ADS1218
ADS
121
8
SBAS187 – SEPTEMBER 2001
8-Channel, 24-Bit
ANALOG-TO-DIGITAL CONVERTER
with FLASH Memory
FEATURES
q
24 BITS NO MISSING CODES
q
0.0015% INL
q
22 BITS EFFECTIVE RESOLUTION
(PGA = 1), 19 BITS (PGA = 128)
q
4K BYTES OF FLASH MEMORY
PROGRAMMABLE FROM 2.7V TO 5.25V
q
PGA FROM 1 TO 128
q
SINGLE CYCLE SETTLING MODE
q
PROGRAMMABLE DATA OUTPUT RATES
UP TO 1kHz
q
PRECISION ON-CHIP 1.25V/2.5V REFERENCE:
ACCURACY: 0.2%
DRIFT: 5ppm/
°
C
q
EXTERNAL DIFFERENTIAL REFERENCE
OF 0.1V TO 2.5V
q
ON-CHIP CALIBRATION
q
PIN COMPATIBLE WITH ADS1216
q
SPI™ COMPATIBLE
q
2.7V TO 5.25V
q
< 1mW POWER CONSUMPTION
AGND
DESCRIPTION
The ADS1218 is a precision, wide dynamic range, delta-sigma, Analog-to-
Digital (A/D) converter with 24-bit resolution and FLASH memory operating
from 2.7V to 5.25V supplies. The delta-sigma, A/D converter provides up to
24 bits of no missing code performance and effective resolution of 22 bits.
The eight input channels are multiplexed. Internal buffering can be selected
to provide a very high input impedance for direct connection to transducers
or low-level voltage signals. Burn out current sources are provided that allow
for the detection of an open or shorted sensor. An 8-bit Digital-to-Analog (D/
A) converter provides an offset correction with a range of 50% of the FSR
(Full-Scale Range).
The PGA (Programmable Gain Amplifier) provides selectable gains of 1 to
128 with an effective resolution of 19 bits at a gain of 128. The A/D
conversion is accomplished with a second-order delta-sigma modulator and
programmable sinc filter. The reference input is differential and can be used
for ratiometric conversion. The on-board current DACs (Digital-to-Analog
Converters) operate independently with the maximum current set by an
external resistor.
The serial interface is SPI compatible. Eight bits of digital I/O are also provided
that can be used for input or output. The ADS1218 is designed for high-resolution
measurement applications in smart transmitters, industrial process control, weight
scales, chromatography, and portable instrumentation.
AV
DD
R
DAC
V
REFOUT
V
RCAP
V
REF+
V
REF–
X
IN
X
OUT
APPLICATIONS
q
q
q
q
q
q
q
INDUSTRIAL PROCESS CONTROL
LIQUID /GAS CHROMATOGRAPHY
BLOOD ANALYSIS
SMART TRANSMITTERS
PORTABLE INSTRUMENTATION
WEIGHT SCALES
PRESSURE TRANSDUCERS
IDAC2
8-Bit
IDAC
1.25V or
2.5V
Reference
Clock Generator
IDAC1
AV
DD
8-Bit
IDAC
2µA
Offset
DAC
A
IN
0
A
IN
1
A
IN
2
A
IN
3
A
IN
4
A
IN
5
A
IN
6
A
IN
7
A
INCOM
POL
Serial Interface
SCLK
D
IN
D
OUT
CS
D0
... D7
PDWN
DSYNC
RESET
DRDY
MUX
IN+
IN–
BUF
+
PGA
2nd-Order
Modulator
A = 1:128
Program-
mable
Digital
Filter
Registers
RAM
4K Bytes
FLASH
Controller
WREN
SPI is a registered trademark of Motorola.
2µA
AGND
DV
DD
DGND
BUFEN
Digital I/O
Interface
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
Copyright © 2001, Texas Instruments Incorporated
www.ti.com
ABSOLUTE MAXIMUM RATINGS
(1)
AV
DD
to AGND ...................................................................... –0.3V to +6V
DV
DD
to DGND ...................................................................... –0.3V to +6V
Input Current ............................................................... 100mA, Momentary
Input Current ................................................................. 10mA, Continuous
A
IN
................................................................... GND –0.5V to AV
DD
+ 0.5V
AV
DD
to DV
DD
........................................................................... –6V to +6V
AGND to DGND ................................................................. –0.3V to +0.3V
Digital Input Voltage to GND .................................... –0.3V to DV
DD
+ 0.3V
Digital Output Voltage to GND ................................. –0.3V to DV
DD
+ 0.3V
Maximum Junction Temperature ................................................... +150°C
Operating Temperature Range ......................................... –40°C to +85°C
Storage Temperature Range .......................................... –60°C to +100°C
Lead Temperature (soldering, 10s) .............................................. +300°C
NOTE: (1) Stresses above those listed under “Absolute Maximum Ratings” may
cause permanent damage to the device. Exposure to absolute maximum
conditions for extended periods may affect device reliability.
ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Texas Instruments
recommends that all integrated circuits be handled with appropriate
precautions. Failure to observe proper handling and installation
procedures can cause damage.
Electrostatic discharge can cause damage ranging from perfor-
mance degradation to complete device failure. Texas Instruments
recommends that all integrated circuits be handled and stored using
appropriate ESD protection methods.
PACKAGE/ORDERING INFORMATION
PACKAGE
DESIGNATOR
PFB
SPECIFIED
TEMPERATURE
RANGE
–40°C to +85°C
PACKAGE
MARKING
ADS1218Y
ORDERING
NUMBER
ADS1218Y/250
ADS1218Y/2K
TRANSPORT
MEDIA, QUANTITY
Tape and Reel, 250
Tape and Reel, 2000
PRODUCT
ADS1218Y
PACKAGE-LEAD
TQFP-48
"
"
"
"
"
NOTE: (1) Models with a slash (/) are available only in Tape and Reel in the quantities indicated (e.g., / 2K indicates 2000 devices per reel). Ordering 2000 pieces
of “ADS1218Y/2K” will get a single 2000-piece Tape and Reel.
ELECTRICAL CHARACTERISTICS: AV
DD
= 5V
All specifications T
MIN
to T
MAX
, AV
DD
= +5V, DV
DD
= +2.7V to 5.25V, f
MOD
= 19.2kHz, f
OSC
= 2.4576MHz, PGA = 1, Buffer ON, R
DAC
= 150kΩ, f
DATA
= 10Hz,
V
REF
≡
(REF IN+) – (REF IN–) = +2.5V, unless otherwise specified.
ADS1218
PARAMETER
ANALOG INPUT (A
IN
0 – A
IN
7, A
INCOM
)
Analog Input Range
Full-Scale Input Voltage Range
Differential Input Impedance
Input Current
Bandwidth
Fast Settling Filter
Sinc
2
Filter
Sinc
3
Filter
Programmable Gain Amplifier
Input Capacitance
Input Leakage Current
Burnout Current Sources
OFFSET DAC
Offset DAC Range
Offset DAC Monotonicity
Offset DAC Gain Error
Offset DAC Gain Error Drift
SYSTEM PERFORMANCE
Resolution
No Missing Codes
Integral Non-Linearity
Offset Error
(1)
Offset Drift
(1)
Gain Error
Gain Error Drift
(1)
Common-Mode Rejection
CONDITIONS
MIN
TYP
MAX
UNITS
Buffer OFF
Buffer ON
(In+) – (In–), See Block Diagram
Buffer OFF
Buffer ON
–3dB
–3dB
–3dB
User Selectable Gain Ranges
Modulator OFF, T = 25°C
AGND – 0.1
AGND + 0.05
5/PGA
0.5
0.469 • f
DATA
0.318 • f
DATA
0.262 • f
DATA
1
9
5
2
±V
REF
/(2 • PGA)
8
±10
1
24
AV
DD
+ 0.1
AV
DD
– 1.5
±V
REF
/PGA
V
V
V
MΩ
nA
Hz
Hz
Hz
128
pF
pA
µA
V
Bits
%
ppm/°C
Bits
Bits
% of FS
ppm of FS
ppm of FS/°C
%
ppm/
°C
dB
dB
dB
dB
dB
dB
dB
sinc
3
End Point Fit
Before Calibration
After Calibration
at DC
60Hz, f
DATA
= 10Hz
50Hz, f
DATA
= 50Hz
60Hz, f
DATA
= 60Hz
50Hz, f
DATA
= 50Hz
60Hz, f
DATA
= 60Hz
100
24
±0.0015
7.5
0.02
0.005
0.5
130
120
120
100
100
See Typical Characteristics
95
Normal-Mode Rejection
Output Noise
Power-Supply Rejection
f
CM
=
f
CM
=
f
CM
=
f
SIG
=
f
SIG
=
at DC, dB = –20 log(∆V
OUT
/∆V
DD
)
(2)
80
2
ADS1218
SBAS187
ELECTRICAL CHARACTERISTICS: AV
DD
= 5V
(Cont.)
All specifications T
MIN
to T
MAX
, AV
DD
= +5V, DV
DD
= +2.7V to 5.25V, f
MOD
= 19.2kHz, f
OSC
= 2.4576MHz, PGA = 1, Buffer ON, R
DAC
= 150kΩ, f
DATA
=10Hz,
V
REF
≡
(REF IN+) – (REF IN–) = +2.5V, unless otherwise specified.
ADS1218
PARAMETER
VOLTAGE REFERENCE INPUT
Reference Input Range
V
REF
Common-Mode Rejection
Common-Mode Rejection
Bias Current
(3)
ON-CHIP VOLTAGE REFERENCE
Output Voltage
Short-Circuit Current Source
Short-Circuit Current Sink
Short-Circuit Duration
Drift
Noise
Output Impedance
Startup Time
IDAC
Full-Scale Output Current
CONDITIONS
REF IN+, REF IN–
V
REF
≡
(REF IN+) – (REF IN–)
at DC
f
VREFCM
= 60Hz, f
DATA
= 60Hz
V
REF
= 2.5V
REF HI = 1 at 25°C
REF HI = 0
MIN
0
0.1
TYP
MAX
AV
DD
2.6
UNITS
V
V
dB
dB
µA
V
V
mA
µA
ppm/°C
µVp-p
Ω
µs
mA
mA
mA
mA
10
8
0
see Typical Characteristics
400
5
75
0.25
15
4.75
1
175
500
250
900
250
480
180
150
230
1
1.8
5.25
275
750
350
1375
375
675
275
AV
DD
– 1
Minutes
Bits
V
ppm/V
%
ppm/°C
%
ppm/°C
V
nA
µA
µA
µA
µA
µA
µA
µA
µA
µA
nA
mW
2.5
120
120
1.3
2.50
1.25
8
50
Indefinite
5
10
3
50
0.5
1
2
20
Indefinite
2.495
2.505
Sink or Source
BW = 0.1Hz to 100Hz
Sourcing 100µA
Maximum Short-Circuit Current Duration
Monotonicity
Compliance Voltage
Output Impedance
PSRR
Absolute Error
Absolute Drift
Mismatch Error
Mismatch Drift
POWER-SUPPLY REQUIREMENTS
Power-Supply Voltage
Analog Current (I
ADC
+ I
VREF
+ I
DAC
)
ADC Current (I
ADC
)
R
DAC
= 150kΩ, Range = 1
R
DAC
= 150kΩ, Range = 2
R
DAC
= 150kΩ, Range = 3
R
DAC
= 15kΩ, Range = 3
R
DAC
= 10kΩ
R
DAC
= 0Ω
R
DAC
= 150kΩ
V
OUT
= AV
DD
/2
Individual IDAC
Individual IDAC
Between IDACs, Same Range and Code
Between IDACs, Same Range and Code
AV
DD
PDWN = 0, or SLEEP
PGA = 1, Buffer OFF
PGA = 128, Buffer OFF
PGA = 1, Buffer ON
PGA = 128, Buffer ON
Excludes Load Current
Normal Mode, DV
DD
= 5V
SLEEP Mode, DV
DD
= 5V
Read Data Continuous Mode, DV
DD
= 5V
PDWN= LOW
PGA = 1, Buffer OFF, REFEN = 0,
I
DACS
OFF, DV
DD
= 5V
–40
–60
V
REF
Current (I
VREF
)
I
DAC
Current (I
DAC
)
Digital Current
Power Dissipation
TEMPERATURE RANGE
Operating
Storage
2.8
+85
+100
°C
°C
NOTES: (1) Calibration can minimize these errors. (2)
∆
V
OUT
is change in digital result. (3) 12pF switched capacitor at f
SAMP
clock frequency.
ADS1218
SBAS187
3
ELECTRICAL CHARACTERISTICS: AV
DD
= 3V
All specifications T
MIN
to T
MAX
, AV
DD
= +3V, DV
DD
= +2.7V to 5.25V, f
MOD
= 19.2kHz, f
OSC
= 2.4576MHz, PGA = 1, Buffer ON, R
DAC
= 75kΩ, f
DATA
=10Hz,
V
REF
≡
(REF IN+) – (REF IN–) = +1.25V unless otherwise specified.
ADS1218
PARAMETER
ANALOG INPUT (A
IN
0 – A
IN
7, A
INCOM
)
Analog Input Range
Full-Scale Input Voltage Range
Input Impedance
Input Current
Bandwidth
Fast Settling Filter
Sinc
2
Filter
Sinc
3
Filter
Programmable Gain Amplifier
Input Capacitance
Input Leakage Current
Burnout Current Sources
OFFSET DAC
Offset DAC Range
Offset DAC Monotonicity
Offset DAC Gain Error
Offset DAC Gain Error Drift
SYSTEM PERFORMANCE
Resolution
No Missing Codes
Integral Non-Linearity
Offset Error
(1)
Offset Drift
(1)
Gain Error
Gain Error Drift
(1)
Common-Mode Rejection
CONDITIONS
MIN
TYP
MAX
UNITS
Buffer OFF
Buffer ON
(In+) – (In–) See Block Diagram
Buffer OFF
Buffer ON
–3dB
–3dB
–3dB
User Selectable Gain Ranges
Modulator OFF, T = 25°C
AGND – 0.1
AGND + 0.05
5/ PGA
0.5
0.469 • f
DATA
0.318 • f
DATA
0.262 • f
DATA
1
9
5
2
±V
REF
/(2 • PGA)
8
±10
2
24
AV
DD
+ 0.1
AV
DD
– 1.5
±V
REF
/PGA
V
V
V
MΩ
nA
Hz
Hz
Hz
128
pF
pA
µA
V
Bits
%
ppm/°C
Bits
Bits
% of FS
ppm of FS
ppm of FS/°C
%
ppm/°C
dB
dB
dB
dB
dB
dB
dB
AV
DD
1.25
120
120
0.65
V
V
dB
dB
µA
V
mA
µA
ppm/°C
µVp-p
Ω
µs
mA
mA
mA
mA
10
Minute
Bits
V
ppm/V
%
ppm/°C
%
ppm/°C
End Point Fit
Before Calibration
After Calibration
at DC
60Hz, f
DATA
=
50Hz, f
DATA
=
60Hz, f
DATA
=
50Hz, f
DATA
=
60Hz, f
DATA
=
100
10Hz
50Hz
60Hz
50Hz
60Hz
75
0
0.1
24
±0.0015
15
0.04
0.010
1.0
130
120
120
100
100
see Typical Characteristics
90
Normal-Mode Rejection
Output Noise
Power-Supply Rejection
VOLTAGE REFERENCE INPUT
Reference Input Range
V
REF
Common-Mode Rejection
Common-Mode Rejection
Bias Current
(3)
ON-CHIP VOLTAGE REFERENCE
Output Voltage
Short-Circuit Current Source
Short-Circuit Current Sink
Short-Circuit Duration
Drift
Noise
Output Impedance
Startup Time
IDAC
Full-Scale Output Current
f
CM
=
f
CM
=
f
CM
=
f
SIG
=
f
SIG
=
at DC, dB = –20 log(∆V
OUT
/∆V
DD
)
(2)
REF IN+, REF IN–
V
REF
≡
(REF IN+) – (REF IN–)
at DC
f
VREFCM
= 60Hz, f
DATA
= 60Hz
V
REF
= 1.25V
REF HI = 0 at 25°C
1.245
Sink or Source
BW = 0.1Hz to 100Hz
Sourcing 100µA
1.25
3
50
Indefinite
5
10
3
50
0.5
1
2
20
Indefinite
1.255
R
DAC
R
DAC
R
DAC
R
DAC
Maximum Short-Circuit Current Duration
Monotonicity
Compliance Voltage
Output Impedance
PSRR
Absolute Error
Absolute Drift
Mismatch Error
Mismatch Drift
= 75kΩ, Range
= 75kΩ, Range
= 75kΩ, Range
= 15kΩ, Range
R
DAC
= 10kΩ
R
DAC
= 0Ω
R
DAC
= 75kΩ
=
=
=
=
1
2
3
3
8
0
see Typical Characteristics
600
5
75
0.25
15
AV
DD
– 1
V
OUT
= AV
DD
/2
Individual IDAC
Individual IDAC
Between IDACs, Same Range and Code
Between IDACs, Same Range and Code
4
ADS1218
SBAS187
ELECTRICAL CHARACTERISTICS: AV
DD
= 3V
(Cont.)
All specifications T
MIN
to T
MAX
, AV
DD
= +3V, DV
DD
= +2.7V to 5.25V, f
MOD
= 19.2kHz, f
OSC
= 2.4576MHz, PGA = 1, Buffer ON, R
DAC
= 75kΩ, f
DATA
=10Hz,
V
REF
≡
(REF IN+) – (REF IN–) = +1.25V unless otherwise specified.
ADS1218
PARAMETER
POWER-SUPPLY REQUIREMENTS
Power-Supply Voltage
Analog Current (I
ADC
+ I
VREF
+ I
DAC
)
ADC Current (I
ADC
)
CONDITIONS
AV
DD
PDWN = 0, or SLEEP
PGA = 1, Buffer OFF
PGA = 128, Buffer OFF
PGA = 1, Buffer ON
PGA = 128, Buffer ON
Excludes Load Current
Normal Mode, DV
DD
= 3V
SLEEP Mode, DV
DD
= 3V
Read Data Continuous Mode, DV
DD
= 3V
PDWN = 0
PGA = 1, Buffer OFF, REFEN = 0,
I
DACS
OFF, DV
DD
= 3V
–40
–60
MIN
2.7
1
160
450
230
850
250
480
90
75
113
1
0.8
TYP
MAX
3.3
250
700
325
1325
375
675
200
UNITS
V
nA
µA
µA
µA
µA
µA
µA
µA
µA
µA
nA
mW
V
REF
Current (I
VREF
)
I
DAC
Current (I
DAC
)
Digital Current
Power Dissipation
TEMPERATURE RANGE
Operating
Storage
1.4
+85
+100
°C
°C
NOTES: (1) Calibration can minimize these errors. (2)
∆
V
OUT
is change in digital result. (3) 12pF switched capacitor at f
SAMP
clock frequency.
DIGITAL CHARACTERISTICS: T
MIN
to T
MAX
, DV
DD
= 2.7V to 5.25V
PARAMETER
Digital Input/Output
Logic Family
Logic Level: V
IH
V
IL
V
OH
V
OL
Input Leakage: I
IH
I
IL
Master Clock Rate: f
OSC(1)
Master Clock Period: t
OSC(1)
CONDITIONS
MIN
TYP
MAX
UNITS
CMOS
0.8 • DV
DD
DGND
DV
DD
– 0.4
DGND
–10
1
200
DV
DD
0.2 • DV
DD
DGND + 0.4
10
5
1000
V
V
V
V
µA
µA
MHz
ns
I
OH
= 1mA
I
OL
= 1mA
V
I
= DV
DD
V
I
= 0
1/f
OSC
NOTE: (1) For FLASH E/W operations, the SPEED bit in the SETUP register must be set appropriately and the device operating frequency must be:
2.3MHz < F
OSC
< 4.13MHz.
FLASH CHARACTERISTICS: T
MIN
to T
MAX
, DV
DD
= 2.7V to 5.25V, unless otherwise specified.
PARAMETER
Operating Current
Page Write
Page Read
Endurance
Data Retention
DV
DD
for Erase/Write
CONDITIONS
MIN
TYP
MAX
UNITS
DV
DD
= 5V, During WR2F Command
DV
DD
= 3V, During WR2F Command
DV
DD
= 5V, During RF2R Command
DV
DD
= 3V, During RF2R Command
at 25°C
100
2.7
6.5
3.75
4.0
1.2
100,000
5.25
mA
mA
mA
mA
E/W Cycles
Years
V
ADS1218
SBAS187
5
Embedded System
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