1
LTC1289
3 Volt Single Chip 12-Bit
Data Acquisition System
S
FEATURE
D
U
ESCRIPTIO
s
Single Supply 3.3V or
3.3V Operation
s
Software Programmable Features
Unipolar/Bipolar Conversions
4 Differential/8 Single-Ended Inputs
Variable Data Word Length
Power Shutdown
s
Built-In Sample and Hold
s
Direct 4-Wire Interface to Most MPU Serial Ports
and all MPU Parallel Ports
s
25kHz Maximum Throughput Rate
U
A
O
PPLICATI
TYPICAL
Single Cell 3V 12-Bit Data Acquisition System
KEY SPECIFICATIO S
U
s
Minimum Guaranteed Supply Voltage ............... 2.7V
s
Resolution ...................................................... 12 Bits
s
Fast Conversion Time .............. 26
s Max Over Temp
s
Low Supply Currents ...................................... 1.0mA
The LTC1289 is a 3V data acquisition component which
contains a serial I/O successive approximation A/D con-
verter. The device specifications are guaranteed at a
supply voltage of 2.7V. It uses LTCMOS
TM
switched ca-
pacitor technology to perform a 12-bit unipolar, or 11-bit
plus sign bipolar A/D conversion. The 8 channel input
multiplexer can be configured for either single-ended or
differential inputs (or combinations thereof). An on-chip
sample and hold is included for all single-ended input
channels. When the LTC1289 is idle it can be powered
down in applications where low power consumption is
desired.
The serial I/O is designed to be compatible with industry
standard full duplex serial interfaces. It allows either MSB-
or LSB- first data and automatically provides 2's comple-
ment output coding in the bipolar mode. The output data
word can be programmed for a length of 8, 12 or 16 bits.
This allows easy interface to shift registers and a variety of
processors.
LTCMOS
TM
is a trademark of Linear Technology Corporation
LTC1289 TA01
LTC1289
1N4148
10
F
+
10
1/4 LTC1079
+3V
3V
TO AND
FROM
MPU
+
22
F
TANTALUM
1N4148
10k
+
LT1004-1.2
0.1
F
22
F
1N5817
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7
COM
DGND
V
CC
ACLK
SCLK
D
IN
D
OUT
CS
REF
+
REF
V
AGND
BOOST
CAP
+
GND
CAP
V
+
OSC
LV
V
OUT
LTC1044
10
F
+
+
22
F
3V
3V
LITHIUM
FOR OVERVOLTAGE PROTECTION ON
ONLY ONE CHANNEL LIMIT THE INPUT
CURRENT TO 15mA. FOR MORE THAN
ONE CHANNEL LIMIT THE INPUT
CURRENT TO 7mA PER CHANNEL AND
28mA FOR ALL CHANNELS.
CONVERSION RESULTS ARE NOT VALID
WHEN THE SELECTED OR ANY OTHER
CHANNEL IS OVERVOLTAGED (V
IN
< V
or V
IN
> V
CC
).
2
LTC1289
LTC1289B
LTC1289C
PARAMETER
CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
Offset Error
V
CC
= 2.7V
q
1.5
1.5
LSB
(Note 4)
Linearity Error (INL)
V
CC
= 2.7V
q
0.5
0.5
LSB
(Notes 4 and 5)
Gain Error
V
CC
= 2.7V
q
0.5
1.0
LSB
(Note 4)
Minimum Resolution for
q
12
12
BITS
Which No Missing Codes are
Guaranteed
Analog and REF Input Range
(Note 7)
(V
) 0.05V to V
CC
+ 0.05V
(V
) 0.05V to V
CC
+ 0.05V
V
On Channel Leakage Current
On Channel = 3V
q
1
1
A
(Note 8)
Off Channel = 0V
On Channel = 0V
q
1
1
A
Off Channel = 3V
Off Channel Leakage Current
On Channel = 3V
q
1
1
A
(Note 8)
Off Channel = 0V
On Channel = 0V
q
1
1
A
Off Channel = 3V
A
U
G
W
A
W
U
W
A
R
BSOLUTE
XI
TI
S
Supply Voltage V
CC
to GND or V
........................... 12V
Negative Supply Voltage (V
) .................... 6V to GND
Voltage
Analog and Reference Inputs (V
) 0.3V to V
CC
+ 0.3V
Digital Inputs ......................................... 0.3V to 12V
Digital Outputs............................ 0.3V to V
CC
+ 0.3V
Power Dissipation ............................................. 500mW
Operating Temperature Range
LTC1289BI, LTC1289CI ..................... 40
C TO 85
C
LTC1289BC, LTC1289CC ......................... 0
C to 70
C
Storage Temperature Range ................ 65
C to 150
C
Lead Temperature (Soldering, 10 sec.) ................ 300
C
(Notes 1 and 2)
W
U
U
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
ORDER PART
NUMBER
LTC1289BIJ
LTC1289CIJ
LTC1289BIN
LTC1289CIN
LTC1289BCJ
LTC1289CCJ
LTC1289BCN
LTC1289CCN
LTC1289BCS
LTC1289CCS
1
2
3
4
5
6
7
8
9
10
TOP VIEW
J PACKAGE
20-LEAD CERAMIC DIP
N PACKAGE
20-LEAD PLASTIC DIP
20
19
18
17
16
15
14
13
12
11
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7
COM
DGND
V
CC
ACLK
SCLK
D
IN
D
OUT
CS
REF
+
REF
V
AGND
1289 PO01
CO VERTER A D ULTIPLEXER CHARACTERISTICS
U
U W
(Note 3)
1
2
3
4
5
6
7
8
9
10
TOP VIEW
S PACKAGE
20-LEAD PLASTIC SOL
20
19
18
17
16
15
14
13
12
11
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7
COM
DGND
V
CC
ACLK
SCLK
DIN
D
OUT
CS
REF
+
REF
V
AGND
LTC1289 PO02
3
LTC1289
LTC1289B
LTC1289C
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
f
SCLK
Shift Clock Frequency
(Note 6)
0
1.0
MHz
f
ACLK
A/D Clock Frequency
(Note 6)
(Note 10)
2.0
MHz
t
ACC
Delay time from CS
to D
OUT
Data Valid
(Note 9)
2
ACLK
Cycles
t
SMPL
Analog Input Sample Time
See Operating Sequence
7
SCLK
Cycles
t
CONV
Conversion Time
See Operating Sequence
52
ACLK
Cycles
t
CYC
Total Cycle Time
See Operating Sequence (Note 6)
12 SCLK +
Cycles
56 ACLK
t
dDO
Delay Time, SCLK
to D
OUT
Data Valid
See Test Circuits
q
200
350
ns
t
dis
Delay Time, CS
to D
OUT
Hi-Z
See Test Circuits
q
70
150
ns
t
en
Delay Time, 2nd ACLK
to D
OUT
Enabled
See Test Circuits
q
130
250
ns
t
hCS
Hold Time, CS After Last SCLK
(Note 6)
0
ns
t
hDI
Hold Time, D
IN
After SCLK
(Note 6)
50
ns
t
hDO
Time Output Data Remains Valid After SCLK
50
ns
t
f
D
OUT
Fall Time
See Test Circuits
q
40
100
ns
t
r
D
OUT
Rise Time
See Test Circuits
q
40
100
ns
t
suDI
Setup Time, D
IN
Stable Before SCLK
(Note 6 and 9)
50
ns
t
suCS
Setup Time, CS
Before Clocking in
(Note 6 and 9)
2 ACLK Cycles
First Address Bit
+ 180ns
t
WHCS
CS High Time During Conversion
(Note 6)
52
ACLK
Cycles
C
IN
Input Capacitance
Analog Inputs On Channel
100
pF
Analog Inputs Off Channel
5
pF
Digital Inputs
5
pF
(Note 3)
AC CHARACTERISTICS
4
LTC1289
LTC1289B
LTC1289C
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IH
High Level Input Voltage
V
CC
= 3.6V
q
2.1
V
V
IL
Low Level Input Voltage
V
CC
= 3.0V
q
0.45
V
I
IH
High Level Input Current
V
IN
= V
CC
q
2.5
A
I
IL
Low Level Input Current
V
IN
= 0V
q
2.5
A
V
OH
High Level Output Voltage
V
CC
= 3.0V
V
I
O
= 20
A
q
2.90
I
O
= 400
A
2.7
2.85
V
OL
Low Level Output Voltage
V
CC
= 3.0V
V
I
O
= 20
A
q
0.05
I
O
= 400
A
0.10
0.3
I
OZ
High Z Output Leakage
V
OUT
= V
CC
, CS High
q
3
A
V
OUT
= 0V, CS High
q
3
A
I
SOURCE
Output Source Current
V
OUT
= 0V
10
mA
I
SINK
Output Sink Current
V
OUT
= V
CC
9
mA
I
CC
Positive Supply Current
CS High
q
1.5
5
mA
CS High, Power Shutdown, ACLK Off
q
1.0
10
A
I
REF
Reference Current
V
REF
= 2.5V
q
10
50
A
I
Negative Supply Current
CS High
q
1
50
A
ELECTRICAL C
C
HARA TER STICS
DIGITAL A D
U
I
DC
(Note 3)
inputs can cause this input diode to conduct, especially at elevated
temperature, and cause errors for inputs near full scale. This spec allows
50mV forward bias of either diode. This means that as long as the analog
input does not exceed the supply voltage by more than 50mV, the output
code will be correct.
Note 8: Channel leakage current is measured after the channel selection.
Note 9: To minimize errors caused by noise at the chip select input, the
internal circuitry waits for two ACLK falling edges after a chip select falling
edge is detected before responding to control input signals. Therefore, no
attempt should be made to clock an address in or data out until the
minimum chip select set-up time has elasped. See Typical Peformance
Characteristics curves for additional information (t
suCS
vs V
CC
).
Note 10: Increased leakage currents at elevated temperatures cause the
S/H to droop, therefore it's recommended that f
ACLK
125kHz at 85
C and
f
ACLK
15kHz at 25
C.
The
q
denotes specifications which apply over the operating temperature
range; all other limits and typicals T
A
= 25
C.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impared.
Note 2: All voltage values are with respect to ground with DGND, AGND
and REF
wired together (unless otherwise noted).
Note 3: V
CC
= 3V, V
REF
+ = 2.5V, V
REF
= 0V, V
= 0V for unipolar mode
and 3V for bipolar mode, ACLK = 2.0MHz unless otherwise specified.
Note 4: These specs apply for both unipolar and bipolar modes. In bipolar
mode, one LSB is equal to the bipolar input span (2V
REF
) divided by 4096.
For example, when V
REF
= 2.5V, 1LSB(bipolar) = 2(2.5)/4096 = 1.22mV.
V
= 2.7V for bipolar mode.
Note 5: 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 6: Recommended operating conditions.
Note 7: Two on-chip diodes are tied to each analog input which will
conduct for analog voltages one diode drop below GND or one diode drop
above V
CC
. Be careful during testing at low V
CC
levels, as high level analog
5
LTC1289
C
C
HARA TERISTICS
U
W
A
TYPICAL PERFOR
CE
Supply Current vs Temperature
Change in Linearity vs Reference
Voltage
Change in Gain vs Reference
Voltage
Supply Current vs Supply Voltage
TEMPERATURE (C)
40
1.3
SUPPLY CURRENT (mA)
1.4
1.5
1.6
1.7
25 10
50
LTC 1289 TPC02
1.8
1.9
5
20
35
65
95
80
ACLK = 2MHz
V
CC
= 3V
Unadjusted Offset Voltage vs
Reference Voltage
Change in Offset vs Temperature
Maximum ACLK Frequency vs
Source Resistance
* MAXIMUM ACLK FREQUENCY REPRESENTS THE ACLK FREQUENCY AT WHICH A 0.1LSB SHIFT
IN THE ERROR AT ANY CODE TRANSITION FROM ITS 2MHZ VALUE IS FIRST DETECTED.
SUPPLY VOLTAGE (V)
2.7
0.8
SUPPLY CURRENT (mA)
1.0
1.4
1.6
1.8
2.8
2.2
2.9
3.1 3.2
3.6
LTC1289 TPC01
1.2
2.4
2.6
2.0
2.8
3.0
3.3 3.4 3.5
ACLK = 2MHz
T
A
= 25C
REFERENCE VOLTAGE (V)
0
0
OFFSET (LSB = 1/4096
V
REF
)
0.1
0.3
0.4
0.5
1.0
2.0
3.0
0.9
LTC1289 TPC03
0.2
0.5
1.5
0.6
0.7
0.8
2.5
V
CC
= 3V
V
OS
= 0.250mV
V
OS
= 0.125mV
REFERENCE VOLTAGE (V)
0
0
CHANGE IN LINEARITY (LSB = 1/4096
V
REF
)
0.1
0.2
0.3
0.4
0.5
0.5
1.0
1.5
2.0
LTC1289 TPC04
2.5
3.0
V
CC
= 3V
Change in Linearity vs
Temperature
AMBIENT TEMPERATURE (C)
60
MAGNITUDE OF LINEARITY CHANGE (LSB)
0.3
0.4
0.5
0
40
100
LTC1289 TPC07
0.2
0.1
0
40 20
20
60
80
V
CC
= 3V
V
REF
= 2.5V
ACLK = 2MHz
AMBIENT TEMPERATURE (C)
60
MAGNITUDE OF GAIN CHANGE (LSB)
0.3
0.4
0.5
0
40
100
LTC1289 TPC08
0.2
0.1
0
40 20
20
60
80
V
CC
= 3V
V
REF
= 2.5V
ACLK = 2MHz
Change in Gain vs Temperature
R
SOURCE
(
)
100
0
MAXIMUM ACLK FREQUENCY* (MHz)
2
3
1k
10 k
100k
LTC1289 TPC09
1
V
CC
= 3V
V
REF
= 2.5V
T
A
= 25C
+
INPUT
INPUT
V
IN
R
SOURCE
AMBIENT TEMPERATURE (C)
60
MAGNITUDE OF OFFSET CHANGE (LSB)
0.3
0.4
0.5
0
40
100
LTC1289 TPC06
0.2
0.1
0
40 20
20
60
80
V
CC
= 3V
V
REF
= 2.5V
ACLK = 2MHz
REFERENCE VOLTAGE (V)
0
CHANGE IN GAIN (LSB = 1/4096
V
REF
)
0.15
0.20
0.25
2.0
LTC1289 TPC05
0.05
0.15
0.25
0.5
1.0
1.5
2.5
3.0
0.10
0.05
0
0.10
0.20
V
CC
= 3V
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