Datasheet ADL5310 (Analog Devices)

120 dB Range (3 nA to 3 mA) Dual Logarithmic Converter Data Sheet ADL5310 FEATURES FUNCTIONAL BLOCK DIAGRAM 2 independent channels optimized for photodiode interfacing 665k
Ω
VREF VRDZ 6-decade input dynamic range VSUM OUT1 Law conformance 0.3 dB from 3 nA to 3 mA COMM VOUT1
Ω
Temperature-stable logarithmic outputs IRF1 4.99k Nominal slope 10 mV/dB (200 mV/dec), externally scalable SCL1 Intercepts may be independently set by external resistors VBIAS 6.69k
Ω
BIN1 User-configurable output buffer amplifiers I TEMPERATURE LOG VNEG Single-supply or dual-supply operation COMPENSATION 451
Ω
LOG1 Space efficient, 24-lead 4 mm × 4 mm LFCSP 14.2k
Ω
Low power: <10 mA quiescent current I INP1 PD1 OUT2 0.5V 2.5V REFERENCE APPLICATIONS GENERATOR VOUT2 20k
Ω
80k
Ω Ω
Gain and absorbance measurements COMM IRF2 4.99k Multichannel power monitoring SCL2 General-purpose baseband log compression VBIAS 14.2k
Ω
BIN2 I TEMPERATURE LOG VNEG COMPENSATION 451
Ω
LOG2 6.69k
Ω
I INP2 PD2 COMM VSUM 665k
Ω
VREF
04415-0-001 Figure 1.
GENERAL DESCRIPTION
The ADL53101 low cost, dual logarithmic amplifier converts input VSUM potential. The VSUM potential is internally set to 500 mV current over a wide dynamic range to a linear-in-dB output but may be externally grounded for dual-supply operation, and voltage. It is optimized to determine the optical power in wide- for additional applications requiring voltage inputs. ranging optical communication system applications, including The logarithmic slope is set to 10 mV/dB (200 mV/decade) control circuitry for lasers, optical switches, atten-uators, and nominal and can be modified using external resistors and the amplifiers, as wel as system monitoring. The device is equivalent independent buffer amplifiers. The logarithmic intercepts for to a dual AD8305 with enhanced dynamic range (120 dB). While each channel are defined by the individual reference currents, the ADL5310 contains two independent signal channels with which are set to 3 μA nominal for maximum input range by individually configurable transfer function constants (slope and connecting 665 kΩ resistors between the 2.5 V VREF pins and intercept), internal bias circuitry is shared between channels for the IRF1 and IRF2 inputs. Tying VRDZ to VREF effectively sets improved power consumption and channel matching. Dual the x-intercept four decades below the reference current, which converters in a single, compact LFCSP package yield space- is typically 300 pA for a 3 µA reference. efficient solutions for measuring gain or attenuation across optical elements. Only a single supply is required; optional The use of individually optimized reference currents may be dual-supply operation offers added flexibility. valuable when using the ADL5310 for gain or absorbance measure- ments where each channel input has a different current range The ADL5310 employs an optimized translinear structure that requirement. The reference current inputs are also ful y functional use the accurate logarithmic relationship between a bipolar dynamic inputs, allowing log ratio operation with the reference transistor’s base emitter voltage and collector current, with input current as the denominator. The ADL5310 is specified for appropriate scaling by precision currents to compensate for the operation from –40°C to +85°C. inherent temperature dependence. Input and reference current pins sink current ranging from 3 nA to 3 mA (limited to ±60 dB between input and reference) into a fixed voltage defined by the 1 Protected by US Patents 4,604,532, and 5,519,308. Other patents pending.
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Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS GENERAL STRUCTURE THEORY MANAGING INTERCEPT AND SLOPE RESPONSE TIME AND NOISE CONSIDERATIONS APPLICATIONS INFORMATION CALIBRATION MINIMIZING CROSSTALK RELATIVE AND ABSOLUTE POWER MEASUREMENTS CHARACTERIZATION METHODS EVALUATION BOARD OUTLINE DIMENSIONS ORDERING GUIDE