.7k
2-WIRE
I
2
C INTERFACE
9-PIN SELECTABLE
ADDRESSES
CH2
CH3
COM
4-CHANNEL
MUX
TEMPERATURE
SENSOR
2487fa
LTC2487
absoluTe MaxiMuM raTings
(Notes 1, 2)
pin conFiguraTion
F
O
CA0
CA1
SCL
SDA
GND
COM
1
2
3
4
5
6
7
15
14 REF
–
13 REF
+
12 V
CC
11 CH3
10 CH2
9 CH1
8 CH0
Supply Voltage (V
CC
) ................................... –0.3V to 6V
Analog Input Voltage
(CH0 to CH3, COM) ..................–0.3V to (V
CC
+ 0.3V)
REF
+
, REF
–
....................................–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
LTC2487C ................................................ 0°C to 70°C
LTC2487I ............................................. –40°C to 85°C
Storage Temperature Range................... –65°C to 150°C
DE PACKAGE
14-LEAD (4mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 37°C/W
EXPOSED PAD (PIN 15) IS GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC2487CDE#PBF
LTC2487IDE#PBF
TAPE AND REEL
LTC2487CDE#TRPBF
LTC2487IDE#TRPBF
PART MARKING*
2487
2487
PACKAGE DESCRIPTION
14-Lead (4mm
×
3mm) Plastic DFN
14-Lead (4mm
×
3mm) Plastic DFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
2487fa
LTC2487
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 13)
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 12)
T
A
= 27°C (Note 13)
●
●
●
●
●
●
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
2
1
0.5
10
32
0.1
32
0.1
15
15
15
0.6
27.8
1
28.0
93.5
256
28.2
20
5
TYP
MAX
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
Output Noise
Internal PTAT Signal
Internal PTAT Temperature Coefficient
Programmable Gain
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
CONDITIONS
0.1V ≤ V
REF
≤ V
CC
, –FS ≤ V
IN
≤ +FS (Note 5)
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
0.2
100
MAX
20
2
32
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
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 13)
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
= 5V, GND ≤ IN
+
= IN
–
≤ V
CC
●
0.1
●
32
0.1
0.85
●
1
128
converTer characTerisTics
PARAMETER
Input Common Mode Rejection DC
Input Common Mode Rejection 50Hz ±2%
Input Common Mode Rejection 60Hz ±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%, 60Hz ±2%
CONDITIONS
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
UNITS
dB
dB
dB
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)
140
140
140
110
110
87
120
140
120
120
120
120
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, 8, 9)
dB
dB
dB
dB
dB
dB
2487fa
LTC2487
analog inpuT anD reFerence
SYMBOL
IN
+
IN
–
V
IN
FS
LSB
REF
+
REF
–
V
REF
CS(IN
+
)
CS(IN
–
)
CS(V
REF
)
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
i
2
c inpuTs anD DigiTal ouTpuTs
SYMBOL
V
IH
V
IL
V
IHA
V
ILA
R
INH
R
INL
R
INF
I
I
V
HYS
V
OL
t
OF
I
IN
C
CAX
PARAMETER
High Level Input Voltage
Low Level Input Voltage
Low Level Input Voltage for Address Pins CA0, CA1
High Level Input Voltage for Address Pins CA0, CA1
Resistance from CA0, CA1 to V
CC
to Set Chip Address
Bit to 1
Resistance from CA0, CA1 to GND to Set Chip Address
Bit to 0
Resistance from CA0, CA1 to GND or V
CC
to Set Chip
Address Bit to Float
Digital Input Current
Hysteresis of Schmitt Trigger Inputs
Low Level Output Voltage (SDA)
Output Fall Time V
IH(MIN)
to V
IL(MAX)
Input Leakage
The
●
denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
●
●
●
●
●
●
●
●
MIN
0.7V
CC
TYP
MAX
0.3V
CC
0.05V
CC
UNITS
V
V
V
V
kW
kW
MW
0.95V
CC
10
10
2
–10
0.05V
CC
0.4
20 + 0.1C
B
250
1
10
10
µA
V
V
ns
µA
pF
(Note 5)
I = 3mA
Bus Load C
B
10pF to
400pF (Note 14)
0.1V
CC
≤ V
IN
≤ V
CC
●
●
●
●
●
External Capacitative Load on Chip Address Pins (CA0, CA1)
for Valid Float
2487fa
LTC2487
power requireMenTs
SYMBOL
V
CC
I
CC
PARAMETER
Supply Voltage
Supply Current
Conversion Current (Note 11)
Temperature Measurement (Note 11)
Sleep Mode (Note 11)
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
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
CONDITIONS
(Note 16)
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
4000
50
50
UNITS
kHz
µs
µs
ms
ms
ms
ms
ms
ms
ms
ms
10
0.125
0.125
157.2
131
144.1
78.7
65.6
72.2
160.3
133.6
146.9
41036/f
EOSC
(in kHz)
80.3
66.9
73.6
50Hz Mode
60Hz Mode
Simultaneous 50Hz/60Hz Mode
External Oscillator (Note 10)
50Hz Mode
60Hz Mode
Simultaneous 50Hz/60Hz Mode
External Oscillator (Note 10)
●
●
●
●
●
●
163.5
136.3
149.9
81.9
68.2
75.1
t
CONV_2
Conversion Time for 2x Speed Mode
20556/f
EOSC
(in kHz)
i
2
c TiMing characTerisTics
SYMBOL
f
SCL
t
HD(STA)
t
LOW
t
HIGH
t
SU(STA)
t
HD(DAT)
t
SU(DAT)
t
r
t
f
t
SU(STO)
PARAMETER
SCL Clock Frequency
Hold Time (Repeated) Start Condition
Low Period of the SCL Pin
High Period of the SCL Pin
Set-Up Time for a Repeated Start Condition
Data Hold Time
Data Set-Up Time
Rise Time for SDA Signals
Fall Time for SDA Signals
Set-Up Time for Stop Condition
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 3, 15)
CONDITIONS
●
●
●
●
●
●
●
MIN
0
0.6
1.3
0.6
0.6
0
100
20 + 0.1C
B
20 + 0.1C
B
0.6
TYP
MAX
400
UNITS
kHz
µs
µs
µs
µs
0.9
300
300
µs
ns
ns
ns
µs
(Note 14)
(Note 14)
●
●
●
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:
Unless otherwise specified: V
CC
= 2.7V to 5.5V
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 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:
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 external oscillator is connected to the F
O
pin. The external
oscillator frequency, f
EOSC
, is expressed in kHz.
Note 11:
The converter uses its internal oscillator.
Note 12:
The output noise includes the contribution of the internal
calibration operations.
Note 13:
Guaranteed by design and test correlation.
Note 14:
C
B
= capacitance of one bus line in pF (10pF ≤ C
B
≤ 400pF).
Note 15:
All values refer to V
IH(MIN)
and V
IL(MAX)
levels.
Note 16:
Refer to Applications Information section for Performance vs
Data Rate graphs.
2487fa
