ADL5306 Analog Devices, Inc., ADL5306 Datasheet

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ADL5306

Manufacturer Part Number
ADL5306
Description
60 Db Range 100 Na To 100 Ua Low Cost Logarithmic Converter
Manufacturer
Analog Devices, Inc.
Datasheet
FEATURES
Optimized for fiber optic photodiode interfacing
Measures current over 3 decades
Single- or dual-supply operation (3 V to ±5.5 V total)
Full log-ratio capabilities
Temperature stable
Nominal slope of 10 mV/dB (200 mV/decade)
Nominal intercept of 1 nA (set by external resistor)
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
APPLICATIONS
Low cost optical power measurement
Wide range baseband logarithmic compression
Measurement of current and voltage ratios
Optical absorbance measurement
GENERAL DESCRIPTION
The ADL5306
optimized for determining optical power in fiber optic systems. The
ADL5306 is derived from the AD8304 and AD8305 translinear
logarithmic converters. This family of devices provides wide
measurement dynamic range in a versatile and easy-to-use form. A
single-supply voltage between 3 V and 5.5 V is adequate; dual
supplies may optionally be used. Low quiescent current (5 mA
typical) permits use in battery-operated applications.
I
the collector current of an optimally scaled NPN transistor that
converts this current to a voltage (V
relationship. A second converter is used to handle the reference
current, I
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
The logarithmic front end’s output is available at VLOG.
The basic logarithmic slope at this output is 200 mV/decade
(10 mV/dB) nominal; a 60 dB range corresponds to a 600 mV
output change. When this voltage (or the buffer output) is applied
to an ADC that permits an external reference voltage to be
employed, the ADL5306’s 2.5 V voltage reference output at VREF
can be used to improve scaling accuracy.
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 companies.
PD
, the 100 nA to 100 µA input current applied to the INPT pin, is
Law conformance 0.1 dB from 100 nA to 100 μA
Optional adjustment of slope and intercept
REF
, applied to IREF. These input nodes are biased slightly
is a low cost microminiature logarithmic converter
BE
) with a precise logarithmic
REF
.
Low Cost Logarithmic Converter
60 dB Range (100 nA to 100 µA)
FUNCTIONAL BLOCK DIAGRAM
The logarithmic intercept (reference current) is nominally
positioned at 1 nA by using the externally generated, 100 µA I
current provided by a 200 kΩ resistor connected between VREF, at
2.5 V, and IREF, at 0.5 V. The intercept can be adjusted over a
narrow range by varying this resistor. The part can also operate in a
log-ratio mode, with limited accuracy, where the numerator and
denominator currents are applied to INPT and IREF, respectively.
A buffer amplifier is provided to drive substantial loads, raise the
basic 10 mV/dB slope, serve as a precision comparator (threshold
detector), or implement 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.
A fundamental aspect of translinear logarithmic converters is that
small-signal bandwidth falls as current level diminishes, and low
frequency noise-spectral density increases. At the 100 nA level, the
ADL5306’s bandwidth is about 100 kHz; it increases in proportion
to I
level at low currents can be addressed by using a buffer amplifier to
realize low-pass filters of up to three poles.
The ADL5306 is available in a 16-lead LFCSP package and is
specified for operation from–40°C to +85°C.
1kΩ
1nF
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.326.8703
V
Protected by US Patents 4,604,532 and 5,519,308; other patents pending.
200kΩ
BIAS
R
1kΩ
1nF
PD
REF
I
PD
1nF
up to a maximum of about 10 MHz. The increase in noise
VSUM
VREF
IREF
INPT
NC
0.5V
0.5V
Figure 1. Functional Block Diagram
20kΩ
© 2003 Analog Devices, Inc. All rights reserved.
COMM
VNEG
Q2
Q1
80kΩ
2.5V
V
V
BE2
BE1
COMPENSATION
GENERATOR
TEMPERATURE
VPOS
BIAS
+5V
COMM
ADL5306
COMM
14.2kΩ
6.69kΩ
0.2 log
www.analog.com
I
LOG
10
451Ω
( )
1nA
I
PD
03727-0-001
REF
VOUT
SCAL
BFIN
VLOG

Related parts for ADL5306

ADL5306 Summary of contents

Page 1

... REF level at low currents can be addressed by using a buffer amplifier to realize low-pass filters three poles. The ADL5306 is available in a 16-lead LFCSP package and is specified for operation from–40°C to +85°C. ∗ Protected by US Patents 4,604,532 and 5,519,308; other patents pending. ...

Page 2

... ADL5306 TABLE OF CONTENTS Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 4 Pin Configuration and Pin Function Descriptions...................... 5 Typical Performance Characteristics ............................................. 6 General Structure.............................................................................. 9 Theory............................................................................................ 9 Managing Intercept and Slope .................................................. 10 REVISION HISTORY Rev. 0: Initial Version Response Time and Noise Considerations ............................. 10 Applications..................................................................................... 11 Using a Negative Supply ............................................................ 11 Characterization Methods ........................................................ 12 Evaluation Board ............................................................................ 14 Outline Dimensions ...

Page 3

... L Load current < GAIN = 1 0 4.8 V output swing VPOS (Pin 8); VNEG (Pin 6) ) ≤ – ≤ – REF Rev Page ADL5306 1 1 Min Typ Max Unit 100n 100µ 100n 100µ A 0.46 0.5 0.54 V 0.015 mV/° ...

Page 4

... ADL5306 ABSOLUTE MAXIMUM RATINGS Table 2. ADL5306 Absolute Maximum Ratings Parameter Supply Voltage V – Input Current Internal Power Dissipation θ JA Maximum Junction Temperature Operating Temperature Range Storage Temperature Range Lead Temperature Range (Soldering 60 sec) Stresses above those listed under Absolute Maximum Ratings Rating may cause permanent damage to the device ...

Page 5

... Figure 2. 16-Lead Leadframe Chip Scale Package (LFCSP) . REF . Usually connected to photodiode anode such that photocurrent flows PD . This pin is usually grounded; for details of usage, see the Applications section. N – ≤ Rev Page VOUT SCAL BFIN VLOG ADL5306 ...

Page 6

... ADL5306 TYPICAL PERFORMANCE CHARACTERISTICS ( 200 kΩ 25°C, unless otherwise noted REF A 1 –40°C, 0°C, +25°C, +70°C, +85° 1.0 0.8 0.6 0.4 0.2 0 10n 100n 1µ 10µ I (A) PD Figure 3. V vs. I for Multiple Temperatures LOG PD 1 –40°C, 0°C, +25°C, +70°C, +85°C ...

Page 7

... TO 10µA: = 5µs, RISE t < 1µs FALL t 10µA TO 100µA: = 1µs, RISE t < 1µs FALL 100 120 140 TIME (µs) Figure 14. Pulse Response REF OUT ADL5306 1m 03727-0-012 PD 160 180 03727-0-013 160 180 03727-0-014 ...

Page 8

... ADL5306 10 5 100nA 0 –5 –10 –15 –20 –25 –30 –35 –40 100 1k 10k 100k 1M FREQUENCY (Hz) Figure 15. Small-Signal AC Response (5% Sine Modulation), from for I in Decade Steps from 100nA 0 –5 –10 –15 –20 –25 –30 –35 –40 100 ...

Page 9

... V, one fifth of the 2.5 V reference voltage appearing on Pin VREF. The resistance at the VSUM pin is nominally 16 kΩ; this voltage is not intended as a general bias source. The ADL5306 also supports the use of an optional negative supply voltage Pin VNEG. When V N negative, VSUM may be connected to ground ...

Page 10

... For more details, see and the AD8304 Data Sheet. P RESPONSE TIME AND NOISE CONSIDERATIONS The response time and output noise of the ADL5306 are fundamentally a function of the signal current I currents, the bandwidth is proportional to I frequency voltage-noise spectral density is a function of I increases for small values of I bandwidth performance of translinear log amps, see the AD8304 Data Sheet ...

Page 11

... APPLICATIONS The ADL5306 is easy to use in optical supervisory systems and in similar situations where a wide-ranging current converted to its logarithmic equivalent (i.e., represented in decibel terms). Basic connections for measuring a single current input are shown in Figure 22, which includes various nonessential components, as will be explained. VPOS +5V NC ...

Page 12

... INPT and IREF signal current. For example, it may be convenient to utilize a forward-biased junction voltage of about 0 Schottky barrier voltage of a little over 0.5 V. With the summing node at ground, the ADL5306 may now be used as a voltage-input log amp, at either the numerator input INPT or the denominator input IREF by inserting a suitably scaled resistor from the voltage source to the relevant pin ...

Page 13

... CELL 03727-0-027 Rev Page ADL5306 TDS5104 CH A 9213 COMM COMM COMM COMM VOUT NC 1 SCAL VREF 2 200kΩ ADL5306 3 IREF BFIN R1 4 INPT VLOG VSUM VNEG VNEG VPOS 50kΩ 1kΩ 1kΩ 1nF 1nF Measurement ...

Page 14

... SMA connector labeled INPT style packaged photodiode can be used in place of the INPT SMA for optical interfacing. By removing R1 and adding a 0 Ω short for R5, a second current can be applied to the IREF input (also SMA) for evaluating the ADL5306 in log-ratio applications. SC Style Photodiode Rev Page ...

Page 15

... VPOS OPEN OPEN AGND 0.01 µ F VOUT VREF C5 0.1 µ F VSUM AGND VPOS VLOG P1 Figure 31. Component Side Silkscreen Rev Page ADL5306 R10 VOUT OPEN R14 VOUT 0 Ω OPEN R8 VLOG OPEN R11 VLOG 0 Ω 03727-0-029 ...

Page 16

... 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. ORDERING GUIDE ADL5306 Products Temperature Package 2 ADL5306ACP –40°C to +85°C ADL5306ACP-R2 – ...

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