 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
SAA7824 Datasheet(PDF) 11 Page - NXP Semiconductors |
|
||||||||||||||||||||||||||||||
SAA7824 Datasheet(HTML) 11 Page - NXP Semiconductors |
|
|
11 / 89 page  2003 Oct 01 11 Philips Semiconductors Product specification CD audio decoder, digital servo and filterless DAC with integrated pre-amp and laser control SAA7824 7.4 Data slicer and bit clock regenerator The SAA7824 has an integrated adaptive data slicer which is clocked at 67 MHz. The slice level is controlled by internal current sources which are switched onto and integrated by the external capacitor connected to the CSLICE pin. The currents are switched under the control of a Digital Phase-Locked loop (DPLL). Regeneration of the bit clock is achieved with an internal fully digital PLL. No external components are required and the bit clock is not output. The PLL has two registers (8 and 9) for selecting bandwidth and equalization. The PLL loop response is illustrated in Fig.5. For certain applications an off-track input is necessary. This is internally connected from the servo part (its polarity can be changed by the foc_parm1 parameter), but may be input via pin V1 if selected by register C. If this flag is HIGH, the SAA7824 will assume that its servo part is following the wrong track, and will flag all incoming HF data as incorrect. 7.5 DC offset cancellation Unwanted DC offsets can exist within the photo-diode signals and are defined as the DC present in the system when the laser diode is switched off. They arise from various sources of imperfection within the system such as leakage in the photo diodes and offsets in the Optical Pick-Up (OPU) circuitry. The SAA7824 is capable of measuring these offsets and minimizing them. 7.5.1 OFFSET CANCELLATION A number of registers are associated with the DC offset cancellation function; these registers are given in Table 3. The measurement time of the DC offset is regulated by new shadow register C (bank 2). A longer time will yield more accurate results but will result in greater measurement durations. New shadow register 3 (bank 3) is used to select which diode is to be measured. 7.5.2 READING BACK THE DC OFFSET VALUE The microcontroller needs to be able to read the DC offset measurements in order to calculate the correct cancellation value [for writing back to new shadow register 7 (bank 3)]. This is achieved by using the STATUS pin and setting decoder register 7 to XX10. Shadow register C (bank 3) can then be used to control the STATUS pin output; the register settings are given in Table 20. Once the measurement time has been set and the diode selected, the STATUS pin should be set to read the DC offset ready flag [new shadow register C (bank 3) = X01X]. This signal will toggle HIGH after the prescribed measurement time. Changing the diode selection will result in the measurement timer being automatically reset. The microcontroller can read back the measurement by setting the STATUS pin to output the DC offset value [new shadow register C (bank 3) = X10X]. The offset value is repeatedly streamed out through the STATUS pin and is UART compatible. It should be noted that the MSB is inverted and will require re-inverting after the offset value has been captured. Timing information for this signal is illustrated in Fig.6. The final DC cancellation value (as calculated by the microcontroller) can then be written to new shadow register 7 (bank 3). This is a multiple write register containing the cancellation values for all six diodes. MGS178 handbook, halfpage f 3. PLL, LPF 2. PLL bandwidth 1. PLL integrator PLL loop response Fig.5 Digital PLL loop response. Points 1, 2 and 3 are all programmable via decoder register 8. |
Similar Part No. - SAA7824 |
|
Similar Description - SAA7824 |
|
|
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 |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
