AD8305ACPZ-REEL7 datasheet, PDF

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AD8305ACPZ-REEL7: DescriptionLOG OR ANTILOG AMPLIFIER, QCC16, 3 X 3 MM, MINIATURE, MO-220-VEED-2, LFCSP-16; CategoryAnalog mixed-signal IC The signal circuit; File Size429KB，24 Pages; ManufacturerADI; Websitehttps://www.analog.com

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AD8305ACPZ-REEL7 Overview

LOG OR ANTILOG AMPLIFIER, QCC16, 3 X 3 MM, MINIATURE, MO-220-VEED-2, LFCSP-16

AD8305ACPZ-REEL7 Parametric

Parameter Name	Attribute value
Is it lead-free?	Contains lead
Is it Rohs certified?	incompatible
Maker	ADI
Parts packaging code	QFN
package instruction	3 X 3 MM, MINIATURE, MO-220-VEED-2, LFCSP-16
Contacts	16
Reach Compliance Code	compliant
ECCN code	EAR99
Analog Integrated Circuits - Other Types	LOG OR ANTILOG AMPLIFIER
JESD-30 code	S-XQCC-N16
JESD-609 code	e0
length	3 mm
Maximum negative supply voltage (Vsup)	-5.5 V
Nominal Negative Supply Voltage (Vsup)
Number of functions	1
Number of terminals	16
Maximum operating temperature	85 °C
Minimum operating temperature	-40 °C
Package body material	UNSPECIFIED
encapsulated code	VQCCN
Package shape	SQUARE
Package form	CHIP CARRIER, VERY THIN PROFILE
Peak Reflow Temperature (Celsius)	220
Certification status	Not Qualified
Maximum seat height	1 mm
Maximum supply voltage (Vsup)	12 V
Minimum supply voltage (Vsup)	3 V
Nominal supply voltage (Vsup)	5 V
surface mount	YES
Temperature level	INDUSTRIAL
Terminal surface	TIN LEAD
Terminal form	NO LEAD
Terminal pitch	0.5 mm
Terminal location	QUAD
Maximum time at peak reflow temperature	30
width	3 mm

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100 dB Range (10 nA to 1 mA)

Logarithmic Converter

AD8305

FEATURES

Optimized for fiber optic photodiode interfacing

Measures current over 5 decades

Law conformance 0.1 dB from 10 nA to 1 mA

Single- or dual-supply operation (3 V to 12 V total)

Full log-ratio capabilities

Nominal slope of 10 mV/dB (200 mV/decade)

Nominal intercept of 1 nA (set by external resistor)

Optional adjustment of slope and intercept

Complete and temperature stable

Rapid response time for a given current level

Miniature 16-lead chip scale package

(LFCSP 3 mm × 3 mm)

Low power: ~5 mA quiescent current

VRDZ

VREF

200kΩ

0.5V

IREF

BIAS

INPT

VSUM

0.5V

VNEG

20kΩ

COMM

SCAL

BE2

–

14.2kΩ

LOG

BFIN

451Ω

VLOG

80kΩ

2.5V

BIAS

GENERATOR

FUNCTIONAL BLOCK DIAGRAM

VPOS

0.20 log

1nA

VOUT

TEMPERATURE

COMPENSATION

BE1

6.69kΩ

03053-001

COMM

APPLICATIONS

Optical power measurement

Wide range baseband logarithmic compression

Measurement of current and voltage ratios

Optical absorbance measurement

Figure 1.

GENERAL DESCRIPTION

The AD8305

is an inexpensive microminiature logarithmic converter

optimized for determining optical power in fiber optic systems. It uses

an advanced implementation of a classic translinear (junction based)

technique to provide a large dynamic range in a versatile and easily

used form. A single-supply voltage of between 3 V and 12 V is

adequate; dual supplies may optionally be used. The low quiescent

current (typically 5 mA) permits use in battery-operated applications.

The input current, I

, of 10 nA to 1 mA applied to the INPT pin is the

collector current of an optimally scaled NPN transistor, which converts

this current to a voltage (V

) with a precise logarithmic relationship. A

second such converter is used to handle the reference current (I

REF

)

applied to pin I

REF

. These input nodes are biased slightly above ground

(0.5 V). This is generally acceptable for photodiode applications where

the anode does not need to be grounded. Similarly, this bias voltage is

easily accounted for in generating I

REF

. The output of the logarithmic

front end is available at Pin VLOG.

The basic logarithmic slope at this output is nominally 200 mV/decade

(10 mV/dB). Thus, a 100 dB range corresponds to an output change of

1 V. When this voltage (or the buffer output) is applied to an ADC that

permits an external reference voltage to be employed, the AD8305

voltage reference output of 2.5 V at Pin VREF can be used to improve

the scaling accuracy. Suitable ADCs include the

AD7810

(serial 10-bit),

AD7823

(serial 8-bit), and

AD7813

(parallel, 8-bit or 10-bit). Other

values of the logarithmic slope can be provided using a simple external

resistor network.

The logarithmic intercept (also known as the reference current) is

nominally positioned at 1 nA by the use of the externally generated

current, I

REF

, of 10 μA, provided by a 200 kΩ resistor connected

between VREF, at 2.5 V, and the reference input, IREF, at 0.5 V. The

intercept can be adjusted over a wide range by varying this resistor.

The AD8305 can also operate in a log ratio mode, with the numerator

current applied to INPT and the denominator current applied to IREF.

A buffer amplifier is provided for driving a substantial load, for use in

raising the basic slope of 10 mV/dB to higher values, as a precision

comparator (threshold detector), or in implementing low-pass filters.

Its rail-to-rail output stage can swing to within 100 mV of the positive

and negative supply rails, and its peak current sourcing capacity is

25 mA.

It is a fundamental aspect of translinear logarithmic converters that the

small signal bandwidth falls as the current level diminishes, and the

low frequency noise-spectral density increases. At the 10 nA level, the

bandwidth of the AD8305 is about 50 kHz and increases in proportion

to I

up to a maximum value of about 15 MHz. Using the buffer

amplifier, the increase in noise level at low currents can be addressed by

using it to realize lowpass filters of up to three poles.

The AD8305 is available in a 16-lead LFCSP package and is specified

for operation from −40°C to +85°C.

Protected by U.S. Patent No. 5,519,308.

Rev. B

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

AD8305

TABLE OF CONTENTS

Features .............................................................................................. 1

Applications ....................................................................................... 1

Functional Block Diagram .............................................................. 1

General Description ......................................................................... 1

Revision History ............................................................................... 2

Specifications..................................................................................... 3

Absolute Maximum Ratings............................................................ 4

ESD Caution .................................................................................. 4

Pin Configuration and Function Descriptions ............................. 5

Typical Performance Characteristics ............................................. 6

General Structure ........................................................................... 11

Theory .......................................................................................... 11

Managing Intercept and Slope .................................................. 12

Response Time and Noise Considerations ............................. 12

Power Supply Sequencing ......................................................... 12

Applications..................................................................................... 14

Calibration ....................................................................................... 15

Using A Negative Supply ............................................................... 16

Log-Ratio Applications .................................................................. 17

Reversing The Input Polarity ........................................................ 18

Characterization Methods ............................................................. 19

Evaluation Board ............................................................................ 21

Outline Dimensions ....................................................................... 24

Ordering Guide .......................................................................... 24

REVISION HISTORY

4/10—Rev. A to Rev. B

Updated Data Sheet ............................................................ Universal

Change to Figure 2 and Table 3 ...................................................... 5

Added Power Supply Sequencing Section ................................... 12

Added Figure 34; Renumbered Sequentially .............................. 12

Changes to Ordering Guide .......................................................... 24

3/03—Rev. 0 to Rev. A

Changes to TPC 3 ............................................................................. 4

Changes to TPC 18 ........................................................................... 6

Changes to Figure 3 ........................................................................ 11

Changes to Figure 8 ........................................................................ 13

Updated Outline Dimensions ....................................................... 18

Rev. B | Page 2 of 24

AD8305ACPZ-REEL7 Related Products

	AD8305ACPZ-REEL7	AD8305ACP
Description	LOG OR ANTILOG AMPLIFIER, QCC16, 3 X 3 MM, MINIATURE, MO-220-VEED-2, LFCSP-16	IC LOG OR ANTILOG AMPLIFIER, QCC16, 3 X 3 MM, MINIATURE, MO-220-VEED-2, LFCSP-16, Analog Computational Function
Is it Rohs certified?	incompatible	incompatible
Maker	ADI	ADI
Parts packaging code	QFN	QFN
package instruction	3 X 3 MM, MINIATURE, MO-220-VEED-2, LFCSP-16	VQCCN, LCC16,.12SQ,20
Contacts	16	16
Reach Compliance Code	compliant	unknown
ECCN code	EAR99	EAR99
Analog Integrated Circuits - Other Types	LOG OR ANTILOG AMPLIFIER	LOG OR ANTILOG AMPLIFIER
JESD-30 code	S-XQCC-N16	S-XQCC-N16
JESD-609 code	e0	e0
length	3 mm	3 mm
Maximum negative supply voltage (Vsup)	-5.5 V	-5.5 V
Number of functions	1	1
Number of terminals	16	16
Maximum operating temperature	85 °C	85 °C
Minimum operating temperature	-40 °C	-40 °C
Package body material	UNSPECIFIED	UNSPECIFIED
encapsulated code	VQCCN	VQCCN
Package shape	SQUARE	SQUARE
Package form	CHIP CARRIER, VERY THIN PROFILE	CHIP CARRIER, VERY THIN PROFILE
Peak Reflow Temperature (Celsius)	220	220
Certification status	Not Qualified	Not Qualified
Maximum seat height	1 mm	1 mm
Maximum supply voltage (Vsup)	12 V	12 V
Minimum supply voltage (Vsup)	3 V	3 V
Nominal supply voltage (Vsup)	5 V	5 V
surface mount	YES	YES
Temperature level	INDUSTRIAL	INDUSTRIAL
Terminal surface	TIN LEAD	Tin/Lead (Sn/Pb)
Terminal form	NO LEAD	NO LEAD
Terminal pitch	0.5 mm	0.5 mm
Terminal location	QUAD	QUAD
Maximum time at peak reflow temperature	30	30
width	3 mm	3 mm

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