 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
SPT7862SIT Datasheet(PDF) 7 Page - List of Unclassifed Manufacturers |
|
||||||||||||||||||||||||||||||
SPT7862SIT Datasheet(HTML) 7 Page - List of Unclassifed Manufacturers |
|
|
7 / 10 page  SPT 7 2/23/00 SPT7862 • Since only 16 comparators are used, a huge power sav- ings is realized. • The auto-zero operation is done using a closed loop sys- tem that uses multiple samples of the comparator’s response to a reference zero. • The auto-calibrate operation, which calibrates the gain of the MSB reference and the LSB reference, is also done with a closed loop system. Multiple samples of the gain error are integrated to produce a calibration volt- age for each SAR ADC section. • Capacitive displacement currents, which can induce sam- pling error, are minimized since only one comparator samples the input during a clock cycle. • The total input capacitance is very low, since sections of the converter which are not sampling the signal are iso- lated from the input by transmission gates. VOLTAGE REFERENCE The SPT7862 requires the use of a single external voltage reference for driving the high side of each reference ladder. Each ladder is totally independent and may operate at dif- ferent voltage levels. The high side of the reference ladder must operate within a range of 3 V to 5 V. The lower side of each ladder is typically tied to AGND (0.0 V), but can be run up to 2.0 V with a second reference. The analog input volt- age range will track the total voltage difference measured between the ladder sense lines, VRHS and VRLS. Force and sense taps are provided to ensure accurate and stable setting of the upper and lower ladder sense line volt- ages across part-to-part and temperature variations. By using the configuration shown in figure 3, offset and gain errors of less than ±2 LSB can be obtained. In cases in which wider variations in offset and gain can be tolerated, the external reference can be tied directly to VRHF and AGND can be tied directly to VRLF as shown in figure 4. Decouple force and sense lines to AGND with a .01 µF ca- pacitor (chip cap preferred) to minimize high-frequency noise injection. If this simplified configuration is used, the following considerations should be taken into account: The reference ladder circuit shown in figure 4 is a simplified representation of the actual reference ladder with force and sense taps shown. Due to the actual internal structure of the ladder, the voltage drop from VRHF to VRHS is not equivalent to the voltage drop from VRLF to VRLS. Figure 3 – Ladder Force/Sense Circuit for Each ADC AGND VRHF VRHS VRLS VRLF VIN 1 2 3 5 6 7 + - All capacitors are 0.01 µF 4 N/C Figure 4 – Simplified Reference Ladder Drive Circuit Without Force/Sense Circuit R/2 R R R R R R R/2 R=30 Ω (typ) All capacitors are 0.01 µF VRLF (AGND) 0.0 V VRLS (0.075 V) VRHS (+3.91 V) 90 mV 75 mV +4.0 V External Reference Typically, the top side voltage drop for VRHF to VRHS will equal: VRHF – VRHS = 2.25 % of (VRHF – VRLF) (typical), and the bottom side voltage drop for VRLS to VRLF will equal: VRLS – VRLF = 1.9 % of (VRHF – VRLF) (typical). Figure 4 shows an example of expected voltage drops for a specific case. VREF of 4.0 V is applied to VRHF and VRLF is tied to AGND. A 90 mV drop is seen at VRHS (= 3.91 V) and a 75 mV increase is seen at VRLS (= 0.075 V). |
Similar Part No. - SPT7862SIT |
|
Similar Description - SPT7862SIT |
|
|
|
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
