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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.

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)

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

µF

Film or ceramic (CH or C0G)

≤5%

C2

0.0047

µF

Film or ceramic (CH or C0G)

≤5%

15

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