Burr Brown Products
from Texas Instruments
ADS1208
SBAS348A – MARCH 2005 – REVISED MARCH 2005
2nd-Order Delta-Sigma Modulator
with Excitation for Hall Elements
FEATURES
•
•
•
•
•
•
•
•
•
•
•
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±100mV Specified Input Range
±125mV Full-Scale Range
95dB typ. CMR, 82dB typ. SNR
Adjustable Current Output for Sensor Biasing
Digital Output Compatible to ADS1202/03
Differential Digital Outputs
Separate 2.7V to 5.5V Digital Supply Pin
DESCRIPTION
The ADS1208 is a 2nd-order
∆Σ
(delta-sigma) modu-
lator operating at a 10MHz clock rate. The specified
input range is ±100mV, optimized for current
measurement with a Hall sensor, especially in motor
control applications. The ADS1208 contains a
programmable current source for sensor biasing and
has integrated input buffers for fast settling of the
sample capacitors; it also requires only a minimum of
external components. The differential analog input
offers low noise and excellent common-mode rejec-
tion.
APPLICATIONS
Motor Control
Current Measurement
Hall Sensors
Bridge Sensors
Instrumentation
AVDD
AVDD
BVDD
ADS1208
IADJ
IOUT
Buffer
Internal 2.5V
Reference
REFOUT
REFIN
Buffer
V
IN+
Buffer
2nd−
Order
∆Σ
Modulator
MDATA
MDATA
MCLK
MCLK
V
IN−
Buffer
Interface
Circuit
RC Oscillator
20MHz
M0
M1
BGND
AGND
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 the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2005, Texas Instruments Incorporated
ADS1208
SBAS348A – MARCH 2005 – REVISED MARCH 2005
www.ti.com
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.
Package/Ordering Information
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.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range (unless otherwise noted)
(1)
ADS1208I
Supply voltage, AGND to AV
DD
Supply voltage, BGND to BV
DD
Analog input voltage with respect to AGND
Reference input voltage with respect to AGND
Digital input voltage with respect to BGND
Ground voltage difference AGND to BGND
Input current to any pin except supply
Power dissipation
Operating virtual junction temperature range, T
J
Operating free-air temperature range, T
A
Storage temperature range, T
STG
(1)
–0.3 to +6
–0.3 to +6
AGND – 0.3 to AV
DD
+ 0.3
AGND – 0.3 to AV
DD
+ 0.3
BGND – 0.3 to BV
DD
+ 0.3
±0.3
±10
See Dissipation Ratings Table
–40 to +150
–40 to +85
–65 to +150
°C
°C
°C
UNIT
V
V
V
V
V
V
mA
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.
RECOMMENDED OPERATING CONDITIONS
PARAMETER
Supply voltage, AGND to AV
DD
Supply voltage, BGND to BV
DD
Reference input voltage
Analog inputs
V
IN+
– V
IN-
Low-voltage levels
5V logic levels
MIN
4.5
2.7
4.5
0.5
–V
REFIN
/20
5.0
2.5
NOM
5.0
MAX
5.5
3.6
5.5
3.0
+V
REFIN
/20
UNIT
V
V
V
V
V
DISSIPATION RATINGS TABLE
BOARD
Low-K
(1)
High-K
(2)
(1)
(2)
PACKAGE
PW
PW
R
θJC
35°C/W
33.6°C/W
R
θJA
147°C/W
108.4°C
DERATING FACTOR
ABOVE T
A
= 25°C
6.8mW/°C
9.225W/°C
T
A
≤
25°C
POWER RATING
850mW
1150mW
T
A
= 70°C
POWER RATING
544mW
738mW
T
A
= 85°C
POWER RATING
442mW
600mW
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.
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
ADS1208
www.ti.com
SBAS348A – MARCH 2005 – REVISED MARCH 2005
ELECTRICAL CHARACTERISTICS
Over recommended operating free-air temperature range at –40°C to +85°C, 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
Resolution
DC Accuracy
Integral nonlinearity
(2)
Integral nonlinearity
Differential nonlinearity
(3)
Input offset
(4)
Input offset drift
Gain error
(4)
Gain error drift
Power-supply rejection ratio
Analog Input
Full-scale range
Operating common-mode signal
Input capacitance
Common-mode rejection
Current Source (IOUT)
Output current
(5)
Voltage at IOUT pin
Voltage between AVDD pin and IADJ
Internal Voltage Reference
Reference output voltage
Reference temperature drift
Output resistance
Output source current
Power-supply rejection ratio
Startup time
Voltage Reference Input
Reference voltage input
Reference input capacitance
Reference input current
Internal Clock for Modes 0, 1 and 2
Clock frequency
External Clock for Mode 3
Clock frequency
(1)
(2)
(3)
(4)
(5)
1.0
24.0
MHz
8.0
10.1
12.0
MHz
-50
REFIN
0.5
5
+50
3.0
V
pF
nA
60
0.1
REFOUT
2.45
2.5
20
0.3
3.0
2.55
V
ppm/°C
Ω
mA
dB
ms
I
OUT
V
OUT
V
ADJ
at I
OUT
= 1mA to 8mA
1.0
0
480
500
5.0
8.0
AVDD – 1.0
520
mA
V
mV
V
IN+
– V
IN–
–125
0.8
1.4
5.0
95
125
2.5
mV
V
pF
dB
Referenced to voltage at REFIN
Referenced to voltage at REFIN
–1.25
16-bit resolution
16-bit resolution
–8
–0.012
–1.0
–2.0
–1.4
2.0
–0.7
15
66
1.6
0.0025
8
0.012
1.0
0
8.0
1.25
LSB
%
LSB
mV
µV/°C
%
ppm/°C
dB
TEST CONDITIONS
MIN
16
TYP
(1)
MAX
UNIT
Bits
All values are at T
A
= 25°C.
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).
Ensured by design.
Maximum values, including temperature drift, are ensured over the full specified temperature range.
It is possible to leave pin IOUT unconnected (I
OUT
= 0mA).
3
ADS1208
SBAS348A – MARCH 2005 – REVISED MARCH 2005
www.ti.com
ELECTRICAL CHARACTERISTICS (continued)
Over recommended operating free-air temperature range at –40°C to +85°C, 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
AC Accuracy
SNR
SINAD
THD
SFDR
Digital Inputs
(6)
Logic family
V
IH
V
IL
I
IN
C
I
Digital
V
OH
V
OL
C
L
High-level input voltage
Low-level input voltage
Input current
Input capacitance
Outputs
(6)
CMOS
BV
DD
= 4.5V, I
OH
= –100µA
BV
DD
= 4.5V, I
OL
= +100µA
Bit stream
LVCMOS
BV
DD
= 3.6V
BV
DD
= 2.7V
V
IN
= BV
DD
or GND
2
–0.3
–50
5
LVCMOS
BV
DD
= 2.7, I
OH
= –100µA
BV
DD
= 2.7, I
OL
= +100µA
Bit stream
4.5
2.7
Modes 0, 1 and 2
Mode 3
Modes 0, 1 and 2
Mode 3
Modes 0, 1 and 2
Mode 3
5.0
5
11.9
11.5
2.3
1.3
71
64
5.5
5.5
15.0
14.5
3.0
2.0
90
82.5
V
V
mA
mA
mA
mA
mW
mW
BV
DD
– 0.2
0.2
30
V
V
pF
BV
DD
+ 0.3
0.8
50
V
V
nA
pF
4.44
0.5
30
V
V
pF
High-level output voltage
Low-level output voltage
Load capacitance
V
IN
= BV
DD
or GND
0.7 x BV
DD
–0.3
–50
5
CMOS
BV
DD
+ 0.3
0.3 x BV
DD
50
V
V
nA
pF
V
IN
= 200mV
PP
at 1kHz
V
IN
= 200mV
PP
at 1kHz
V
IN
= 200mV
PP
at 1kHz
V
IN
= 200mV
PP
at 1kHz
80
80
77
82
81.5
–91
93
–80
dB
dB
dB
dB
TEST CONDITIONS
MIN
TYP
(1)
MAX
UNIT
Logic family
Data format
Digital Inputs
(7)
Logic family
V
IH
V
IL
I
IN
C
I
Digital
V
OH
V
OL
C
L
High-level input voltage
Low-level input voltage
Input current
Input capacitance
Outputs
(7)
High-level output voltage
Low-level output voltage
Load capacitance
Logic family
Data format
Power Supply
Analog supply voltage, AV
DD
Digital interface supply voltage, BV
DD
Operating supply current, AI
DD
Operating supply current, AI
DD
Operating supply current, BI
DD
Operating supply current, BI
DD
Power dissipation
Power dissipation
(6)
(7)
Applicable for 5.0V nominal supply; BV
DD
(min) = 4.5V and BV
DD
(max) = 5.5V.
Applicable for 3.0V nominal supply; BV
DD
(min) = 2.7V and BV
DD
(max) = 3.6V
4
ADS1208
www.ti.com
SBAS348A – MARCH 2005 – REVISED MARCH 2005
PARAMETER MEASUREMENT INFORMATION
t
C1
MCLK
t
W1
MDATA
t
D1
Figure 1. Mode 0 Operation
TIMING CHARACTERISTICS: MODE 0
Over recommended operating free-air temperature range at –40°C to +85°C, and AV
DD
= +5V, BV
DD
= +2.7 to +5.5V, unless
otherwise noted.
PARAMETER
t
C1
t
W1
t
D1
Clock period
Clock high time
Data delay after rising edge of clock
MIN
83
(t
C1
/2) – 5
–2
MAX
125
(t
C1
/2) + 5
+2
UNIT
ns
ns
ns
t
C2
MCLK
t
W2
MDATA
t
D2
t
D3
Figure 2. Mode 1 Operation
TIMING CHARACTERISTICS: MODE 1
Over recommended operating free-air temperature range at –40°C to +85°C, and AV
DD
= +5V, BV
DD
= +2.7 to +5.5V, unless
otherwise noted.
PARAMETER
t
C1
t
W2
t
D2
t
D3
Clock period
Clock high time
Data delay after rising edge of clock
Data delay after falling edge of clock
MIN
166
(t
C2
/2) – 5
(t
W2
/2) – 2
(t
W2
/2) – 2
MAX
250
(t
C2
/2) + 5
(t
W2
/2) + 2
(t
W2
/2) + 2
UNIT
ns
ns
ns
ns
5
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