ADL5315

Precision Wide Range (3 nA to 3 mA) High-Side Current Mirror ADL5315 FEATURES Accurately mirrors input current (1:1 ratio) over 6 decades Linearity 1% from 3 nA to 3 mA Stable mirror input voltage Voltage held 1 V below supply using internal reference or can be set externally Adjustable input current limit 2.7 V to 8 V single-supply operation Miniature 8-lead LFCSP (2 mm × 3 mm) FUNCTIONAL BLOCK DIAGRAM ADL5315 VOLTAGE REFERENCE 4 CURRENT LIMITING RLIM CURRENT MIRROR 1:1 VPOS NC 7 5 COMM 20kΩ 3 6 SREF VSET 2 APPLICATIONS Optical power monitoring from a single photodiode General voltage biasing with precision current monitoring Voltage-to-current conversion INPT 1 IOUT IPD IPD 05694-001 8 Figure 1. GENERAL DESCRIPTION The ADL5315 is a wide input current range, precision high-side current mirror featuring a stable and user-adjustable input voltage. It is optimized for use with PIN photodiodes, but its flexibility and wide operating range make it suitable for a broad array of additional applications. Over the 3 nA to 3 mA range, the current sourced from the INPT pin is accurately mirrored with a 1:1 ratio and sourced from the IOUT output pin. In a typical photodiode application, the output drives a currentinput logarithmic amplifier to produce a linear-in-dB output representing the optical power incident upon the photodiode. For linear voltage output, a single resistor to ground is all that is required. The photodiode anode can be connected to a high speed transimpedance amplifier for the extraction of the data stream. The voltage at the INPT pin is temperature stable with respect to the voltage at the VSET input pin, which it tracks. A temperature stable reference voltage is provided at the SREF pin, which, when tied to VSET, fixes the voltage at INPT 1.0 V below VPOS. VSET can also be driven from an external source. The VSET input has very low input current and can be driven as low as the bottom rail, facilitating nonloading voltage-tocurrent conversion as well as minimizing dark current in photodiode applications. The ADL5315 also features adjustable input current limiting using an external resistor from RLIM to VPOS. The maximum current sourced by INPT (and IOUT) can be set between 1 mA and 16 mA, beyond which the voltage at INPT falls rapidly from its setpoint. Connecting RLIM directly to VPOS provides basic input short-circuit protection with the default current limit of 16 mA typical. The ADL5315 is available in a 2 mm × 3 mm, 8-lead LFCSP and is specified for operation from −40°C to +85°C. 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 owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 © 2005 Analog Devices, Inc. All rights reserved. ADL5315 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 Theory of Operation ........................................................................ 9 Bias Control Interface .................................................................. 9 Noise Performance ..................................................................... 10 Mirror Response Time............................................................... 10 Input Current Limiting.............................................................. 10 Applications..................................................................................... 11 Average Power Monitoring ....................................................... 11 Translinear Log Amp Interfacing............................................. 12 Extended Operating Range....................................................... 13 Using RLIM as a Secondary Monitor ...................................... 13 Characterization Methods ........................................................ 14 Evaluation Board ............................................................................ 16 Outline Dimensions ....................................................................... 17 Ordering Guide .......................................................................... 17 REVISION HISTORY 10/05—Revision 0: Initial Version Rev. 0 | Page 2 of 20 ADL5315 SPECIFICATIONS VPOS = 5 V, VSET = 4 V, IINPT = 3 μA, TA = 25°C, unless otherwise noted. Table 1. Parameter CURRENT MIRROR OUTPUT Current Gain from INPT to IOUT Current Gain from INPT to IOUT Nonlinearity Small Signal Bandwidth Wideband Noise at IPDM Specified Output Voltage Range IOUT × ROUT Product MIRROR INPUT, VOLTAGE CONTROL Specified Input Current Range, IINPT Specified VSET Voltage Range Incremental Gain from VSET to INPT Incremental Input Resistance at VSET Input Bias Current at VSET SREF Voltage, Relative to VPOS OVERCURRENT PROTECTION INPT Current Limit POWER SUPPLY Supply Voltage Range Quiescent Current Conditions IOUT (Pin 8) −40°C < TA < +85°C 3 nA < IPD < 3 mA IINPT = 3 nA IINPT = 3 μA IINPT = 3 μA, CSET = 2.2 nF IINPT = 3 μA INPT (Pin 1), VSET (Pin 2), SREF (Pin 3) Flows from INPT pin 2.7 V < VPOS < 6.5 V 6.5 V < VPOS < 8 V 0.2 V < VSET < 7.0 V VSET = 4.0 V VSET = 4.0 V 2.7 V < VPOS < 8 V VINPT drops to 0 V, RLIM = 0 Ω VINPT drops to 0 V, RLIM = 3 kΩ VPOS (Pin 6) IINPT = 3 μA IINPT = 3 mA Min 0.99 0.97 Typ 1.00 1.00 0.25 1 1 20 900 3n 0 VPOS − 6.5 0.98 3m VPOS − 1 VPOS − 1 1.02 Max 1.01 1.03 1.00 Unit 0 VPOS − 1 A/A % kHz MHz nA rms V V A V V V/V GΩ pA V mA mA V mA mA −1.04 1 >100