High Speed, 200 dB Range, Logarithmic Converter Data Sheet ADL5304 A single positive supply of 5 V is all that is required for operation FEATURES over a specified 1 pA to 3 mA input range. Dual-supply operation Optimized for very fast response at all input currents extends the specified input current range to 10 mA. Overall bandwidth of >4 MHz for inputs >1 A Bandwidth: 25 kHz at input of 1 nA and 350 kHz at 10 nA The ADL5304 accepts two current inputs to the logarithmic 10 decades of input range: 1 pA to 10 mA argument. The numerator input, I , flows in the collector of an NUM Law conformance: 0.25 dB from 100 pA to 100 A NPN transistor, connected in a feedback path around a low offset Log ratio or fixed-intercept operation JFET amplifier. The denominator current, IDEN, is treated in the Precision voltage references and reference current same way, which allows for log ratio operation. The input summing Adaptive photodiode (PD) bias for low dark current nodes (INUM and IDEN) operate at a constant default voltage of Programmable log slope and intercept 1.5 V. The VSM1 to VSM4 pins flank the INUM and IDEN inputs Default log slope of 10 mV/dB at VLOG pin to provide a guard voltage to minimize leakage currents. Single- or dual-supply operation Adaptive photodiode biasing is provided for optical measurements. A monitor current 1.1 times I is output at the IMON pin, and NUM APPLICATIONS an external resistor, R , at 10 times the photodiode series MNTR High accuracy optical power measurement resistance (RS) applies a voltage across the photodiode that Wide range baseband log compression 1st order keeps the internal PD junction at 0 V to minimize Versatile detector for high speed APC loops dark current. GENERAL DESCRIPTION The VLOG output is buffered and can be rescaled through The ADL5304 is a high speed logarithmic converter with fast internal gain setting resistors. The internal I varies from LOG response and low noise over a 200 dB (1 pA to 10 mA) measure- 400 A to +400 A as I changes over 10 decades from 1 pA NUM ment range. The ADL5304 provides a nominal logarithmic slope of to 10 mA. This corresponds to 0.5 V to 2.5 V at the VLOG pin 10 mV/dB (200 mV/decade) other values are easily configured. in the default configuration shown in Figure 1. Logarithmic intercept can be programmed over a wide range Accurate 1.5 V (Pin 1P5V) and 2.0 V (Pin 2VLT) reference outputs with the internal 100 nA current source or externally for log ratio allow precise repositioning of the intercept using external resistors. applications. The default intercept value of 3.162 fA places the The ADL5304 is available in a 32-lead, 5 mm 5 mm LFCSP midpoint of the measurement range of 100 nA at V = 1.5 V. LOG and specified for operation from 40C to +85C. SIMPLIFIED BLOCK DIAGRAM BSDC 2VLT VPOS IMON VNUM INNM 1P5V DCBI 30 32 31 26 28 17 29 27 INPS 24 1.5V 2V MONITOR AND R PD BIAS BIAS AND INMS MNTR 100nA VSM1 23 (1.1 I ) V 2 NUM REF VLOG 1.5V VSM2 22 3 ADL5304 INUM SCL1 4 V I NUM 21 LOG 5k 5k IDEN SCL2 5 TEMPERATURE 20 COMPENSATION 7.5k IREF 6 19 SCL3 V DEN VSM3 7 ACOM 18 VSM4 1.5V COMM NMFS VNEG DNFS ACOM HFCP 8 9 10 11 12 13 14 15 16 VDEN INDN 1k 1k V NEG Figure 1. Rev. A Document Feedback 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 20112016 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. 09459-001ADL5304 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Terminology .................................................................................... 16 Applications ....................................................................................... 1 Theory of Operation ...................................................................... 17 General Description ......................................................................... 1 Basic Concepts ............................................................................ 17 Simplified Block Diagram ............................................................... 1 Optical Measurements ............................................................... 17 Revision History ............................................................................... 2 Circuit Description .................................................................... 18 Specifications ..................................................................................... 3 Applications Information .............................................................. 25 Absolute Maximum Ratings ............................................................ 5 Using the ADL5304 .................................................................... 25 ESD Caution .................................................................................. 5 Using a Negative Supply ............................................................ 26 Pin Configuration and Function Descriptions ............................. 6 Evaluation Board Schematic and Silkscreens ............................. 27 Typical Performance Characteristics ............................................. 7 Outline Dimensions ....................................................................... 29 Test Circuits ..................................................................................... 13 Ordering Guide .......................................................................... 29 REVISION HISTORY 3/16Rev. 0 to Rev. A Changes to Specified Current Range Parameter, Table 1 ............ 3 Changes to Figure 2 and Table 3 ..................................................... 6 Changes to Figure 58 ...................................................................... 27 Updated Outline Dimensions ....................................................... 29 Changes to Ordering Guide .......................................................... 29 9/11Revision 0: Initial Version Rev. A Page 2 of 32