 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LT1994CMS8 Datasheet(PDF) 11 Page - Linear Technology |
|
||||||||||||||||||||||||||||||
LT1994CMS8 Datasheet(HTML) 11 Page - Linear Technology |
|
|
11 / 20 page  LT1994 11 1994fa a need for ADCs to process signals differentially in order to maintain good signal to noise ratios. These ADCs are typically supplied from a single supply voltage that can be as low as 2.5V and will have an optimal common mode input range near mid-supply. The LT1994 makes interfac- ing to these ADCs trivial, by providing both single ended to differential conversion as well as common mode level shifting. Figure 1 shows a general single supply application with perfectly matched feedback networks from OUT+ and OUT–. The gain to VOUTDIFF from VINM and VINP is: VV V R R VV OUTDIFF OUT OUT F I INP INM =≈ () + –• – – Note from the above equation that the differential output voltage (VOUT + – V OUT –) is completely independent of input and output common mode voltages, or the voltage at the common mode pin. This makes the LT1994 ideally suited pre-amplification, level shifting, and conversion of single ended signals to differential output signals in preparation for driving differential input ADCs. Effects of Resistor Pair Mismatch Figure 2 shows a circuit diagram that takes into consid- eration that real world resistors will not perfectly match. Assuming infinite open loop gain, the differential output relationship is given by the equation: VV V R R V VV OUTDIFF OUT OUT F I INDIFF AVG ICM AVG OCM =≅ + ∆∆ + –• •– • , – β β β β where: RF is the average of RF1 and RF2, and RI is the average of RI1 and RI2. βAVG is defined as the average feedback factor (or gain) from the outputs to their respective inputs: βAVG I IF I IF R RR R RR = + + + ⎛ ⎝⎜ ⎞ ⎠⎟ 1 2 2 22 1 11 • Δβ is defined as the difference in feedback factors: ∆= ++ β R RR R RR I IF I IF 2 22 1 11 – VICM is defined as the average of the two input voltages, VINP and VINM (also called the input common mode voltage): VV V ICM INP INM =+ () 1 2 • and VINDIFF is defined as the difference of the input voltages: VV V INDIFF INP INM = – When the feedback ratios mismatch (Δβ), common mode to differential conversion occurs. Setting the differential input to zero (VINDIFF = 0), the de- gree of common mode to differential conversion is given APPLICATIO S I FOR ATIO VOCM 0.1 µF 1994 F01 RI RF RL V+ 0.1 µF 0.1 µF VCM VSHDN VINM VINP VOUTCM 3 7 6 8 1 2 5 4 V– VOUT + VIN – VOUT – VIN + RBAL RBAL 0.1 µF RI RF RL + – – + LT1994 VOCM Figure 1. Test Circuit Figure 2. Real-World Application 1994 F02 RI2 RF2 RL VS VSHDNB VINM VINP + – – + 3 7 6 8 1 2 5 4 LT1994 VOCM VOCM VOUT + VIN – VOUT – VIN + 0.1 µF 0.1 µF RI1 RF1 RL SHDN |
Similar Part No. - LT1994CMS8 |
|
Similar Description - LT1994CMS8 |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.NET |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
