ADL5304-EVALZ

High Speed, 200 dB Range, Logarithmic Converter ADL5304 Data Sheet FEATURES A single positive supply of 5 V is all that is required for operation over a specified 1 pA to 3 mA input range. Dual-supply operation extends the specified input current range to 10 mA. Optimized for very fast response at all input currents Overall bandwidth of >4 MHz for inputs >1 µA Bandwidth: 25 kHz at input of 1 nA and 350 kHz at 10 nA 10 decades of input range: 1 pA to 10 mA Law conformance: ±0.25 dB from 100 pA to 100 µA Log ratio or fixed-intercept operation Precision voltage references and reference current Adaptive photodiode (PD) bias for low dark current Programmable log slope and intercept Default log slope of 10 mV/dB at VLOG pin Single- or dual-supply operation The ADL5304 accepts two current inputs to the logarithmic argument. The numerator input, INUM, flows in the collector of an NPN transistor, connected in a feedback path around a low offset JFET amplifier. The denominator current, IDEN, is treated in the same way, which allows for log ratio operation. The input summing nodes (INUM and IDEN) operate at a constant default voltage of 1.5 V. The VSM1 to VSM4 pins flank the INUM and IDEN inputs to provide a guard voltage to minimize leakage currents. Adaptive photodiode biasing is provided for optical measurements. A monitor current 1.1 times INUM is output at the IMON pin, and an external resistor, RMNTR, at 10 times the photodiode series resistance (RS) applies a voltage across the photodiode that 1st order keeps the internal PD junction at 0 V to minimize dark current. APPLICATIONS High accuracy optical power measurement Wide range baseband log compression Versatile detector for high speed APC loops GENERAL DESCRIPTION The VLOG output is buffered and can be rescaled through internal gain setting resistors. The internal ILOG varies from −400 µA to +400 µA as INUM changes over 10 decades from 1 pA to 10 mA. This corresponds to 0.5 V to 2.5 V at the VLOG pin in the default configuration shown in Figure 1. The ADL5304 is a high speed logarithmic converter with fast response and low noise over a 200 dB (1 pA to 10 mA) measurement range. The ADL5304 provides a nominal logarithmic slope of 10 mV/dB (200 mV/decade); other values are easily configured. Logarithmic intercept can be programmed over a wide range with the internal 100 nA current source or externally for log ratio applications. The default intercept value of 3.162 fA places the midpoint of the measurement range of 100 nA at VLOG = 1.5 V. Accurate 1.5 V (Pin 1P5V) and 2.0 V (Pin 2VLT) reference outputs allow precise repositioning of the intercept using external resistors. The ADL5304 is available in a 32-lead, 5 mm × 5 mm LFCSP and specified for operation from −40°C to +85°C. SIMPLIFIED BLOCK DIAGRAM IMON VNUM INNM 32 30 BSDC 2VLT VPOS 1P5V 31 26 28 17 RMNTR VSM1 VSM2 2 3 100nA DCBI 27 2V 24 BIAS AND VREF 23 1.5V MONITOR AND PD BIAS (1.1× INUM ) 29 1.5V 22 INPS INMS VLOG ADL5304 INUM 4 IREF VSM3 VSM4 ILOG 21 5kΩ TEMPERATURE COMPENSATION 5 6 5kΩ 20 19 VDEN 18 1.5V SCL2 7.5kΩ 7 8 SCL1 SCL3 ACOM COMM NMFS VNEG DNFS ACOM HFCP 9 VDEN 10 11 INDN 12 13 1kΩ VNEG 14 1kΩ 15 16 09459-001 IDEN VNUM 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 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. 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Technical Support www.analog.com ADL5304 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 3/16—Rev. 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 9/11—Revision 0: Initial Version Rev. A | Page 2 of 32 Data Sheet ADL5304 SPECIFICATIONS VPOS = 5 V, VNEG = 0 V, TA = 25°C; IDEN = IREF; VSM1 to VSM4, 1P5V, DCBI, and INPS tied together; SCL1 = VLOG; SCL2 = INMS; SCL3 = open; scale = 200 mV/dec; VLOG output load RL > 2 kΩ, unless otherwise noted. Upper case indicates a pin name (for example, VLOG) and subscripted indicates signal name (for example, VLOG). Table 1. Parameter INPUT INTERFACES Specified Current Range Temperature Drift (INUM and IDEN) Input Guard Offset Voltage LOGARITHMIC OUTPUT Logarithmic Slope, VY Logarithmic Intercept, IZ 2 Logarithmic Offset Logarithmic Law Conformance Error VLOG OUTPUT Output Buffer Offset Voltage Output Buffer Bias Current Incremental Input Resistance Output Range Output Noise Spectral Density 3 Small Signal Bandwidth Falling Edge Settling Times 4 Nominal Voltage Swing Output Impedance REFERENCE OUTPUTS 1P5V (Referenced to ACOM) Output Current 2VLT (Referenced to ACOM) Output Current IREF 5 PHOTODIODE BIAS Midrange Value Maximum Value Test Conditions/Comments INUM, IDEN, VSMx pins Flows toward each input pin (INUM and IDEN), −5 V ≤ VNEG ≤ −2 V VNEG = 0 V −40°C < TA < +85°C VINUM − VVSUM VLOG pin, referenced to ACOM; input applied to INUM 1 25°C −40°C < TA < +85°C Extrapolated input current at VLOG = 0 V Difference between VLOG and VSUM with INUM = IDEN −40°C < TA < +85°C Maximum deviation from best fit over 1 nA to 100 µA range INPS, INMS, VLOG, SCL1, SCL2, SCL3 pins Min Max Unit 1 × 10−12 1 × 10−3 A 1 × 10−12 3 × 10−3 A mV/°C mV −2 195 −2 25°C −40°C < TA < +85°C Sourcing only 25°C −40°C < TA < +85°C IMON pin; IMON = 1.1 × INUM At a photodiode current = INUM = 100 nA At INUM = 1 mA (RS ≤ 100 Ω), RMNTR = 10 × RS (RS = photodiode series resistance) IMON Compliance Rev. A | Page 3 of 32 0.01 ±0.6 200 +2 205 +3 3.162 −8 −0.7 −3 Flowing out of the INPS pin Pin INPS RL open INUM > 1 nA INUM = 1 nA INUM = 10 nA INUM = 100 nA INUM > 1 µA INUM = 100 nA to 10 nA INUM = 1 µA to 100 nA INUM = 10 µA to 1 µA INUM > 10 µA For input current range of 1 pA to 10 mA Frequency < 1 MHz 1P5V, 2VLT, IREF pins 25°C −40°C < TA < +85°C Typ +5 25 ±0.2 +0.1 −1.3 12 VNEG + 0.2 +0.7 +3 VPOS − 0.2