Electronic Components Datasheet Search |
|
PCM1738E Datasheet(PDF) 11 Page - Burr-Brown (TI) |
|
|
PCM1738E Datasheet(HTML) 11 Page - Burr-Brown (TI) |
11 / 33 page PCM1738 11 SBAS174B SYSTEM CLOCK AND RESET FUNCTIONS SYSTEM CLOCK INPUT The PCM1738 requires a system clock for operating the digital interpolation filters and advanced segment DAC modulators. The system clock is applied at the SCKI input (pin 7). The PCM1738 has a system-clock detection circuit that automatically senses if the system clock is operating at 128fS to 768fS. Table I shows examples of system-clock frequencies for common audio sampling rates. Figure 1 shows the timing requirements for the system clock input. For optimal performance, it is important to use a clock source with low phase jitter and noise. The PLL1700 multi- clock generator is an excellent choice for providing the PCM1738 system clock. SYSTEM CLOCK OUTPUT A buffered version of the system clock input is available at the SCKO output (pin 10). SCKO can operate at either full (fSCKI) or half (fSCKI/2) rate. The SCKO output frequency may be programmed using the CLKD bit of Control Regis- ter 19. The SCKO output pin can also be enabled or disabled using the CLKE bit of Control Register 19. The default is SCKO enabled. POWER-ON AND EXTERNAL RESET FUNCTIONS The PCM1738 includes a power-on reset function (see Figure 2). The system clock input at SCKI should be active for at least one clock period prior to VDD = 2.0V. With the system clock active, and VDD > 2.0V, the power-on reset function will be enabled. The initialization sequence re- quires 1024 system clocks from the time VDD > 2.0V. After the initialization period, the PCM1738 will be set to its reset default state, as described in the Mode Control Register section of this data sheet. The PCM1738 also includes an external reset capability using the RST input (pin 1). This allows an external control- ler or master reset circuit to force the PCM1738 to initialize to its reset default state. See Figure 3 for external reset operation and timing. The RST pin is set to a logic “0” for a minimum of 20ns. The RST pin is then set to a logic “1” state that starts the initialization sequence that requires 1024 system clock peri- ods. After the initialization sequence is complete, the PCM1738 will be set to its reset default state, as described in the Mode Control Register section of this data sheet. The external reset is especially useful in applications where there is a delay between the PCM1738 power-up and system clock activation. In this case, the RST pin should be held at a logic “0” level until the system clock has been activated. The RST pin may then be set to a logic “1” state to start the initialization sequence. FIGURE 1. System Clock Input Timing. SAMPLING FREQUENCY 128fS 192fS 256fS 384fS 512fS 768fS 32kHz 4.0960 6.1440 8.1920 12.2880 16.3840 24.5760 44.1kHz 5.6488 8.4672 11.2896 16.9344 22.5792 33.8688 48kHz 6.1440 9.2160 12.2880 18.4320 24.5760 36.8640 96kHz 12.2880 18.4320 24.5760 36.8640 49.1520 73.7280 192kHz 24.5760 36.8640 49.1520 73.7280 See Note (1) See Note (1) NOTE: (1) This system clock is not supported for the given sampling frequency. TABLE I. System Clock Rates for Common Audio Sampling Frequencies. SYSTEM CLOCK FREQUENCY (fSCLK) (MHz) t SCKH t SCKL 2.0V 0.8V System Clock System clock pulse cycle time(1) “H” “L” System Clock Pulse Width HIGH t SCKH: 5ns (min) System Clock Pulse Width LOW t SCKL: 5ns (min) |
Similar Part No. - PCM1738E |
|
Similar Description - PCM1738E |
|
|
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 |