ANALOG DEVICES AD8508 Service Manual

20 μA Maximum, Rail-to-Rail I/O,

www.BDTIC.com/ADI

Zero Input, Crossover Distortion Amplifiers

Preliminary Technical Data

FEATURES

PSRR: 100 dB minimum CMRR: 105 dB typical Very low supply current: 20 μA per amp maximum

1.8 V to 5 V single-supply or ±0.9 V to ±2.5 V dual-supply operation

Rail-to-rail input and output

2.5 mV offset voltage maximum

Very low input bias current: 1 pA typical

APPLICATIONS

Pressure and position sensors Remote security Bio sensors IR thermometers Battery-powered consumer equipment Hazard detectors

GENERAL DESCRIPTION

The AD8508 is a quad micropower amplifiers featuring rail-torail input and output swings while operating from a 1.8 V to 5 V single or from ±0.9 V to ±2.5 V dual power supply.

Using a novel circuit technology, these low cost amplifiers offer zero crossover distortion (excellent PSRR and CMRR performance) and very low bias current, while operating with a supply current of less than 20 μA per amplifier. This amplifier offers the lowest noise in its power class.

This combination of features makes the AD8508 amplifiers ideal choices for battery-powered applications because they minimize errors due to power supply voltage variations over the lifetime of the battery and maintain high CMRR even for a railto-rail input op amp.

AD8508

PIN CONFIGURATION

OUT A

–IN A

+IN A

+IN B –IN B

OUT B

Figure 1. 14-Lead TSSOP (RU-14)

V+

AD8508

TOP VIEW

(Not to Scale)

5 6 7

Remote battery-powered sensors, handheld instrumentation and consumer equipment, hazard detection (for example, smoke, fire, and gas), and patient monitors can benefit from the features of the AD8508 amplifiers.

The AD8508 are specified for both the industrial temperature range of −40°C to +85°C and the extended industrial temperature range of −40°C to +125°C. The AD8508 quad amplifiers are available in the 14-lead TSSOP package.

14 13 12 11 10

9 8

OUT D –IN D +IN D V– +IN C –IN C OUT C

06900-045

Rev. PrA

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.

AD8508 Preliminary Technical Data

www.BDTIC.com/ADI

SPECIFICATIONS

ELECTRICAL CHARACTERISTICS—5 V OPERATION

VSY = 5 V, VCM = VSY/2, TA = 25°C, RL = 100 kΩ to GND, unless otherwise noted.

Table 1.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage VOS 0 V ≤ VCM ≤ 5 V 0.5 2.5 mV

−40°C ≤ TA ≤ +125°C 3.5 mV Input Bias Current IB 1 10 pA

−40°C ≤ TA ≤ +85°C 100 pA

−40°C ≤ TA ≤ +125°C 600 pA Input Offset Current IOS 0.5 5 pA

−40°C ≤ TA ≤ +85°C 50 pA

−40°C ≤ TA ≤ +125°C 130 pA Input Voltage Range −40°C ≤ TA ≤ +125°C 0 5 V Common-Mode Rejection Ratio CMRR 0 V ≤ VCM ≤ 5 V 90 105 dB

−40°C ≤ TA ≤ +85°C 90 dB

−40°C ≤ TA ≤ +125°C 85 dB Large Signal Voltage Gain AVO 0.05 V ≤ V

−40°C ≤ TA ≤ +125°C 100 dB Offset Voltage Drift

Input Capacitance Differential Mode Input Capacitance Common Mode

OUTPUT CHARACTERISTICS

Output Voltage High VOH R

−40°C ≤ TA ≤ +125°C 4.98 V R

−40°C ≤ TA ≤ +125°C 4.9 V Output Voltage Low VOL R

−40°C ≤ TA ≤ +125°C 5 mV R

−40°C ≤ TA ≤ +125°C 30 mV Short-Circuit Limit ISC ±55 mA

POWER SUPPLY

Power Supply Rejection Ratio PSRR VSY = 1.8 V to 5 V 100 110 dB

−40°C ≤ TA ≤ +85°C 100 dB

−40°C ≤ TA ≤ +125°C 95 dB Supply Current per Amplifier ISY V

−40°C ≤ TA ≤ +125°C 25 μA

DYNAMIC PERFORMANCE

Slew Rate SR RL = 100 kΩ, CL = 10 pF, G = 1 13 mV/μs Gain Bandwidth Product GBP RL = 1 MΩ, CL = 20 pF, G = 1 95 kHz Phase Margin ΦM R

NOISE PERFORMANCE

Voltage Noise en p-p f = 0.1 Hz to 10 Hz 2.8 μV p-p Voltage Noise Density en f = 1 kHz 45 nV/√Hz Current Noise Density in f = 1 kHz 15 fA/√Hz

ΔV C

DIFF

CCM

/ΔT

−40°C ≤ T 3 pF

4.2 pF

= 100 kΩ to GND 4.98 4.99 V

= 10 kΩ to GND 4.9 4.95 V

= 100 kΩ to VSY 2 5 mV

= 10 kΩ to VSY 10 25 mV

= VSY/2 15 20 μA

OUT

= 1 MΩ, CL = 20 pF, G = 1 60 Degrees

≤ 4.95 V 105 120 dB

OUT

≤ +125°C 2 μV/°C

Rev. PrA | Page 2 of 4

+ 2 hidden pages