Datasheet

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Required PLL Loop Filter Description
DIR9001
PLL Section
Charge
Pump
VCO
FILT
AGND DGND
C2
R1
C1
DIR9001
SLES198 – DECEMBER 2006
In PLL mode (CKSEL = L), output clocks (SCKO, BCKO, LRCKO) are generated from the PLL source clock.
The relationship between frequencies of LRCKO, BCKO, and SCKO at different sampling frequencies f
S
of the
biphase input signal are shown in Table 4 .
Table 4. Output Clock Frequency in PLL Locked State (CKSEL = L)
LRCKO BCKO SCKO (Depending on PSCK[1:0] Setting)
f
S
64 f
S
128 f
S
256 f
S
384 f
S
512 f
S
32 kHz 2.048 MHz 4.096 MHz 8.192 MHz 12.288 MHz 16.384 MHz
44.1 kHz 2.8224 MHz 5.6448 MHz 11.2896 MHz 16.9344 MHz 22.5792 MHz
48 kHz 3.072 MHz 6.144 MHz 12.288 MHz 18.432 MHz 24.576 MHz
88.2 kHz 5.6448 MHz 11.2896 MHz 22.5792 MHz 33.8688 MHz 45.1584 MHz
96 kHz 6.144 MHz 12.288 MHz 24.576 MHz 36.864 MHz 49.152 MHz
The DIR9001 incorporates a PLL for generating a clock synchronized with the biphase input signal.
The built-in PLL requires an external loop filter, which is specified as follows.
Operation and performance is assured for recommended filter components R1, C1, and C2.
Notes about Loop Filter Components and Layout
• The resistor and capacitors which comprise the filter should be located and routed as close as possible to the
DIR9001.
• A carbon film resistor or metal film resistor, with tolerance less than 5%, is recommended.
• Film capacitors, with tolerance is less than 5%, is recommended.
• If ceramic capacitors are used for C1 and C2, parts with a low voltage coefficient and low temperature
coefficient, such as CH or C0G, are recommended.
• The external loop filter must be placed on FILT pins.
• The GND node of the external loop filter must be directly connected with the AGND pin of the DIR9001; it
must be not combined with other signals.
The configuration of external loop filter and the connection with the DIR9001 is shown in Figure 8 .
Figure 8. Loop Filter Connection
The recommended values of loop filter components is shown in Table 5 .
Table 5. Recommended Value of Loop Filter Components
REF. NO. RECOMMENDED VALUE PARTS TYPE TOLERANCE
R1 680 Ω Metal film or carbon ≤ 5%
C1 0.068 µ F Film or ceramic (CH or C0G) ≤ 5%
C2 0.0047 µ F Film or ceramic (CH or C0G) ≤ 5%
15
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