LTC1289
3 Volt Single Chip 12-Bit
Data Acquisition System
FEATURES
s
s
DESCRIPTIO
s
s
s
Single Supply 3.3V or
±3.3V
Operation
Software Programmable Features
Unipolar/Bipolar Conversions
4 Differential/8 Single-Ended Inputs
Variable Data Word Length
Power Shutdown
Built-In Sample and Hold
Direct 4-Wire Interface to Most MPU Serial Ports
and all MPU Parallel Ports
25kHz Maximum Throughput Rate
KEY SPECIFICATIO S
s
s
s
s
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
Minimum Guaranteed Supply Voltage ............... 2.7V
Resolution ...................................................... 12 Bits
Fast Conversion Time .............. 26µs Max Over Temp
Low Supply Currents ...................................... 1.0mA
TYPICAL APPLICATI
+3V
Single Cell 3V 12-Bit Data Acquisition System
CH0
1N4148
CH1
CH2
CH3
10µF
–3V
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
).
V
CC
ACLK
SCLK
D
IN
TO AND
FROM
MPU
+
–
1/4 LTC1079
22µF
TANTALUM
10k
BOOST
V
+
OSC
LTC1044
LV
10Ω
+
CH4 LTC1289 D
OUT
CH5
CS
CH6
CH7
COM
DGND
REF
+
REF
–
V
–
AGND
1N4148
+
22µF
LT1004-1.2
0.1µF
1N5817
LTC1289 TA01
+
U
3V
LITHIUM
UO
U
+
10µF
CAP
+
GND
CAP
–
V
OUT
–3V
22µF
1
LTC1289
ABSOLUTE
AXI U
RATI GS
(Notes 1 and 2)
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
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
PACKAGE/ORDER I FOR ATIO
TOP VIEW
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7
COM
1
2
3
4
5
6
7
8
9
20 V
CC
19 ACLK
18 SCLK
17 D
IN
16 D
OUT
15 CS
14 REF
+
13 REF
–
12 V
–
11 AGND
N PACKAGE
20-LEAD PLASTIC DIP
1289 PO01
ORDER PART
NUMBER
CH0
1
2
3
4
5
6
7
8
9
DGND 10
J PACKAGE
20-LEAD CERAMIC DIP
LTC1289BIJ
LTC1289CIJ
LTC1289BIN
LTC1289CIN
LTC1289BCJ
LTC1289CCJ
LTC1289BCN
LTC1289CCN
CO VERTER A D
PARAMETER
Offset Error
Linearity Error (INL)
Gain Error
Minimum Resolution for
Which No Missing Codes are
Guaranteed
Analog and REF Input Range
On Channel Leakage Current
(Note 8)
ULTIPLEXER CHARACTERISTICS
(Note 3)
MIN
q
CONDITIONS
V
CC
= 2.7V
(Note 4)
V
CC
= 2.7V
(Notes 4 and 5)
V
CC
= 2.7V
(Note 4)
q
q
q
(Note 7)
On Channel = 3V
Off Channel = 0V
On Channel = 0V
Off Channel = 3V
On Channel = 3V
Off Channel = 0V
On Channel = 0V
Off Channel = 3V
q
q
q
q
(V
–
) – 0.05V to V
CC
+ 0.05V
±1
±1
±1
±1
Off Channel Leakage Current
(Note 8)
2
U
U
W
W W
U
W U
W
TOP VIEW
20 V
CC
19 ACLK
18 SCLK
17 DIN
16 D
OUT
15 CS
14 REF
+
13 REF
–
12 V
–
11 AGND
ORDER PART
NUMBER
LTC1289BCS
LTC1289CCS
CH1
CH2
CH3
CH4
CH5
CH6
CH7
COM
DGND 10
S PACKAGE
20-LEAD PLASTIC SOL
LTC1289 PO02
U
LTC1289B
TYP
MAX
±1.5
±0.5
±0.5
12
MIN
LTC1289C
TYP
MAX
±1.5
±0.5
±1.0
12
UNITS
LSB
LSB
LSB
BITS
(V
–
) – 0.05V to V
CC
+ 0.05V
±1
±1
±1
±1
V
µA
µA
µA
µA
LTC1289
AC CHARACTERISTICS
(Note 3)
SYMBOL
f
SCLK
f
ACLK
t
ACC
t
SMPL
t
CONV
t
CYC
t
dDO
t
dis
t
en
t
hCS
t
hDI
t
hDO
t
f
t
r
t
suDI
t
suCS
t
WHCS
C
IN
PARAMETER
Shift Clock Frequency
A/D Clock Frequency
Delay time from CS↓ to D
OUT
Data Valid
Analog Input Sample Time
Conversion Time
Total Cycle Time
Delay Time, SCLK↓ to D
OUT
Data Valid
Delay Time, CS↑ to D
OUT
Hi-Z
Delay Time, 2nd ACLK↓ to D
OUT
Enabled
Hold Time, CS After Last SCLK↓
Hold Time, D
IN
After SCLK↑
Time Output Data Remains Valid After SCLK↓
D
OUT
Fall Time
D
OUT
Rise Time
Setup Time, D
IN
Stable Before SCLK↑
Setup Time, CS↓ Before Clocking in
First Address Bit
CS High Time During Conversion
Input Capacitance
See Test Circuits
See Test Circuits
(Note 6 and 9)
(Note 6 and 9)
(Note 6)
Analog Inputs On Channel
Analog Inputs Off Channel
Digital Inputs
q
q
CONDITIONS
(Note 6)
(Note 6)
(Note 9)
See Operating Sequence
See Operating Sequence
See Operating Sequence (Note 6)
See Test Circuits
See Test Circuits
See Test Circuits
(Note 6)
(Note 6)
q
q
q
LTC1289B
LTC1289C
MIN
TYP
MAX
0
(Note 10)
2
7
52
12 SCLK +
56 ACLK
200
70
130
0
50
50
40
40
50
2 ACLK Cycles
+ 180ns
52
100
5
5
100
100
350
150
250
1.0
2.0
UNITS
MHz
MHz
ACLK
Cycles
SCLK
Cycles
ACLK
Cycles
Cycles
ns
ns
ns
ns
ns
ns
ns
ns
ns
ACLK
Cycles
pF
pF
pF
3
LTC1289
DIGITAL A D DC ELECTRICAL CHARACTERISTICS
(Note 3)
SYMBOL
V
IH
V
IL
I
IH
I
IL
V
OH
PARAMETER
High Level Input Voltage
Low Level Input Voltage
High Level Input Current
Low Level Input Current
High Level Output Voltage
CONDITIONS
V
CC
= 3.6V
V
CC
= 3.0V
V
IN
= V
CC
V
IN
= 0V
V
CC
= 3.0V
I
O
= 20µA
I
O
= 400µA
V
CC
= 3.0V
I
O
= 20µA
I
O
= 400µA
V
OUT
= V
CC
, CS High
V
OUT
= 0V, CS High
V
OUT
= 0V
V
OUT
= V
CC
CS High
CS High, Power Shutdown, ACLK Off
V
REF
= 2.5V
CS High
q
q
q
q
q
q
q
q
q
V
OL
Low Level Output Voltage
I
OZ
I
SOURCE
I
SINK
I
CC
I
REF
I
–
High Z Output Leakage
Output Source Current
Output Sink Current
Positive Supply Current
Reference Current
Negative Supply Current
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
4
U
LTC1289B
LTC1289C
MIN
TYP
MAX
2.1
0.45
2.5
– 2.5
2.90
2.85
UNITS
V
V
µA
µA
V
2.7
q
q
q
V
0.05
0.10
0.3
3
–3
–10
9
1.5
1.0
10
1
5
10
50
50
µA
µA
mA
mA
mA
µA
µA
µA
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.
LTC1289
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Supply Voltage
2.8
2.6
2.4
SUPPLY CURRENT (mA)
ACLK = 2MHz
T
A
= 25°C
OFFSET (LSB = 1/4096
×
V
REF
)
SUPPLY CURRENT (mA)
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6
SUPPLY VOLTAGE (V)
LTC1289 TPC01
Change in Linearity vs Reference
Voltage
CHANGE IN LINEARITY (LSB = 1/4096
×
V
REF
)
0.5
0.25
CHANGE IN GAIN (LSB = 1/4096
×
V
REF
)
0.20
0.15
0.10
0.05
0
MAGNITUDE OF OFFSET CHANGE (LSB)
V
CC
= 3V
0.4
0.3
0.2
0.1
0
0
0.5
2.5
1.0
1.5
2.0
REFERENCE VOLTAGE (V)
Change in Linearity vs
Temperature
0.5
MAGNITUDE OF LINEARITY CHANGE (LSB)
0.4
0.3
0.4
0.3
MAXIMUM ACLK FREQUENCY* (MHz)
MAGNITUDE OF GAIN CHANGE (LSB)
V
CC
= 3V
V
REF
= 2.5V
ACLK = 2MHz
0.2
0.1
0
20
–60 –40 –20 0
40 60 80 100
AMBIENT TEMPERATURE (°C)
LTC1289 TPC07
U W
3.0
LTC1289 TPC04
Supply Current vs Temperature
1.9
1.8
1.7
1.6
1.5
1.4
1.3
–40 –25 –10
ACLK = 2MHz
V
CC
= 3V
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Unadjusted Offset Voltage vs
Reference Voltage
V
CC
= 3V
V
OS
= 0.250mV
V
OS
= 0.125mV
5 20 35 50 65
TEMPERATURE (°C)
80
95
0
0
0.5
2.5
2.0
1.5
1.0
REFERENCE VOLTAGE (V)
3.0
LTC 1289 • TPC02
LTC1289 TPC03
Change in Gain vs Reference
Voltage
0.5
V
CC
= 3V
Change in Offset vs Temperature
V
CC
= 3V
V
REF
= 2.5V
ACLK = 2MHz
0.4
0.3
–0.05
–0.10
0.2
–0.15
–0.20
0
0.5
1.5
2.0
2.5
1.0
REFERENCE VOLTAGE (V)
3.0
0.1
–0.25
0
20
–60 –40 –20 0
40 60 80 100
AMBIENT TEMPERATURE (°C)
LTC1289 • TPC06
LTC1289 TPC05
Change in Gain vs Temperature
0.5
V
CC
= 3V
V
REF
= 2.5V
ACLK = 2MHz
3
Maximum ACLK Frequency vs
Source Resistance
V
CC
= 3V
V
REF
= 2.5V
T
A
= 25°C
2
V
IN
R
SOURCE –
+
INPUT
–
INPUT
0.2
1
0.1
0
20
40 60 80 100
–60 –40 –20 0
AMBIENT TEMPERATURE (°C)
LTC1289 TPC08
0
100
1k
10 k
R
SOURCE
(Ω)
100k
LTC1289 TPC09
* 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.
5
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