Datenblatt-Suchmaschine für elektronische Bauteile |
|
DAC1006LCN Datenblatt(PDF) 8 Page - National Semiconductor (TI) |
|
|
DAC1006LCN Datenblatt(HTML) 8 Page - National Semiconductor (TI) |
8 / 22 page 42 Op Amp Bias Current Input Leads The op amp bias current (IB) CAN CAUSE DC ERRORS BI- FETTM op amps have very low bias current and therefore the error introduced is negligible BI-FET op amps are strongly recommended for these DACs The distance from the IOUT1 pin of the DAC to the inverting input of the op amp should be kept as short as possible to prevent inadvertent noise pickup 50 ANALOG APPLICATIONS The analog section of these DACs uses an R-2R ladder which can be operated both in the current switching mode and in the voltage switching mode The major product changes (compared with the DAC1020) have been made in the digital functioning of the DAC The analog functioning is reviewed here for completeness For additional analog applications such as multipliers attenua- tors digitally controlled amplifiers and low frequency sine wave oscillators refer to the DAC1020 data sheet Some basic circuit ideas are presented in this section in addition to complete applications circuits 51 Operation in Current Switching Mode The analog circuitry Figure 2 consists of a silicon-chromi- um (Si-Cr) thin film R-2R ladder which is deposited on the surface oxide of the monolithic chip As a result there is no parasitic diode connected to the VREF pin as would exist if diffused resistors were used The reference voltage input (VREF) can therefore range from b10V to a10V The digital input code to the DAC simply controls the posi- tion of the SPDT current switches SW0 to SW9 A logical 1 digital input causes the current switch to steer the avail- able ladder current to the IOUT1 output pin These MOS switches operate in the current mode with a small voltage drop across them and can therefore switch currents of ei- ther polarity This is the basis for the 4-quadrant multiplying feature of this DAC 511 Providing a Unipolar Output Voltage with the DAC in the Current Switching Mode A voltage output is provided by making use of an external op amp as a current-to-voltage converter The idea is to use the internal feedback resistor RFB from the output of the op amp to the inverting (b) input Now when current is entered at this inverting input the feedback action of the op amp keeps that input at ground potential This causes the applied input current to be diverted to the feedback resistor The output voltage of the op amp is forced to a voltage given by VOUT eb(IOUT1cRFB) Notice that the sign of the output voltage depends on the direction of current flow through the feedback resistor In current switching mode applications both current output pins (IOUT1 and IOUT2) should be operated at 0 VDC This is accomplished as shown in Figure 3 The capacitor CC is used to compensate for the output capacitance of the DAC and the input capacitance of the op amp The required feed- back resistor RFB is available on the chip (one end is inter- nally tied to IOUT1) and must be used since an external resistor will not provide the needed matching and tempera- ture tracking This circuit can therefore be simplified as DIGITAL INPUT CODE FIGURE 2 Current Mode Switching OP AMP CC pF Rj ts mS LF356 22 % 3 LF351 24 % 4 LF357 10 24k 15 TLH5688 – 10 FIGURE 3 Converting IOUT to VOUT 8 |
Ähnliche Teilenummer - DAC1006LCN |
|
Ähnliche Beschreibung - DAC1006LCN |
|
|
Link URL |
Privatsphäre und Datenschutz |
ALLDATASHEETDE.COM |
War ALLDATASHEET hilfreich? [ DONATE ] |
Über Alldatasheet | Werbung | Kontakt | Privatsphäre und Datenschutz | Linktausch | Hersteller 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 |