Burr Brown Products
from Texas Instruments
FEATURES
DESCRIPTION
APPLICATIONS
Internal 2.5V
Reference
RC Oscillator
20MHz
Interface
Circuit
MDATA
IADJ
IOUT
AVDD
ADS1208
REFOUT
REFIN
V
IN+
V
IN
-
MDATA
BVDD
MCLK
M0
M1
MCLK
Buffer
Buffer
Buffer
Buffer
2nd-Order
Modulator
BGND
AGND
AVDD
ADS1208
SBAS348A MARCH 2005 REVISED MARCH 2005
2nd-Order Delta-Sigma Modulator
with Excitation for Hall Elements
100mV Specified Input Range
The ADS1208 is a 2nd-order
(delta-sigma) modu-
lator operating at a 10MHz clock rate. The specified
125mV Full-Scale Range
input
range
is
100mV,
optimized
for
current
95dB typ. CMR, 82dB typ. SNR
measurement with a Hall sensor, especially in motor
Adjustable Current Output for Sensor Biasing
control
applications.
The
ADS1208
contains
a
Digital Output Compatible to ADS1202/03
programmable current source for sensor biasing and
has integrated input buffers for fast settling of the
Differential Digital Outputs
sample capacitors; it also requires only a minimum of
Separate 2.7V to 5.5V Digital Supply Pin
external components. The differential analog input
offers low noise and excellent common-mode rejec-
tion.
Motor Control
Current Measurement
Hall Sensors
Bridge Sensors
Instrumentation
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.
Copyright 2005, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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Package/Ordering Information
ABSOLUTE MAXIMUM RATINGS
RECOMMENDED OPERATING CONDITIONS
DISSIPATION RATINGS TABLE
ADS1208
SBAS348A MARCH 2005 REVISED MARCH 2005
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.
ESD damage can range from subtle performance degradation to complete device failure. Precision
integrated circuits may be more susceptible to damage because very small parametric changes could
cause the device not to meet its published specifications.
For the most current package and ordering information, see the Package Option Addendum at the end of this
document, or see the TI web site at
www.ti.com
.
over operating free-air temperature range (unless otherwise noted)
(1)
ADS1208I
UNIT
Supply voltage, AGND to AV
DD
0.3 to +6
V
Supply voltage, BGND to BV
DD
0.3 to +6
V
Analog input voltage with respect to AGND
AGND 0.3 to AV
DD
+ 0.3
V
Reference input voltage with respect to AGND
AGND 0.3 to AV
DD
+ 0.3
V
Digital input voltage with respect to BGND
BGND 0.3 to BV
DD
+ 0.3
V
Ground voltage difference AGND to BGND
0.3
V
Input current to any pin except supply
10
mA
Power dissipation
See Dissipation Ratings Table
Operating virtual junction temperature range, T
J
40 to +150
C
Operating free-air temperature range, T
A
40 to +85
C
Storage temperature range, T
STG
65 to +150
C
(1)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating
Conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
PARAMETER
MIN
NOM
MAX
UNIT
Supply voltage, AGND to AV
DD
4.5
5.0
5.5
V
Low-voltage levels
2.7
3.6
V
Supply voltage, BGND to BV
DD
5V logic levels
4.5
5.0
5.5
V
Reference input voltage
0.5
2.5
3.0
V
Analog inputs
V
IN+
V
IN-
V
REFIN
/20
+V
REFIN
/20
V
DERATING FACTOR
T
A
25C
T
A
= 70C
T
A
= 85C
BOARD
PACKAGE
R
JC
R
JA
ABOVE T
A
= 25C
POWER RATING
POWER RATING
POWER RATING
Low-K
(1)
PW
35C/W
147C/W
6.8mW/C
850mW
544mW
442mW
High-K
(2)
PW
33.6C/W
108.4C
9.225W/C
1150mW
738mW
600mW
(1)
The JEDEC low-K (1s) board used to derive this data was a 3in x 3in, two-layer board with 2-ounce copper traces on top of the board.
(2)
The JEDEC high-K (2s2p) board used to derive this data was a 3in x 3in, multilayer board with 1-ounce internal power and ground
planes and 2-ounce copper traces on top and bottom of the board.
2
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ELECTRICAL CHARACTERISTICS
ADS1208
SBAS348A MARCH 2005 REVISED MARCH 2005
Over recommended operating free-air temperature range at 40C to +85C, AV
DD
= BV
DD
= +5V, V
REF
= internal +2.5V,
Mode 3, MCLK input = 20MHz, differential input voltage = 200mV
PP
, common-mode voltage = 1.4V, and 16-bit Sinc
3
filter with
OSR = 256, unless otherwise noted.
ADS1208I
PARAMETER
TEST CONDITIONS
MIN
TYP
(1)
MAX
UNIT
Resolution
16
Bits
DC Accuracy
Integral nonlinearity
(2)
16-bit resolution
8
1.6
8
LSB
Integral nonlinearity
0.012
0.0025
0.012
%
Differential nonlinearity
(3)
16-bit resolution
1.0
1.0
LSB
Input offset
(4)
2.0
1.4
0
mV
Input offset drift
2.0
8.0
V/C
Gain error
(4)
Referenced to voltage at REFIN
1.25
0.7
1.25
%
Gain error drift
Referenced to voltage at REFIN
15
ppm/C
Power-supply rejection ratio
66
dB
Analog Input
Full-scale range
V
IN+
V
IN
125
125
mV
Operating common-mode signal
0.8
1.4
2.5
V
Input capacitance
5.0
pF
Common-mode rejection
95
dB
Current Source (IOUT)
Output current
(5)
I
OUT
1.0
5.0
8.0
mA
Voltage at IOUT pin
V
OUT
0
AVDD 1.0
V
Voltage between AVDD pin and IADJ
V
ADJ
at I
OUT
= 1mA to 8mA
480
500
520
mV
Internal Voltage Reference
Reference output voltage
REFOUT
2.45
2.5
2.55
V
Reference temperature drift
20
ppm/C
Output resistance
0.3
Output source current
3.0
mA
Power-supply rejection ratio
60
dB
Startup time
0.1
ms
Voltage Reference Input
Reference voltage input
REFIN
0.5
3.0
V
Reference input capacitance
5
pF
Reference input current
-50
+50
nA
Internal Clock for Modes 0, 1 and 2
Clock frequency
8.0
10.1
12.0
MHz
External Clock for Mode 3
Clock frequency
1.0
24.0
MHz
(1)
All values are at T
A
= 25C.
(2)
Integral nonlinearity is defined as the maximum deviation of the line through the end points of the specified input range of the transfer
curve for V
IN+
V
IN
= 100mV to +100mV, expressed either as the number of LSBs or as a percent of the measured input range
(200mV).
(3)
Ensured by design.
(4)
Maximum values, including temperature drift, are ensured over the full specified temperature range.
(5)
It is possible to leave pin IOUT unconnected (I
OUT
= 0mA).
3
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ADS1208
SBAS348A MARCH 2005 REVISED MARCH 2005
ELECTRICAL CHARACTERISTICS (continued)
Over recommended operating free-air temperature range at 40C to +85C, AV
DD
= BV
DD
= +5V, V
REF
= internal +2.5V,
Mode 3, MCLK input = 20MHz, differential input voltage = 200mV
PP
, common-mode voltage = 1.4V, and 16-bit Sinc
3
filter with
OSR = 256, unless otherwise noted.
ADS1208I
PARAMETER
TEST CONDITIONS
MIN
TYP
(1)
MAX
UNIT
AC Accuracy
SNR
V
IN
= 200mV
PP
at 1kHz
80
82
dB
SINAD
V
IN
= 200mV
PP
at 1kHz
77
81.5
dB
THD
V
IN
= 200mV
PP
at 1kHz
91
80
dB
SFDR
V
IN
= 200mV
PP
at 1kHz
80
93
dB
Digital Inputs
(6)
Logic family
CMOS
V
IH
High-level input voltage
0.7 x BV
DD
BV
DD
+ 0.3
V
V
IL
Low-level input voltage
0.3
0.3 x BV
DD
V
I
IN
Input current
V
IN
= BV
DD
or GND
50
50
nA
C
I
Input capacitance
5
pF
Digital Outputs
(6)
Logic family
CMOS
V
OH
High-level output voltage
BV
DD
= 4.5V, I
OH
= 100A
4.44
V
V
OL
Low-level output voltage
BV
DD
= 4.5V, I
OL
= +100A
0.5
V
C
L
Load capacitance
30
pF
Data format
Bit stream
Digital Inputs
(7)
Logic family
LVCMOS
V
IH
High-level input voltage
BV
DD
= 3.6V
2
BV
DD
+ 0.3
V
V
IL
Low-level input voltage
BV
DD
= 2.7V
0.3
0.8
V
I
IN
Input current
V
IN
= BV
DD
or GND
50
50
nA
C
I
Input capacitance
5
pF
Digital Outputs
(7)
Logic family
LVCMOS
V
OH
High-level output voltage
BV
DD
= 2.7, I
OH
= 100A
BV
DD
0.2
V
V
OL
Low-level output voltage
BV
DD
= 2.7, I
OL
= +100A
0.2
V
C
L
Load capacitance
30
pF
Data format
Bit stream
Power Supply
Analog supply voltage, AV
DD
4.5
5.0
5.5
V
Digital interface supply voltage, BV
DD
2.7
5
5.5
V
Operating supply current, AI
DD
Modes 0, 1 and 2
11.9
15.0
mA
Operating supply current, AI
DD
Mode 3
11.5
14.5
mA
Operating supply current, BI
DD
Modes 0, 1 and 2
2.3
3.0
mA
Operating supply current, BI
DD
Mode 3
1.3
2.0
mA
Power dissipation
Modes 0, 1 and 2
71
90
mW
Power dissipation
Mode 3
64
82.5
mW
(6)
Applicable for 5.0V nominal supply; BV
DD
(min) = 4.5V and BV
DD
(max) = 5.5V.
(7)
Applicable for 3.0V nominal supply; BV
DD
(min) = 2.7V and BV
DD
(max) = 3.6V
4
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MCLK
MDATA
t
C1
t
W1
t
D1
TIMING CHARACTERISTICS: MODE 0
MCLK
MDATA
t
C2
t
W2
t
D2
t
D3
TIMING CHARACTERISTICS: MODE 1
ADS1208
SBAS348A MARCH 2005 REVISED MARCH 2005
PARAMETER MEASUREMENT INFORMATION
Figure 1. Mode 0 Operation
Over recommended operating free-air temperature range at 40C to +85C, and AV
DD
= +5V, BV
DD
= +2.7 to +5.5V, unless
otherwise noted.
PARAMETER
MIN
MAX
UNIT
t
C1
Clock period
83
125
ns
t
W1
Clock high time
(t
C1
/2) 5
(t
C1
/2) + 5
ns
t
D1
Data delay after rising edge of clock
2
+2
ns
Figure 2. Mode 1 Operation
Over recommended operating free-air temperature range at 40C to +85C, and AV
DD
= +5V, BV
DD
= +2.7 to +5.5V, unless
otherwise noted.
PARAMETER
MIN
MAX
UNIT
t
C1
Clock period
166
250
ns
t
W2
Clock high time
(t
C2
/2) 5
(t
C2
/2) + 5
ns
t
D2
Data delay after rising edge of clock
(t
W2
/2) 2
(t
W2
/2) + 2
ns
t
D3
Data delay after falling edge of clock
(t
W2
/2) 2
(t
W2
/2) + 2
ns
5
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