1、adi adl5304高速200db對數(shù)轉換解決方案 公司確實adl5304是高速200db測量范圍的對數(shù)轉換器,具有迅速響應和低噪音,正常對數(shù)斜率10 mv/db(200 mv/decade),單電源工作的輸入在1pa到3ma,雙電源工作的輸入電流可擴展至10ma,輸入電流大于1ua時的帶寬大于4mhz,主要用在高精度光功率測量,寬范圍基帶對數(shù)壓縮和高速apc回路的檢測.本文介紹了adl5304主要特性,簡化方框圖,多種參數(shù)測量以及單電源工作基本銜接圖,評估板圖和布局圖. the adl5304 is a high speed logarithmic converter with fast

2、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 fo

3、r 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.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

4、current range to 10 ma.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

5、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 cu

6、rrent 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.the vlog output is buffered and can be rescaled thr

7、ough internal gain setting resistors. the internal ilog varies from 400 a to +400 a 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.accurate 1.5 v (pin 1p5v) and 2.0 v (pin 2vlt) reference outputs a

8、llow 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.adl5304主要特性:optimized for very fast response at all input currentsoverall bandwidth of >4 mhz for inputs >

9、1 abandwidth: 25 khz at input of 1 na and 350 khz at 10 na10 decades of input range: 1 pa to 10 malaw conformance: ±0.25 db from 100 pa to 100 alog ratio or fixed-intercept operationprecision voltage references and reference currentadaptive photodiode (pd) bias for low dark currentprogrammable log slope and interceptdefault log slope of 10 mv/db at vlog pinsingle- or dual-supply o