ANALOG DEVICES AD8553 Service Manual

1.8 V to 5 V Auto-Zero, In-Amp

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FEATURES

Low offset voltage: 20 μV max Low input offset drift: 0.1 μV/°C max High CMR: 120 dB min @ G = 100 Low noise: 0.7 μV p-p from 0.01 Hz to 10 Hz Wide gain range: 0.1 to 10,000 Single-supply operation: 1.8 V to 5.5 V Rail-to-rail output Shutdown capability

APPLICATIONS

Strain gauge Weigh scales Pressure sensors Laser diode control loops Portable medical instruments Thermocouple amplifiers

with Shutdown

AD8553

PIN CONFIGURATION

RGA

1

2

VINP

VCC

VFB

AD8553

3

TOP VIEW

(Not to Scale)

VO

4

5

Figure 1. 10-Lead MSOP

10

9

8

7

6

RGB

VINN

GND

V

REF

ENABLE

05474-001

GENERAL DESCRIPTION

The AD85531 is a precision instrumentation amplifier featuring low noise, rail-to-rail output and a power-saving shutdown mode. The AD8553 also features low offset voltage and drift coupled with high common-mode rejection. In shutdown mode, the total supply current is reduced to less than 4 µA. The AD8553 is capable of operating from 1.8 V to 5.5 V.

With a low offset voltage of 20 µV, an offset voltage drift of

0.1 µV/°C, and 10 Hz), the AD8553 is ideal for applications where error sources cannot be tolerated. Precision instrumentation, position and pressure sensors, medical instrumentation, and strain gauge amplifiers benefit from the low noise, low input bias current, and high common-mode rejection. The small footprint and low cost are ideal for high volume applications.

a voltage noise of only 0.7 µV p-p (0.01 Hz to

The small package and low power consumption allow max

imum channel density and minimum board size for

space-critical equipment and portable systems.

The AD8553 is specified over the industrial temperature range

rom −40°C to +85°C. The AD8553 is available in a Pb-free,

f 10-lead MSOP.

1

Patent pending.

Rev. 0

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Anal og Devices for its use, nor for any infringements of patents or ot her 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.

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REVISION HISTORY

10/05—Revision 0: Initial Version

Rev. 0 | Page 2 of 20

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SPECIFICATIONS

ELECTRICAL CHARACTERISTICS

VCC = 5.0 V, VCM = 2.5 V, V resistor values. Temperature specifications guaranteed by characterization.

Table 1.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Input Offset Voltage V G = 100 4 20 μV G = 10 15 50 μV G = 1 120 375 μV

vs. Temperature ΔVOS/ΔT G = 1000, −40°C ≤ TA ≤ +85°C 0.02 0.1 μV/°C G = 100, −40°C ≤ TA ≤ +85°C 0.02 0.1 μV/°C G = 10, −40°C ≤ TA ≤ +85°C 0.1 0.3 μV/°C G = 1, −40°C ≤ TA ≤ +85°C 1 3 μV/°C

Input Bias Current I

−40°C ≤ TA ≤ +85°C 2 nA

Input Offset Current I

VREF Pin Current I

Input Operating Impedance

Differential 50||1 MΩ||pF

Common Mode 10||10 GΩ||pF Input Voltage Range 0 3.3 V Common-Mode Rejection CMR G = 100, VCM = 0 V to 3.3 V, −40°C ≤ TA ≤ +85°C 120 140 dB G = 10, VCM = 0 V to 3.3 V, −40°C ≤ TA ≤ +85°C 100 120 dB Gain Error G = 100, VCM = 12.125 mV, VO = 0.075 V to 4.925 V 0.10 0.3 %

G = 10, VCM = 121.25 mV , VO = 0.075 V to 4.925 V 0.15 0.4 %

Gain Drift G = 10, 100, 1000, −40°C ≤ TA ≤ +85°C 5 25 ppm/°C G = 1, −40°C ≤ TA ≤ +85°C 30 50 ppm/°C Nonlinearity G = 100, VCM = 12.125 mV, VO = 0.075 V to 4.925 V 0.001 0.003 % FS G = 10, VCM = 121.25 mV, VO = 0.075 V to 4.925 V 0.040 0.060 % FS V

Range 0.8 4.2 V

REF

OUTPUT CHARACTERISITICS

Output Voltage High V Output Voltage Low V Short-Circuit Current I

POWER SUPPLY

Power Supply Rejection PSR G = 100, VS = 1.8 V to 5.5 V, VCM = 0 V 100 120 dB G = 10, VS = 1.8 V to 5.5 V, VCM = 0 V 90 110 dB Supply Current I

−40°C ≤ TA ≤ +85°C 1.5 mA Supply Current Shutdown Mode I

ENABLE INPUTS

Logic High Voltage 2.40 V Logic Low Voltage 0.80 V

NOISE PERFORMANCE

Voltage Noise e Voltage Noise Density e G = 10, f = 1 kHz 150 nV/√Hz Internal Clock Frequency 60 kHz Signal Bandwidth

1

Higher bandwidths result in higher noise.

1

= VCC/2, VIN = V

REF

G = 1 to 1000 1 kHz

B

OS

REF

SC

SY

SD

OS

OH

OL

n p-p

n

− V

, R

INP

INN

G = 1000 4 20 μV

0.4 1 nA

2 nA

0.01 1 nA

4.925 V

0.075 V ±35 mA

IO = 0 mA, VIN = 0 V 1.1 1.3 mA

2 4 μA

f = 0.01 Hz to 10 Hz 0.7 μV p-p G = 100, f = 1 kHz 30 nV/√Hz

= 10 kΩ, TA = 25°C, G = 100, unless specified. See Tab l e 5 for gain setting

LOAD

Rev. 0 | Page 3 of 20

AD8553

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= 1.8 V, VCM = -0 V, V

V

S

= VS/2, VIN = V

REF

INP

− V

INN

, R

= 10 kΩ, TA = 25°C, G = 100, unless specified. See Ta b le 5 for gain setting

LOAD

resistor values. Temperature specifications guaranteed by characterization.

Table 2.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Input Offset Voltage V

OS

G = 1000 3 20 μV G = 100 3 20 μV G = 10 14 50 μV G = 1 130 375 μV Vs. Temperature ΔVOS/ΔT G = 1000, −40°C ≤ TA ≤ +85°C 0.02 0.25 μV/°C

G = 100, −40°C ≤ TA ≤ +85°C 0.02 0.25 μV/°C G = 10, −40°C ≤ TA ≤ +85°C 0.1 3 μV/°C G = 1, −40°C ≤ TA ≤ +85°C 1 10 μV/°C

Input Bias Current I

B

0.05 1 nA

−40°C ≤ TA ≤ +85°C 2 nA Input Offset Current I VREF Pin Current I

OS

REF

2 nA

0.02 1 nA Input Operating Impedance Differential 50||1 MΩ||pF Common Mode 10||10 GΩ||pF

Input Voltage Range 0 0.15 V Common-Mode Rejection CMR G = 100, VCM = 0 V to 0.15 V, −40°C ≤ TA ≤ +85°C 100 110 dB G = 10, VCM = 0 V to 0.15 V, −40°C ≤ TA ≤ +85°C 90 110 dB Gain Error G = 100, VCM =4.125 mV, VO = 0.075 V to 1.725 V 0.2 0.4 %

G = 10, VCM = 41.25 mV, VO = 0.075 V to 1.725 V 0.2 0.4 %

Gain Drift G = 10, 100, 1000, −40°C ≤ TA ≤ +85°C 25 ppm/°C G = 1, −40°C ≤ TA ≤ +85°C 50 ppm/°C Nonlinearity G = 100, VCM = 4.125 mV, VO = 0.075 V to 1.725 V 0.003 % FS G = 10, VCM = 41.25 mV, VO = 0.075 V to 1.725 V 0.010 % FS V

Range 0.8 1.0 V

REF

OUTPUT CHARACTERISITICS

Output Voltage High V Output Voltage Low V Short-Circuit Current I

OH

OL

SC

1.725 V

0.075 V

±5 mA

POWER SUPPLY

Power Supply Rejection PSR G = 100, VS = 1.8 V to 5.5 V, VCM = 0 V 100 120 dB Supply Current I

SY

IO = 0 mA, VIN = 0 V 0.8 1.2 mA

−40°C ≤ TA ≤ +85°C 1.4 mA Supply Current Shutdown Mode I

SD

2 4 μA

ENABLE INPUTS

Logic High Voltage 1.4 V Logic Low Voltage 0.5 V

NOISE PERFORMANCE

Voltage Noise e Voltage Noise Density e

n p-p

n

f = 0.01 Hz to 10 Hz 0.7 μV p-p

G = 100, f = 1 kHz 30 nV/√Hz G = 10, f = 1 kHz 150 nV/√Hz Internal Clock Frequency 60 kHz Signal Bandwidth

1

Higher bandwidths result in higher noise.

1

G = 1 to 1000 1 kHz

Rev. 0 | Page 4 of 20

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ABSOLUTE MAXIMUM RATINGS

Table 3.

Parameter Ratings

Supply Voltage 6 V Input Voltage +V Differential Input Voltage Output Short-Circuit Duration to GND Indefinite Storage Temperature Range (RM Package) −65°C to +150°C Operating Temperature Range −40°C to +85°C Junction Temperature Range (RM Package) −65°C to +150°C Lead Temperature Range (Soldering, 10 sec) 300°C

1

Differential input voltage is limited to ±5.0 V, the supply voltage, or

whichever is less.

1

±V

SUPPLY

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 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.

THERMAL RESISTANCE

θ JA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages.

Table 4.

Package Type θ

10-Lead MSOP (RM) 110 32.2 °C/W

1

θJA is specified for the nominal conditions, that is, θJA is specified for the

device soldered on a circuit board.

1

JA

θ

JC

Unit

ESD CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.

Rev. 0 | Page 5 of 20

AD8553

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TYPICAL PERFORMANCE CHARACTERISTICS

TA = 25°C, G = 100, unless specified, see Tab l e 5 for gain setting resistor values. Filters as noted are the combination of R2/C2 and R3/C3 as in Figure 31.

80

GAIN = 1000

60

VCC = 1.8V AND 5V FILTER = 1kHz

80

GAIN = 1000

60

VCC = 1.8V AND 5V FILTER = 10kHz

GAIN = 100

40

GAIN = 10

20

GAIN (dB)

GAIN = 1

0

–20

–40

10 100 1k 10k 100k

FREQUENCY ( Hz)

Figure 2. Gain vs. Frequency

180

VCC = 5V FILTER = 1kHz

160

GAIN = 100

140

GAIN = 10

120

GAIN = 1

100

CMR (dB)

80

60

40

20

10 100 1k 10k 100k

FREQUENCY ( Hz)

Figure 3. Common-Mode Rejection (CMR) vs. Frequency

160

GAIN = 100

140

GAIN = 10

120

GAIN = 1

100

80

PSR (dB)

60

40

GAIN = 100

40

GAIN = 10

20

GAIN (dB)

GAIN = 1

0

–20

05474-002

–40

10 100 1k 10k 100k

FREQUENCY ( Hz)

05474-003

Figure 5. Gain vs. Frequency

180

VCC = 5V FILTER = 10kHz

160

GAIN = 100

140

GAIN = 10

120

GAIN = 1

100

CMR (dB)

80

60

40

05474-004

20

10 100 1k 10k 100k

FREQUENCY ( Hz)

05474-005

Figure 6. Common-Mode Rejection (CMR) vs. Frequency

10k

GAIN = 1

1k

Hz)

100

NOISE (nV/

10

GAIN = 10

GAIN = 100, 1000

20

FILTE R = 10kHz FILTER = 1kHz

10

10 100 1k 10k 100k

FREQUENCY (Hz)

Figure 4. Power Supply Rejection vs. Frequency

VCC=5VAND1.8V

05474-006

1

0.01 1001010.1 1k 10k 100k

Figure 7. Voltage Noise Density

Rev. 0 | Page 6 of 20

FREQUENCY (Hz)

05474-007

AD8553

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VCC=5V TURN ON TIME = 10µs

FILTER SETTLING

20µV/DI

V

CC

TURN ON TIME = 15µs V

=1.8V

CC

–0.1 0 0.1 0.2 0. 3 0.4 0.5 0.6 0. 7 0.8 0.9

VCC=5V

=1.8V

TIME (ms)

GAIN = 100

FILTER = 1kHz

Figure 8. Input Offset Voltage vs. Turn-On Time

05474-008

80

70

60

50

40

30

20

10

0

INPUT OFFSET VOLTAGE (µV)

–10

–20

03

50 100 150 200 250 300

FILTER SETTLING

VCC=5V

VCC=1.8V

TIME (µs)

GAIN = 100 FILTER = 10kHz

05474-009

50

Figure 11. Input Offset Voltage vs. Turn-On Time

10kHz FIL TER

50mV/DI

1kHz FIL TER

POPULATION

VCC= 5V, G = 1 , 10, 100, 1000 V

= 1.8V, G = 1, 10, 100, 1000

CC

500µs/DIV

Figure 9. Small Signal Step Response

VCC=5V GAIN = 100, 1000

VCC = 5V, G = 1, 10, 100, 1000

10kHz FILT ER

1V/DIV

05474-010

1kHz FILT ER

500µs/DIV

05474-011

Figure 12. Large Signal Step Response

VCC=5V GAIN = 100, 1000

POPULATION

05474-017

16 18

Figure 10. Input Offset Voltage (μV)

200 2 4 6 8 101214

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10

Figure 13. Input Offset Voltage Drift (μV/°C)

Rev. 0 | Page 7 of 20

05474-014

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VCC = 5V GAIN = 10

POPULATION

0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0

Figure 14. Input Offset Voltage (μV)

POPULATION

–50 –10 30 70 110 150 190 230 270 310 350

Figure 15. Input Offset Voltage (μV)

VCC = 5V GAIN = 1

POPULATION

05474-016

0 0.03 0.06 0.09 0.12 0.15 0.18 0.21 0.24 0.27 0.30

05474-013

Figure 17. Input Offset Voltage Drift (μV/°C)

VCC = 5V GAIN = 1

POPULATION

05474-015

0 0.30 0.60 0.90 1.20 1.50 1.80 2.10 2.40 2.70 3.00

05474-012

Figure 18. Input Offset Voltage Drift (μV/°C)

VCC = 5V GAIN = 100

= 12.125mV

V

CM

POPULATION

–250 –225 –200 –175 –150 –125 –100 –75 –50 –25 0

Figure 16. Gain Error (m%)

05474-020

POPULATION

0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0

Figure 19. Nonlinearity (m%)

Rev. 0 | Page 8 of 20

VCC = 5V GAIN = 100 V

= 12.125mV

CM

05474-019

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180

160

140

120

100

CMR (dB)

80

VCC = 1.8V FILTE R = 1kHz

GAIN = 100

GAIN = 10

GAIN = 1

180

160

140

120

100

CMR (dB)

80

VCC = 1.8V FILTER = 10kHz

GAIN = 100

GAIN = 10

GAIN = 1

60

40

20

10 100 1k 10k 100k

FREQUENCY ( Hz)

Figure 20. Common-Mode Rejection (CMR) vs. Frequency

VCC=1.8V GAIN = 100, 1000

POPULATION

–2 0 4 6 8 10 12 14 16 18 20

2

Figure 21. Input Offset Voltage (μV)

60

40

05474-021

20

10 100 1k 10k 100k

FREQUENCY ( Hz)

05474-022

Figure 23. Common-Mode Rejection (CMR) vs. Frequency

VCC = 1.8V GAIN = 100, 1000

POPULATION

05474-025

0

0.01 0. 02 0.03 0.04 0.05 0. 06 0. 07 0.08 0.09 0.10

05474-028

Figure 24. Input Offset Voltage Drift (μV/°C)

VCC = 1.8V GAIN = 10

POPULATION

3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60

0

05474-024

Figure 22. Input Offset Voltage (μV)

POPULATION

0 0.030.060.090.120.150.180.210.240.270.30

Figure 25. Input Offset Voltage Drift (μV/°C)

Rev. 0 | Page 9 of 20

VCC = 1.8V GAIN = 10

05474-027

AD8553

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VCC = 1.8V GAIN = 1

POPULATION

0 40 32080 120 160 200 240 280 360

VCC = 5.0V GAIN = 100

200nV/DI

Figure 26. Input Offset Voltage (μV)

Figure 27. 0.01 Hz to 10 Hz Voltage Noise

10SEC/DIV

POPULATION

05474-023

05474-036

0 0.4 0.8 1. 2 1.6 2. 0 2.4 2.8 3.2 3.6 4.0 4.4 4.8

Figure 28. Input Offset Voltage Drift (μV/°C)

500mV/DI

Figure 29. Large Signal Step Response

10kHz FIL TER

1kHz FILTER

500µs/DIV

VCC=1.8V, G = 10, 100, 1000

05474-033

05474-029

Rev. 0 | Page 10 of 20

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THEORY OF OPERATION

The AD8553 is a precision current-mode correction instrumentation amplifier capable of single-supply operation. The current-mode correction topology results in excellent accuracy without the need for trimmed resistors on the die.

Figure 30 shows a simplified diagram illustrating the basic o

peration of the AD8553 (without correction). The circuit consists of a voltage-to-current amplifier (M1 to M6), followed by a current-to-voltage amplifier (R2 and A1). Application of a differential input voltage forces a current through External Resistor R1, resulting in conversion of the input voltage to a signal current. Transistor M3 to Transistor M6 transfer twice this signal current to the inverting input of the op amp A1. Amplifier A1 and External Resistor R2 form a current-tovoltage converter to produce a rail-to-rail output voltage at V

.

OUT

Op amp A1 is a high precision auto-zero amplifier. This

mplifier preserves the performance of the autocorrecting,

a current-mode amplifier topology while offering the user a true voltage-in, voltage-out instrumentation amplifier. Offset errors are corrected internally.

An external reference voltage is applied to the noninverting

nput of A1 to set the output reference level. External Capacitor

i C2 is used to filter out correction noise.

HIGH PSR AND CMR

Common-mode rejection and power supply rejection indicate the amount that the offset voltage of an amplifier changes when its common-mode input voltage or power supply voltage changes. The autocorrection architecture of the AD8553 continuously corrects for offset errors, including those induced by changes in input or supply voltage, resulting in exceptional rejection performance. The continuous autocorrection provides great CMR and PSR performances over the entire operating temperature range (−40°C to +85°C).

The parasitic resistance in series with R2 does not degrade

ut causes a small gain error and a very small offset error.

CMR b Therefore, an external buffer amplifier is not required to drive the V

pin to maintain excellent CMR performance. This

REF

helps reduce system costs over conventional instrumentation amplifiers.

1/f NOISE CORRECTION

Flicker noise, also known as 1/f noise, is noise inherent in the physics of semiconductor devices and decreases 10 dB per decade. The 1/f corner frequency of an amplifier is the frequency at which the flicker noise is equal to the broadband noise of the amplifier. At lower frequencies, flicker noise dominates causing large errors in low frequency or dc applications.

The pinout of the AD8553 allows the user to access the signal c

urrent from the output of the voltage-to-current converter (Pin 5). The user can choose to use the AD8553 as a currentoutput device instead of a voltage-output device. See Figure 35 fo

r circuit connections.

Flicker noise is seen effectively as a slowly varying offset error, wh

ich is reduced by the autocorrection topology of the AD8553. This allows the AD8553 to have lower noise near dc than standard low noise instrumentation amplifiers.

Rev. 0 | Page 11 of 20

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APPLICATIONS

GAIN SELECTION (GAIN-SETTING RESISTORS)

The gain of the AD8553 is set according to

G = 2 × (R2/R1) (1)

Tabl e 5 lists the recommended resistor values. Resistor R1 must b

e at least 3.92 k for proper operation. Use of resistors larger than the recommended values results in higher offset and higher noise.

Gain accuracy depends on the matching of R1 and R2. Any misma

tch in resistor values results in a gain error. Resistor value errors due to drift affect gain by the amount indicated by Equation 1. However, due to the current-mode operation of the AD8553, a mismatch in R1 and R2 does not degrade the CMR.

Care should be taken when selecting and positioning the gain

etting resistors. The resistors should be made of the same

s material and package style. Surface-mount resistors are recommended. They should be positioned as close together as possible to minimize TC errors.

To maintain good CMR vs. frequency, the parasitic capacitance

n the R1 gain setting pins should be minimized and matched.

o This also helps maintain a low gain error at G < 10.

If resistor trimming is required to set a precise gain, trim

tor R2 only. Using a potentiometer for R1 degrades the

Resis amplifier’s performance.

REFERENCE CONNECTION

Unlike traditional three op amp instrumentation amplifiers, parasitic resistance in series with V CMR performance. This allows the AD8553 to attain its extremely high CMR performance without the use of an external buffer amplifier to drive the V standard instrumentation amplifiers. This helps save valuable printed circuit board space and minimizes system costs.

For optimal performance in single-supply applications, V should be set with a low noise precision voltage reference. However, for a lower system cost, the reference voltage can be set with a simple resistor voltage divider between the supply and ground (see output ideal values. In dual-supply applications, V connected to ground.

The V external buffer is not required.

Figure 31). This configuration results in degraded

offset performance if the resistors deviate from their

pin current is approximately 20 pA, and as a result, an

REF

pin, which is required by industry-

REF

(Pin 7) does not degrade

REF

can simply be

REF

DISABLE FUNCTION

The AD8553 provides a shutdown function to conserve power when the device is not needed. Although there is a 1 µA pull-up current on the ENABLE pin, Pin 6 should be connected to the positive supply for normal operation and to the negative supply to turn the device off. It is not recommended to leave Pin 6 floating.

Turn-on time upon switching Pin 6 high is dominated by the o

utput filters. When the device is disabled, the output becomes high impedance enabling muxing application of multiple AD8553 instrumentation amplifiers.

OUTPUT FILTERING

Filter Capacitor C2 is required to limit the amount of switching noise present at the output. The recommended bandwidth of the filter created by C2 and R2 is 1.4 kHz. The user should first select R1 and R2 based on the desired gain, then select C2 based on

C2 = 1/(1400 × 2 × π × R2) (2)

Addition of another single-pole RC filter of 1.4 kHz on the output

(R3 and C3 in Figure 31 to Figure 33) is required for

ndwidths greater than 10 Hz. These two filters produce an

ba overall bandwidth of 1 kHz.

When driving an ADC, the recommended values for the second f

ilter are R3 = 100 Ω and C3 = 1 µF. This filter is required to achieve the specified performance. It also acts as an antialiasing filter for the ADC. If a sampling ADC is not being driven, the value of the capacitor can be reduced, but the filter frequency should remain unchanged.

For applications with low bandwidths (<10 Hz), only the first f

ilter is required. In this case, the high frequency noise from the auto-zero amplifier (output amplifier) is not filtered before the following stage.

CLOCK FEEDTHROUGH

The AD8553 uses two synchronized clocks to perform the autocorrection. The input voltage-to-current amplifiers are corrected at 60 kHz.

Trace amounts of these clock frequencies can be observed at the

. The amount of feedthrough is dependent upon the gain,

output because the autocorrection noise has an input and output referred term. The correction feedthrough is also dependent upon the values of the external filters R2/C2, and R3/C3.

LOW IMPEDANCE OUTPUT

For applications where a low output impedance is required, the circuit in Figure 33 should be used. This provides the same f

iltering performance as shown in the configuration in Figure 34.

Rev. 0 | Page 12 of 20

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MAXIMIZING PERFORMANCE THROUGH PROPER LAYOUT

To achieve the maximum performance of the AD8553, care should be taken in the circuit board layout. The PC board surface must remain clean and free of moisture to avoid leakage currents between adjacent traces. Surface coating of the circuit board reduces surface moisture and provides a humidity barrier, reducing parasitic resistance on the board.

Care must be taken to minimize parasitic capacitance on Pin 1 a

nd Pin 10 (Resistor R1 connections). Traces from Pin 1 and Pin 10 to R1 should be kept short and symmetric. Excessive capacitance on these pins will result in a gain error. This effect is most prominent at low gains (G < 10).

For high impedance sources, the PC board traces from the AD8553 in

puts should be kept to a minimum to reduce input

bias current errors.

POWER SUPPLY BYPASSING

The AD8553 uses internally generated clock signals to perform the autocorrection. As a result, proper bypassing is necessary to achieve optimum performance. Inadequate or improper bypassing of the supply lines can lead to excessive noise and offset voltage.

For single-supply operation, a 0.1 µF surface-mount capacitor

ld be connected from the supply line to ground.

shou

All bypass capacitors should be positioned as close to the DUT su

pply pins as possible, especially the bypass capacitor between the supplies. Placement of the bypass capacitor on the back of the board directly under the DUT is preferred.

INPUT OVERVOLTAGE PROTECTION

All terminals of the AD8553 are protected against ESD. In the case of a dc overload voltage beyond either supply, a large current would flow directly through the ESD protection diodes. If such a condition should occur, an external resistor should be used in series with the inputs to limit current for voltages beyond the supply rails. The AD8553 can safely handle 5 mA of continuous current, resulting in an external resistor selection of R

= (VIN − VS)/5 mA.

EXT

CAPACITIVE LOAD DRIVE

The output buffer, Pin 4, can drive capacitive loads up to 100 pF.

A 0.1 µF surface-mount capacitor should be connected between th

e supply lines. This capacitor is necessary to minimize ripple from the correction clocks inside the IC. For dual-supply operation (see Figure 33), a 0.1 µF (ceramic) surface-mount ca

pacitor should be connected from each supply pin to ground.

CC

I

V

INP

M1

2I 2I

EXTERNAL

R1

– V

INN

I

)

M2

R1

(V

INP

=

R1

M5

I – I

R1

V

INN

M3 M4

Figure 30. Simplified AD8553 Schematic

M6

I – I

I + I

V

R1

BIAS

C2

R2

2I

R1

= V

V

A1

V

REF

OUT

REF

2R2

V

– V

INP

+

R2

INN

05474-030

Rev. 0 | Page 13 of 20

AD8553

V

www.BDTIC.com/ADI

CIRCUIT DIAGRAMS/CONNECTIONS

S+

0.1µF

GND

3

V

IN+

R1

V

IN–

2

+

1

AD8553

10

–

8

9

GND

100kΩ

V

S+

6

4

5

7

R2

C2

0.1µF

R3

100Ω

R3 AND C3 VALUES ARE RECOMMENDED T O DRIVE AN A/D CONVERTER

GND

C3 1µF

V

OUT

GND

05474-032

Figure 31. Single-Supply Connection Diagram Using Voltage Divider Reference

S+

0.1µF

GND

V

IN+

V

IN–

0.1µF

V

S–

2

3

+

1

R1

0.1µF

AD8553

10

–

8

9

VS–

GND

6

4

5

7

R2

C2

R3

100Ω

R3 AND C3 VALUES ARE RECOMMENDED T O DRIVE AN A/D CONVERTER

GND

C3 1µF

V

OUT

05474-031

Figure 32. Dual-Supply Connection Diagram

Rev. 0 | Page 14 of 20

AD8553

V

www.BDTIC.com/ADI

S+

0.1µF

GND

V

IN+

V

IN–

Figure 33. Dual-Supply Connection Diagram with

0.1µF

V

S–

3

2

+

GND

6

5

7

R3

100Ω

4

C2

GND

R2

R3 AND C3 VALUES ARE RECOMMENDED T O DRIVE AN A/D CONVERTER

C3 1µF

V

OUT

05474-034

1

R1

0.1µF

10

9

GND

–

AD8553

8

VS–

Low Impedance Output

S+

0.1µF

GND

2

V

IN+

R1

V

IN–

3

+

1

AD8553

10

–

9

8

V

S–

6

4

5

7

R2

C2

R3

100Ω

R3 AND C3 VALUES ARE RECOMMENDED T O DRIVE AN A/D CONVERTER

GND

C3 1µF

V

OUT

V

CC

1.0µF

0.1µF

V

IN

V

OUT

GND

Figure 34. Dual-Supply Connection Diagram Using IC Voltage Reference

Rev. 0 | Page 15 of 20

05474-035

AD8553

V

www.BDTIC.com/ADI

S+

2

IN

1

R1

10 9

+

AD8553

_

3

8

V

S–

Figure 35. Voltage-to-Current Converter, 0 μA to 30 μA Source

V

S+

2

3

+

1

AD8553

R1

10

9

_

Figure 36. Example of an AD8553 Driving a Converter at V

7

5

8

6

7

4

NC (NO CONNECT )

V

IN

5

0.1µF

6

4

V

REF

C2

R2

10kΩ

= 2.5V

AMMETER

100Ω

IO=

A

R1

S+

1µF

= 5 V

05474-037

A/D

CONVERTER

05474-038

Rev. 0 | Page 16 of 20

AD8553

www.BDTIC.com/ADI

V

S+

LOGIC

2

3

+

1

AD8553

R1

10

9

2 1

R6

10

9

_

+

AD8553

_

8

V

S–

V

S+

3

8

6

V

7

5

6

7

5

REF

4

C2

R2

V

REF

4

C3

R7

R3

100Ω

R8

100Ω

1µF

V

OUT

V

S+

6

V

7

5

REF

4

C4

R12

R13

100Ω

05474-039

R11

10

2 1

9

+

AD8553

_

3

8

Figure 37. Multiplexed Output

Table 5. Recommended External Component Values for Selected Gains

Desired Gain (V/V) R1 (Ω) R2 || C2 (Ω || F) Calculated Gain

1 200 k 100 k || 1200p 1 2 100 k 100 k || 1200p 2 5 40.2 k 100 k || 1200p 10 20 k 100 k || 1200p 50 4.02 k 100 k || 1200p 100 3.92 k 196 k || 560p 500 3.92 k 976 k || 120p

4.975 10

49.75 100

497.95

1000 3.92 k 1.96 M || 56p 1000

Rev. 0 | Page 17 of 20

AD8553

www.BDTIC.com/ADI

OUTLINE DIMENSIONS

3.10

3.00

2.90

6

10

3.10

3.00

2.90

1

PIN 1

0.50 BSC

0.95

0.85

0.75

0.15

0.05

0.33

0.17

COPLANARITY

0.10

COMPLIANT TO JEDEC STANDARDS MO-187-BA

Figure 38. 10-Lead Mini Small Outline Package [MSOP]

5.15

4.90

4.65

5

1.10 MAX

SEATING PLANE

(R

M-10)

0.23

0.08

8° 0°

Dimensions shown in millimeters

0.80

0.60

0.40

ORDERING GUIDE

Model Temperature Range Package Description Package Option Branding

AD8553ARMZ-R2 AD8553ARMZ-REEL

1

Z = Pb-free part.

1

−40°C to +85°C 10-Lead MSOP RM-10 A09

Rev. 0 | Page 18 of 20

AD8553

www.BDTIC.com/ADI

NOTES

Rev. 0 | Page 19 of 20

AD8553

www.BDTIC.com/ADI

NOTES

D05474-0-10/05(0)

Rev. 0 | Page 20 of 20

ANALOG DEVICES AD8553 Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

FEATURES

APPLICATIONS

PIN CONFIGURATION

GENERAL DESCRIPTION

TABLE OF CONTENTS

REVISION HISTORY

SPECIFICATIONS

ELECTRICAL CHARACTERISTICS

ABSOLUTE MAXIMUM RATINGS

THERMAL RESISTANCE

ESD CAUTION

TYPICAL PERFORMANCE CHARACTERISTICS

THEORY OF OPERATION

HIGH PSR AND CMR

1/f NOISE CORRECTION

APPLICATIONS

GAIN SELECTION (GAIN-SETTING RESISTORS)

REFERENCE CONNECTION

DISABLE FUNCTION

OUTPUT FILTERING

CLOCK FEEDTHROUGH

LOW IMPEDANCE OUTPUT

MAXIMIZING PERFORMANCE THROUGH PROPER LAYOUT

POWER SUPPLY BYPASSING

INPUT OVERVOLTAGE PROTECTION

CAPACITIVE LOAD DRIVE

CIRCUIT DIAGRAMS/CONNECTIONS

OUTLINE DIMENSIONS

ORDERING GUIDE