FEATURES
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LTC1286/LTC1298
Micropower Sampling
12-Bit A/D Converters In
S0-8 Packages
DESCRIPTION
The LTC1286/LTC1298 are micropower, 12-bit, succes-
sive approximation sampling A/D converters. They typi-
cally draw only 250µA of supply current when converting
and automatically power down to a typical supply current
of 1nA whenever they are not performing conversions.
They are packaged in 8-pin SO packages and operate on
5V to 9V supplies. These 12-bit, switched-capacitor, suc-
cessive approximation ADCs include sample-and-holds.
The LTC1286 has a single differential analog input. The
LTC1298 offers a software selectable 2-channel MUX.
On-chip serial ports allow efficient data transfer to a wide
range of microprocessors and microcontrollers over three
wires. This, coupled with micropower consumption, makes
remote location possible and facilitates transmitting data
through isolation barriers.
These circuits can be used in ratiometric applications or
with an external reference. The high impedance analog
inputs and the ability to operate with reduced spans (to
1.5V full scale) allow direct connection to sensors and
transducers in many applications, eliminating the need for
gain stages.
s
s
s
s
12-Bit Resolution
8-Pin SOIC Plastic Package
Low Cost
Low Supply Current: 250µA Typ.
Auto Shutdown to 1nA Typ.
Guaranteed
±3/4LSB
Max DNL
Single Supply 5V to 9V Operation
On-Chip Sample-and-Hold
60µs Conversion Time
Sampling Rates:
12.5 ksps (LTC1286)
11.1 ksps (LTC1298)
I/O Compatible with SPI, Microwire, etc.
Differential Inputs (LTC1286)
2-Channel MUX (LTC1298)
3V Versions Available: LTC1285/LTC1288
APPLICATIONS
s
s
s
s
s
s
Battery-Operated Systems
Remote Data Acquisition
Battery Monitoring
Handheld Terminal Interface
Temperature Measurement
Isolated Data Acquisition
TYPICAL APPLICATIONS
N
25µW, S0-8 Package, 12-Bit ADC
Samples at 200Hz and Runs Off a 5V Supply
4.7µF
5V
Supply Current vs Sample Rate
1000
T
A
= 25°C
V
CC
= V
REF
= 5V
f
CLK
= 200kHz
100
MPU
(e.g., 8051)
1
ANALOG INPUT
0V TO 5V RANGE
2
3
4
V
REF
+IN
–IN
GND
V
CC
LTC1286 CLK
D
OUT
CS/SHDN
8
7
6
5
SERIAL DATA LINK
LTC1286/98 • TA01
P1.4
P1.3
P1.2
SUPPLY CURRENT (µA)
10
1
0.1k
1k
10k
SAMPLE FREQUENCY (Hz)
100k
U
U
U
LTC1286/98 • TA02
1
LTC1286/LTC1298
ABSOLUTE
MAXIMUM
RATINGS
Supply Voltage (V
CC
) to GND ................................... 12V
Voltage
Analog and Reference ................ –0.3V to V
CC
+ 0.3V
Digital Inputs ......................................... –0.3V to 12V
Digital Output ............................. –0.3V to V
CC
+ 0.3V
PACKAGE/ORDER INFORMATION
TOP VIEW
V
REF
1
+IN 2
–IN 3
GND 4
8
7
6
5
V
CC
CLK
D
OUT
CS/SHDN
ORDER PART
NUMBER
LTC1286CN8
LTC1286IN8
N8 PACKAGE
8-LEAD PLASTIC DIP
T
JMAX
= 150°C,
θ
JA
= 130°C/W
TOP VIEW
CS/SHDN 1
CH0 2
CH1 3
GND 4
8
7
6
5
V
CC
(V
REF
)
CLK
D
OUT
D
IN
ORDER PART
NUMBER
LTC1298CN8
LTC1298IN8
N8 PACKAGE
8-LEAD PLASTIC DIP
T
JMAX
= 150°C,
θ
JA
= 130°C/W
Consult factory for military grade parts.
RECOM ENDED OPERATING CONDITIONS
SYMBOL
V
CC
f
CLK
t
CYC
t
hDI
t
suCS
t
suDI
t
WHCLK
t
WLCLK
t
WHCS
t
WLCS
PARAMETER
Supply Voltage (Note 3)
Clock Frequency
Total Cycle Time
Hold Time, D
IN
After CLK↑
Setup Time CS↓ Before First CLK↑ (See Operating Sequence)
Setup Time, D
IN
Stable Before CLK↑
CLK High Time
CLK Low Time
CS High Time Between Data Transfer Cycles
CS Low Time During Data Transfer
CONDITIONS
LTC1286
LTC1298
V
CC
= 5V
LTC1286, f
CLK
= 200kHz
LTC1298, f
CLK
= 200kHz
V
CC
= 5V
LTC1286, V
CC
= 5V
LTC1298, V
CC
= 5V
V
CC
= 5V
V
CC
= 5V
V
CC
= 5V
V
CC
= 5V
LTC1286, f
CLK
= 200kHz
LTC1298, f
CLK
= 200kHz
MIN
4.5
4.5
(Note 4)
80
90
150
2
2
400
2
2
2
75
85
TYP
MAX
9.0
5.5
200
UNITS
V
V
kHz
µs
µs
ns
µs
µs
ns
µs
µs
µs
µs
µs
2
U
U
U
U
W
W W
U
W
(Notes 1 and 2)
Power Dissipation .............................................. 500mW
Operating Temperature Range
LTC1286C/LTC1298C............................. 0°C to 70°C
LTC1286I/LTC1298I ........................... –40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec.)................ 300°C
TOP VIEW
V
REF
1
+IN 2
–IN 3
GND 4
8
7
6
5
V
CC
CLK
D
OUT
CS/SHDN
ORDER PART
NUMBER
LTC1286CS8
LTC1286IS8
PART MARKING
1286
1286I
ORDER PART
NUMBER
LTC1298CS8
LTC1298IS8
PART MARKING
1298
1298I
S8 PACKAGE
8-LEAD PLASTIC SOIC
T
JMAX
= 150°C,
θ
JA
= 175°C/W
TOP VIEW
CS/SHDN 1
CH0 2
CH1 3
GND 4
8
7
6
5
V
CC
(V
REF
)
CLK
D
OUT
D
IN
S8 PACKAGE
8-LEAD PLASTIC SOIC
T
JMAX
= 150°C,
θ
JA
= 175°C/W
U WW
LTC1286/LTC1298
CONVERTER AND
MULTIPLEXER
CHARACTERISTICS
PARAMETER
Resolution (No Missing Codes)
Integral Linearity Error
Differential Linearity Error
Offset Error
Gain Error
Analog Input Range
REF Input Range (LTC1286)
(Notes 7, 8, and 9)
Analog Input Leakage Current (Note 10)
(Note 7 and 8)
4.5
≤
V
CC
≤
5.5V
5.5V < V
CC
≤
9V
q
DIGITAL AND DC ELECTRICAL CHARACTERISTICS
SYMBOL
V
IH
V
IL
I
IH
I
IL
V
OH
V
OL
I
OZ
I
SOURCE
I
SINK
R
REF
I
REF
PARAMETER
High Level Input Voltage
Low Level Input Voltage
High Level Input Current
Low Level Input Current
High Level Output Voltage
Low Level Output Voltage
Hi-Z Output Leakage
Output Source Current
Output Sink Current
Reference Input Resistance
(LTC1286)
Reference Current (LTC1286)
CONDITIONS
V
CC
= 5.25V
V
CC
= 4.75V
V
IN
= V
CC
V
IN
= 0V
V
CC
= 4.75V, I
O
= 10µA
V
CC
= 4.75V, I
O
= 360µA
V
CC
= 4.75V, I
O
= 1.6mA
CS = High
V
OUT
= 0V
V
OUT
= V
CC
CS = V
CC
CS = GND
CS = V
CC
t
CYC
≥
640µs, f
CLK
≤
25kHz
t
CYC
= 80µs, f
CLK
= 200kHz
CS = V
CC
LTC1286, t
CYC
≥
640µs, f
CLK
≤
25kHz
LTC1286, t
CYC
= 80µs, f
CLK
= 200kHz
LTC1298, t
CYC
≥
720µs, f
CLK
≤
25kHz
LTC1298, t
CYC
= 90µs, f
CLK
= 200kHz
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
I
CC
Supply Current
DYNAMIC ACCURACY
SYMBOL
S/(N +D)
THD
SFDR
PARAMETER
Signal-to-Noise Plus Distortion Ratio
Total Harmonic Distortion (Up to 5th Harmonic)
Spurious-Free Dynamic Range
Peak Harmonic or Spurious Noise
W U
U
W U
U
(Note 5)
LTC1298
MIN
TYP
MAX
12
±3/4
±1/4
3/4
±2
±2
±3/4
±3
±8
UNITS
Bits
LSB
LSB
LSB
LSB
V
V
V
±1
µA
CONDITIONS
q
LTC1286
MIN
TYP
MAX
12
±3/4
±1/4
3/4
±2
±2
±3/4
±3
q
q
q
q
q
(Note 6)
±8
–0.05V to V
CC
+ 0.05V
1.5V to V
CC
+ 0.05V
1.5V to 5.55V
±1
(Note 5)
MIN
2
0.8
2.5
– 2.5
4.0
2.4
4.64
4.62
0.4
±3
– 25
45
5000
55
0.001
90
90
0.001
220
260
320
360
2.5
140
140
±3.0
460
500
600
640
TYP
MAX
UNITS
V
V
µA
µA
V
V
V
µA
mA
mA
MΩ
kΩ
µA
µA
µA
µA
µA
µA
µA
µA
f
SMPL
= 12.5kHz (LTC1286), f
SMPL
= 11.1kHz (LTC1298) (Note 5)
CONDITIONS
1kHz/7kHz Input Signal
1kHz/7kHz Input Signal
1kHz/7kHz Input Signal
1kHz/7kHz Input Signal
MIN
TYP
71/68
– 84/–80
90/86
– 90/–86
MAX
UNITS
dB
dB
dB
dB
3
LTC1286/LTC1298
AC CHARACTERISTICS
SYMBOL
t
SMPL
PARAMETER
Analog Input Sample Time
f
SMPL (MAX)
Maximum Sampling Frequency
t
CONV
t
dDO
t
dis
t
en
t
hDO
t
f
t
r
C
IN
Conversion Time
(Note 5)
CONDITIONS
See Operating Sequence
LTC1286
LTC1298
See Operating Sequence
See Test Circuits
See Test Circuits
See Test Circuits
C
LOAD
= 100pF
See Test Circuits
See Test Circuits
Analog Inputs, On Channel
Analog Inputs, Off Channel
Digital Input
q
q
q
q
q
MIN
q
q
12.5
11.1
TYP
1.5
MAX
UNITS
CLK Cycles
kHz
kHz
12
250
135
75
230
20
20
20
5
5
75
75
600
300
200
CLK Cycles
ns
ns
ns
ns
ns
ns
pF
pF
pF
Delay Time, CLK↓ to D
OUT
Data Valid
Delay Time, CS↑ to D
OUT
Hi-Z
Delay Time, CLK↓ to D
OUT
Enable
Time Output Data Remains Valid After CLK↓
D
OUT
Fall Time
D
OUT
Rise Time
Input Capacitance
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1:
Absolute maximum ratings are those values beyond which the life
of a device may be impaired.
Note 2:
All voltage values are with respect to GND.
Note 3:
These devices are specified at 5V. For 3V specified devices, see
LTC1285 and LTC1288.
Note 4:
Increased leakage currents at elevated temperatures cause the S/H
to droop, therefore it is recommended that f
CLK
≥
120kHz at 85°C, f
CLK
≥
75kHz at 70° and f
CLK
≥
1kHz at 25°C.
Note 5:
V
CC
= 5V, V
REF
= 5V and CLK = 200kHz unless otherwise specified.
Note 6:
Linearity error is specified between the actual end points of the
A/D transfer curve.
Note 7:
Two on-chip diodes are tied to each reference and analog input
which will conduct for reference or analog input voltages one diode drop
below GND or one diode drop above V
CC
. This spec allows 50mV forward
bias of either diode for 4.5V
≤
V
CC
≤
5.5V. This means that as long as the
reference or analog input does not exceed the supply voltage by more than
50mV the output code will be correct. To achieve an absolute 0V to 5V
input voltage range will therefore require a minimum supply voltage of
4.950V over initial tolerance, temperature variations and loading. For 5.5V
< V
CC
≤
9V, reference and analog input range cannot exceed 5.55V. If
reference and analog input range are greater than 5.55V, the output code
will not be guaranteed to be correct.
Note 8:
The supply voltage range for the LTC1286 is from 4.5V to 9V, but
the supply voltage range for the LTC1298 is only from 4.5V to 5.5V.
Note 9:
Recommended operating conditions
Note 10:
Channel leakage current is measured after the channel selection.
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Sample Rate
1000
T
A
= 25°C
V
CC
= V
REF
= 5V
f
CLK
= 200kHz
SUPPLY CURRENT (µA)
450
T
A
= 25°C
V
CC
= V
REF
= 5V
f
CLK
= 200kHz
SUPPLY CURRENT (µA)
SUPPLY CURRENT (µA)
100
LTC1298
LTC1286
10
1
0.1k
1k
10k
SAMPLE RATE (kHz)
100k
LT1286/98 G03
4
U W
Supply Current vs Temperature
35
30
25
20
15
10
5
1
LTC1286 f
SMPL
=12.5kHz
200
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
LT1286/98 G04
Shutdown Supply Current vs Clock
Rate with CS High and CS Low
T
A
= 25°C
V
CC
= V
REF
= 5V
400
350
LTC1298 f
SMPL
=11.1kHz
300
CS = 0
(AFTER CONVERSION)
250
0.002
0
CS = V
CC
1 20 40 60 80 100 120 140 160 180 200
FREQUENCY (kHz)
LT1286/98 G01
LTC1286/LTC1298
TYPICAL PERFORMANCE CHARACTERISTICS
Reference Current vs
Sample Rate (LTC1286)
100
90
T
A
= 25°C
V
CC
= 5V
V
REF
= 5V
f
CLK
= 200kHz
95
94.5
REFERENCE CURRENT (µA)
94
93.5
93
92.5
92
–55 –35 –15
CHANGE IN OFFSET (LSB = 1/4096 V
REF
)
REFERENCE CURRENT (µA)
80
70
60
50
40
30
20
10
0
0
2
4
8
6
10
FREQUENCY (kHz)
Change in Offset vs Temperature
0
-0.5
–0.5
–0.45
CHANGE IN LINEARITY (LSB)
CHANGE IN OFFSET (LSB)
-1
1.5
-2
-2.5
-3
-55
V
CC
= V
REF
= 5V
f
CLK
= 200kHz
f
SMPL
= f
SMPL (MAX)
-35
45
-15
5
25
TEMPERATURE (°C)
65
85
–0.35
–0.3
–.25
–0.2
–0.15
–0.1
–0.05
0
1
1.5
3.5 4
2 2.5 3
REFERENCE VOLTAGE (V)
4.5
5
CHANGE IN GAIN (LSB)
Peak-to-Peak ADC Noise vs
Reference Voltage
T
A
= 25°C
V
CC
= 5V
f
CLK
= 200kHz
1.5
ADC NOISE IN LBSs
DIFFERENTIAL NONLINEARITY ERROR (LBS)
2
EFFECTIVE NUMBER OF BITS (ENOBs)
1
0.5
0
1
3
4
2
REFERENCE VOLTAGE (V)
U W
12
14
LT1286/98 G06
Reference Current vs Temperature
3
V
CC
= V
REF
= 5V
f
SMPL
= 12.5kHz
f
CLK
= 200kHz
T
A
= 25°C
Change in Offset vs
Reference Voltage
T
A
= 25°C
V
CC
= 5V
f
CLK
= 200kHz
f
SMPL
= 12.5kHz
2.5
2
1.5
1
0.5
0
1
1.5
5 25 45 65 85 105 125
TEMPERATURE (°C)
LT1286/98 G07
3.5 4
2 2.5 3
REFERENCE VOLTAGE (V)
4.5
5
LT1286/98 G08
Change In Linearity vs
Reference Voltage
–10
T
A
= 25°C
V
CC
= 5V
f
CLK
= 200kHz
f
SMPL
= 12.5kHz
–9
–8
–7
–6
–5
–4
–3
–2
–1
0
Change In Gain vs
Reference Voltage
T
A
= 25°C
V
CC
= 5V
f
CLK
= 200kHz
f
SMPL
= 12.5kHz
–0.4
1
1.5
3.5 4
2 2.5 3
REFERENCE VOLTAGE (V)
4.5
5
LT1286/98 G09
LT1286/98 G10
LT1286/98 G11
Differential Nonlinearity vs Code
1.0
0.80
0.60
0.40
0.20
0.00
–0.20
–0.40
–0.60
–0.80
–1.0
0
2048
CODE
4096
Effective Bits and S/(N + D)
vs Input Frequency
12
11
10
9
8
7
6
5
4
3
2
1
0
1
10
100
INPUT FREQUENCY (kHz)
1000
T
A
= 25°C
V
CC
= 5V
f
CLK
= 200kHz
f
SMPL
= 12.5kHz
74
68
62
56
50
44
38
5
LT1286/98 G15
LTC 1286/98 G20
5
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