ANALOG DEVICES AD8275 Service Manual
G = 0.2, Level Translation,
–
www.BDTIC.com/ADI
FEATURES
Translates ±10 V to +4 V
Drives 16-bit SAR ADCs
Small MSOP package
Input overvoltage: +40 V to −35 V (V
Fast settling time: 450 ns to 0.001%
Rail-to-rail output
Wide supply operation: +3.3 V to +15 V
High CMRR: 80 dB
Low gain drift: 1 ppm/°C
Low offset drift: 2.5 μV/°C
APPLICATIONS
Level translator
ADC driver
Instrumentation amplifier building block
Automated test equipment
= 5 V)
S
16-Bit ADC Driver
AD8275
PIN CONFIGURATION
REF1
+10V
10V
1
AD8275
–IN
2
TOP VIEW
3
+IN
(Not to Scale)
–V
4
S
Figure 1.
TYPICAL APPLICATION
+5V
+V
50k
2
–IN
50k
3
VIN
+IN
–V
AD8275
Figure 2. Translating ±10 V to 4.096 V ADC Full Scale
7
S
10k
S
4
20k
20k
0.1µF
SENSE
OUT
REF2
REF1
REF2
8
+V
7
S
6
OUT
SENSE
5
+4.048V
+2.048V
+0.048V
5
33
6
2.7nF
8
1
VREF
4.096V
07546-001
0.1µF
IN+
IN–
AD7685
10µF
VDD
GNDREF
07546-002
GENERAL DESCRIPTION
The AD8275 is a G = 0.2 difference amplifier that can be used
to translate ±10 V signals to a +4 V level. It solves the problem
typically encountered in industrial and instrumentation applications where ±10 V signals must be interfaced to a single-supply
4 V or 5 V ADC. The AD8275 interfaces the two signal levels,
simplifying design.
The AD8275 has fast settling time of 450 ns and low distortion,
making it suitable for driving medium speed successive approximation (SAR) ADCs. Its wide input voltage range and rail-torail outputs make it an easy to use building block. Single-supply
operation reduces the power consumption of the amplifier and
helps to protect the ADC from overdrive conditions.
Internal, matched, precision laser-trimmed resistors ensure
low gain error, low gain drift of 1 ppm/°C (maximum), and
high common-mode rejection of 80 dB. Low offset and low
offset drift, combined with its fast settling time, make the
AD8275 suitable for a variety of data acquisition applications
where accurate and quick capture is required.
The AD8275 can be used as an analog front end, or it can follow
buffers to level translate high voltages to a voltage range accepted
by the ADC. In addition, the AD8275 can be configured for differential outputs if used with a differential ADC.
The AD8275 is available in a space-saving, 8-lead MSOP
and is specified for performance over the −40°C to +85°C
temperature range.
Table 1. Difference Amplifiers by Category
Single-Supply
Low Distortion High Voltage
Current Sense
AD8270 AD628 AD8202
AD8273 AD629 AD8203
AD8274 AD8205
AD8275 AD8206
AMP03 AD8216
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©2008 Analog Devices, Inc. All rights reserved.
AD8275
www.BDTIC.com/ADI
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
Pin Configuration ............................................................................. 1
Typical Application ........................................................................... 1
General Description ......................................................................... 1
Revision History ............................................................................... 2
Specifications ..................................................................................... 3
Absolute Maximum Ratings ............................................................ 4
Maximum Power Dissipation ..................................................... 4
ESD Caution .................................................................................. 4
Pin Configuration and Function Descriptions ............................. 5
Typical Performance Characteristics ............................................. 6
Theory of Operation ...................................................................... 11
Basic Connection ........................................................................ 11
Power Supplies ............................................................................ 12
Reference ..................................................................................... 12
Common-Mode Input Voltage Range ..................................... 12
Input Protection ......................................................................... 12
Configurations ............................................................................ 13
Applications Information .............................................................. 14
Driving a Single-Ended ADC ................................................... 14
Differential Outputs ................................................................... 14
Increasing Input Impedance ..................................................... 15
AC Coupling ............................................................................... 15
Using the AD8275 as a Level Translator in a Data Acquisition
System .......................................................................................... 15
Outline Dimensions ....................................................................... 16
Ordering Guide .......................................................................... 16
REVISION HISTORY
10/08—Revision 0: Initial Version
Rev. 0 | Page 2 of 16
AD8275
www.BDTIC.com/ADI
SPECIFICATIONS
VS = 5 V, G = 0.2, REF1 connected to GND and REF2 connected to 5 V, RL = 2 kΩ connected to VS/2, TA = 25°C, unless otherwise noted.
Specifications referred to output unless otherwise noted.
Table 2.
A Grade B Grade
Parameter Test Conditions/Comments Min Typ Max Min Typ Max Unit
DYNAMIC PERFORMANCE
Small Signal Bandwidth −3 dB 10 15 10 15 MHz
Slew Rate 4 V step 20 25 20 25 V/μs
Settling Time to 0.01% 4 V step on output, CL = 100 pF 350 350 450 ns
Settling Time to 0.001% 4 V step on output, CL = 100 pF 450 450 550 ns
Overload Recovery Time 50% overdrive 300 300 ns
NOISE/DISTORTION
THD + N f = 1 kHz, V
Voltage Noise f = 0.1 Hz to 10 Hz, referred to output 1 4 1 4 μV p-p
Spectral Noise Density f = 1 kHz, referred to output 40 40 nV/√Hz
GAIN V
Gain Error 0.024 0.024 %
Gain Drift −40°C to +85°C 1 3 0.3 1 ppm/°C
Gain Nonlinearity V
OFFSET AND CMRR
2
Offset
vs. Temperature −40°C to +85°C 2.5 2.5 7 μV/°C
vs. Power Supply VS = 3.3 V to 5 V 90 100 dB
Reference Divider Accuracy 0.024 0.024 %
Common-Mode Rejection
3
Ratio
INPUT CHARACTERISTICS
Input Voltage Range
Impedance
Differential VCM = VS/2 108||2 108||2 kΩ||pF
Common Mode 27.5||2 27.5||2 kΩ||pF
OUTPUT CHARACTERISTICS
Output Swing V
Capacitive Load
Short-Circuit Current Limit 30 30 mA
POWER SUPPLY
Specified Voltage Range 5 5 V
Operating Voltage Range 3.3 15 3.3 15 V
Supply Current IO = 0 mA, VS = ±2.5 V, reference and
Over Temperature IO = 0 mA, VS = ±2.5 V, reference and
TEMPERATURE RANGE
Specified Performance −40 +85 −40 +85 °C
1
Includes amplifier voltage and current noise, as well as noise of internal resistors.
2
Includes input bias and offset current errors.
3
See for CMRR vs. temperature. Figure 7
4
The input voltage range is a function of the voltage supplies, reference voltage, and ESD diodes. When operating on other supply voltages, see the
section, Figure 11, and for more information.
Ratings Table 5
5
Internal resistors are trimmed to be ratio matched but have ±20% absolute accuracy.
6
See Figure 25 to Figure 28 in the section for more information. Typical Performance Characteristics
1
= 4 V p-p, 22 kHz band
OUT
106 106 dB
pass filter
= 4.096 V, REF1 and RL connected
REF2
to GND, (V
= 4 V p-p, RL = 600 Ω, 2 kΩ, 10 kΩ 2.5 2.5 3 ppm
OUT
IN+
) − (V
) = −10 V to +10 V
IN−
Referred to output, VS = ±2.5 V,
0.2 0.2 V/V
300 700 150 500 μV
reference and input pins grounded
VCM = ±10 V, referred to output 80 96 86 dB
4
5
−12.3 +12 −12.3 +12 V
= 4.096 V, REF1 and RL connected
REF2
to GND, R
6
100 100 pF
= 2 kΩ
L
−V
+
S
0.048
+VS −
0.1
−VS +
0.048
+VS −
0.1
V
1.9 2.3 1.9 2.3 mA
input pins grounded
2.1 2.7 2.1 2.7 mA
input pins grounded, −40°C to +85°C
Absolute Maximum
Rev. 0 | Page 3 of 16
AD8275
www.BDTIC.com/ADI
ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter Rating
Supply Voltage 18 V
Output Short-Circuit Current
See derating curve
(Figure 3)
midsupply, the total drive power is V
dissipated in the package and some of which is dissipated in the
load (V
The difference between the total drive power and the load
power is the drive power dissipated in the package.
Voltage at +IN, −IN Pins −VS + 40 V, +VS − 40 V
−V
Voltage at REFx, +VS, − VS, SENSE,
− 0.5 V, +VS + 0.5 V
S
and OUT Pins
Current into REFx, +IN, −IN, SENSE,
and OUT Pins
Storage Temperature Range −65°C to +130°C
Specified Temperature Range −40°C to +85°C
Thermal Resistance (θJA) 135°C/W
Package Glass Transition Temperature
)
(T
G
ESD Human Body Model 2 kV
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
3 mA
140°C
In single-supply operation with R
case is V
Airflow increases heat dissipation, effectively reducing θ
addition, more metal directly in contact with the package leads
from metal traces, through holes, ground, and power planes
reduces θ
Figure 3 shows the maximum safe power dissipation in the
package vs. the ambient temperature on a 4-layer JEDEC
standard board.
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
MAXIMUM POWER DISSIPATION
The maximum safe power dissipation in the AD8275 package is
limited by the associated rise in junction temperature (T
the die. The plastic encapsulating the die locally reaches the
junction temperature. At approximately 140°C, which is the
glass transition temperature, the plastic changes its properties.
Even temporarily exceeding this temperature limit can change
the stresses that the package exerts on the die, permanently
shifting the parametric performance of the AD8275. Exceeding
a junction temperature of 140°C for an extended period can
result in changes in silicon devices, potentially causing failure.
The still air thermal properties of the package and PCB (θ
the ambient temperature (T
the package (P
) determine the junction temperature of the die.
D
), and the total power dissipated in
A
The junction temperature is calculated as follows:
T
= TA + (PD × θJA)
J
The power dissipated in the package (P
) is the sum of the
D
quiescent power dissipation and the power dissipated in the
package due to the load drive for all outputs. The quiescent
power is the voltage between the supply pins (V
quiescent current (I
). Assuming the load (RL) is referenced to
S
) times the
S
) on
J
JA
),
ESD CAUTION
/2 × I
S
× I
OUT
= Quiescent Power + (Total Drive Power − Load Power)
P
D
D
OUT
2.00
1.75
1.50
1.25
1.00
0.75
0.50
MAXIMUM POWER DISSIPATION (W)
0.25
0
Figure 3. Maximum Power Dissipation vs. Ambient Temperature
).
OUT
⎛
V
()
⎜
IVP
SS
⎜
2
⎝
⎞
V
×+×=
V
OUTS
⎟
–
⎟
R
L
⎠
referenced to –VS, the worst
L
= VS/2.
.
JA
–40 0–20 20 40 60 80 100 120
AMBIENT TEMPERATURE (°C)
, some of which is
OUT
2
OUT
R
L
JA
. In
07546-003
Rev. 0 | Page 4 of 16
AD8275
www.BDTIC.com/ADI
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
REF1
1
AD8275
–IN
2
TOP VIEW
3
+IN
(Not to Scale)
–V
4
S
Figure 4. Pin Configuration
Table 4. Pin Function Descriptions
Pin No. Mnemonic Description
1 REF1 Reference Pin. Sets the output voltage level (see the Reference section).
2 −IN Negative Input Pin.
3 +IN Positive Input Pin.
4 −VS Negative Supply Pin.
5 SENSE Sense Output Pin. Tie this pin to the OUT pin.
6 OUT Output Pin (Force Output).
7 +VS Positive Supply Pin.
8 REF2 Reference Pin. Sets the output voltage level (see the Reference section).
8
7
6
5
REF2
+V
S
OUT
SENSE
07546-001
Rev. 0 | Page 5 of 16
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