18-Bit, 500kHz, Unipolar Input, Micro Power Sampling Analog-to-Digital Converter (Rev. B)
ADS8381
SLAS364B - APRIL 2002 - REVISED JUNE 2003
18 BIT, 580 kHz, UNIPOLAR INPUT, MICRO POWER SAMPLING
ANALOG TO DIGITAL CONVERTER WITH PARALLEL INTERFACE
FEATURES
D
580-kHz Sample Rate
D
18-Bit NMC Ensured Over Temperature
D
Zero Latency
D
Low Power: 110 mW at 580 kHz
D
Unipolar Input Range
D
Onboard Reference Buffer
D
High-Speed Parallel Interface
D
Wide Digital Supply, 2.7 V to 5.25 V
D
8-/16-/18-Bit Bus Transfer
D
48-Pin TQFP Package
APPLICATIONS
D
Medical Instruments
D
Optical Networking
D
Transducer Interface
D
High Accuracy Data Acquisition Systems
D
Magnetometers
DESCRIPTION
The ADS8381 is an 18-bit, 580 kHz A/D converter. The
device includes a 18-bit capacitor-based SAR A/D
converter with inherent sample and hold. The ADS8381
offers a full 18-bit interface, a 16-bit option where data is
read using two read cycles, or an 8-bit bus option using
three read cycles.
The ADS8381 is available in a 48-lead TQFP package and
is characterized over the industrial -40
C to 85
C
temperature range.
CDAC
_
+
Output
Latches
and
3-State
Drivers
BUS 18/16
BYTE
18-/16-/8-Bit
Parallel DATA
Output Bus
SAR
Conversion
and
Control Logic
Comparator
Clock
+IN
-IN
REFIN
CONVST
BUSY
CS
RD
PRODUCT PREVIEW
PRODUCT PREVIEW information concerns products in the formative or design
phase of development. Characteristic data and other specifications are design
goals. Texas Instruments reserves the right to change or discontinue these
products without notice.
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.
Copyright
2002-2003, Texas Instruments Incorporated
ADS8381
SLAS364B - APRIL 2002 - REVISED JUNE 2003
www.ti.com
2
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during
storage or handling to prevent electrostatic damage to the MOS gates.
ORDERING INFORMATION
MODEL
MAXIMUM
INTEGRAL
LINEARITY
(LSB)
MAXIMUM
DIFFERENTIAL
LINEARITY
(LSB)
NO
MISSING
CODES
RESOLU-
TION (BIT)
PACKAGE
TYPE
PACKAGE
DESIGNATOR
TEMPER-
ATURE
RANGE
ORDERING
INFORMATION
TRANS-
PORT
MEDIA
QUANTITY
ADS8381I
10
-2~7
17
48 Pin
PFB
-40
C to
ADS8381IPFBT
Tape and
reel 250
ADS8381I
10
-2~7
17
48 Pin
TQFP
PFB
-40 C to
85
C
ADS8381IPFBR
Tape and
reel 1000
ADS8381IB
7
-1~2.5
18
48 Pin
PFB
-40
C to
ADS8381IBPFBT
Tape and
reel 250
ADS8381IB
7
-1~2.5
18
48 Pin
TQFP
PFB
-40 C to
85
C
ADS8381IBPFBR
Tape and
reel 1000
NOTE: For the most current specifications and package information, refer to our website at www.ti.com.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range unless otherwise noted(1)
UNIT
Voltage
+IN to AGND
-0.4 V to +VA + 0.1 V
Voltage
-IN to AGND
-0.4 V to 0.5 V
+VA to AGND
-0.3 V to 7 V
Voltage range
+VBD to BDGND
-0.3 V to 7 V
Voltage range
+VA to +VBD
-0.3 V to 2.55 V
Digital input voltage to BDGND
-0.3 V to +VBD + 0.3 V
Digital output voltage to BDGND
-0.3 V to +VBD + 0.3 V
Operating free-air temperature range, TA
-40
C to 85
C
Storage temperature range, Tstg
-65
C to 150
C
Junction temperature (TJ max)
150
C
TQFP package
Power dissipation
(TJMax - TA)/
JA
TQFP package
JA thermal impedance
86
C/W
Lead temperature, soldering
Vapor phase (60 sec)
215
C
Lead temperature, soldering
Infrared (15 sec)
220
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.
PRODUCT PREVIEW
ADS8381
SLAS364B - APRIL 2002 - REVISED JUNE 2003
www.ti.com
3
SPECIFICATIONS
TA = -40
C to 85
C, +VA = 5 V, +VBD = 3 V or 5 V, Vref = 4.096 V, fSAMPLE = 580 kHz (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Analog Input
Full-scale input voltage (see Note 1)
+IN - -IN
0
Vref
V
Absolute input voltage
+IN
-0.2
Vref + 0.2
V
Absolute input voltage
-IN
-0.2
0.2
V
Input capacitance
45
pF
Input leakage current
1
nA
System Performance
Resolution
18
Bits
ADS8381I
(+IN - -IN) < 0.5 FS
18
No missing codes
ADS8381I
(+IN - -IN)
0.5 FS
17
Bits
No missing codes
ADS8381IB
18
Bits
(+IN - -IN) < 0.125 FS
-4
4
Integral linearity (see Notes 2 and 3)
ADS8381I
(+IN - -IN) < 0.5 FS
-6
6
LSB
Integral linearity (see Notes 2 and 3)
ADS8381I
(+IN - -IN)
0.5 FS
-10
10
LSB
(18 bit)
ADS8381IB
-7
-2/3
7
(18 bit)
(+IN - -IN) < 0.125 FS
-1
2
Differential linearity
ADS8381I
(+IN - -IN) < 0.5 FS
-1
3
LSB
Differential linearity
ADS8381I
(+IN - -IN)
0.5 FS
-2
7
LSB
(18 bit)
ADS8381IB
-1
-1/1.4
2.5
(18 bit)
Offset error (see Note 4)
ADS8381I
-1
0.5
1
mV
Offset error (see Note 4)
ADS8381IB
-0.75
0.25
0.75
mV
Gain error (see Note 4)
ADS8381I
Vref = 4.096 V
-0.1
0.1
%FS
Gain error (see Note 4)
ADS8381IB
Vref = 4.096 V
-0.06
0.06
%FS
Noise
60
V RMS
Power supply rejection ratio
At 3FFFFh output code
75
dB
Sampling Dynamics
Conversion time
1.3
s
Acquisition time
0.35
s
Throughput rate
570
kHz
Aperture delay
4
ns
Aperture jitter
15
ps
Step response
150
ns
Over voltage recovery
150
ns
(1) Ideal input span, does not include gain or offset error.
(2) LSB means least significant bit
(3) This is endpoint INL, not best fit.
(4) Measured relative to an ideal full-scale input (+IN - -IN) of 4.096 V
PRODUCT PREVIEW
ADS8381
SLAS364B - APRIL 2002 - REVISED JUNE 2003
www.ti.com
4
SPECIFICATIONS (CONTINUED)
TA = -40
C to 85
C, +VA = +5 V, +VBD = 3 V or 5 V, Vref = 4.096 V, fSAMPLE = 580 kHz (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Dynamic Characteristics
ADS8381I
VIN = 4 Vpp at 1 kHz
-110
ADS8381IB
VIN = 4 Vpp at 1 kHz
-112
ADS8381I
VIN = 4 Vpp at 10 kHz
-98
Total harmonic distortion (THD) (see Note 1)
ADS8381IB
VIN = 4 Vpp at 10 kHz
-108
dB
Total harmonic distortion (THD) (see Note 1)
ADS8381I
VIN = 4 Vpp at 50 kHz
-98
dB
ADS8381IB
VIN = 4 Vpp at 50 kHz
-99
ADS8381I
VIN = 4 Vpp at 100 kHz
-90
ADS8381IB
VIN = 4 Vpp at 100 kHz
-91
ADS8381I
VIN = 4 Vpp at 1 kHz
87
ADS8381IB
VIN = 4 Vpp at 1 kHz
88
ADS8381I
VIN = 4 Vpp at 10 kHz
87
Signal to noise ratio (SNR) (see Note 1)
ADS8381IB
VIN = 4 Vpp at 10 kHz
87
dB
Signal to noise ratio (SNR) (see Note 1)
ADS8381I
VIN = 4 Vpp at 50 kHz
87
dB
ADS8381IB
VIN = 4 Vpp at 50 kHz
87
ADS8381I
VIN = 4 Vpp at 100 kHz
87
ADS8381IB
VIN = 4 Vpp at 100 kHz
87
ADS8381I
VIN = 4 Vpp at 1 kHz
86
ADS8381IB
VIN = 4 Vpp at 1 kHz
87
ADS8381I
VIN = 4 Vpp at 10 kHz
86
Signal to noise + distortion
ADS8381IB
VIN = 4 Vpp at 10 kHz
86
dB
Signal to noise + distortion
(SINAD) (see Note 1)
ADS8381I
VIN = 4 Vpp at 50 kHz
86
dB
(SINAD) (see Note 1)
ADS8381IB
VIN = 4 Vpp at 50 kHz
86
ADS8381I
VIN = 4 Vpp at 100 kHz
85
ADS8381IB
VIN = 4 Vpp at 100 kHz
85
ADS8381I
VIN = 4 Vpp at 1 kHz
110
ADS8381IB
VIN = 4 Vpp at 1 kHz
112
ADS8381I
VIN = 4 Vpp at 10 kHz
98
Spurious free dynamic range (SFDR) (see
ADS8381IB
VIN = 4 Vpp at 10 kHz
107
dB
Spurious free dynamic range (SFDR) (see
Note 1)
ADS8381I
VIN = 4 Vpp at 50 kHz
98
dB
Note 1)
ADS8381IB
VIN = 4 Vpp at 50 kHz
98
ADS8381I
VIN = 4 Vpp at 100 kHz
90
ADS8381IB
VIN = 4 Vpp at 100 kHz
94
-3dB Small signal bandwidth
3
MHz
Voltage Reference Input
Reference voltage at REFIN, Vref
2.5
4.096
4.2
V
Reference resistance (see Note 2)
500
k
Reference current drain
fs = 580 kHz
1
mA
(1) Calculated on the first nine harmonics of the input frequency
(2) Can vary
20%
PRODUCT PREVIEW
ADS8381
SLAS364B - APRIL 2002 - REVISED JUNE 2003
www.ti.com
5
SPECIFICATIONS (CONTINUED)
TA = -40
C to 85
C, +VA = +5 V, +VBD = 3 V or 5 V, Vref = 4.096 V, fSAMPLE = 580 kHz (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Digital Input/Output
Logic family
CMOS
VIH
IIH = 5
A
+VBD-1
+VBD + 0.3
Logic level
VIL
IIL = 5
A
-0.3
0.8
V
Logic level
VOH
IOH = 2 TTL loads
+VBD - 0.6
V
VOL
IOL = 2 TTL loads
0.4
Data format
Straight
Binary
Power Supply Requirements
Power supply voltage
+VBD
2.7
3.3
5.25
V
Power supply voltage
+VA
4.75
5
5.25
V
Supply current, 500-kHz sample rate (see Note 1)
22
26
mA
Power dissipation, 500-kHz sample rate (see Note 1)
110
130
mW
Temperature Range
Operating free-air
-40
85
C
(1) This includes only +VA current. +VBD current is typical 1 mA with 5 pF load capacitance on all output pins.
PRODUCT PREVIEW
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