Electronic Components Datasheet Search |
|
ADC0804LCN Datasheet(PDF) 12 Page - Renesas Technology Corp |
|
ADC0804LCN Datasheet(HTML) 12 Page - Renesas Technology Corp |
12 / 17 page ADC0803, ADC0804 FN3094 Rev 4.00 Page 12 of 17 August 2002 Finally, if time is short and capacitive loading is high, external bus drivers must be used. These can be three-state buffers (low power Schottky is recommended, such as the 74LS240 series) or special higher-drive-current products which are designed as bus drivers. High-current bipolar bus drivers with PNP inputs are recommended. Power Supplies Noise spikes on the V+ supply line can cause conversion errors as the comparator will respond to this noise. A low-inductance tantalum filter capacitor should be used close to the converter V+ pin, and values of 1 F or greater are recommended. If an unregulated voltage is available in the system, a separate 5V voltage regulator for the converter (and other analog circuitry) will greatly reduce digital noise on the V+ supply. An lCL7663 can be used to regulate such a supply from an input as low as 5.2V. Wiring and Hook-Up Precautions Standard digital wire-wrap sockets are not satisfactory for breadboarding with this A/D converter. Sockets on PC boards can be used. All logic signal wires and leads should be grouped and kept as far away as possible from the analog signal leads. Exposed leads to the analog inputs can cause undesired digital noise and hum pickup; therefore, shielded leads may be necessary in many applications. A single-point analog ground should be used which is separate from the logic ground points. The power supply bypass capacitor and the self-clockIng capacitor (if used) should both be returned to digital ground. Any VREF/2 bypass capacitors, analog input filter capacitors, or input signal shielding should be returned to the analog ground point. A test for proper grounding is to measure the zero error of the A/D converter. Zero errors in excess of 1/4 LSB can usually be traced to improper board layout and wiring (see Zero Error for measurement). Further information can be found in Application Note AN018. Testing the A/D Converter There are many degrees of complexity associated with testing an A/D converter. One of the simplest tests is to apply a known analog input voltage to the converter and use LEDs to display the resulting digital output code as shown in Figure 18. For ease of testing, the VREF/2 (pin 9) should be supplied with 2.560V and a V+ supply voltage of 5.12V should be used. This provides an LSB value of 20mV. If a full scale adjustment is to be made, an analog input voltage of 5.090V (5.120 - 11/2 LSB) should be applied to the VIN(+) pin with the VIN(-) pin grounded. The value of the VREF/2 input voltage should be adjusted until the digital output code is just changing from 1111 1110 to 1111 1111. This value of VREF/2 should then be used for all the tests. The digital-output LED display can be decoded by dividing the 8 bits into 2 hex characters, one with the 4 most- significant bits (MS) and one with the 4 least-significant bits (LS). The output is then interpreted as a sum of fractions times the full scale voltage: . For example, for an output LED display of 1011 0110, the MS character is hex B (decimal 11) and the LS character is hex (and decimal) 6, so: . Figures 19 and 20 show more sophisticated test circuits. VOUT MS 16 --------- LS 256 ---------- + 5.12 V = START VIN (+) DGND 2.560V AGND 10 F 150pF N.O. 0.1 F 0.1 F TANTALUM 5.120V 5V 1.3k LEDs (8) (8) MSB LSB 10k VREF/2 + 11 12 13 14 15 16 17 18 20 19 10 9 8 7 6 5 4 3 2 1 ADC0803- ADC0804 FIGURE 18. BASIC TESTER FOR THE A/D VOUT 11 16 ------ 6 256 ---------- + 5.12 3.64V == ANALOG INPUTS “A” R “B” R R R “C” 100R - + A2 8-BIT A/D UNDER TEST 10-BIT DAC VANALOG OUTPUT 100X ANALOG - + A1 ERROR VOLTAGE FIGURE 19. A/D TESTER WITH ANALOG ERROR OUTPUT. THIS CIRCUIT CAN BE USED TO GENERATE “ERROR PLOTS” OF FIGURE 11. A/D UNDER TEST 10-BIT DAC DIGITAL VANALOG INPUTS DIGITAL OUTPUTS FIGURE 20. BASIC “DIGITAL” A/D TESTER |
Similar Part No. - ADC0804LCN |
|
Similar Description - ADC0804LCN |
|
|
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 |