AD8305 Analog Devices, AD8305 Datasheet
AD8305
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AD8305 Summary of contents
Page 1
... fundamental aspect of translinear logarithmic converters that the small signal bandwidth falls as the current level dimin- ishes, and the low frequency noise-spectral density increases. At the 10 nA level, the bandwidth of the AD8305 is about 50 kHz, and increases in proportion to I about 15 MHz. Using the buffer amplifier, the increase in noise level at low currents can be addressed by using it to realize low- pass filters three poles ...
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... AD8305–SPECIFICATIONS Parameter INPUT INTERFACE Specified Current Range Input Current Min/Max Limits Reference Current Range REF Summing Node Voltage Temperature Drift Input Offset Voltage LOGARITHMIC OUTPUT Logarithmic Slope 1 Logarithmic Intercept Law Conformance Error 2 Wideband Noise 2 Small Signal Bandwidth Maximum Output Voltage ...
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... ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD8305 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 ...
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... AD8305–Typical Performance Characteristics 1 – +25 C, + 1.4 N 1.2 –40 C 1.0 +25 C +85 C 0.8 0 0.4 + 10n 100n – TPC 1. V vs. I for Multiple Temperatures LOG PD 1 – +25 C, +70 C, +85 C – 1.2 +70 C 1.0 + ...
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... T-RISE = 5 s, T-FALL = < 0 100 A: T-RISE = 1 s, T-FALL = < 0.6 100 A TO 1mA: T -RISE = < T-FALL = < 0.4 0.2 0 – 100 120 140 TIME – REF OUT AD8305 10m 160 180 ( 160 180 ( ...
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... AD8305 10 10nA 100nA 0 –10 –20 1mA – –40 –50 100 1k 10k 100k FREQUENCY – Hz TPC 13. Small Signal AC Response (5% Sine Modulation), from OUT Decade Steps from mA 10nA 100nA 0 –10 –20 1mA – –40 –50 100 ...
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... C, + –1 –2 –3 –4 –5 –40 100 1m 10m TPC 24. V Side of Mean) –7– AD8305 MEAN + 3 MEAN – 3 –30 –20 – TEMPERATURE – C Drift vs. Temperature (3 to Either REF MEAN + 3 MEAN – 3 –30 – ...
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... AD8305 MEAN + –2 MEAN – 3 –4 –6 –8 –10 –40 –30 –20 – TEMPERATURE – C TPC 25. Slope Drift vs. Temperature (3 to Either Side of Mean of 200 mV/decade) 350 250 MEAN + 3 150 50 –50 –150 MEAN – 3 –250 –350 –40 – ...
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... This is internally set to 0.5 V, that is, one fifth of the reference voltage of 2.5 V appearing on Pin VREF. The resistance at the VSUM pin is nominally 16 kW; this voltage is not intended as a general bias source. The AD8305 also supports the use of an optional negative supply voltage Pin VNEG. When V is –0 more negative, ...
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... Details of the noise and bandwidth performance of translinear log amps can be found in the AD8304 Data Sheet. APPLICATIONS The AD8305 is easy to use in optical supervisory systems and in similar situations where a wide ranging current converted to its logarithmic equivalent, which is represented in decibel terms. Basic connections for measuring a single-current input are shown in Figure 2, which also includes various nonessential com- ponents, as will be explained ...
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... Schottky barrier voltage of a little over 0.5 V. The effect of supply on the dynamic range and accuracy can be seen in TPC 8. With the summing node at ground, the AD8305 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 ...
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... LOG and also allow the input pins INPT and IREF to be set to ground potential. Thus, the AD8305 may also be used to deter- mine the log ratio of two voltages. Figure 5 also illustrates how a second order Sallen-Key low-pass filter can be realized using two external capacitors and one resistor ...
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... The modified Wilson mirror provides a current gain very close to unity and a high output resistance. Figure 8 shows measured transfer function and law conformance performance of the AD8305 in conjunc- tion with this current mirror interface. 5V 0.1 F ...
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... MW. The LeCroy’s output is offset to create the initial pedestal current for a given value of R1, the pulse then creates one-decade current step. EVALUATION BOARD An evaluation board is available for the AD8305, the schematic for which is shown in Figure 16. It can be configured for a wide 14 13 variety of experiments ...
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... R11, R17, R18 the VRDZ, VREF, VSUM, VOUT, and VLOG pin voltages can be monitored using a high impedance probe. R2, R3, R4, R6, R14, Buffer Amplifier/Output Interface. The logarithmic slope of the AD8305 C2, C7, C9, C10 can be altered using the buffer’s gain-setting resistors, R2 and R3. R4, R14, and C2 allow variation in the buffer loading ...
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... AD8305 Figure 14. Component Side Layout Figure 15. Component Side Silkscreen –16– REV. A ...
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... Figure 16. Evaluation Board Schematic –17– 13 COMM VOUT OPEN SCAL 11 OPEN OPEN R6 BFIN 10 0 C10 OPEN 9 VLOG C7 OPEN 8 VRDZ AGND C4 0.01 F VOUT C5 VREF 0.1 F VSUM 3 VPOS P1 VLOG AD8305 R10 VOUT OPEN R14 VOUT 0 R4 OPEN R8 VLOG OPEN R11 VLOG ...
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... AD8305 PIN 1 INDICATOR 12 MAX 1.00 0.90 0.80 SEATING PLANE OUTLINE DIMENSIONS 16-Lead Leadframe Chip-Scale Package [LFCSP Body (CP-16) Dimensions shown in millimeters 3.00 0.60 MAX BSC SQ 0.45 2.75 TOP BOTTOM VIEW BSC SQ VIEW 0.50 BSC 1.50 REF 0.80 MAX 0.65 NOM 0.05 MAX 0.01 NOM 0.30 0.20 REF 0.23 0.18 COMPLIANT TO JEDEC STANDARDS MO-220-VEED-2 –18– 0.50 0.40 0.30 PIN 1 INDICATOR ...
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... Revision History Location 3/03—Data Sheet changed from REV REV. A. Changes to TPC Changes to TPC Changes to Figure Changes to Figure Updated OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 REV. A –19– AD8305 Page ...
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