![]() |
Electronic Components Datasheet Search |
|
LTC2220 Datasheet(PDF) 21 Page - Linear Technology |
|
|
LTC2220 Datasheet(HTML) 21 Page - Linear Technology |
21 / 32 page ![]() LTC2220/LTC2221 21 22201fa The AIN+ and AIN– inputs each have two pins to reduce package inductance. The two AIN+ and the two AIN– pins should be shorted together. For input frequencies above 100MHz the input circuits of Figure 6, 7 and 8 are recommended. The balun trans- former gives better high frequency response than a flux coupled center tapped transformer. The coupling capaci- tors allow the analog inputs to be DC biased at 1.6V. In Figure 8 the series inductors are impedance matching elements that maximize the ADC bandwidth. Figure 7. Recommended Front End Circuit for Input Frequencies Between 250MHz and 500MHz Reference Operation Figure 9 shows the LTC2220/LTC2221 reference circuitry consisting of a 1.6V bandgap reference, a difference amplifier and switching and control circuit. The internal voltage reference can be configured for two pin selectable input ranges of 2V ( ±1V differential) or 1V (±0.5V differ- ential). Tying the SENSE pin to VDD selects the 2V range; typing the SENSE pin to VCM selects the 1V range. The 1.6V bandgap reference serves two functions: its output provides a DC bias point for setting the common mode voltage of any external input circuitry; additionally, the reference is used with a difference amplifier to gener- ate the differential reference levels needed by the internal ADC circuitry. An external bypass capacitor is required for the 1.6V reference output, VCM. This provides a high frequency low impedance path to ground for internal and external circuitry. The difference amplifier generates the high and low refer- ence for the ADC. High speed switching circuits are connected to these outputs and they must be externally bypassed. Each output has four pins: two each of REFHA and REFHB for the high reference and two each of REFLA and REFLB for the low reference. The multiple output pins are needed to reduce package inductance. Bypass capaci- tors must be connected as shown in Figure 9. 25 Ω 25 Ω 0.1 µF AIN + AIN + AIN – AIN – 2pF 2.2 µF VCM LTC2220/ LTC2221 ANALOG INPUT 0.1 µF 0.1 µF T1 T1 = MA/COM ETC1-1-13 RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE 22201 F08 4.7nH 4.7nH APPLICATIO S I FOR ATIO Figure 6. Recommended Front End Circuit for Input Frequencies Between 100MHz and 250MHz 25 Ω 25 Ω 12 Ω 12 Ω 0.1 µF AIN + AIN + AIN – AIN – 8pF 2.2 µF VCM LTC2220/ LTC2221 ANALOG INPUT 0.1 µF 0.1 µF T1 T1 = MA/COM ETC1-1-13 RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE 22201 F06 Figure 8. Recommended Front End Circuit for Input Frequencies Above 500MHz 25 Ω 25 Ω 0.1 µF AIN + AIN + AIN – AIN – 2.2 µF VCM LTC2220/ LTC2221 ANALOG INPUT 0.1 µF 0.1 µF T1 T1 = MA/COM ETC1-1-13 RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE 22201 F07 VCM REFHA REFLB SENSE TIE TO VDD FOR 2V RANGE; TIE TO VCM FOR 1V RANGE; RANGE = 2 • VSENSE FOR 0.5V < VSENSE < 1V 1.6V REFLA REFHB 2.2 µF 2.2 µF INTERNAL ADC HIGH REFERENCE BUFFER 0.1 µF 22201 F09 LTC2220/LTC2221 4 Ω DIFF AMP 1 µF 1 µF 0.1 µF INTERNAL ADC LOW REFERENCE 1.6V BANDGAP REFERENCE 1V 0.5V RANGE DETECT AND CONTROL Figure 9. Equivalent Reference Circuit |
Similar Part No. - LTC2220 |
|
Similar Description - LTC2220 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | 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 |